Merge remote-tracking branch 'origin/main' into chore/release-3.5.0

fix(thumbnails): never let an older folder check overwrite a newer answer (#611 ) (#612 )
Two refresh() callers could publish out of order. A check that looked before the folder was removed could set "available" after a newer check said "missing", and the state stayed wrong until the next probe. Each check now has an order number, and an older answer is dropped.
2026-11-01 13:39:04 -08:00 · 2026-11-01 21:16:55 +00:00 · 2026-11-01 12:20:10 -08:00 · 2026-11-01 19:58:19 +00:00 · 2026-11-01 11:16:26 -08:00 · 2026-11-01 16:38:29 +00:00
261 changed files with 18705 additions and 2111 deletions
@@ -17,6 +17,11 @@ updates:
      prefix: "deps(pip)"
      include: "scope"
    rebase-strategy: "auto"
+    # These floors follow ComfyUI's requirements.txt, never the newest release.
+    ignore:
+      - dependency-name: "Pillow"
+      - dependency-name: "aiohttp"
+      - dependency-name: "numpy"
    # Optional: group non-breaking updates to reduce PR noise
    groups:
      python-minor-and-patch:
@@ -1,9 +1,9 @@
-name: Windows and macOS
+name: Windows

 permissions:
  contents: read

-# Non-blocking portability runs (#420): never on pull requests or in the merge queue, and no context
+# Non-blocking Windows runs (#420; macOS dropped from CI in #571): never on pull requests or in the merge queue, and no context
 # here is a required check. A red run is fixed at its cause before the workspace cutover (#334).
 on:
  push:
@@ -25,10 +25,7 @@ env:
 # run counts (tests/vendor/ci-workflow.test.mjs recomputes it, #493).
 # Measured 2026-10-29 on main runs 40935337099 (dd247e3), 40938407252 (dd247e3), 40941240624 (dd247e3):
 #   slowest leg: 7m24s (py3.12 windows) / 7m31s (py3.13 windows) / 7m32s (py3.14 windows) -> 15 min
-#     (windows 4m56s-7m32s, macos 4m39s-6m14s)
-#   native-trash (#499) has no green main runs yet: its probe, run 40949370943 (2026-10-29), took
-#     about 1 minute per macOS leg, so ceil(1.5 x 2) + 3 gives it 6 minutes (step 4). Recalibrate
-#     after three green runs.
+#     (windows 4m56s-7m32s)
 #   native-trash-linux (#543) has no green main runs yet: it installs the dev requirements and runs
 #     one test module, about 1 minute by the same estimate, so ceil(1.5 x 2) + 3 gives it 6 minutes.
 #     Recalibrate after three green runs.
@@ -40,7 +37,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        os: [windows-latest, macos-latest]
+        os: [windows-latest]
        python-version: ["3.12", "3.13", "3.14"]

    steps:
@@ -60,7 +57,7 @@ jobs:

      # The runner's TEMP is on C:, the OS disk, where a flush took about 6 ms
      # and a test database's create-to-delete about 111 ms; on the D: work
-      # disk the same took 0.5 ms and 23 ms (macOS: 19 ms). Tests write their
+      # disk the same took 0.5 ms and 23 ms. Tests write their
      # databases under TEMP, so it moves to a folder on D: (measured in #487,
      # run 40915866444). The runner's TEMP was an 8.3 short name
      # (C:\Users\RUNNER~1\...), so the new one is spelled by its short name too
@@ -83,31 +80,6 @@ jobs:
          PM_TEST_SLOWEST: "40"
        run: python -m tests.run_suite -v

-  # The real Trash on both macOS CPUs (#499 design §10.2). It runs apart from the suite, so a red
-  # suite never skips the native proof.
-  native-trash:
-    name: native trash on ${{ matrix.os }}
-    runs-on: ${{ matrix.os }}
-    timeout-minutes: 6
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [macos-latest, macos-15-intel]
-
-    steps:
-      - uses: actions/checkout@v7
-
-      - name: Set up Python
-        uses: actions/setup-python@v7
-        with:
-          python-version: "3.12"
-
-      - name: Native trash proof
-        timeout-minutes: 4
-        env:
-          PM_NATIVE_TRASH: macos
-        run: python -m unittest tests.test_trash_macos_native tests.test_trash_macos -v
-
  # The same tests as the fake mount table, on a real ext4 mount used as the output root (#543). A
  # runner can mount with sudo; the tests run as the normal user, so owner and mode checks are real.
  native-trash-linux:
@@ -28,7 +28,7 @@ env:
 #   py matrix, slowest py3.10 on windows-latest: 12m43s / 15m54s / 14m53s -> 27 min
 #     (ubuntu 5m27s-6m27s, macos 6m14s-8m30s, windows 11m42s-15m54s)
 #     3.10 and 3.11 left the matrix and 3.14 joined it in #356; re-measure after three green main runs.
-#     Windows and macOS moved to portability.yml (#420), which has its own measured limit (#493);
+#     Windows moved to portability.yml (#420; macOS left CI in #571), which has its own measured limit (#493);
 #     this Linux-only matrix keeps 27 minutes until it is re-measured.
 #   real ComfyUI compatibility: 13m32s / 8m55s / 11m46s -> 24 min
 #   coverage gate (85%): 7m26s / 7m22s / 7m54s -> 15 min
@@ -39,7 +39,7 @@ env:
 # Pull requests run a fast subset (#420): Python 3.12 on ubuntu-latest, coverage, lint and frontend
 # modules. The merge queue (merge_group), pushes to main and manual runs add Python 3.13 and 3.14 on
 # Linux and the real ComfyUI job. "all tests" is the required gate that holds the queue to that set.
-# Windows and macOS run in portability.yml (push to main, nightly, on demand) and never gate a merge.
+# Windows runs in portability.yml (push to main, nightly, on demand) and never gate a merge.
 jobs:
  test:
    name: py${{ matrix.python-version }} on ${{ matrix.os }}
@@ -80,7 +80,7 @@ jobs:
    # pulled them from Ubuntu's apt mirror on every run, and three runs (#349, #378, #382) crawled at
    # ~26 kB/s for 11-12 minutes until the job hit its limit after every test had passed.
    container:
-      image: mcr.microsoft.com/playwright:v1.64.1-noble
+      image: mcr.microsoft.com/playwright:v1.64.1-noble@sha256:47b510dd9230bf0b9bfc9b20102241e577ea7a99334ab4c3ca19f19770e9b8ea
      options: --user 1001
    timeout-minutes: 24
    steps:
@@ -41,15 +41,19 @@ concurrency:
 # 7.3m-12.2m), because --shard splits by test count and the slow concept specs sort into shard 1. The page
 # workflows now run in three shards per browser with the limits unchanged; the per-shard times are
 # re-measured after three green main runs.
+# #563: coverage shards reached their 18-minute step limit three times on 2026-10-31 with no failing
+# test (PR #560 shard 2/3: 814 passed in 17.9m; queue run 41206495451 shard 1/3: 827 passed; PR #564
+# shard 2/3 twice), against recent green shards of 11m-17m. Coverage now runs in four shards with the
+# limits unchanged; the per-shard times are re-measured after three green main runs.
 jobs:
  frontend-coverage:
-    name: frontend coverage (shard ${{ matrix.shard }}/3)
+    name: frontend coverage (shard ${{ matrix.shard }}/4)
    runs-on: ubuntu-latest
    # Layout comparisons depend on the fonts each browser falls back to, so browser jobs run in the
    # same pinned Playwright image as local runs (tag = @playwright/test in tools/vendor/package-lock.json;
    # tests/vendor/browser-image.test.mjs checks it). Browsers and fonts come from the image.
    container:
-      image: mcr.microsoft.com/playwright:v1.64.1-noble
+      image: mcr.microsoft.com/playwright:v1.64.1-noble@sha256:47b510dd9230bf0b9bfc9b20102241e577ea7a99334ab4c3ca19f19770e9b8ea
      options: --user 1001
    timeout-minutes: 20
    # Public-repo ubuntu-latest runners have 4 vCPUs: three Playwright workers, each with its own test
@@ -59,7 +63,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        shard: [1, 2, 3]
+        shard: [1, 2, 3, 4]
    steps:
      - uses: actions/checkout@v7
      # The image's own Python 3.12 and Node 24: setup-python/setup-node install the runner's toolcache
@@ -88,13 +92,13 @@ jobs:
      - run: npm ci --prefix tools/vendor --ignore-scripts
      # Shard 1 also runs the node units and the viewer suite, so the vendor pins and the tooling tests
      # run on the lightest shard instead.
-      - if: matrix.shard == 3
+      - if: matrix.shard == 4
        run: npm run --prefix tools/vendor check
-      - if: matrix.shard == 3
+      - if: matrix.shard == 4
        run: npm run --prefix tools/vendor test
-      - name: Page workflows with coverage, shard ${{ matrix.shard }}/3
+      - name: Page workflows with coverage, shard ${{ matrix.shard }}/4
        timeout-minutes: 18
-        run: npm run --prefix tools/vendor test:coverage:shard -- ${{ matrix.shard }}/3
+        run: npm run --prefix tools/vendor test:coverage:shard -- ${{ matrix.shard }}/4
      - name: Upload raw coverage
        uses: actions/upload-artifact@v7
        with:
@@ -117,7 +121,7 @@ jobs:
    runs-on: ubuntu-latest
    # Same image as the shards: the raw files name sources by the container's workspace path.
    container:
-      image: mcr.microsoft.com/playwright:v1.64.1-noble
+      image: mcr.microsoft.com/playwright:v1.64.1-noble@sha256:47b510dd9230bf0b9bfc9b20102241e577ea7a99334ab4c3ca19f19770e9b8ea
      options: --user 1001
    timeout-minutes: 10
    steps:
@@ -136,13 +140,13 @@ jobs:
        with:
          pattern: coverage-raw-*
          path: ${{ runner.temp }}/coverage-raw
-      # coverage:merge only checks that raw files exist; merging two of three shards would report
+      # coverage:merge only checks that raw files exist; merging three of four shards would report
      # partial coverage, so a missing or empty shard artifact fails here.
      - name: Verify every shard's raw coverage arrived
        shell: bash
        env:
          STAGED_RAW: ${{ runner.temp }}/coverage-raw
-          EXPECTED_SHARDS: 3
+          EXPECTED_SHARDS: 4
        run: |
          found=0
          for shard in $(seq 1 "$EXPECTED_SHARDS"); do
@@ -188,7 +192,7 @@ jobs:
    # same pinned Playwright image as local runs (tag = @playwright/test in tools/vendor/package-lock.json;
    # tests/vendor/browser-image.test.mjs checks it). Browsers and fonts come from the image.
    container:
-      image: mcr.microsoft.com/playwright:v1.64.1-noble
+      image: mcr.microsoft.com/playwright:v1.64.1-noble@sha256:47b510dd9230bf0b9bfc9b20102241e577ea7a99334ab4c3ca19f19770e9b8ea
      options: --user 1001
    timeout-minutes: 20
    # Public-repo ubuntu-latest runners have 4 vCPUs: three Playwright workers, each with its own test
@@ -74,14 +74,14 @@ V8 files it writes under `coverage/js/raw`:

 ```sh
 PM_TEST_WORKERS=8 npm run --prefix tools/vendor test:coverage            # whole run, one report
-npm run --prefix tools/vendor test:coverage:shard -- 1/3                 # node units, viewer suite, workflows 1/3
-npm run --prefix tools/vendor test:coverage:shard -- 2/3                 # workflows 2/3 (likewise 3/3)
+npm run --prefix tools/vendor test:coverage:shard -- 1/4                 # node units, viewer suite, workflows 1/4
+npm run --prefix tools/vendor test:coverage:shard -- 2/4                 # workflows 2/4 (likewise 3/4, 4/4)
 npm run --prefix tools/vendor coverage:merge                             # report and baseline check of every raw file
 npm run --prefix tools/vendor test:workflows -- --project webkit --shard 2/2
 ```

 `coverage:merge` refuses an empty raw directory; it does not count shards, so run
-every shard first (CI's merge job checks all three arrived). Measured on a 32-CPU
+every shard first (CI's merge job checks all four arrived). Measured on a 32-CPU
 machine in the pinned image (2026-10-21): `test:coverage` takes about 5 minutes
 with 8 workers and 24 minutes with 1; all four projects, 8 workers, each test 3
 times (6132 tests), 24 minutes. A CI-sized run (`docker run --cpus=4`,
@@ -111,8 +111,11 @@ distributions, browser system dependencies may need manual installation. For a
 quick browser run, use `test:workflows -- --project chromium`.

 CI runs the browser jobs inside the pinned image
-`mcr.microsoft.com/playwright:v<@playwright/test version>-noble`
+`mcr.microsoft.com/playwright:v<@playwright/test version>-noble@sha256:<digest>`
 (`tests/vendor/browser-image.test.mjs` keeps the tag in step with the lockfile).
+The digest is part of the pin, because Microsoft re-pushes tags: `v1.64.1-noble`
+moved from Node 24 to Node 26 on 2026-11-01 (#609). To bump it, change the tag and
+digest together and check the new image's Node against the Node 24 guard.
 Concept comparisons measure geometry, and geometry follows the fonts a browser
 falls back to: the concept names Inter, which neither the image nor a stock
 runner ships. On a plain `ubuntu-latest` runner the fallback is DejaVu Sans,
@@ -189,14 +192,14 @@ check, so run it before pushing a new or deleted frontend file instead of
 waiting for the `frontend coverage` jobs.

 The `viewerjs` check runs on every PR, including backend-only changes. It is an
-aggregate job. It requires the three `frontend coverage (shard N/3)` jobs and
+aggregate job. It requires the four `frontend coverage (shard N/4)` jobs and
 `frontend coverage (merge)` to succeed on every event. The four
 `page workflows (firefox|webkit, shard N/2)` jobs run only in the merge queue,
 on `main` and on `workflow_dispatch` (see "Pull requests and the merge queue").
 `viewerjs` requires them to be skipped on a pull request and to succeed
 everywhere else. Any other failed, cancelled or skipped job fails it. Every browser job runs with `PM_TEST_WORKERS: 3` (the public
-runners have 4 vCPUs). Each coverage shard runs `test:coverage:shard -- N/3`
-(shard 1 also runs the node units and the viewer suite, shard 3 the vendor pins
+runners have 4 vCPUs). Each coverage shard runs `test:coverage:shard -- N/4`
+(shard 1 also runs the node units and the viewer suite, shard 4 the vendor pins
 and tooling tests) and uploads its raw V8 files as `coverage-raw-N` (kept 3
 days). The merge job downloads them, fails unless all three arrived with raw
 files and without clashing names, then runs `coverage:merge` (report plus
@@ -261,7 +264,7 @@ the process exits non-zero.
  job fails anyway and the dump is what matters.
 - `PM_TEST_SLOWEST=N` (off by default) lists the N slowest tests after the
  summary, each timed from its `start:` line to the next one like the hang
-  limit. The Windows and macOS jobs (`portability.yml`) set it to 40, so every
+  limit. The Windows jobs (`portability.yml`) set it to 40, so every
  run shows where its time went (#487). The list prints only when the run
  ends: a job GitHub cancels or a watchdog exit prints none, so read the
  timestamps between `start:` lines instead.
@@ -327,7 +330,7 @@ Python 3.13/3.14, real ComfyUI and Firefox/WebKit failures first show up in the
 merge queue, on the merge-group commit rather than the
 pushed one. Find that run with `gh run list --event merge_group --workflow test.yml`
 (or `viewerjs-check.yml`) and match its head branch
-(`gh-readonly-queue/main/pr-<N>-...`). Windows and macOS failures show up only
+(`gh-readonly-queue/main/pr-<N>-...`). Windows failures show up only
 after the merge, in `gh run list --workflow portability.yml`.

 Start fixing as soon as a failed log shows the cause, but push the fix only after
@@ -345,11 +348,16 @@ and the time left. The steps, in order:
   monitor's callbacks (Needs review recorder, preview queue, Images listing
   listener).
 2. `ImageMonitor.stop_monitoring` works against one 5 s deadline. Closing the
-   image handler joins the image worker; watchdog's `observer.stop()` (not
-   bounded here) and the observer join get what is left, which can be 0 s.
-3. `close_auto_thumbnails(final=True)` stops the preview worker (30 s) and
-   kills ffmpeg.
-4. `PromptTracker.shutdown` stops the prompt cleanup thread (2 s).
+   image handler joins the image worker; watchdog's `observer.stop()` and the
+   observer join get what is left, which can be 0 s. `stop()` joins watchdog's
+   emitters without a limit, so it runs on a daemon thread and is waited for
+   only until the deadline; a later stop waits for that same call (#561).
+3. `close_auto_thumbnails(final=True)` stops the preview worker (30 s),
+   kills ffmpeg and shuts the interactive image pool down.
+4. `shutdown_job_pool` (`utils/parallel.py`) cancels the long-lived job pool's
+   queued items and joins its threads (5 s; part `workers`, only when a job
+   used the pool, #523).
+5. `PromptTracker.shutdown` stops the prompt cleanup thread (2 s).

 A failing step, or a second Ctrl+C, is logged with its traceback and does not
 skip the later steps. A clean run logs one INFO line to PromptManager's log:
@@ -361,6 +369,15 @@ stored, with the parts not reached False, and the `atexit` callback is
 removed: the later steps are skipped, no summary line is logged, and a later
 call returns that result and runs nothing.

+The observer is started from a short-lived daemon thread, so every thread it
+creates is a daemon (a thread inherits that flag from the thread that creates
+it). watchdog 7 on Windows starts a plain `threading.Thread` per watch for its
+`ReadDirectoryChangesW` reader; created from ComfyUI's main thread it would not
+be a daemon, and the interpreter waits for every such thread before it runs any
+`atexit` callback, so the teardown would never start (#561).
+`tests/test_package_exit.py` runs a child whose observer does both (a plain
+reader thread, a `stop()` that never returns) and requires its exit.
+
 ComfyUI never runs aiohttp's `on_cleanup` hooks, because it never calls
 `runner.cleanup()`. So `atexit` is the live host's path. It runs on Ctrl+C
 (`main.py` catches `KeyboardInterrupt` and returns) and on a normal exit.
@@ -445,12 +462,44 @@ A hot SQLite read that returns many rows aggregates them into one step
 (`json_group_array`) instead of stepping once per row, so it does not wait for
 the GIL once per row while ComfyUI generates (#354, `get_image_link_matches`).

+A metadata read never decodes pixels (#523). Pillow's `PngImageFile.text` loads
+every pixel to reach text chunks after IDAT; the scan (`_extract_comfyui_metadata`)
+and the image monitor (`ComfyUIMetadataExtractor.extract_metadata`) read PNG text
+through `utils/png_text.py`, which runs Pillow's own chunk handlers after the
+first IDAT and seeks over pixel data. The legacy `.text` read is the floor:
+`tests/test_png_text.py` compares both readers on every image under
+`tests/fixtures`, a curated corpus (text after IDAT, zTXt, iTXt, split IDAT, bad
+checksums, truncations, oversized text, APNG) and a seeded fuzz, and asserts that
+neither reader decodes pixels by patching `ImageFile.load`. The only reads that
+differ are files whose pixel data is undecodable or cut short: legacy found
+nothing, the walk keeps the text before the pixels. Animated PNGs still use
+`.text`.
+
+Image work runs on PromptManager's own threads (#523). glibc keeps each thread's
+malloc arena at its high-water mark, so image buffers spread over the default
+executor's threads stay resident. Interactive image work (view previews behind their
+gate, workspace card facts, both inspector routes) runs on the API's fixed
+`pm-image` pool (`IMAGE_POOL_SIZE` 3, `_run_image`, `_map_image`; card facts already
+cached answer without a trip; while the gate's 3 preview writes hold every thread, a
+card or inspector read waits for one of them, by design of the merged pool; after the
+package teardown the pool is not recreated and late calls use the default executor). Jobs (scan metadata and file facts, thumbnail and
+convert jobs, the legacy gallery generation, capture previews) run through
+`map_parallel` on one long-lived `pm-worker` pool of Worker threads, reused between
+jobs; a new Worker threads value replaces it (the teardown also joins a replaced pool
+still finishing), and a call made from a job thread runs inline. After a scan, thumbnail or convert job, or the legacy gallery generation,
+`release_free_memory` (`utils/native_memory.py`) calls glibc's `malloc_trim(0)` once;
+it does nothing on Windows, macOS and musl and never raises. No allocator setting
+changes. `tests/test_image_pools.py` asserts the thread of each read and write and the
+trim; `tests/test_utils_parallel.py` the pool's reuse, resize, nesting and shutdown.
+`tools/perf/memory_drive.py` (manual, Linux, never in CI) measures RSS, heap, threads
+and arenas under the #523 load against the disposable browser test server.
+
 The `perf budget` job in `.github/workflows/test.yml` is the reference
 measurement: `ubuntu-latest`, one Python, no coverage, only the wall-clock tests.
 It runs on every push to `main` and on `workflow_dispatch`, never on pull
 requests, because shared-runner timing must not block a merge. Dispatch it on a
 branch to measure before merging.
-Shared Windows and macOS runners do not run them; the structural tests cover
+Shared Windows runners do not run them; the structural tests cover
 portability. Run it locally with
 `PROMPTMANAGER_PERF_BUDGET=1 python -m unittest tests.test_api_workspace_images.TestWorkspaceImages.test_filter_budget`
 and quote the printed p95 in the PR body.
@@ -646,10 +695,10 @@ Before changing paths, SQLite, streams, restore or cleanup:
  ordinary busy timeout; cross-thread handoffs wait on events with generous
  ceilings, never a short wall clock (#242).
 - Run native Windows CI early for these changes. Pull requests and the merge
-  queue run only Linux, so start Windows and macOS on the branch with
+  queue run only Linux, so start Windows on the branch with
  `gh workflow run portability.yml --ref <branch>`.
-  Include a Windows impact and evidence note in the PR. All six Windows/macOS
-  combinations in that run, every Linux leg and every applicable
+  Include a Windows impact and evidence note in the PR. All three Windows
+  legs in that run, every Linux leg and every applicable
  exact-head check must pass before merge. Portable `ntpath`/`PureWindowsPath`
  controls do not establish native filesystem, locking or cleanup success.

@@ -664,11 +713,11 @@ what runs:
 | `py3.13 on ubuntu-latest`, `py3.14 on ubuntu-latest` | not created | run |
 | `real ComfyUI compatibility` | skipped | runs |
 | `coverage gate (85%)`, `black and flake8`, `frontend modules`, `bandit (high severity)` | run | run |
-| `frontend coverage (shard N/3)`, `frontend coverage (merge)` (vendor pins and tooling tests on shard 3) | run | run |
+| `frontend coverage (shard N/4)`, `frontend coverage (merge)` (vendor pins and tooling tests on shard 4) | run | run |
 | `page workflows (firefox\|webkit, shard N/2)` | skipped | run |
 | `all tests`, `viewerjs` (gates) | run | run |
 | `perf budget` | skipped | push and dispatch only (not in the queue) |
-| `py3.12-3.14 on windows-latest/macos-latest` (`portability.yml`) | not run | push to `main`, nightly, `workflow_dispatch` only; never required |
+| `py3.12-3.14 on windows-latest` (`portability.yml`) | not run | push to `main`, nightly, `workflow_dispatch` only; never required |

 GitHub has one required set for pull requests and the queue. A job skipped by
 its `if:` reports Success. A dropped matrix leg never reports, so it would stay
@@ -681,8 +730,9 @@ guarantee:
 So a merge group cannot turn green unless all three Linux Python legs, real
 ComfyUI and the four browser shards passed.

-Windows and macOS (Python 3.12-3.14) are out of the blocking path for now
-(maintainer, 2026-10-28). They run in `portability.yml` on every push to `main`,
+Windows (Python 3.12-3.14) is out of the blocking path for now
+(maintainer, 2026-10-28). macOS is not tested in CI (maintainer, 2026-10-31, #571);
+its code stays and support is best-effort. They run in `portability.yml` on every push to `main`,
 nightly and on demand, and no context there is required. A red portability run
 is still a failure: fix it at its cause, not by rerunning, and have every one
 green before the workspace cutover (#334). `tests/vendor/ci-workflow.test.mjs` pins the
@@ -1407,6 +1457,8 @@ is shorter than the row it reserves.
 Each Overview card is the count of the page it names: the shell's Library, Images and Tags sidebar counts, one source,
 so a card and its badge cannot differ. `/prompt_manager/stats` is for the legacy page and counts raw rows. A visit re-reads
 the three unless a read is in flight. An unread or failed card shows a dash; Retry re-reads only the failed counts.
+System › Overview's Images metric reads the same shell count (#555), so it, the Overview card and the Images badge show
+one number; its Statistics dialog labels the legacy row counts as "Database records".
 Tests: `tests/js/workspace-state.test.js`, `tests/browser/workspace.spec.mjs`, `tests/comfyui/workspace.spec.mjs`.

 ### Images page controls and recorded deviations (#249 PR C)
@@ -1837,7 +1889,8 @@ Inspect plan keeps D60–D66 (plan D60 → D83, D61 → D84, D65 → D88, D68
  engines in the mock's order with legacy labels and sizes (`WD14 SwinV2 · ~400
  MB`, `WD14 ViT · ~400 MB`, `GGUF JoyCaption (Recommended) · ~4.5 GB` in the
  mock's Ollama slot, `HuggingFace JoyCaption · ~16 GB`); the instructions start
-  from the server's `default_prompt`.
+  from the chosen engine's default saved instructions (#431, D204; before, the
+  server's `default_prompt`).
 - **D91** (plan D68, ruling T3-bulk): a **Suggestions** number field (1–100) for
  every model, prefilled from `autotag.defaults.suggestion_limit` (10); a model
  change keeps it.
@@ -2549,8 +2602,8 @@ files to the system trash. **No code path unlinks or overwrites a media file.**
  ("Moving files to the Recycle Bin isn't available on Windows: files larger than the bin's
  capacity would be deleted permanently."). Library-only removal works everywhere. Tests use `tests/fake_trash.py`; the
  browser test server installs it, so no test touches a real trash. The native proof,
-  `tests/test_trash_macos_native.py`, runs only with `PM_NATIVE_TRASH=macos` in
-  portability.yml's `native-trash` job (`macos-latest` and `macos-15-intel`): the startup
+  `tests/test_trash_macos_native.py`, runs only with `PM_NATIVE_TRASH=macos` on a Mac, by hand
+  (CI dropped its `native-trash` macOS job in #571; it last passed on `macos-latest` and `macos-15-intel`): the startup
  volume, a name clash, fresh APFS and FAT32 disk images, an image used as an output root,
  a read-only image and an unwritable folder (design and probe:
  `docs/egm/499-macos-trash/`, local).
@@ -2929,7 +2982,8 @@ change: ComfyUI needs a restart.
 A Pair save, by a run or the node's Save pair button, writes the category and tags to the positive prompt only when that
 save creates the prompt row (maintainer ruling). An existing prompt never changes on a run: empty, cleared or set by a person, including one first seen as
 another pair's negative. The negative stays empty, the saved pair keeps its own metadata, and `save_prompt_pair` writes
-no prompt metadata unless called with `fill_new_positive`. No backfill; optional repair is #550.
+no prompt metadata unless called with `fill_new_positive`. No backfill on a run; the opt-in repair for prompts older
+Pair runs saved is System › Maintenance › "Pair category and tags" (#550, "Pair category and tags repair" below).
 Tests: `tests/test_prompt_pair_node.py`, `tests/test_api_pairs.py`, `tests/comfyui/pair-node.spec.mjs`. A Python change: ComfyUI needs a restart.

 ### Delete… on the archived shelf (#492)
@@ -3844,8 +3898,8 @@ workspace never asks; previews are a cache the server keeps:
 - `GET /images/serve/thumbnails/<rel>_thumb<ext>` for a missing preview is refused as
  text first (traversal, a backslash, a drive or stream colon, empty or dot segments, so
  `D:/x`, `\\server\share` and a leading `/` never reach a joined path), then admitted
-  on the event loop (`_PreviewGate`): 3 previews are written at once on the API's own
-  `pm-preview` pool (never the default executor), one flight runs per file (the history
+  on the event loop (`_PreviewGate`): 3 previews are written at once on the API's
+  interactive `pm-image` pool (never the default executor; #523), one flight runs per file (the history
  route shares the flight key and the admission), and at most 64 requests wait; one
  more gets its fallback at once without listing a folder. Inside the admission the
  preview maps back to its media file under the same root (exact names, then one folder
@@ -3878,7 +3932,7 @@ workspace never asks; previews are a cache the server keeps:
  `exclusive` job runs (`_auto_thumbnail_blocker`), checked when a write starts (after
  its slot) and again just before its rename.
 - Shutdown is bounded and logged: the worker stops at a file boundary, ffmpeg is
-  killed, an idle worker leaves (the next output starts a fresh one), the view pool
+  killed, an idle worker leaves (the next output starts a fresh one), the image pool
  shuts down, and after the app's cleanup a late monitor event
  starts nothing. A package reload stops the workers the previous import left.
 - Cards and strips load previews only: Images in every layout and size, Library cards,
@@ -4006,7 +4060,11 @@ the per-section hand-off panel, was retired by S12 (#329): every section is nati
  "Save preferences" is `aria-disabled` (opacity .55, `not-allowed`) while clean or
  saving; a setting the last save could not save gets a red outline. CSS under D92.
 - **D93** (Overview): real values. The metrics are the Library's eligible positives
-  and active saved negatives and the indexed `generated_images` rows (Q2). "Database
+  and active saved negatives and the Images count (#555, amending Q2's indexed
+  `generated_images` rows): the shell's Images sidebar count, the Images page's own
+  total, which also lists files no row links, as the concept's `images.length` is
+  both. A visit re-reads it unless a read is in flight; "–" until read or after a
+  failed read. `images.indexed` stays in the API and is not shown. "Database
  integrity" is "Not checked" until a check ran this session, then "N issues" (checks
  that found issues, even beside a check that could not run), "Passed" or "Incomplete".
  The review row is "N ambiguous image links" (the Needs review queue's pending count,
@@ -4044,10 +4102,11 @@ the per-section hand-off panel, was retired by S12 (#329): every section is nati
 - **D96** (Statistics; amended by D153): "Usage statistics" without the sample note: the
  concept's "Runs by category" table without its Avg. rating column (Category / Runs)
  with the real runs of eligible parents per category ("Uncategorized"), then a second
-  table "Library totals" (Total / Count: Prompts, Tags, Images from the legacy
-  statistics; no Rated images). The API still reports `average_rating` and
+  table "Database records" (Total / Count: Prompt records, Tags on prompts, Image
+  records: the raw row counts of the legacy statistics, labelled as rows so they never
+  read as the Library or Images page counts, #555; no Rated images). The API still reports `average_rating` and
  `rated_images`; the workspace does not show them.
-  The Overview row says "Runs by category, with library totals." because
+  The Overview row says "Runs by category, with database record counts." because
  that is what the dialog shows (the concept's own dialog shows only "Runs by
  category"); per-prompt run counts, prompt tags and dated runs are recorded, but no
  table of them exists yet. A failed read toasts "Statistics could not
@@ -4253,6 +4312,12 @@ the per-section hand-off panel, was retired by S12 (#329): every section is nati
  primary stays the concept's plain button; the plan it opens has the primary.
  `duplicates dialog matches the concept` and `duplicates comparison detects mutations`
  (system-maintenance-concept.spec) pin the mapping.
+- **D192** (Maintenance, #550, beyond the concept): Database adds "Pair category and
+  tags" after "Unused prompt components", a plain Review plan row (no danger mark: it
+  deletes nothing) with the line "Fill an empty category or tags on prompts older Pair
+  node runs saved, from their saved pairs. Only empty fields of never-edited prompts."
+  `system-maintenance-concept.spec.mjs` maps it (`mapPairRow`) as a copy of Optimize
+  database's row.
 - **D102** (Maintenance, S7, Q5, #222): Metadata cache clears only the browser entries
  Prompt Manager owns as a cache (`web/js/cache-ownership.js`). The inventory of every
  storage writer has none (see "Browser cache ownership" below), so the row's line adds
@@ -4350,6 +4415,23 @@ the per-section hand-off panel, was retired by S12 (#329): every section is nati
  choice. The host's checks still refuse a linked field or a changed workflow, and the
  sender also refuses if the destination's `revision` (node object plus graph version)
  moved since discovery; it is undefined on an older tab, which skips the comparison. A host error reads as a refusal, not "may have applied".
+- **D191** (#542, beyond the concept; maintainer 2026-10-31, Q542-1 A to 5 A): a window with two or more
+  eligible nodes adds a last Destination node option "All N eligible nodes" (`ALL_NODES` in
+  `prompt-sender.mjs`), never selected for you (D173). Eligible is D173's filter; the nodes it leaves out
+  stay counted in the discovery sentence. One window only. Preview stays optional (D175): Preview changes
+  shows one `section.prompt-sender-node` per node, headed "#<id> <title>", in send order (node id,
+  numeric). Apply previews every node first and writes nothing if any refuses ("#<id> <title>: <reason>
+  Nothing was sent."). Then it sends one node after another. Only the first node of a pass taken in that
+  click keeps its ticket; every other node, and every node of a held Preview (host tickets expire after
+  30 s), takes a fresh ticket that is refused unless its Before texts and composition equal the reviewed
+  ones. That fresh preview checks the discovered revision until something has been posted, and not after,
+  since our own write may move the graph version. Refusals are best effort: "Sent to 2 of 3 nodes in
+  <window>. #12 <title>: <host's refusal>."; Apply stays available and a retry sends to every node again
+  (rewriting the same text). A lost reply stops the run, names that node as unknown and lists the nodes
+  not sent. Closing the dialog stops after the current node. The review sections are labelled by their
+  `h4` node heading. Unit tests in `tests/js/prompt-sender.test.js`, a fake three-node host in
+  `tests/browser/prompt-inspector.spec.mjs`, real Classic and Nodes 2.0 widgets in
+  `tests/comfyui/prompt-sender.spec.mjs`.
 - **D106** (Integrations, S10, Q8): the send bridge always asks for the ComfyUI window
  and node, and the nodes always follow ComfyUI's own renderer, so "Default send
  destination" offers only "Ask each time" and "Host compatibility" only "Follow host
@@ -4535,9 +4617,9 @@ the per-section hand-off panel, was retired by S12 (#329): every section is nati
  engine and policy (read-only) and opens "Review tag output images" in the concept's
  record-changing review (its `maintenancePlan` shell): `h3` "Tag output images", the
  `dl.meta-grid` Model, Existing tags, Images, Already auto-tagged, Images to tag
-  ("about N"), Time, Settings ("General <g> · Character <c>" or "Template of N
-  characters", then " · up to L tags per image" with the preview's saved
-  `suggestion_limit`) and Backup, the estimate sentence ("Nothing is written until you
+  ("about N"), Time, Settings ("General <g> · Character <c>", then " · up to L tags
+  per image" with the preview's saved `suggestion_limit`; for a language model, since
+  D205, an "Instructions" row and "Up to L tags per image") and Backup, the estimate sentence ("Nothing is written until you
  start. The number to tag is an estimate: images changed since they were tagged are
  tagged again, and missing files are skipped. Activity reports what was tagged.") in the
  `p.small`, the D55 backup box and Cancel / "Start tagging", which starts the
@@ -4559,6 +4641,71 @@ the per-section hand-off panel, was retired by S12 (#329): every section is nati
  Cancel-only review matches the concept review shell` (system-tagging-concept.spec) and
  the batch tests of workspace-system-tagging.spec; the mutation check renames each grid
  label in turn.
+- **D202** (Auto-tagging, #431, beyond the concept): a "Skipped tags" block
+  (`.setting-block`, `data-setting="tag-skipped"`, `data-key="autotag_skipped_tags"`)
+  follows "Suggestions per image": the label and description in the concept's
+  setting-row tokens ("Suggested tags that contain one of these words are hidden.
+  Words are separated by spaces, _ or -; other characters such as ( ) belong to the
+  word."), an "Add a word or words" input (`#tag-skipped-input`) with Add (Enter adds
+  too), the entries as removable chips in the Tag image dialog's D83 chip markup (each
+  with its count, title "Hides N tags", or muted "none" with "Hides no known tag"), and
+  a `role="status"` preview line: "**Hides N tags from suggestions**: <up to 12>[ and K
+  more]. Tags already on images are not changed." ("Checked against library tags only;
+  no WD14 label list is downloaded." before the last sentence without a label list;
+  "No tags are skipped." for an empty list; "Checking…" while waiting; "The preview
+  could not be read." on failure). The client refuses an entry with "Enter a word.",
+  "No commas or line breaks.", "At most 50 characters.", "Already in the list." or "The
+  list is full (200)." under the input. The Tag image dialog's chip hint adds "N skipped
+  tags were not suggested." when the server hid any (the static mock's copy). Pinned by
+  the comparison's mapping (system-tagging-concept.spec: the block's tokens are the
+  concept row's), `skipped tags add, preview, remove, save and reload (D202)`, `skipped
+  tags preview checks library tags only …` (workspace-system-tagging.spec) and
+  `suggestions omit skipped tags and say how many were hidden` (workspace-tagging.spec).
+- **D203** (Auto-tagging, #431, beyond the concept): "Saved instructions" replaces the
+  concept's "LLM tag template" field (the mock's state 2): a `.setting-block`
+  (`data-setting="tag-instructions"`, `data-key="autotag_instructions"`) with the label,
+  "Instructions for the language-model engines. Built-in can’t be changed; duplicate it
+  to make your own. N of 20 saved · Built‑in is not counted.", a `role="listbox"` list
+  (Built-in first with a "Read-only" chip, then the saved entries; "Default for GGUF" /
+  "Default for HuggingFace" chips), "+ New" ("New instructions", "(2)" if taken),
+  "Duplicate" ("<name> copy"), "Delete" (`.danger`, disabled for Built-in), "At most 20
+  saved instructions." at the cap, and the editor beside the list (under it below 700px):
+  "Name" ("N of 60") and "Text" ("N of 4,000 characters"), read-only for Built-in with
+  "Built-in instructions can’t be changed. Duplicate them to make your own.", else the
+  entry's problem ("The name “X” is already used.", "The text must not be empty."…).
+  Then two concept select rows, "Default for GGUF JoyCaption" and "Default for
+  HuggingFace JoyCaption" ("The Tag image dialog and batches start from this.",
+  `data-key="autotag_default_instructions"`), and the note a deleted default leaves
+  ("GGUF now uses Built-in."; nothing is written until Save preferences). Pinned by the
+  comparison's mapping (system-tagging-concept.spec: the block in the concept row's
+  tokens, the two rows on the concept's select row) and `saved instructions: new, edit,
+  per-engine default, delete, save and reload (D203)`, `a refused instructions save names
+  the entry and highlights the block (D203)` (workspace-system-tagging.spec).
+- **D204** (Tag image and Auto-tag selected dialogs, #431, beyond the concept): for a
+  language-model engine a "Saved instructions" select (`#image-tag-instructions-pick`,
+  `#bulk-tag-instructions-pick`) sits above "Tagging instructions" (the mock's state 3),
+  on the concept's select field: Built-in, then the saved entries (`GET /autotag/models`
+  `instructions`, full text), the engine's default marked "<name> · default". It starts
+  at that default; a pick replaces the text. The text stays editable for the run: while
+  it differs from the picked entry the select shows a disabled "Edited for this run" and
+  a muted line under the textarea reads "Edits apply to this run only. Manage saved
+  instructions in System › Auto-tagging." Choosing an entry again replaces the edit.
+  Switching between GGUF and HF starts from the new engine's default and drops an edit;
+  WD14 hides both. A preset (Preview tagging review, the bulk review) shows the entry
+  with its text, else "Edited for this run". When the read fails the select holds only
+  Built-in with the client's copy (`BUILTIN_INSTRUCTIONS`, pinned equal to
+  `DEFAULT_TAG_TEMPLATE` by workspace-image-tagging-state.test). Request bodies are
+  unchanged (`options.instructions` is the textarea's text); there is no "Save as new".
+  The workspace no longer reads `default_prompt`. Pinned by the tagging comparison's
+  mapping (tagging-canonical-comparison.mjs: the select before the instructions),
+  `the saved instructions picker fills, edits one-off and resets per engine (D204)`
+  (workspace-tagging.spec) and `Auto-tag selected picks saved instructions and sends the
+  text shown (D204)` (workspace-tagging-bulk.spec).
+- **D205** (Auto-tagging, #431; amends D134): for a language-model engine the batch
+  review adds a read-only "Instructions" row with the drafted engine default's name
+  before "Settings", which reads "Up to L tags per image"; the batch and Preview tagging
+  review send that entry's text. WD14 is unchanged. Pinned by `the batch review names the
+  language model's default instructions (D205)` (workspace-system-tagging.spec).
 - **D158** (Sources, #247 D-Q4): the concept has no switch for prompts from workflows
  without a PromptManager node; the maintainer chose a visible switch over a config key.
  A `.setting-row` in the concept's toggle markup follows "Watch for new outputs":
@@ -4790,6 +4937,47 @@ replaced the database since the review; the plan is dropped). The job:
   prompt ids only), logs the backup by its file name, and prunes safety backups to the
   newest 10. With no backup the log and the status line say "No safety backup".

+#### Pair category and tags repair (#550)
+
+`pair_metadata` ("Pair category and tags", D192; `database/pair_metadata_repair.py`) fills
+the empty category and the empty tag set of prompts that Pair node runs before #546
+saved, from their saved pairs. It is reviewed and applied like the operations above and
+follows the safety backup policy like them (no forced backup). Rules
+(`docs/egm/post-3.4.1/550-design.md`):
+
+- Considered: prompts the Pair node created as a positive: their earliest pair (lowest
+  id, either role, archived included) has them as the positive and its `created_at` is
+  within 2 s of theirs. A prompt first saved by the PromptManager node, or first as a
+  negative, is out of scope and not counted.
+- Sources: the prompt's non-archived pairs where it is the positive; pairs with a blank
+  category or no tags are ignored for that field. Category values are trimmed and
+  case-sensitive, tag sets compared by tag id; a field fills when exactly one value is
+  left. A whitespace-only category counts as empty.
+- Kept, per field, in this order: archived prompt, edited prompt (`updated_at` not within
+  2 s of `created_at`; NULL or unreadable counts as edited), pairs that disagree, a tag
+  set over 20 tags. A prompt can fill one field and keep the other.
+- The plan lists protected rows first, then fills, then a "Record" row, within the 50
+  detail rows; at most 20,000 prompts per plan ("review again for the rest").
+- The fingerprint covers each considered prompt's computed result (values, tag ids and
+  names, source pair ids), never a pair's title, notes, rating, run count or use
+  stamps, so a Pair run between review and apply still applies.
+- The apply's writes are guarded (`category` still blank, no `prompt_tags` row) and a
+  guard that hits nothing rolls the whole transaction back as `plan-changed`. It never
+  writes `prompt_pairs`, `prompt_pair_tags`, `updated_at`, a tag or Library state.
+- The job lists 200 changed rows ("Prompt 12: category “night”; tags a, b"); its
+  Download report lists every one (`truncated: false`, `Job.record_counted(complete=True)`).
+  Protected lists one row per kept prompt in the review's wording and order ("Prompt 7:
+  kept, pairs disagree on category: Adult, asian"), also complete in the report.
+- Activity shows a row with no path as a record: its detail as plain text, never an open
+  or locate action, and the filter reads the detail. A maintenance job of records (every
+  operation but Missing-file links) says "No records in this group.", "No listed record
+  matches this filter." and "Filter records…" (`groupCopy`); file jobs keep "files".
+
+Tests: `tests/test_maintenance_pair_metadata.py`, `tests/test_api_maintenance_pair_metadata.py`,
+`tests/test_jobs.py`, `tests/js/workspace-system-maintenance.test.js`,
+`tests/browser/workspace-system-maintenance.spec.mjs` (hook `/__test__/system/pair-metadata`).
+A Python change: ComfyUI needs a restart.
+
 The legacy restore (`POST /prompt_manager/restore`) takes a backup of any size the disks
 have room for, so a real library's safety backup restores: the upload, its staged copy
 and the swap (the upload twice in the temporary folder, once more plus the current
@@ -5144,16 +5332,16 @@ server-side tagging configuration, `autotag.defaults` in config.json: `model_typ
 (`wd14-swinv2`, `wd14-vit`, `gguf`, `hf`), `existing` (`skip`, `merge`,
 `replace_after_review`), `general_threshold` and `character_threshold` (0–1 in
 steps of 0.05, #369),
-`template` (non-blank, at most 4,000 characters and 16 KiB) and `suggestion_limit`
-(1–100). They are host drafts (`autotag_model_type`, `autotag_existing`,
-`autotag_general_threshold`, `autotag_character_threshold`, `autotag_template`,
-`autotag_suggestion_limit`) saved by the one Save row through `POST
+`suggestion_limit` (1–100), and since #431 `skipped_tags`, `instructions` and
+`default_instructions` (below). They are host drafts (`autotag_model_type`, `autotag_existing`,
+`autotag_general_threshold`, `autotag_character_threshold`, `autotag_suggestion_limit`,
+`autotag_skipped_tags`, `autotag_instructions`, `autotag_default_instructions`) saved by the one Save row through `POST
 /prompt_manager/settings` with `expected_revision`; a bad value is refused with a 400
 naming the setting by its row label ("General-tag confidence must be between 0 and
 1."), nothing is written, the Save row shows that sentence (`invalid-setting`, set by
 `settingRefusal` in system.mjs only for a save that carried `autotag_*` keys; every
 other section's plain 400 keeps the generic status) and the control is highlighted.
-The template's limit counts code points, as Python's `len` does. A hand-edited bad value
+Instruction text limits count code points, as Python's `len` does. A hand-edited bad value
 falls back to its default on load, one key at a time. Every page shows the thresholds in
 steps of 0.05 (the System rows, the Tag image dialogs, the legacy sliders), so a saved
 threshold off that grid is refused ("General-tag confidence must be a multiple of
@@ -5164,8 +5352,70 @@ stored exactly on the grid (#369). A per-request threshold keeps its own check:
 `validate_options` and starts the `autotag` job titled "Tag output images (legacy page)";
 the legacy `/autotag/single` only requires a number. `GET /autotag/models` reports the
 saved values (`wd14_general_threshold`, `wd14_character_threshold`, `suggestion_limit`,
-`default_prompt`, `model_type`, `existing`), so the Tag image and Auto-tag selected
-dialogs start from them; a preset (the bulk review, Preview tagging review) wins.
+`default_prompt`, `model_type`, `existing`, and since #431 `instructions` and
+`default_instructions`), so the Tag image and Auto-tag selected dialogs start from them;
+a preset (the bulk review, Preview tagging review) wins.
+
+**Saved instructions** (#431, D203, D205): `autotag.defaults.instructions` holds the
+saved entries `[{id, name, text}]` in order (at most 20; `id` 12 lowercase hex made by
+the client, unique, `builtin` reserved; `name` trimmed, 1–60 characters, no control
+character, unique case-folded, not "Built-in"; `text` as `validate_template`), and
+`autotag.defaults.default_instructions` is `{gguf, hf}`, each `builtin` or a saved id.
+Built-in (`{id: "builtin", name: "Built-in", text: DEFAULT_TAG_TEMPLATE}`) is never
+stored; readers put it first (`AutotagConfig.all_instructions`), so a later release's
+built-in text reaches everyone who uses it. Refusals (400, the Save row shows them and
+highlights the editor): "Saved instructions: at most 20 entries besides Built-in.",
+"Saved instructions: entry N has an invalid id.", "… repeats the id of entry M.", "…
+needs a name.", "… name must be at most 60 characters.", "… name must not contain a line
+break.", "… name “X” is already used.", "Saved instructions: the name “Built-in” is
+reserved.", "Saved instructions: entry N text must be …", "Default for GGUF JoyCaption
+must be one of the saved instructions." (and HuggingFace). A save carrying either key
+without `expected_revision` is refused ("Reload the page and try again."); a save
+carrying one is paired with the other from the running configuration and both are
+written, plus the old `template` key as the GGUF default's text (deleted when that
+default is Built-in), so an older build reads that default as its one template. `POST`
+with `autotag_template` is refused ("LLM tag template was replaced by Saved instructions.
+Reload the page."); `GET` keeps returning it (the GGUF default's text, read-only) for one
+release and adds `autotag_builtin_instructions` (Built-in's text, read-only). Load: each
+key alone (a damaged list → Built-in only, a default naming nothing → Built-in, each with
+one warning), then the in-memory migration of the old `template`: with no `instructions`
+key, a template other than Built-in becomes "Custom template" (id = first 12 hex of its
+SHA-256), the default of both engines unless `default_instructions` is stored; with the
+key, a template matching no entry (edited on an older build) is appended as "Custom
+template (n)" with one INFO line (a full list: one WARNING, nothing imported). Nothing is
+written at load; the next save that carries either key writes the list.
+`AutotagConfig.default_instructions_text(engine)` feeds the legacy batch and single
+blank-prompt fallbacks (by the request's engine) and `default_prompt`. Tests:
+`tests/test_saved_instructions.py`, `tests/test_saved_instructions_routes.py`,
+`tests/js/workspace-system-instructions.test.js`.
+
+**Skipped tags** (#431, D202): `autotag.defaults.skipped_tags`, host draft
+`autotag_skipped_tags`, a list of at most 200 entries, each trimmed, 1–50 code points,
+no comma or control character, at least one word, no two with the same words (refused
+with "Skipped tags: at most 200 entries.", "Skipped tags: entry N is empty.", "… must be
+at most 50 characters.", "… must not contain a comma or a line break.", "… repeats entry
+M."); a save carrying it without `expected_revision` is refused ("Reload the page and try
+again."). A damaged saved list falls back to none with one warning. Words are the
+NFC, case-folded text split on runs of space, `_` and `-` (`tag_words`); an entry hides
+a suggested tag whose words contain the entry's words consecutively (`SkipMatcher`:
+`blurry` hides `very_blurry` and `blurry_background`, not `unblurry`; `(fate)` hides
+`saber_(fate)`, `fate` does not). `generate_tag_suggestions(skip=)` drops a match after
+the name check and before the dedupe and the limit, so skipped tags use up no slot
+(WD14 fills from lower scores; a language model may return fewer). Every path filters:
+`/image-annotations/suggest` (compiled per request; the answer adds `skipped`, the
+number of distinct names it hid), `/autotag/single`, and the `image-tags` (Auto-tag
+selected) and `autotag` (System batch, legacy `/autotag/start`) jobs, which snapshot the
+list at their start and log "Skipped tags: N entries" or "Skipped tags: none"; a save
+during a run does not change it. Hand-typed and stored tags are never filtered; the
+language models' hard-coded exclude list (`_parse_tags`) runs first. `POST
+/prompt_manager/autotag/skipped-tags/preview {entries}` (validated as a save) answers
+`count`, `sample` (12, library tags first, each part sorted case-folded),
+`sample_limit`, `per_entry [{entry, count}]` and `sources {library, wd14}` over the
+library's tags plus the category 0/4 names of each downloaded WD14 `selected_tags.csv`
+(read as UTF-8, cached by mtime and size; a missing list is skipped). It loads no model,
+opens no image, writes nothing and is `409 busy` while an exclusive job runs. Tests:
+`tests/test_skipped_tags.py`, `tests/test_skipped_tags_routes.py`, the settings and
+config tests, `tests/js/workspace-system-skipped-tags.test.js`.

 `GET /prompt_manager/autotag/models` reads the disk in the executor, never loads or
 downloads a model and carries no absolute path: per engine `name`, `label`,
@@ -5413,7 +5663,7 @@ list stay unscoped: any row's control proves them.
 | Worker threads | `admin.html:437–445` | S4 Sources | covered | `sources` · slider · "Worker threads" | worker range max is cpu_count (workspace-system-sources.spec.mjs) |
 | LoraManager badge, enable, path, trigger words, CivitAI key, clear key | `admin.html:448–490`; `admin.js:1052–1156` | S10 Integrations | covered | `integrations` · switch · "LoraManager integration" | LoRA rows show detected / enabled / cache-loaded separately (workspace-system-integrations.spec.mjs) |
 | LoRA data import with progress | `admin.html:492–498,517–541`; `admin.js:1157` | S10 Integrations | covered | `integrations` · button · "Review import" | Review import shows replacement, blocked items and network effects with the backup box; Start opens the job (D107) (workspace-system-integrations.spec.mjs) |
-| Statistics | `admin.html:159`; `admin.js:1627` | S2 Overview | covered | `overview` · button · "Explore" | statistics dialog lists runs by category and library totals (workspace-system.spec.mjs) |
+| Statistics | `admin.html:159`; `admin.js:1627` | S2 Overview | covered | `overview` · button · "Explore" | statistics dialog lists runs by category and database record counts (workspace-system.spec.mjs) |
 | Export components JSON `/export` | `admin.html:163`; `admin.js:1607`; `py/api/prompts.py:238` | S9 Backup & export | covered | `backups` · button · "Export all prompts JSON" | Export JSON downloads /library/export; secondary buttons download all prompts (/export) and /pairs/export (D103) (workspace-system-backups.spec.mjs) |
 | Saved pairs export | `py/api/pairs.py:84` | S9 Backup & export | covered | `backups` · button · "Export saved pairs JSON" | Export JSON downloads /library/export; secondary buttons download all prompts (/export) and /pairs/export (D103) (workspace-system-backups.spec.mjs) |
 | Library export | `py/api/library.py:223` | S9 Backup & export | covered | `backups` · button · "Export JSON" | Export JSON downloads /library/export; secondary buttons download all prompts (/export) and /pairs/export (D103) (workspace-system-backups.spec.mjs) |
@@ -5652,6 +5902,73 @@ are closed before `os.replace`; renames stay inside one folder; folder identity
 folder are refused. The browser test server closes its own log handlers before its temp
 root (which now holds the logs) is removed.

+### Thumbnail location contract (#320)
+
+Previews live in each source's `thumbnails/` (the default) or in one folder, `<folder>/<source key>/…`. Every reader,
+writer and remover asks `py/api/preview_store.py`; `tests/test_preview_store.py` fails on a `thumbnails` path join
+anywhere else. The setting is `thumbnails.location` in config.json, and only the Move thumbnails job writes it: POST
+`/settings` answers 409 `location-needs-move`.
+
+- **Keys and marker.** A key is a slug plus a hash of the source's identity. The folder's
+  `.promptmanager-thumbnails.json` stores each key with its identity and install. Only a single `<slug>-<hex>` name
+  is ever joined onto the folder, and anything else in a marker is dropped. Every write and delete passes
+  `preview_store.may_write`: below a key folder, with no link, junction or reparse point on the way
+  (`tests/test_preview_store_folder.py`, including tampered markers).
+- **Unavailable.** A folder is unavailable when it is missing, is a link, holds no marker or holds another
+  folder's marker. A probe checks it every 5 s, and a store call that fails or stalls marks it at once. While it is
+  unavailable:
+  - originals are served and nothing is written anywhere;
+  - generate, convert, clear and prune answer 409 `location-unavailable`;
+  - the folder is never made again except by Recreate folder.
+
+  The configured location is in force before any request. A bad value is `invalid`, never a fall-back to the
+  sources.
+- **Move thumbnails.** The job is a `thumbnails` job with `scope.mode` `move` (`tests/test_thumbnail_move.py`). It
+  runs in this order:
+  1. The review answers `POST /images/thumbnails/plan`; not enough space answers 507.
+  2. A token starts the job.
+  3. Automatic previews are held.
+  4. Copies run on the job pool in chunks of 2 or 4 files, each with its size checked and its mtime rounded up to
+     2 s.
+  5. One config commit makes the switch and records the old stores under `cleanup`. The job cannot be cancelled
+     from here.
+  6. The old copies are removed.
+
+  If it fails or is cancelled before the switch, nothing changes. A crash leaves
+  `<data>/data/thumbnail-move.json`, which the next start undoes. Old copies still held open are removed by the
+  next start's "Move thumbnails (finishing)" job. Leaving a folder also removes the previews of this install's
+  sources that are no longer listed (Q320-8).
+- **Remove thumbnails of removed sources** (`scope.mode` `prune`). It is offered in Thumbnail maintenance only in
+  folder mode, and it touches only this install's keys.
+- **Page tests.** `tests/browser/workspace-thumbnail-location.spec.mjs` covers the row, both moves, the in-place
+  refusal, the confirmation, the notice with Recreate and with Use this folder. The legacy gallery runs once in
+  folder mode (`workflows.spec.mjs`). The hooks are `tests/browser/thumbnail_location_fixture.py`.
+
+Beyond the concept, against the approved static mock `docs/egm/post-3.4.1/320-mock`:
+
+- D196: the Thumbnail location row in System › Sources & scans, after Thumbnail generation.
+  - The status line is "Now: inside each source." or "Now: one folder, <path>.". It does not show the mock's
+    "(3 sources, 8,512 thumbnails)" counts, because counting means walking every preview on each view. It says
+    "Using the default folder next to your library." and names old copies that wait to be removed.
+- D197: the Move thumbnails review uses the shared review.
+  - A grid value may be a lead sentence with a list (`[lead, items]`).
+  - Sources no longer listed appear under "Removed after the move", where the mock has a "Not moved" row
+    (maintainer answer to Q320-8: remove).
+  - The Free space line is "<size> free", without naming the disk.
+- D198: Activity's view of `mode: move` and `mode: prune`.
+  - Tiles for a move: Moved, Already there, Left in place, Errors. Tiles for a prune: Removed, Left in place,
+    Errors.
+  - The step line under the bar is `#job-phase`.
+  - Cancel shows only until the switch.
+- D199: the unavailable notice on Overview and Sources & scans.
+  - Recreate folder appears for a missing folder, after a confirmation.
+  - Use this folder appears for another folder's marker.
+  - Change location focuses the row; on Overview it opens Sources & scans.
+- D200: Thumbnail maintenance's "Remove thumbnails of removed sources" scope, with the plan line and a grid of
+  key folders.
+- D201: Move library's review adds "Thumbnails: Stay in <path>. Move them in System › Sources & scans." in folder
+  mode.
+
 ### Backup and restore contract (#249 System S8)

 A restore is staged, then published (`database/restore_stage.py`). The upload is
@@ -6797,7 +7114,7 @@ checkout or point this harness at a live ComfyUI checkout.

 The package-qualified config import also corrects #211: the configured database
 path is honored when PromptManager runs as a ComfyUI custom node. Follow the
-[database path compatibility and safe backup sequence](README.md#database-path-compatibility-211)
+[database path compatibility and safe backup sequence](README-legacy.md#database-path-compatibility-211)
 before restarting an existing deployment.

 The ledger records only new dequeued jobs and observed outcomes. Existing
@@ -92,10 +92,21 @@ try:
    routes = config.routes
    api = PromptManagerAPI()
    api.add_routes(routes)
-    # Temp files of preview writes a crash interrupted (#317), off the
-    # import path: the walk may cover a large thumbnails folder.
+
+    # The thumbnail location's startup check (#320), then the temp files of
+    # preview writes a crash interrupted (#317), off the import path: the
+    # walk may cover a large thumbnails folder.
+    # #320: the configured thumbnail location is in force before any request
+    # (no I/O); the thread below checks it.
+    api.use_preview_location()
+
+    def _preview_startup():
+        api.start_preview_location()
+        api.recover_thumbnail_move()  # an interrupted move, before the sweep
+        api.sweep_thumbnail_temps()
+
    threading.Thread(
-        target=api.sweep_thumbnail_temps,
+        target=_preview_startup,
        name="PromptManagerPreviewTempSweep",
        daemon=True,
    ).start()
@@ -108,6 +119,8 @@ try:
        # Build each output root's Images listing once the server's loop runs,
        # so the first open does not wait for the walk (#348).
        host_app.on_startup.append(api.warm_gallery_listings)
+        # #320: old thumbnails a move left to remove, once it is checked.
+        host_app.on_startup.append(api.finish_thumbnail_move)
    if host_app is not None and hasattr(host_app, "on_shutdown"):
        # Open Needs review change streams end before the server waits on them.
        host_app.on_shutdown.append(api.close_review_events)
@@ -120,6 +133,7 @@ except Exception as e:
        logger = get_logger("prompt_manager.init")
        logger.error(f"Failed to register API routes: {e}")
    except Exception:
+        # logging failed too; a report must never stop the node loading
        pass

 # Shared database, set up with the monitoring system below. Stays None when that
@@ -279,11 +293,11 @@ def _teardown_logger():


 def _stop_background_work():
-    """Stop the image monitor, the preview worker and the prompt cleanup
-    thread against one TEARDOWN_SECONDS deadline, once.
+    """Stop the image monitor, the preview worker, the job worker threads
+    and the prompt cleanup thread against one TEARDOWN_SECONDS deadline, once.

-    Returns ``{"monitor", "thumbnails", "tracker"}`` booleans (True: it
-    stopped), leaving out parts that never started. Later calls return a
+    Returns ``{"monitor", "thumbnails", "workers", "tracker"}`` booleans
+    (True: it stopped), leaving out parts that never started. Later calls return a
    copy of the first result. A Ctrl+C inside a step is logged and the
    step is False; one between steps is re-raised after the result (parts
    not reached are False) is stored and the ``atexit`` entry removed.
@@ -297,11 +311,14 @@ def _stop_background_work():
            api,
            _global_prompt_tracker,
        )
+        from .utils import parallel
+
        # A part whose global is set has started; False until its step says
        # otherwise, so an interrupt between steps leaves an honest result.
        started = (
            ("monitor", monitor),
            ("thumbnails", thumbnails),
+            ("workers", parallel.job_pool_started() or None),
            ("tracker", tracker),
        )
        result = {name: False for name, part in started if part is not None}
@@ -344,6 +361,16 @@ def _stop_background_work():
                result["thumbnails"] = _teardown_step(
                    "the preview worker", close_previews, logger
                )
+            if "workers" in result:
+
+                def stop_workers():
+                    from .utils.parallel import JOB_POOL_JOIN_SECONDS
+
+                    return parallel.shutdown_job_pool(left(JOB_POOL_JOIN_SECONDS))
+
+                result["workers"] = _teardown_step(
+                    "the job worker threads", stop_workers, logger
+                )
            if tracker is not None:

                def stop_tracker():
@@ -411,6 +438,7 @@ except Exception as e:
            f"Failed to register the exit signal: {e}"
        )
    except Exception:
+        # logging failed too; a report must never stop the node loading
        pass

 try:
@@ -428,16 +456,17 @@ except Exception as e:
            f"Failed to register the background work teardown: {e}"
        )
    except Exception:
+        # logging failed too; a report must never stop the node loading
        pass

 __all__ = ["NODE_CLASS_MAPPINGS", "NODE_DISPLAY_NAME_MAPPINGS", "WEB_DIRECTORY"]

-# Print startup message with loaded tools
-print()
-print(f"\033[94m[ComfyUI-PromptManager] Version:\033[0m {get_version()}")
-for node_key, display_name in NODE_DISPLAY_NAME_MAPPINGS.items():
-    # ASCII only: a Windows console using a legacy code page cannot print emoji,
-    # and a UnicodeEncodeError here would abort loading the whole node.
-    print(f"  \033[94mLoaded:\033[0m {display_name}")
-print(f"\033[94mTotal: {len(NODE_CLASS_MAPPINGS)} tools loaded\033[0m")
-print()
+# One startup line, printed at import on purpose: it is the package's banner on
+# stdout, as ComfyUI's other custom nodes print theirs. Not a log record: the
+# console log handler hides INFO by default, so a logger would drop it. ASCII
+# only: a Windows console using a legacy code page cannot print emoji, and a
+# UnicodeEncodeError here would abort loading the node.
+print(
+    f"\033[94m[ComfyUI-PromptManager] Version:\033[0m {get_version()}"
+    f" - {len(NODE_CLASS_MAPPINGS)} tools loaded"
+)
@@ -199,6 +199,23 @@ def link_states(rows, roots, readable):
    check's ``missing_files`` and the maintenance missing-link plan both
    judge links this way, so their counts agree.
    """
+    for row, owner, state in _placed_links(rows, roots, readable):
+        if state is None:
+            state = "present" if os.path.exists(row[1]) else "missing"
+        yield row, owner, state
+
+
+def held_links(rows, roots, readable):
+    """``(row, owner, state)`` for each link ``link_states`` holds back
+    (``unavailable`` or ``outside``), without looking at any file (#586)."""
+    for row, owner, state in _placed_links(rows, roots, readable):
+        if state is not None:
+            yield row, owner, state
+
+
+def _placed_links(rows, roots, readable):
+    """``link_states`` before any file is looked at: state None means the
+    link lies under a readable source."""
    prefixes = [_root_prefix(root) for root in roots]
    for row in rows:
        owner = _image_owner(row[1], row[3], prefixes)
@@ -206,10 +223,8 @@ def link_states(rows, roots, readable):
            yield row, None, "outside"
        elif not readable[owner]:
            yield row, owner, "unavailable"
-        elif os.path.exists(row[1]):
-            yield row, owner, "present"
        else:
-            yield row, owner, "missing"
+            yield row, owner, None


 def _unavailable_line(unavailable, *, partial):
@@ -78,6 +78,10 @@ MESSAGES = {
    ),
    "same-folder": "The new folder is the node folder itself.",
    "target-invalid": "The new folder cannot hold the library.",
+    "data-dir-served": (
+        "The new folder is inside Prompt Manager's thumbnail folder. Nothing was "
+        "moved."
+    ),
    "target-has-library": (
        "The new folder already holds a Prompt Manager library. Nothing was moved."
    ),
@@ -590,6 +594,7 @@ class _Move:
            try:
                os.rmdir(self.plan.target_dir)
            except OSError:
+                # not empty or already gone: the undo leaves it alone
                pass


@@ -2,7 +2,8 @@

 Four operations, each the native owner of a legacy ``/maintenance`` one and
 built on the same queries, so a preview counts what the legacy cleanup would
-change:
+change (``workflow_storage`` and #550's ``pair_metadata``, which fills old
+Pair prompts' empty category and tags, live in their own modules):

 - ``duplicate_prompts``: prompts whose text is equal ignoring case and outer
  spaces (``DUPLICATE_PROMPTS_SQL``, legacy ``cleanup_duplicates``); each
@@ -42,7 +43,7 @@ from dataclasses import dataclass, field
 from pathlib import Path

 from .execution_contexts import LIVE_HINT_CTES
-from .health import BATCH_ROWS, link_states, readable_roots, readonly_uri
+from .health import BATCH_ROWS, held_links, link_states, readable_roots, readonly_uri
 from .image_removal_schema import TABLE as MARKS_TABLE
 from .image_removal_schema import clear_marks, has_marks_table
 from .pairs import PairDependencyError
@@ -60,6 +61,9 @@ MAINTENANCE_OPERATIONS = (
    "missing_links",
    # Applied as its own batched job (database/workflow_storage.py).
    "workflow_storage",
+    # #550: fill old Pair prompts' empty category and tags
+    # (database/pair_metadata_repair.py).
+    "pair_metadata",
 )
 MAX_DETAILS = 50  # detail rows a plan lists
 MAX_RESULT_ROWS = 200  # changed records an apply describes (the job lists 200)
@@ -126,6 +130,16 @@ _UNLINKED_PROTECTIONS_SQL = (
    + "), 0) FROM prompts p WHERE NOT EXISTS "
    "(SELECT 1 FROM generated_images gi WHERE gi.prompt_id = p.id)"
 )
+# Each prompt no image links to, with which protections keep it (#586); the
+# ones with none are filtered out in Python, so each predicate runs once.
+_UNLINKED_KEPT_SQL = (
+    "WITH "
+    + LIVE_HINT_CTES
+    + " SELECT p.id, "
+    + ", ".join(f"({predicate})" for predicate, _many, _one in PROTECTIONS)
+    + " FROM prompts p WHERE NOT EXISTS "
+    "(SELECT 1 FROM generated_images gi WHERE gi.prompt_id = p.id) ORDER BY p.id"
+)

 # Duplicate prompt groups, as the legacy cleanup finds them (case-insensitive
 # text; GROUP_CONCAT order is sorted by created_at afterwards).
@@ -155,6 +169,14 @@ _PROMPT_STATE_SQL = (
    "ORDER BY id",
 )

+# Why the missing-link cleanup holds a link back: (one, many) (#586).
+HELD_LINK_REASONS = {
+    "unavailable": (
+        "link under an unavailable source",
+        "links under unavailable sources",
+    ),
+    "outside": ("link outside the image sources", "links outside the image sources"),
+}
 NO_FILES_DELETED = "No image file is deleted."
 LINKS_ONLY = "Database links only; no image file is deleted."
 UNUSED_DETAIL = "No image, saved pair, Library state or recorded run uses it"
@@ -168,6 +190,7 @@ CONFLICT_REASONS = {
        "groups have their own Library titles",
    ),
 }
+PAIRED_DETAIL = "Kept: belongs to a saved pair"
 CONFLICT_DETAILS = {
    "collision": "Kept: two copies link the same image",
    "title": "Kept: a copy has its own Library title",
@@ -409,6 +432,35 @@ def _source_name(root, index):
    return os.path.basename(str(root).rstrip("\\/")) or f"Source {index + 1}"


+def _kept_duplicates(paired, conflicted):
+    """``{prompt_id, reasons}`` for each prompt of a group kept whole (#586).
+
+    The reasons are the review's details without "Kept: ".
+    """
+    held = [(ids, PAIRED_DETAIL) for ids in paired] + [
+        (ids, CONFLICT_DETAILS[reason]) for ids, reason in conflicted
+    ]
+    return [
+        {"prompt_id": prompt_id, "reasons": [detail.removeprefix("Kept: ")]}
+        for ids, detail in held
+        for prompt_id in ids
+    ]
+
+
+def _kept_unused(conn):
+    """``{prompt_id, reasons}`` for each prompt the unused prune keeps (#586).
+
+    The reasons are the review's, one per protection that applies, in the
+    order the plan names them.
+    """
+    kept = []
+    for row in conn.execute(_UNLINKED_KEPT_SQL):
+        reasons = [one for flag, (_p, _m, one) in zip(row[1:], PROTECTIONS) if flag]
+        if reasons:
+            kept.append({"prompt_id": row[0], "reasons": reasons})
+    return kept
+
+
 class MaintenanceOperations:
    """Mixin for PromptDatabase: maintenance previews and their apply."""

@@ -533,6 +585,10 @@ class MaintenanceOperations:
                lambda conn: (self._link_rows(conn), _mark_rows(conn)),
            )
            return self._plan_missing_links(rows, roots, _stale_marks(marks, roots))
+        if operation == "pair_metadata":
+            from .pair_metadata_repair import plan_pair_metadata
+
+            return _read_snapshot(self.model.db_path, plan_pair_metadata)
        reader = (
            self._plan_duplicate_prompts
            if operation == "duplicate_prompts"
@@ -584,7 +640,7 @@ class MaintenanceOperations:
            + [
                {
                    "label": _excerpt(texts.get(group[0])),
-                    "detail": "Kept: belongs to a saved pair",
+                    "detail": PAIRED_DETAIL,
                }
                for group in paired
            ]
@@ -662,6 +718,24 @@ class MaintenanceOperations:
            ],
        )

+    def kept_links(self, roots):
+        """``{image_path, owner, reason}`` for each link the missing-link
+        cleanup holds back under ``roots`` (blocking, reads only, no file
+        opened); ``owner`` indexes ``roots`` (None outside every source).
+
+        ``reason`` is the review's (``HELD_LINK_REASONS``), one link each.
+        """
+        roots = [str(root) for root in roots]
+        rows = _read_snapshot(self.model.db_path, self._link_rows)
+        return [
+            {
+                "image_path": row[1],
+                "owner": owner,
+                "reason": HELD_LINK_REASONS[state][0],
+            }
+            for row, owner, state in held_links(rows, roots, readable_roots(roots))
+        ]
+
    @staticmethod
    def _links_fingerprint(candidates, stale=()):
        fingerprint = _Fingerprint("missing_links")
@@ -681,23 +755,11 @@ class MaintenanceOperations:
                unavailable += 1
            elif state == "outside":
                outside += 1
-        reasons = []
-        if unavailable:
-            reasons.append(
-                _plural(
-                    unavailable,
-                    "link under an unavailable source",
-                    "links under unavailable sources",
-                )
-            )
-        if outside:
-            reasons.append(
-                _plural(
-                    outside,
-                    "link outside the image sources",
-                    "links outside the image sources",
-                )
-            )
+        reasons = [
+            _plural(count, *HELD_LINK_REASONS[state])
+            for state, count in (("unavailable", unavailable), ("outside", outside))
+            if count
+        ]
        count = len(candidates)
        parts = []
        if count:
@@ -800,7 +862,11 @@ class MaintenanceOperations:
        records changed and up to ``MAX_RESULT_ROWS`` descriptions of them
        (``{prompt_id[, kept_id]}`` or ``{image_path}``). ``marks`` are a
        missing-links plan's stale removal marks; that apply also returns
-        ``marks``, how many it forgot.
+        ``marks``, how many it forgot. ``pair_metadata`` returns every filled
+        prompt, uncapped (its job keeps the complete record, #550). The
+        prompt operations also return ``kept``: every prompt the plan keeps,
+        ``{prompt_id, reasons}`` in the review's wording (#550, #586); the
+        links a missing-links plan keeps are read by ``kept_links``.
        """
        if operation not in MAINTENANCE_OPERATIONS or operation == "workflow_storage":
            raise ValueError(f"Unknown maintenance operation {operation!r}")
@@ -815,6 +881,10 @@ class MaintenanceOperations:
            "unused_components": self._apply_unused_components,
        }
        with self._pair_transaction() as conn:
+            if operation == "pair_metadata":
+                from .pair_metadata_repair import apply_pair_metadata
+
+                return apply_pair_metadata(conn, fingerprint, targets)
            if operation == "missing_links":
                return self._apply_missing_links(
                    conn, fingerprint, targets, roots, list(marks)
@@ -822,10 +892,11 @@ class MaintenanceOperations:
            return appliers[operation](conn, fingerprint, targets, roots)

    def _apply_duplicate_prompts(self, conn, fingerprint, targets, _roots):
-        groups, _paired, _conflicted, current = self._duplicates_fingerprint(conn)
+        groups, paired, conflicted, current = self._duplicates_fingerprint(conn)
        if current != fingerprint or groups != targets:
            raise PlanChanged("duplicate_prompts")
        changed, rows = 0, []
+        kept = _kept_duplicates(paired, conflicted)
        for sorted_ids in groups:
            removed, _moved = self._merge_duplicate_group(conn, sorted_ids, strict=True)
            changed += removed
@@ -833,7 +904,7 @@ class MaintenanceOperations:
                {"prompt_id": duplicate_id, "kept_id": sorted_ids[0]}
                for duplicate_id in sorted_ids[1:]
            )
-        return {"changed": changed, "rows": rows[:MAX_RESULT_ROWS]}
+        return {"changed": changed, "rows": rows[:MAX_RESULT_ROWS], "kept": kept}

    def _apply_unused_components(self, conn, fingerprint, targets, _roots):
        ids, current = self._unused_fingerprint(conn)
@@ -845,7 +916,7 @@ class MaintenanceOperations:
            {"prompt_id": prompt_id, "text": _excerpt(texts.get(prompt_id))}
            for prompt_id in ids[:MAX_RESULT_ROWS]
        ]
-        return {"changed": changed, "rows": rows}
+        return {"changed": changed, "rows": rows, "kept": _kept_unused(conn)}

    def _apply_missing_links(self, conn, fingerprint, targets, roots, marks):
        rows = []
@@ -35,38 +35,51 @@ from __future__ import annotations

 import contextlib
 import logging
+import operator
+import sys
 import threading
 import time
 import weakref
-from typing import Iterable, Iterator, List, Optional
+from collections import deque
+from typing import Any, Callable, Iterable, Iterator, List, Optional

 import sqlite3

 CLOSED_MESSAGE = "Cannot operate on a closed database."
 # Rows fetched per step when a cursor is iterated: the connection is marked
 # in use once per chunk instead of once per row (iteration costs about what
-# a plain cursor costs). A loop that stops early leaves up to this many rows
-# fetched; ``fetchone``/``fetchmany`` after a partial loop skip them.
+# a plain cursor costs). Prefetched rows belong to the cursor so iteration
+# and explicit fetches always advance the same position.
 ITER_CHUNK = 128


 class ManagedCursor(sqlite3.Cursor):
    """A cursor whose calls into SQLite count as its connection being in use."""

+    def __init__(self, *args: Any, **kwargs: Any) -> None:
+        super().__init__(*args, **kwargs)
+        self._pending = deque()
+        self._closed = False
+
    def execute(self, sql, parameters=(), /):
-        conn = self.connection
-        conn._enter()
-        try:
-            return super().execute(sql, parameters)
-        finally:
-            conn._leave()
+        return self._run_statement(super().execute, sql, parameters)

    def executemany(self, sql, seq_of_parameters, /):
+        return self._run_statement(super().executemany, sql, seq_of_parameters)
+
+    def _run_statement(self, operation: Callable, *args: Any) -> ManagedCursor:
        conn = self.connection
        conn._enter()
+        description = self.description
+        completed = False
        try:
-            return super().executemany(sql, seq_of_parameters)
+            result = operation(*args)
+            completed = True
+            return result
        finally:
+            # Argument parsing can fail before SQLite replaces the old statement.
+            if completed or self.description is not description:
+                self._pending.clear()
            conn._leave()

    def executescript(self, sql_script, /):
@@ -81,6 +94,8 @@ class ManagedCursor(sqlite3.Cursor):
        conn = self.connection
        conn._enter()
        try:
+            if self._pending and not self._closed:
+                return self._pending.popleft()
            return super().fetchone()
        finally:
            conn._leave()
@@ -89,7 +104,20 @@ class ManagedCursor(sqlite3.Cursor):
        conn = self.connection
        conn._enter()
        try:
-            return super().fetchmany(*args, **kwargs)
+            # Let SQLite validate the original arguments, including version-specific
+            # handling of zero/negative sizes, before touching prefetched rows.
+            rows = super().fetchmany(*args, **kwargs)
+            if not self._pending:
+                return rows
+            size = operator.index(
+                kwargs.get("size", args[0] if args else self.arraysize)
+            )
+            # Python 3.12 reads all rows for size=0; 3.13+ reads none.
+            if size == 0 and sys.version_info >= (3, 13):
+                return rows
+            self._pending.extend(rows)
+            count = len(self._pending) if size <= 0 else min(size, len(self._pending))
+            return [self._pending.popleft() for _ in range(count)]
        finally:
            conn._leave()

@@ -97,25 +125,31 @@ class ManagedCursor(sqlite3.Cursor):
        conn = self.connection
        conn._enter()
        try:
-            return super().fetchall()
+            rows = super().fetchall()
+            pending = list(self._pending)
+            self._pending.clear()
+            return pending + rows
        finally:
            conn._leave()

    def __iter__(self) -> Iterator:
-        return self._chunks()
-
-    def _chunks(self) -> Iterator:
-        while True:
-            rows = self.fetchmany(ITER_CHUNK)
-            if not rows:
-                return
-            yield from rows
+        return self

    def __next__(self):
        conn = self.connection
+        pending = self._pending
+        # Buffered Python rows need no SQLite lock, but retirement and cursor
+        # close must still stop an iterator obtained before either operation.
+        if conn._retired or self._closed:
+            raise sqlite3.ProgrammingError(CLOSED_MESSAGE)
+        if pending:
+            return pending.popleft()
        conn._enter()
        try:
-            return super().__next__()
+            pending.extend(super().fetchmany(ITER_CHUNK))
+            if not pending:
+                raise StopIteration
+            return pending.popleft()
        finally:
            conn._leave()

@@ -126,7 +160,10 @@ class ManagedCursor(sqlite3.Cursor):
        except sqlite3.ProgrammingError:
            return super().close()  # the connection is closed or closing
        try:
-            return super().close()
+            result = super().close()
+            self._pending = deque()
+            self._closed = True
+            return result
        finally:
            conn._leave()

@@ -293,6 +330,9 @@ class ManagedConnection(sqlite3.Connection):
            cursors = list(self._cursors)
        try:
            for cursor in cursors:
+                if isinstance(cursor, ManagedCursor):
+                    cursor._pending = deque()
+                    cursor._closed = True
                with contextlib.suppress(sqlite3.Error):
                    sqlite3.Cursor.close(cursor)
            super().close()
@@ -34,7 +34,7 @@ from .history_reads import HistoryReadOperations
 from .health import HealthOperations, iter_consistency_issues
 from .duplicate_copies import DuplicateCopyOperations
 from .workflow_storage import WorkflowStorageOperations
-from .category_import import CategoryImportOperations, EmptyReplacement  # noqa: F401
+from .category_import import CategoryImportOperations
 from .image_categories import ImageCategoryOperations
 from .workflow_documents import (
    DocumentReader,
@@ -0,0 +1,452 @@
+"""Pair category and tags repair (#550): the ``pair_metadata`` maintenance plan.
+
+Before #546 a Pair node run saved its category and tags on the saved pair
+only; the positive prompt it created stayed Uncategorized and untagged. This
+plan fills the **empty** category and the **empty** tag set of those prompts
+from their saved pairs (``docs/egm/post-3.4.1/550-design.md``):
+
+- Considered: prompts the Pair node created as a positive (their earliest
+  pair, in either role, has them as the positive and its ``created_at`` is
+  within ``PAIR_CREATED_TOLERANCE`` of theirs) whose category is blank
+  and/or that have no tags.
+- Sources: the prompt's non-archived pairs where it is the positive. Pairs
+  with a blank category or no tags are ignored for that field. A field fills
+  when exactly one value remains (category: trimmed, case-sensitive; tags:
+  the tag-id set).
+- Kept (protected), in this order: archived prompt, edited prompt
+  (``updated_at`` not within the tolerance of ``created_at``), pairs that
+  disagree, a tag set over ``MAX_LIBRARY_TAGS``.
+
+The apply runs in the caller's ``BEGIN IMMEDIATE`` transaction, recomputes
+the fingerprint, then writes guarded statements (the field must still be
+empty) that never touch a pair, a negative or ``updated_at``. A guard that
+hits nothing raises ``PlanChanged`` so the whole transaction rolls back.
+"""
+
+import datetime
+
+from . import maintenance as _maintenance
+from .library_commands import MAX_LIBRARY_TAGS
+from .maintenance import (
+    MAX_DETAILS,
+    MaintenanceDraft,
+    PlanChanged,
+    _excerpt,
+    _Fingerprint,
+    _marks,
+    _plural,
+)
+
+OPERATION = "pair_metadata"
+# Seconds: the Pair save stamps its new prompt and its pair with separate
+# utc_now_iso() calls in one transaction (microseconds apart).
+PAIR_CREATED_TOLERANCE = 2.0
+# Fill prompts one plan applies; the rest are applied by the next review.
+# Bounds the complete record a job keeps in memory (about 100 bytes a row).
+MAX_PLAN_FILLS = 20000
+DETAIL_VALUES = 3
+DETAIL_TAGS = 5
+MEDIA_LABEL = "No image file or saved pair is changed."
+EMPTY_LABEL = "No Pair prompts are missing a category or tags"
+RECORD_NOTE = (
+    "The job's report lists every filled field. Download it to keep it: "
+    "Activity forgets jobs after a restart."
+)
+# Protected classes in precedence order: (key, detail, reason one, many).
+EDITED_DETAIL = (
+    "Kept: edited after it was saved; its empty category or tags may be intentional"
+)
+PROTECTED = (
+    (
+        "archived",
+        "Kept: archived in the Library",
+        "archived in the Library",
+        "archived in the Library",
+    ),
+    (
+        "edited",
+        EDITED_DETAIL,
+        "edited after it was saved",
+        "edited after they were saved",
+    ),
+    ("conflict", None, "where pairs disagree", "where pairs disagree"),
+    (
+        "too-many-tags",
+        f"Kept: its pair has more than {MAX_LIBRARY_TAGS} tags",
+        f"whose pair has more than {MAX_LIBRARY_TAGS} tags",
+        f"whose pair has more than {MAX_LIBRARY_TAGS} tags",
+    ),
+)
+_PROTECTED_ORDER = [key for key, *_rest in PROTECTED]
+# Detail rows: what the user can act on (a conflict) first.
+DETAIL_ORDER = ("conflict", "edited", "archived", "too-many-tags")
+
+_CANDIDATES_SQL = """
+    SELECT p.id, p.hash, p.text, p.created_at, p.updated_at,
+           COALESCE(TRIM(p.category), '') = '' AS blank_category,
+           NOT EXISTS (SELECT 1 FROM prompt_tags pt WHERE pt.prompt_id = p.id)
+               AS untagged,
+           EXISTS (SELECT 1 FROM prompt_archive pa WHERE pa.prompt_id = p.id)
+               AS archived,
+           (SELECT CASE WHEN pp.positive_prompt_id = p.id
+                        THEN pp.created_at END
+              FROM prompt_pairs pp
+             WHERE pp.positive_prompt_id = p.id OR pp.negative_prompt_id = p.id
+             ORDER BY pp.id LIMIT 1) AS first_pair_at
+      FROM prompts p
+     WHERE EXISTS (SELECT 1 FROM prompt_pairs pp WHERE pp.positive_prompt_id = p.id)
+       AND (COALESCE(TRIM(p.category), '') = ''
+            OR NOT EXISTS (SELECT 1 FROM prompt_tags pt WHERE pt.prompt_id = p.id))
+     ORDER BY p.id
+"""
+_SOURCES_SQL = (
+    "SELECT id, positive_prompt_id, TRIM(COALESCE(category, '')) FROM prompt_pairs "
+    "WHERE archived = 0 AND positive_prompt_id IN ({marks}) ORDER BY id"
+)
+_PAIR_TAGS_SQL = (
+    "SELECT ppt.pair_id, t.id, t.name FROM prompt_pair_tags ppt "
+    "JOIN tags t ON t.id = ppt.tag_id WHERE ppt.pair_id IN ({marks}) "
+    "ORDER BY ppt.pair_id, t.id"
+)
+
+
+def parse_stamp(value):
+    """A stored timestamp as an aware UTC datetime, or None when unreadable."""
+    if not isinstance(value, str) or not value.strip():
+        return None
+    try:
+        stamp = datetime.datetime.fromisoformat(value.strip())
+    except ValueError:
+        return None
+    if stamp.tzinfo is None:
+        stamp = stamp.replace(tzinfo=datetime.timezone.utc)
+    return stamp
+
+
+def _close(first, second):
+    """Whether two stored stamps parse and lie within the tolerance."""
+    a, b = parse_stamp(first), parse_stamp(second)
+    if a is None or b is None:
+        return False
+    return abs((a - b).total_seconds()) <= PAIR_CREATED_TOLERANCE
+
+
+def _batches(ids):
+    size = _maintenance.ID_BATCH
+    for start in range(0, len(ids), size):
+        yield ids[start : start + size]
+
+
+def _sources(conn, ids):
+    """``{prompt_id: [(pair_id, category, ((tag_id, name), ...)), ...]}``."""
+    pairs = {}
+    for batch in _batches(ids):
+        for pair_id, prompt_id, category in conn.execute(
+            _SOURCES_SQL.format(marks=_marks(batch)), batch
+        ):
+            pairs.setdefault(prompt_id, []).append([pair_id, category, []])
+    by_pair = {pair[0]: pair for group in pairs.values() for pair in group}
+    pair_ids = sorted(by_pair)
+    for batch in _batches(pair_ids):
+        for pair_id, tag_id, name in conn.execute(
+            _PAIR_TAGS_SQL.format(marks=_marks(batch)), batch
+        ):
+            by_pair[pair_id][2].append((tag_id, name))
+    return {
+        prompt_id: [(pid, category, tuple(tags)) for pid, category, tags in group]
+        for prompt_id, group in pairs.items()
+    }
+
+
+def _field(values, guard):
+    """``(class, value)`` of one field from its distinct values, or None."""
+    if not values:
+        return None
+    if guard:
+        return (guard, None)
+    if len(values) > 1:
+        return ("conflict", sorted(values))
+    return ("fill", next(iter(values)))
+
+
+def _classify(row, sources):
+    """The result of one considered prompt, or None when nothing applies."""
+    guard = None
+    if row["archived"]:
+        guard = "archived"
+    elif not _close(row["updated_at"], row["created_at"]):
+        guard = "edited"
+    category = tags = None
+    tag_pair = None
+    if row["blank_category"]:
+        category = _field({c for _p, c, _t in sources if c}, guard)
+    if row["untagged"]:
+        sets = {}
+        for pair_id, _category, pair_tags in sources:
+            if pair_tags:
+                sets.setdefault(frozenset(pair_tags), pair_id)
+        tags = _field(set(sets), guard)
+        if tags and tags[0] == "fill":
+            tag_pair = sets[tags[1]]
+            if len(tags[1]) > MAX_LIBRARY_TAGS:
+                tags = ("too-many-tags", None)
+            else:
+                tags = ("fill", tuple(sorted(tags[1])))
+        elif tags and tags[0] == "conflict":
+            tags = ("conflict", [sorted(s) for s in sorted(sets, key=sorted)])
+    if category is None and tags is None:
+        return None
+    return {
+        "id": row["id"],
+        "hash": row["hash"],
+        "text": row["text"],
+        "category": category,
+        "tags": tags,
+        "tag_pair": tag_pair if tags and tags[0] == "fill" else None,
+        "pairs": [pair_id for pair_id, _c, _t in sources],
+    }
+
+
+def _state(conn):
+    """``(results, fingerprint)``: every considered prompt's result, by id."""
+    considered = []
+    for row in conn.execute(_CANDIDATES_SQL):
+        row = dict(
+            zip(
+                (
+                    "id",
+                    "hash",
+                    "text",
+                    "created_at",
+                    "updated_at",
+                    "blank_category",
+                    "untagged",
+                    "archived",
+                    "first_pair_at",
+                ),
+                tuple(row),
+            )
+        )
+        if _close(row["created_at"], row["first_pair_at"]):
+            considered.append(row)
+    sources = _sources(conn, [row["id"] for row in considered])
+    fingerprint = _Fingerprint(OPERATION)
+    results = []
+    for row in considered:
+        result = _classify(row, sources.get(row["id"], []))
+        if result is None:
+            continue
+        results.append(result)
+        fingerprint.add(
+            [
+                result["id"],
+                result["hash"],
+                result["category"],
+                result["tags"],
+                result["tag_pair"],
+                result["pairs"],
+            ]
+        )
+    return results, fingerprint.hexdigest()
+
+
+def _fills(result):
+    return (
+        bool(result["category"] and result["category"][0] == "fill"),
+        bool(result["tags"] and result["tags"][0] == "fill"),
+    )
+
+
+def _targets(results):
+    targets = []
+    for result in results:
+        category, tags = _fills(result)
+        if category or tags:
+            targets.append([result["id"], category, tags])
+    return targets[:MAX_PLAN_FILLS]
+
+
+def _protected_classes(result):
+    """The protected classes of a result's fields, in precedence order."""
+    found = {
+        field[0]
+        for field in (result["category"], result["tags"])
+        if field and field[0] != "fill"
+    }
+    return [key for key in _PROTECTED_ORDER if key in found]
+
+
+def _more(values, limit):
+    shown = ", ".join(values[:limit])
+    return shown + (", …" if len(values) > limit else "")
+
+
+def _fill_detail(result):
+    parts = []
+    category, tags = _fills(result)
+    if category:
+        parts.append(f"category “{result['category'][1]}”")
+    if tags:
+        names = sorted(name for _id, name in result["tags"][1])
+        noun = "tag" if len(names) == 1 else "tags"
+        parts.append(f"{len(names)} {noun}: {_more(names, DETAIL_TAGS)}")
+    pairs = [str(pair_id) for pair_id in result["pairs"]]
+    label = "pair" if len(pairs) == 1 else "pairs"
+    return f"Fills {' and '.join(parts)} ({label} {_more(pairs, DETAIL_VALUES)})"
+
+
+def _protected_detail(result, key):
+    if key != "conflict":
+        return next(detail for k, detail, *_r in PROTECTED if k == key)
+    if result["category"] and result["category"][0] == "conflict":
+        values = result["category"][1]
+        return f"Kept: pairs disagree on category: {_more(values, DETAIL_VALUES)}"
+    return "Kept: pairs disagree on tags"
+
+
+def _kept(results):
+    """One row per kept prompt, its review reasons without "Kept: " (#550)."""
+    rows = []
+    for result in results:
+        classes = set(_protected_classes(result))
+        if classes:
+            rows.append(
+                {
+                    "prompt_id": result["id"],
+                    "reasons": [
+                        _protected_detail(result, key).removeprefix("Kept: ")
+                        for key in DETAIL_ORDER
+                        if key in classes
+                    ],
+                }
+            )
+    return rows
+
+
+def _details(results, targets):
+    rows = []
+    for key in DETAIL_ORDER:
+        for result in results:
+            if key in _protected_classes(result):
+                rows.append(
+                    {
+                        "label": _excerpt(result["text"]),
+                        "detail": _protected_detail(result, key),
+                    }
+                )
+    planned = {target[0] for target in targets}
+    for result in results:
+        if result["id"] in planned:
+            rows.append(
+                {"label": _excerpt(result["text"]), "detail": _fill_detail(result)}
+            )
+    if not targets:
+        return rows[:MAX_DETAILS]
+    return rows[: MAX_DETAILS - 1] + [{"label": "Record", "detail": RECORD_NOTE}]
+
+
+def _scope_label(targets, total):
+    if not targets:
+        return EMPTY_LABEL
+    categories = sum(1 for _id, category, _tags in targets if category)
+    tag_sets = sum(1 for _id, _category, tags in targets if tags)
+    label = (
+        f"{_plural(len(targets), 'prompt')} to fill: "
+        f"{_plural(categories, 'category', 'categories')}, "
+        f"{_plural(tag_sets, 'tag set')}"
+    )
+    if total > len(targets):
+        label += (
+            f" (the first {len(targets):,} of {total:,}; review again for the rest)"
+        )
+    return label
+
+
+def plan_pair_metadata(conn):
+    """The reviewed ``pair_metadata`` plan on ``conn``'s snapshot."""
+    results, fingerprint = _state(conn)
+    targets = _targets(results)
+    total = sum(1 for result in results if any(_fills(result)))
+    counts = {key: 0 for key in _PROTECTED_ORDER}
+    held = 0
+    for result in results:
+        classes = _protected_classes(result)
+        held += bool(classes)
+        for key in classes:
+            counts[key] += 1
+    reasons = [
+        f"{counts[key]:,} {one if counts[key] == 1 else many}"
+        for key, _detail, one, many in PROTECTED
+        if counts[key]
+    ]
+    return MaintenanceDraft(
+        operation=OPERATION,
+        fingerprint=fingerprint,
+        targets=targets,
+        scope={"count": len(targets), "label": _scope_label(targets, total)},
+        protected={"count": held, "reasons": reasons},
+        media={"deletes_files": False, "label": MEDIA_LABEL},
+        details=_details(results, targets),
+    )
+
+
+def _fill_categories(conn, fills):
+    """Set each blank category; raises PlanChanged when one is no longer blank."""
+    cursor = conn.executemany(
+        "UPDATE prompts SET category = ? WHERE id = ? "
+        "AND COALESCE(TRIM(category), '') = ''",
+        fills,
+    )
+    if cursor.rowcount != len(fills):
+        raise PlanChanged(OPERATION)
+
+
+def _fill_tags(conn, fills, expected):
+    """Copy each source pair's tags onto its untagged prompt."""
+    cursor = conn.executemany(
+        "INSERT INTO prompt_tags(prompt_id, tag_id) "
+        "SELECT ?, ppt.tag_id FROM prompt_pair_tags ppt "
+        "JOIN tags t ON t.id = ppt.tag_id WHERE ppt.pair_id = ? "
+        "AND NOT EXISTS (SELECT 1 FROM prompt_tags WHERE prompt_id = ?)",
+        fills,
+    )
+    if cursor.rowcount != expected:
+        raise PlanChanged(OPERATION)
+
+
+def apply_pair_metadata(conn, fingerprint, targets):
+    """Apply the reviewed fills on ``conn`` (inside BEGIN IMMEDIATE).
+
+    Returns ``{changed, categories, tag_sets, rows, kept}``; ``rows`` lists
+    every filled prompt (``{prompt_id, category?, tags?}``) and ``kept`` every
+    prompt the plan keeps (``{prompt_id, reasons}``, in the review's wording
+    and order), both never capped.
+    """
+    results, current = _state(conn)
+    if current != fingerprint or _targets(results) != targets:
+        raise PlanChanged(OPERATION)
+    by_id = {result["id"]: result for result in results}
+    categories, tags, rows = [], [], []
+    tag_count = 0
+    for prompt_id, fill_category, fill_tags in targets:
+        result = by_id[prompt_id]
+        row = {"prompt_id": prompt_id}
+        if fill_category:
+            row["category"] = result["category"][1]
+            categories.append((row["category"], prompt_id))
+        if fill_tags:
+            row["tags"] = sorted(name for _id, name in result["tags"][1])
+            tags.append((prompt_id, result["tag_pair"], prompt_id))
+            tag_count += len(result["tags"][1])
+        rows.append(row)
+    if categories:
+        _fill_categories(conn, categories)
+    if tags:
+        _fill_tags(conn, tags, tag_count)
+    return {
+        "changed": len(rows),
+        "categories": len(categories),
+        "tag_sets": len(tags),
+        "rows": rows,
+        "kept": _kept(results),
+    }
@@ -46,6 +46,7 @@ def remove_quietly(*paths):
            if path and os.path.exists(path):
                os.remove(path)
        except OSError:
+            # cleanup after a failure must not replace that failure
            pass


@@ -66,7 +66,6 @@ def _tag_rows(page: str, order: str = "page.id") -> str:
    )


-_TAG_PAGE = _tag_rows("SELECT id,name FROM tags WHERE id>? ORDER BY id LIMIT ?")
 # #444 tag sorts: sort -> (key expression on tags/counted, direction). Ties and
 # "created" follow the id, so every order is total and keyset pages are exact.
 TAG_SORTS = {
@@ -112,20 +112,22 @@ QUERY_PLAN_STATEMENTS = {


 def _rewrite_row(conn, image_id, row, verified, checked):
-    """Store the row's inline texts as documents; returns (changed, protected, size).
+    """Store the row's inline texts as documents; returns (changed, kept, size).
+
+    ``kept`` names the columns whose value stays inline (not text).

    ``verified`` maps document ids already read back in this batch to their
    text, and ``checked`` holds the reused ids ``store_text`` already
    checked, so a document shared by many rows is decompressed once.
    """
-    changes, replaced = {}, []
-    protected = size = 0
+    changes, replaced, kept = {}, [], []
+    size = 0
    for index, (column, reference) in enumerate(TEXT_COLUMNS):
        value, current = row[index], row[index + len(TEXT_COLUMNS)]
        if value is None:
            continue
        if not storable(value):
-            protected += 1
+            kept.append(column)
            continue
        document_id = store_text(conn, value, checked)
        if document_id not in verified:
@@ -143,7 +145,7 @@ def _rewrite_row(conn, image_id, row, verified, checked):
            [*changes.values(), image_id],
        )
    release_documents(conn, replaced)
-    return bool(changes), protected, size
+    return bool(changes), kept, size


 def migrate_batch(
@@ -160,9 +162,10 @@ def migrate_batch(
    savepoint: a row that cannot be rewritten (``_row_error``) is rolled
    back alone, stays inline and is listed in ``errors``; anything else rolls
    the whole batch back and propagates. Returns ``{last_id, rows,
-    protected, errors, done}``: the last row looked at, rows rewritten,
-    inline values kept (not text), the ids kept by an error and whether
-    there was nothing left to look at.
+    protected, kept, errors, done}``: the last row looked at, rows
+    rewritten, inline values kept (not text) and each of them as ``(image
+    id, column)`` (#586), the ids kept by an error and whether there was
+    nothing left to look at.
    """
    if conn.in_transaction:
        raise RuntimeError("The migration needs its own transaction")
@@ -174,6 +177,7 @@ def migrate_batch(
            "last_id": after_id,
            "rows": 0,
            "protected": 0,
+            "kept": [],
            "errors": [],
            "done": not ids,
        }
@@ -182,7 +186,7 @@ def migrate_batch(
            conn.execute("SAVEPOINT workflow_row")
            try:
                row = conn.execute(ROW_SQL, (image_id,)).fetchone()
-                changed, protected, row_size = _rewrite_row(
+                changed, kept, row_size = _rewrite_row(
                    conn, image_id, row, verified, checked
                )
            except Exception as error:
@@ -194,11 +198,12 @@ def migrate_batch(
                checked.clear()
                logger.warning(f"Image record {image_id} kept inline: {error}")
                result["errors"].append(image_id)
-                changed, protected, row_size = False, 0, 0
+                changed, kept, row_size = False, [], 0
            else:
                conn.execute("RELEASE workflow_row")
            result["rows"] += int(changed)
-            result["protected"] += protected
+            result["protected"] += len(kept)
+            result["kept"].extend((image_id, column) for column in kept)
            result["last_id"] = image_id
            size += row_size
            if size >= max_bytes or _clock() - started >= max_seconds:
@@ -11,6 +11,7 @@ Split into domain-specific mixins for maintainability:
 - JobRoutesMixin: the session job registry behind Activity (py/api/jobs.py)
 - ImageTagJobsMixin: bulk Add tags / Auto-tag as image-tags jobs
 - ThumbnailJobsMixin: thumbnail plan, thumbnail job and the gallery stream on it
+- ThumbnailLocationMixin: the thumbnail location check and payloads (#320)
 - ThumbnailConvertMixin: Convert outdated thumbnails (#317), a thumbnail job mode
 - AutoThumbnailMixin: previews made on first view, on capture and after a scan
 - ReviewRoutesMixin: the Needs review queue, item detail and decisions
@@ -60,6 +61,11 @@ from .settings_routes import SettingsRoutesMixin
 from .job_routes import JobRoutesMixin
 from .image_tag_jobs import ImageTagJobsMixin
 from .thumbnail_jobs import ThumbnailJobsMixin
+from .thumbnail_location import ThumbnailLocationMixin
+from .thumbnail_move import ThumbnailMoveMixin
+from .thumbnail_move_plan import ThumbnailMovePlanMixin
+from .thumbnail_move_recovery import ThumbnailMoveRecoveryMixin
+from .thumbnail_prune import ThumbnailPruneMixin
 from .thumbnail_convert import ThumbnailConvertMixin
 from .thumbnail_auto import AutoThumbnailMixin
 from .system import SystemRoutesMixin
@@ -85,6 +91,8 @@ try:
    from ...database.operations import PromptDatabase
    from ...utils.file_prompt import parse_comfyui_prompt
    from ...utils.logging_config import get_logger
+    from ...utils.native_memory import release_free_memory
+    from ...utils.png_text import png_text
    from ...utils.video_metadata import is_video_path, read_video_metadata
 except ImportError:
    import sys
@@ -95,6 +103,8 @@ except ImportError:
    from database.operations import PromptDatabase
    from utils.file_prompt import parse_comfyui_prompt
    from utils.logging_config import get_logger
+    from utils.native_memory import release_free_memory
+    from utils.png_text import png_text
    from utils.video_metadata import is_video_path, read_video_metadata


@@ -334,6 +344,11 @@ class PromptManagerAPI(
    JobRoutesMixin,
    ImageTagJobsMixin,
    ThumbnailJobsMixin,
+    ThumbnailLocationMixin,
+    ThumbnailMovePlanMixin,
+    ThumbnailMoveMixin,
+    ThumbnailMoveRecoveryMixin,
+    ThumbnailPruneMixin,
    ThumbnailConvertMixin,
    AutoThumbnailMixin,
    SystemRoutesMixin,
@@ -526,6 +541,14 @@ class PromptManagerAPI(
            return await loop.run_in_executor(None, call)
        return await loop.run_in_executor(None, func, *args)

+    async def _release_job_memory(self):
+        """After a scan or thumbnail job: glibc's free heap pages go back to
+        the OS once (``malloc_trim(0)``; nothing elsewhere, #523)."""
+        try:
+            await self._run_in_executor(release_free_memory)
+        except Exception:  # best effort: the job's result already stands
+            self.logger.debug("Releasing free memory failed", exc_info=True)
+
    def _root_listing(self, root) -> RootListing:
        """The shared listing record of one output root (created empty)."""
        return self._root_listings.setdefault(str(root), RootListing())
@@ -704,6 +727,7 @@ class PromptManagerAPI(
        # ── Register domain-specific routes from mixins ───────────────

        self._register_pair_routes(routes)
+        self._register_thumbnail_move_routes(routes)
        self._register_library_routes(routes)
        self._register_library_delete_routes(routes)
        self._register_vocabulary_routes(routes)
@@ -840,20 +864,11 @@ class PromptManagerAPI(
                        f"{url_quote(rel_path.as_posix(), safe='/')}"
                    )

-                    # Any preview the file owns, the current format first (#317)
-                    from . import thumbnail_settings
-                    from .prompts import thumbnail_url_for
+                    # Any preview the file owns, the current format first
+                    # (#317); no store I/O here in folder mode (#320).
+                    from .images import listing_thumbnail_url

-                    existing = thumbnail_settings.existing_thumbnail(
-                        output_path, rel_path
-                    )
-                    thumbnail_url = None
-                    if existing is not None:
-                        thumb_rel = (
-                            thumbnail_settings.thumbnail_stem_rel(rel_path)
-                            + existing.suffix
-                        )
-                        thumbnail_url = thumbnail_url_for(thumb_rel, existing)
+                    thumbnail_url = listing_thumbnail_url(output_path, rel_path)
                    if thumbnail_url:
                        image["thumbnail_url"] = thumbnail_url
                    break  # Found matching root, stop searching
@@ -1048,6 +1063,8 @@ class PromptManagerAPI(
    def _extract_comfyui_metadata(self, image_path):
        """Embedded ComfyUI metadata of an image (PNG text chunks) or a video.

+        PNG text is read without decoding the pixels (``utils.png_text``, #523).
+
        Videos go through ffprobe (see utils/video_metadata). Unreadable files
        are a warning, not an error: a scan over a large output tree meets
        truncated and foreign files, and it carries on past them.
@@ -1056,7 +1073,7 @@ class PromptManagerAPI(
            return read_video_metadata(image_path)
        try:
            with Image.open(image_path) as img:
-                return dict(getattr(img, "text", None) or {})
+                return png_text(img)
        except Exception as e:
            self.logger.warning(
                f"Unreadable image {os.path.basename(str(image_path))}: {e}"
@@ -176,7 +176,7 @@ def _physical_file_key(path, stat):
    volumes on Windows) falls back to the resolved, case-folded path.
    """
    if stat.st_ino:
-        return ("inode", stat.st_dev, stat.st_ino)
+        return ("inode", (stat.st_dev, stat.st_ino))
    return ("path", os.path.normcase(os.path.realpath(str(path))))


@@ -539,6 +539,7 @@ def _diagnose_output_dirs(configured_dirs, public_path=None):

        candidates.append(folder_paths.get_output_directory())
    except ImportError:
+        # outside ComfyUI there is no output folder to add
        pass

    output_dirs = []
@@ -1453,6 +1454,7 @@ class AdminRoutesMixin:
            verb = "cancelled" if state == "cancelled" else "finished"
            job.log_line(f"Scan {verb} · {_plural(job.processed, 'file')} processed")
        job.finish(state)
+        await self._release_job_memory()
        if state == "finished":
            # After the scan, so the guarded thumbnail job is admitted (#249).
            await self._hand_off_scan_thumbnails(job, output_dirs)
@@ -1667,9 +1669,10 @@ class AdminRoutesMixin:
    def _extract_batch_metadata_sync(self, file_batch):
        """Extract metadata from a batch of files in one executor call.

-        Files are read on ``PromptManagerConfig.WORKER_THREADS`` threads:
-        Pillow decodes the whole image to reach trailing text chunks and
-        releases the GIL while doing so.
+        Files are read on the long-lived job pool of
+        ``PromptManagerConfig.WORKER_THREADS`` threads (#523).
+        PNG text is read chunk by chunk without decoding pixels (#523); file
+        reads and ffprobe release the GIL.
        """
        from ..config import PromptManagerConfig

@@ -13,7 +13,6 @@ import math
 from ..tagging_defaults import (  # noqa: F401 - re-exported for the route
    LLM_MODEL_TYPES as LLM_MODELS,
    MAX_INSTRUCTION_BYTES,
-    MAX_INSTRUCTION_CHARS,
    MODEL_TYPES,
    WD14_MODEL_TYPES as WD14_MODELS,
    validate_template,
@@ -103,11 +102,14 @@ def model_refusal(status: dict, model_type: str, model_name: str):
    return None


-def run_suggestions(service, capture_path: str, model_type: str, options: dict):
+def run_suggestions(
+    service, capture_path: str, model_type: str, options: dict, skip=None
+):
    """Blocking: load (or swap to) *model_type*, then suggest for the capture.

    The caller holds the model gate for the whole call; nothing is ever
-    downloaded (``load_model`` refuses a model that is not on disk).
+    downloaded (``load_model`` refuses a model that is not on disk). ``skip``
+    is the request's or job's compiled Skipped tags (#431).
    """
    if not service.is_model_loaded() or service.get_loaded_model_type() != model_type:
        service.load_model(model_type, options["use_gpu"])
@@ -117,6 +119,7 @@ def run_suggestions(service, capture_path: str, model_type: str, options: dict):
        prompt=options.get("instructions"),
        general_threshold=options.get("general_threshold"),
        character_threshold=options.get("character_threshold"),
+        skip=skip,
    )


@@ -35,6 +35,7 @@ from .media_target import media_target as _target
 from .images import _unavailable_link, _verified_title
 from .prompts import bad_request
 from .. import model_gate
+from ..tagging_defaults import SkipMatcher

 try:
    from ...database.annotations import (
@@ -640,6 +641,8 @@ class AnnotationRoutesMixin:
            owner = model_gate.new_owner("image-annotations")
            if not model_gate.try_acquire(owner):
                return model_busy_response()
+            # #431: the Skipped tags as they are when the request is accepted.
+            skip = SkipMatcher(AutotagConfig.SKIPPED_TAGS).counting()
            try:
                # From here the pin is the gate's to end: the worker ends it,
                # or ``on_skipped`` does when the worker never starts.
@@ -653,6 +656,7 @@ class AnnotationRoutesMixin:
                    capture,
                    model_type,
                    options,
+                    skip,
                    on_skipped=functools.partial(store.release_use, token),
                )
            except MissingBackendPackages as exc:
@@ -677,6 +681,8 @@ class AnnotationRoutesMixin:
                "model_type": model_type,
                "options": options,
                "suggestions": suggestion_rows(pairs),
+                # How many distinct suggestions the Skipped tags hid (#431).
+                "skipped": len(skip.hidden),
            },
            headers={"Cache-Control": "no-store"},
        )
@@ -732,10 +738,10 @@ def _byte_range(request: web.Request, size: int):
    return start, stop


-def _pinned_suggestions(store, token, service, capture, model_type, options):
+def _pinned_suggestions(store, token, service, capture, model_type, options, skip=None):
    """Worker thread: infer on the capture, then end its pin (even on error)."""
    try:
-        return run_suggestions(service, capture.path, model_type, options)
+        return run_suggestions(service, capture.path, model_type, options, skip)
    finally:
        store.release_use(token)

@@ -19,8 +19,8 @@ from .jobs import (
 )

 from .maintenance import disk_plan
-from .prompts import thumbnail_url_for
-from . import thumbnail_settings
+from .images import listing_thumbnail_url
+from . import preview_store
 from .. import model_gate

 try:
@@ -40,6 +40,12 @@ BATCH_PREVIEW_BODY_MAX = 1024
 APPLY_BODY_MAX = 64 * 1024  # POST /autotag/apply: one image and its tags
 _HEX64 = re.compile(r"[0-9a-f]{64}")
 BATCH_JOB_BODY_MAX = 32 * 1024
+# Skipped tags preview (#431): 200 entries of 50 characters, with room for JSON.
+SKIPPED_PREVIEW_BODY_MAX = 64 * 1024
+SKIPPED_PREVIEW_LEASE = "Skipped tags preview"
+SKIPPED_PREVIEW_SAMPLE = 12
+# WD14 label lists the preview found missing or unreadable (logged once each).
+_MISSING_LABEL_LISTS = set()
 REVIEW_REQUIRED = (
    "Replacing tags needs a review of each image. Use Preview tagging review, "
    "or choose Skip or Merge for a batch run."
@@ -72,6 +78,12 @@ MODEL_DOWNLOAD_BODY_MAX = 1024
 _download_titles = {}


+def _instruction_engine(model_type: str) -> str:
+    """The language-model engine whose default instructions ``model_type``
+    reads: itself, or GGUF for a WD14 engine (which takes none)."""
+    return model_type if model_type in ("gguf", "hf") else "gguf"
+
+
 def _holder_label(holder: Optional[str]) -> str:
    if not holder:
        return ANOTHER_OPERATION
@@ -247,6 +259,10 @@ class AutotagRoutesMixin:
        async def preview_autotag_batch_route(request):
            return await self.preview_autotag_batch(request)

+        @routes.post("/prompt_manager/autotag/skipped-tags/preview")
+        async def preview_skipped_tags_route(request):
+            return await self.preview_skipped_tags(request)
+
        @routes.post("/prompt_manager/autotag/start")
        async def start_autotag_route(request):
            return await self.start_autotag(request)
@@ -284,7 +300,15 @@ class AutotagRoutesMixin:
                    "success": True,
                    "models": public_models(status, loaded_type),
                    # The saved tagging defaults (#328, System › Auto-tagging).
-                    "default_prompt": AutotagConfig.TEMPLATE,
+                    # The saved engine's default instructions (GGUF for a
+                    # WD14 engine); kept one release for cached pages (#431).
+                    "default_prompt": AutotagConfig.default_instructions_text(
+                        _instruction_engine(AutotagConfig.MODEL_TYPE)
+                    ),
+                    # #431: Built-in first, with every text, and each
+                    # language-model engine's default.
+                    "instructions": AutotagConfig.all_instructions(),
+                    "default_instructions": dict(AutotagConfig.DEFAULT_INSTRUCTIONS),
                    "model_loaded": loaded,
                    "loaded_model_type": loaded_type,
                    "wd14_general_threshold": AutotagConfig.GENERAL_THRESHOLD,
@@ -424,6 +448,7 @@ class AutotagRoutesMixin:
        title = f"Tagging model download · {label}"
        _download_titles.clear()
        _download_titles[owner] = title
+        admitted = False
        try:
            job = self._jobs.start(
                MODEL_DOWNLOAD_JOB_KIND,
@@ -439,13 +464,13 @@ class AutotagRoutesMixin:
                    self._run_model_download, service, model_type, owner
                ),
            )
-        except BaseException as refused:
-            # JobBusy, or anything else the registry raised: give the gate back.
-            model_gate.release(owner)
-            _download_titles.pop(owner, None)
-            if isinstance(refused, JobBusy):
-                return None, busy_response(refused)
-            raise
+            admitted = True
+        except JobBusy as refused:
+            return None, busy_response(refused)
+        finally:
+            if not admitted:  # JobBusy, or anything else: give the gate back.
+                model_gate.release(owner)
+                _download_titles.pop(owner, None)

        def ended(_task):
            model_gate.release(owner)
@@ -538,7 +563,10 @@ class AutotagRoutesMixin:
        else:
            prompt = params.get("prompt")
            template = prompt if isinstance(prompt, str) and prompt.strip() else None
-            options = {"instructions": template or AutotagConfig.TEMPLATE}
+            options = {
+                "instructions": template
+                or AutotagConfig.default_instructions_text(model_type)
+            }
        try:
            _model, options = validate_options(
                model_type,
@@ -698,6 +726,86 @@ class AutotagRoutesMixin:
            return None, "existing must be one of " + ", ".join(EXISTING_POLICIES)
        return MODELS[model_type], None

+    async def preview_skipped_tags(self, request):
+        """Which known tags a Skipped tags list would hide (#431); no write.
+
+        ``{entries}`` is checked as a save checks it (the same 400 sentence).
+        The known tags are the library's plus the general and character names
+        of each downloaded WD14 label list; no model is loaded and no image is
+        opened. Refused (409 ``busy``) while an exclusive job runs.
+        """
+        from ..tagging_defaults import validate_skipped_tags
+
+        data, error = await self._batch_body(
+            request, ("entries",), SKIPPED_PREVIEW_BODY_MAX
+        )
+        if error is not None:
+            return error
+        try:
+            entries = validate_skipped_tags(data["entries"])
+        except ValueError as exc:
+            return web.json_response({"success": False, "error": str(exc)}, status=400)
+        try:
+            async with self._jobs.lease(SKIPPED_PREVIEW_LEASE):
+                result = await self._run_in_executor(self._skipped_preview, entries)
+        except JobBusy as busy:
+            return busy_response(busy)
+        except Exception:
+            self.logger.exception("The Skipped tags preview failed")
+            return web.json_response(
+                {"success": False, "error": _INTERNAL_ERROR}, status=500
+            )
+        return web.json_response({"success": True, **result})
+
+    def _skipped_preview(self, entries):
+        """Worker thread: the preview's counts over the known tags."""
+        from ..autotag import MODELS, get_autotag_service
+        from ..tagging_defaults import (
+            WD14_MODEL_TYPES,
+            SkipMatcher,
+            wd14_label_names,
+        )
+
+        library = self.db.get_all_tags()
+        known = {}  # case-folded -> (0 library / 1 label list, spelling)
+        for name in library:
+            known.setdefault(name.casefold(), (0, name))
+        lists = []
+        models_dir = getattr(get_autotag_service(), "models_dir", None)
+        for model_type in sorted(WD14_MODEL_TYPES, key=lambda t: MODELS[t]["name"]):
+            if models_dir is None:
+                break
+            path = Path(models_dir) / MODELS[model_type]["subdir"] / "selected_tags.csv"
+            try:
+                names = wd14_label_names(path)
+            except (OSError, ValueError) as exc:
+                if path not in _MISSING_LABEL_LISTS:  # logged once per list
+                    _MISSING_LABEL_LISTS.add(path)
+                    self.logger.debug(f"No WD14 label list for {model_type}: {exc}")
+                continue
+            _MISSING_LABEL_LISTS.discard(path)
+            lists.append(MODELS[model_type]["name"])
+            for name in names:
+                known.setdefault(name.casefold(), (1, name))
+        matchers = [(entry, SkipMatcher([entry])) for entry in entries]
+        whole = SkipMatcher(entries)
+        hidden = [item for item in known.values() if whole.matches(item[1])]
+        hidden.sort(key=lambda item: (item[0], item[1].casefold()))
+        per_entry = [
+            {
+                "entry": entry,
+                "count": sum(1 for _, name in hidden if matcher.matches(name)),
+            }
+            for entry, matcher in matchers
+        ]
+        return {
+            "count": len(hidden),
+            "sample": [name for _, name in hidden[:SKIPPED_PREVIEW_SAMPLE]],
+            "sample_limit": SKIPPED_PREVIEW_SAMPLE,
+            "per_entry": per_entry,
+            "sources": {"library": len(library), "wd14": lists},
+        }
+
    async def preview_autotag_batch(self, request):
        """Review Tag output images: counts, model, backup and disk; no write.

@@ -1001,7 +1109,10 @@ class AutotagRoutesMixin:
        else:
            prompt = data.get("prompt")
            template = prompt if isinstance(prompt, str) and prompt.strip() else None
-            options = {"instructions": template or AutotagConfig.TEMPLATE}
+            options = {
+                "instructions": template
+                or AutotagConfig.default_instructions_text(model_type)
+            }
        use_gpu = data.get("use_gpu", True)
        options["use_gpu"] = use_gpu if isinstance(use_gpu, bool) else True
        return validate_options(
@@ -1041,12 +1152,12 @@ class AutotagRoutesMixin:
                return self._bad_request('existing must be "skip" or "merge"')
            try:
                options = self._single_options(data, model_type)
+            except OptionError as error:
+                return self._bad_request(str(error))
            except (ValueError, TypeError):
                return self._bad_request(
                    "general_threshold and character_threshold must be numeric"
                )
-            except OptionError as error:
-                return self._bad_request(str(error))
            target, error = await self._select_autotag_target(data)
            if error is not None:
                return error
@@ -1095,6 +1206,8 @@ class AutotagRoutesMixin:

    async def _suggest_single(self, target, model_type, options, base):
        from ..autotag import MODELS, MissingBackendPackages, get_autotag_service
+        from ..config import AutotagConfig
+        from ..tagging_defaults import SkipMatcher
        from .annotation_suggest import model_refusal
        from .annotations import _pinned_suggestions, _settled, _submit

@@ -1111,6 +1224,8 @@ class AutotagRoutesMixin:
        owner = model_gate.new_owner("legacy-single")
        if not model_gate.try_acquire(owner):
            return model_busy_response()
+        # #431: the legacy review hides the Skipped tags too (19A).
+        skip = SkipMatcher(AutotagConfig.SKIPPED_TAGS)
        store = self._capture_store()
        try:
            epoch = await self._run_in_executor(self.db.get_execution_epoch)
@@ -1150,6 +1265,7 @@ class AutotagRoutesMixin:
                    capture,
                    model_type,
                    options,
+                    skip,
                    on_skipped=functools.partial(store.release_use, capture.token),
                )
            except MissingBackendPackages as exc:
@@ -1370,23 +1486,21 @@ class AutotagRoutesMixin:
            files = await self._run_in_executor(
                self._without_removed, output_path, files
            )
-            has_thumbnails = (output_path / "thumbnails").is_dir()
+            location = preview_store.current()
+            if location.mode == preview_store.FOLDER_MODE:
+                has_thumbnails = location.available  # no store I/O here (#320)
+            else:
+                store = preview_store.store_dir(output_path)
+                has_thumbnails = store is not None and store.is_dir()

            images = []
            for image_path in files:
                rel_path = image_path.relative_to(output_path)
                thumbnail_url = None
                if has_thumbnails:
-                    # Any preview the file owns, the current format first (#317)
-                    existing = thumbnail_settings.existing_thumbnail(
-                        output_path, rel_path
-                    )
-                    if existing is not None:
-                        thumb_rel = (
-                            thumbnail_settings.thumbnail_stem_rel(rel_path)
-                            + existing.suffix
-                        )
-                        thumbnail_url = thumbnail_url_for(thumb_rel, existing)
+                    # Any preview the file owns, the current format first
+                    # (#317); in folder mode without store I/O (#320).
+                    thumbnail_url = listing_thumbnail_url(output_path, rel_path)
                images.append(
                    {
                        "filename": image_path.name,
@@ -971,6 +971,7 @@ class BackupRestoreRoutesMixin:
        line = restored_line(staged.summary)
        job.log_line(line)
        job.update(progress=100, status_line=line)
+        return None


 async def _outlive_cancel(future):
@@ -65,6 +65,7 @@ from .duplicate_review import (  # noqa: F401 (CHANGED, OUTSIDE_SOURCE: public)
    NOT_ATTEMPTED,
    OUTSIDE_SOURCE,
    RECORDS_FAILED,
+    REVIEW_KEPT_DETAILS,
    ROW_DETAILS,
    SAME_FILE,
    SOURCES_CHANGED,
@@ -434,6 +435,7 @@ class DuplicateFilesMixin:
            {
                "targets": review["targets"],
                "kept": review["kept"],
+                "held": review["held"],
                "protected": review["public"]["protected"]["count"],
            },
        )
@@ -446,7 +448,7 @@ class DuplicateFilesMixin:
        job hashes each file again right before it unlinks it.
        """
        listed = self._listed_sources()
-        targets, kept, protected = [], [], {}
+        targets, kept, protected, held = [], [], {}, []
        for group, keepers in selection.values():
            removals = [r for r in group["files"] if r not in keepers]
            for record in removals:
@@ -467,6 +469,7 @@ class DuplicateFilesMixin:
                    problem = _bound_problem(record, group, keeper)
                if problem:
                    protected[problem] = protected.get(problem, 0) + 1
+                    held.append(self._copy_row(record, REVIEW_KEPT_DETAILS[problem]))
                    continue
                reviewed.append(self._target(group, record, keeper))
            if reviewed:
@@ -488,6 +491,7 @@ class DuplicateFilesMixin:
        return {
            "targets": targets,
            "kept": kept,
+            "held": held,
            "fingerprint": _fingerprint(targets),
            "public": _public_plan(targets, protected, records),
        }
@@ -574,15 +578,23 @@ class DuplicateFilesMixin:
            return _fail_job(job, "sources-changed", SOURCES_CHANGED)
        ok, backup = await self._safety_backup_step(job, db, backup_on)
        if not ok:
-            return
+            return None
        try:
            await self._remove_duplicates(job, db, plan, backup)
        finally:
            if backup:
                await self._prune_backup_pool(job, db)
+        return None

    async def _remove_duplicates(self, job, db, plan, backup):
        targets = plan.payload["targets"]
+        # #586: every copy the review protected, with its reason, and the
+        # whole group in the report.
+        held = plan.payload["held"]
+        job.record_counted("kept", len(held), held, complete=True)
+        if held:
+            copies = _plural(len(held), "copy", "copies")
+            job.log_line(f"Kept {copies} the review protected")
        for row in plan.payload["kept"]:
            job.record("kept", row, f"= {row['root']}/{row['path']} · {KEPT_COPY}")
        job.update(total=len(targets), status_line="Removing duplicate files")
@@ -70,6 +70,18 @@ PROTECTED_REASONS = {
        "files kept: their kept copy changed or is gone",
    ),
 }
+# The job's row for a copy the review protected (#586): the review's reason.
+REVIEW_KEPT_DETAILS = {
+    MAYBE_SAME: "Kept: may be the same file reached through another mount or share",
+    NO_FILE_ID: "Kept: can't confirm this is a separate file on this drive",
+    SAME: "Kept: the same file as its kept copy",
+    OUTSIDE_SOURCE: "Kept: not inside a configured source",
+    LINK: "Kept: a link, not a regular file",
+    CHANGED_CONTENT: "Kept: changed since the search",
+    GONE: "Kept: no longer exists",
+    UNREADABLE: "Kept: could not be read",
+    KEEPER: "Kept: its kept copy changed or is gone",
+}
 # Job outcome rows (never an OS error text).
 CHANGED = "The file changed since the review; it was kept."
 KEEPER_CHANGED = "The kept copy changed or is gone; this file was kept."
@@ -27,7 +27,7 @@ def _identity(path):
    except OSError:
        return None
    if info.st_ino:
-        return ("inode", info.st_dev, info.st_ino)
+        return ("inode", (info.st_dev, info.st_ino))
    return ("path", os.path.normcase(os.path.realpath(str(path))))


@@ -843,7 +843,10 @@ class HistoryRoutesMixin:
                raise

        async def execute():
-            pending = asyncio.create_task(self._run_in_executor(project))
+            # An inspection reads the file's header and text: the
+            # interactive image pool (#523); media stays on the default.
+            run = self._run_image if kind == "inspection" else self._run_in_executor
+            pending = asyncio.create_task(run(project))
            try:
                return await asyncio.shield(pending)
            except asyncio.CancelledError:
@@ -15,10 +15,10 @@ from typing import BinaryIO

 from aiohttp import web

-from . import thumbnail_settings
+from . import preview_store, thumbnail_settings
 from .images import _canonical, _public_path, SERVABLE_EXTENSIONS, VIDEO_EXTENSIONS
 from .images import in_trash_below_roots
-from .images import existing_media_thumbnail, media_thumbnail_rel
+from .images import existing_media_thumbnail, media_preview_path

 try:
    from ...utils.execution_outputs import (
@@ -244,19 +244,36 @@ def resolve_current_candidate(
        return _unavailable("temporary_unavailable", error=True)


+def _target_authorized(target, namespace, scope, store_root=None) -> bool:
+    """A preview in the thumbnail folder (#320, folder mode) is authorized by
+    the store of its source (``preview_store.owns``: inside the key folder,
+    no link); everything else by the output namespace and the roots."""
+    if (
+        store_root is not None
+        and preview_store.current().mode == preview_store.FOLDER_MODE
+    ):
+        return preview_store.owns(store_root, target)
+    return _authorized(target, namespace, scope)
+
+
 def _open_current_target(
-    target: Path, namespace: Path, scope: CurrentOutputScope, preview: bool = False
+    target: Path,
+    namespace: Path,
+    scope: CurrentOutputScope,
+    preview: bool = False,
+    store_root: Path | None = None,
 ) -> BinaryIO:
    """Open only the canonical target and verify authority against the actual handle.

-    A *preview* (a file under ``thumbnails/``) may also be JPEG XL (#317)."""
+    A *preview* (a file under ``thumbnails/``) may also be JPEG XL (#317); in
+    folder mode it is authorized by the store of *store_root* (#320)."""
    if _canonical(target) != target:
        raise CurrentLocationUnavailable("not_authorized", stale=True)
    if in_trash_below_roots(target, [namespace]):
        # Also at the open: the cover chooses its preview after the candidate
        # check, and a preview can be a link into a trash folder (#543).
        raise CurrentLocationUnavailable("missing")
-    if not _authorized(target, namespace, scope):
+    if not _target_authorized(target, namespace, scope, store_root):
        raise CurrentLocationUnavailable("not_authorized")
    suffix = target.suffix.lower()
    if suffix not in SERVABLE_EXTENSIONS and not (
@@ -289,7 +306,7 @@ def _open_current_target(
        if (
            _canonical(target) != target
            or (observed.st_dev, observed.st_ino) != (current.st_dev, current.st_ino)
-            or not _authorized(target, namespace, scope)
+            or not _target_authorized(target, namespace, scope, store_root)
        ):
            raise CurrentLocationUnavailable("not_authorized", stale=True)
        return os.fdopen(fd, "rb")
@@ -326,12 +343,10 @@ class _OpenedCurrentMedia:


 def _preview_writable(root: Path, preview: Path) -> bool:
-    """A preview may be written: ``thumbnails`` and every link segment of the
-    preview's folder resolve inside *root* (the serve route's rule, #249)."""
-    folder = root / "thumbnails"
-    return _canonical(folder).is_relative_to(_canonical(root)) and _canonical(
-        preview
-    ).is_relative_to(_canonical(folder))
+    """A preview may be written: the store of *root* and every link segment
+    of the preview's folder resolve inside it (the serve route's rule, #249;
+    ``preview_store.owns``)."""
+    return preview_store.owns(root, preview)


 def _is_jxl(path) -> bool:
@@ -381,8 +396,12 @@ def _cover_target(resolved, ensure_preview, placeholder, accepts_jxl):
        return _canonical(preview)
    if preview is not None:
        return _canonical(preview)
-    preview = resolved.gallery_root / media_thumbnail_rel(relative)
-    if ensure_preview is not None and _preview_writable(resolved.gallery_root, preview):
+    preview = media_preview_path(resolved.gallery_root, relative, create=True)
+    if (
+        ensure_preview is not None
+        and preview is not None
+        and _preview_writable(resolved.gallery_root, preview)
+    ):
        ensure_preview(target, preview, is_video)
    if is_video and placeholder is not None:
        return _placeholder_media(placeholder)
@@ -418,7 +437,13 @@ def _prepare_current_media(
            return chosen
        if chosen is not None:
            target, is_preview = chosen, True
-    handle = _open_current_target(target, resolved.namespace, scope, is_preview)
+    handle = _open_current_target(
+        target,
+        resolved.namespace,
+        scope,
+        is_preview,
+        resolved.gallery_root if is_preview else None,
+    )
    try:
        return _OpenedCurrentMedia(
            handle,
@@ -330,12 +330,13 @@ class ImageDeleteMixin:
            return _fail_job(job, "sources-changed", SOURCES_CHANGED)
        ok, backup = await self._safety_backup_step(job, db, backup_on)
        if not ok:
-            return
+            return None
        try:
            await self._delete_images(job, db, targets, mode, backup)
        finally:
            if backup:
                await self._prune_backup_pool(job, db)
+        return None

    async def _delete_images(self, job, db, targets, mode, backup):
        job.update(total=len(targets), status_line=TITLES[mode])
@@ -39,6 +39,7 @@ from typing import NamedTuple
 from aiohttp import web

 from .. import model_gate
+from ..tagging_defaults import SkipMatcher
 from .admin import _plural, _time_left
 from .annotation_suggest import (
    OptionError,
@@ -170,6 +171,8 @@ class _Run:
    owner: object
    service: object = None
    roots: dict = field(default_factory=dict)
+    # The job's Skipped tags, compiled once at its start (#431).
+    skip: object = None


@dataclass(frozen=True)
@@ -183,6 +186,9 @@ class _Spec:
    options: dict | None = None
    # A listing filter the start resolves into ``targets`` (#392).
    filter: dict | None = None
+    # The Skipped tags when the job was requested (#431); a later save does
+    # not change a running job.
+    skip: tuple = ()

    @property
    def title(self) -> str:
@@ -238,7 +244,11 @@ def _parse_auto(targets, data):
        )
    except OptionError as exc:
        return None, bad_request(str(exc))
-    return _Spec("auto", targets, model_type=model_type, options=options), None
+    skip = tuple(AutotagConfig.SKIPPED_TAGS)
+    return (
+        _Spec("auto", targets, model_type=model_type, options=options, skip=skip),
+        None,
+    )


 def parse_image_tag_request(data: dict):
@@ -329,6 +339,8 @@ class AutotagRun:
    keep_in_memory: bool
    backup_on: bool
    owner: object
+    # The Skipped tags when the job was started (#431).
+    skip: tuple = ()


@dataclass(frozen=True)
@@ -400,6 +412,14 @@ def _load_model(service, model_type: str, use_gpu: bool) -> None:
        raise RuntimeError(f"{model_type} could not be loaded")


+def _skipped_tags_line(entries: tuple) -> str:
+    """The job log's one line about the Skipped tags it runs with (#431)."""
+    if not entries:
+        return "Skipped tags: none"
+    count = len(entries)
+    return f"Skipped tags: {count} {'entry' if count == 1 else 'entries'}"
+
+
 def _refusal(status: int, code: str, message: str) -> Refusal:
    response = web.json_response(
        {"success": False, "code": code, "error": message}, status=status
@@ -507,6 +527,7 @@ class ImageTagJobsMixin:
        released when the task ends, also before its runner ever starts.
        """
        from ..autotag import MODELS, get_autotag_service
+        from ..config import AutotagConfig

        backup_on = self._safety_backup_policy() == "on"
        status = await self._run_in_executor(get_autotag_service().get_models_status)
@@ -529,8 +550,15 @@ class ImageTagJobsMixin:
            response = model_busy_response()
            return None, Refusal(409, "model-busy", MODEL_BUSY_ERROR, response)
        run = AutotagRun(
-            model_type, existing, options, keep_in_memory, backup_on, owner
+            model_type,
+            existing,
+            options,
+            keep_in_memory,
+            backup_on,
+            owner,
+            skip=tuple(AutotagConfig.SKIPPED_TAGS),
        )
+        admitted = False
        try:
            job = self._jobs.start(
                AUTOTAG_BATCH_JOB_KIND,
@@ -541,11 +569,12 @@ class ImageTagJobsMixin:
                groups=AUTOTAG_GROUP_NAMES,
                runner=functools.partial(self._run_autotag_batch, run),
            )
-        except BaseException as refused:
-            model_gate.release(owner)
-            if isinstance(refused, JobBusy):
-                return None, _busy_refusal(refused)
-            raise
+            admitted = True
+        except JobBusy as refused:
+            return None, _busy_refusal(refused)
+        finally:
+            if not admitted:
+                model_gate.release(owner)
        job.task.add_done_callback(lambda _task: model_gate.release(owner))
        return job, None

@@ -596,7 +625,9 @@ class ImageTagJobsMixin:
            return _batch_cancelled(job)
        job.publish({"type": "phase", "phase": "model"})
        job.update(status_line="Loading the tagging model")
-        spec = _Spec("auto", (), model_type=run.model_type, options=run.options)
+        spec = _Spec(
+            "auto", (), model_type=run.model_type, options=run.options, skip=run.skip
+        )
        service = await self._prepare_tagging_model(job, spec, run.owner)
        if service is None:
            return "failed"
@@ -622,6 +653,7 @@ class ImageTagJobsMixin:
            f"Tagging started · {job.scope.get('label') or run.model_type} · "
            f"{_plural(total, 'image')} · {policy}"
        )
+        job.log_line(_skipped_tags_line(spec.skip))
        if job.cancelled:
            return _batch_cancelled(job)
        remaining = await self._autotag_prepass(job, targets, run.existing == "skip")
@@ -631,7 +663,9 @@ class ImageTagJobsMixin:
        spec = dataclasses.replace(
            spec, targets=tuple(item.target for item in remaining)
        )
-        loop_run = _Run(job, spec, epoch, run.owner, service)
+        loop_run = _Run(
+            job, spec, epoch, run.owner, service, skip=SkipMatcher(spec.skip)
+        )
        if not await self._tag_each_file(loop_run, done_before=done):
            job.update(status_line=STORAGE_RESTORED)
            job.log_line(f"Tagging stopped · {STORAGE_RESTORED}")
@@ -737,6 +771,9 @@ class ImageTagJobsMixin:
            started += f" · {spec.model_type}"
        job.log_line(started)
        run = _Run(job, spec, epoch, owner)
+        if spec.mode == "auto":
+            job.log_line(_skipped_tags_line(spec.skip))
+            run.skip = SkipMatcher(spec.skip)
        try:
            if spec.mode == "auto":
                run.service = await self._prepare_tagging_model(job, spec, owner)
@@ -892,6 +929,7 @@ class ImageTagJobsMixin:
                capture,
                spec.model_type,
                spec.options,
+                run.skip,
                on_skipped=functools.partial(store.release_use, capture.token),
            )
        except Exception:
@@ -34,15 +34,14 @@ from .gallery_listing import (
    WalkOutcome,
    walk_root,
 )
-from . import thumbnail_settings
+from . import preview_store, thumbnail_settings
+from .thumbnail_location import location_refusal
 from .thumbnail_encode import (
    PREVIEW_HELD,
    EncoderClosed,
    PreviewWriteHeld,
-    replace_unless_held,
    run_encoder,
    sweep_stray_temps,
-    temp_sibling,
    thumbnail_frame,
    writer_settings,
    write_thumbnail,
@@ -339,11 +338,6 @@ def _thumbnail_batch_size(workers):
    return max(4, workers * 2)


-# Preview files are written by thumbnail_encode in the configured format
-# (thumbnail_settings, #317); these names stay importable from here.
-_temp_sibling = temp_sibling
-_replace_unless_held = replace_unless_held
-
 # A preview that could not be replaced (#249 S5 M6). Windows refuses to rename
 # over a file another process has open (WinError 5 or 32), such as a preview
 # the gallery is serving; the old preview stays and the file counts as an error.
@@ -396,6 +390,7 @@ def _video_placeholder_image(thumbnail_size):
            font=font,
        )
    except (OSError, AttributeError):
+        # a placeholder without its label still works
        pass
    return img

@@ -499,6 +494,7 @@ def _preview_names(folders, folder):
                    except OSError:
                        continue
        except OSError:
+            # an unreadable folder lists as empty; nothing there to cache
            pass
        folders[folder] = names
    return names
@@ -1073,13 +1069,24 @@ def _iter_media_files(output_path, max_files):


 def media_thumbnail_rel(rel_path, settings=None):
-    """``thumbnails/<rel>_thumb<ext>`` (POSIX) for the media file *rel_path*:
-    the name the preview gets when it is written now (#317), images and
-    videos alike (``writer_settings``' extension)."""
+    """``thumbnails/<rel>_thumb<ext>`` (POSIX URL text) for the media file
+    *rel_path*: the name the preview gets when it is written now (#317),
+    images and videos alike (``writer_settings``' extension). Where it is on
+    disk is ``media_preview_path``."""
    settings = settings or writer_settings()
    return thumbnail_settings.thumbnail_rel(rel_path, settings.extension)


+def media_preview_path(output_path, rel_path, settings=None, *, create=False):
+    """Where the preview of *rel_path* is written now (``preview_store``);
+    *create* for a writer (a new source gets its key). None when nothing
+    may be written (the thumbnail folder is unavailable)."""
+    settings = settings or writer_settings()
+    return preview_store.preview_path(
+        output_path, rel_path, settings.extension, create=create
+    )
+
+
 def existing_media_thumbnail(output_path, rel_path):
    """The existing preview *rel_path* owns that a listing or cover shows
    (the format written now first, then older ones), or None. The Images
@@ -1089,6 +1096,27 @@ def existing_media_thumbnail(output_path, rel_path):
    )


+def listing_thumbnail_url(output_path, rel_path):
+    """The thumbnail URL of an older listing (``_enrich_images``, the
+    auto-tag scan), or None. These run on the event loop: in folder mode
+    (#320) the store is never touched there, so the URL names the preview
+    as it is written now and the serve route finds or makes it off the loop
+    (None while the thumbnail folder is unavailable)."""
+    from .prompts import thumbnail_url_for
+
+    location = preview_store.current()
+    if location.mode == preview_store.FOLDER_MODE:
+        if not location.available:
+            return None
+        quoted = urllib.parse.quote(media_thumbnail_rel(rel_path), safe="/")
+        return f"/prompt_manager/images/serve/{quoted}"
+    existing = thumbnail_settings.existing_thumbnail(output_path, rel_path)
+    if existing is None:
+        return None
+    thumb_rel = thumbnail_settings.thumbnail_stem_rel(rel_path) + existing.suffix
+    return thumbnail_url_for(thumb_rel, existing)
+
+
 def media_thumbnail(output_path, rel_path, root_index, *, root_scope=None):
    """``(thumbnail_url, ready)`` for *rel_path* under *output_path* (a few
    blocking stats). The Images listing, the Needs review queue cards and the
@@ -2803,13 +2831,56 @@ class ImageRoutesMixin:
                    output_dirs[0], filepath, int(root_param), len(outputs)
                )

+            # Preview text is mapped by the resolver (#320); any other text,
+            # ``Thumbnails/...`` media on a case-sensitive disk included,
+            # keeps the plain join.
+            preview_parts = (
+                tuple(filepath.split("/"))
+                if preview_store.is_preview_text(filepath)
+                else None
+            )
+            location = preview_store.current()
+            if location.mode == preview_store.FOLDER_MODE:
+                if preview_parts is None and await self._run_image(
+                    self._in_source_thumbnails, output_dirs, filepath
+                ):
+                    # Previews live in the thumbnail folder: anything else
+                    # under a source's thumbnails/ is a leftover (#320), in
+                    # any case on a case-insensitive disk.
+                    return _forbidden()
+                if preview_parts is not None:
+                    # Store I/O never runs on the event loop (a share may
+                    # stall): the lookup runs on the image pool.
+                    found = await self._run_image(
+                        self._find_preview, output_dirs, preview_parts, location
+                    )
+                    if found == "forbidden":
+                        return _forbidden()
+                    if found is not None:
+                        return self._file_response(found)
            for output_path in output_dirs:
-                image_path = output_path / filepath
+                if (
+                    preview_parts is not None
+                    and location.mode == preview_store.FOLDER_MODE
+                ):
+                    break  # looked up above
+                if preview_parts is None:
+                    image_path = output_path / filepath
+                else:
+                    image_path = preview_store.request_path(output_path, preview_parts)
+                    if image_path is None:
+                        continue
                if not image_path.exists():
                    continue
-                # A symlink that points outside the root is a hard deny, not
-                # a fall-through to the next root.
-                if not _is_within(image_path, output_path):
+                # A symlink that points outside the root (a preview: outside
+                # the folder holding its store) is a hard deny, not a
+                # fall-through to the next root.
+                container = (
+                    output_path
+                    if preview_parts is None
+                    else preview_store.store_container(output_path)
+                )
+                if not _is_within(image_path, container):
                    return _forbidden()
                if in_trash_below_roots(image_path, output_dirs):
                    return _file_not_found()
@@ -2835,6 +2906,48 @@ class ImageRoutesMixin:
                {"success": False, "error": _safe_error(e)}, status=500
            )

+    @staticmethod
+    def _in_source_thumbnails(output_dirs, filepath):
+        """Whether *filepath* lies in a source's ``thumbnails`` folder: its
+        first part is ``thumbnails`` exactly, or another case of it that is
+        the same folder (a case-insensitive disk). ``Thumbnails/`` media on
+        a case-sensitive disk is another folder and stays served."""
+        first = filepath.split("/", 1)[0]
+        if first == "thumbnails":
+            return True
+        if first.casefold() != "thumbnails":
+            return False
+        for output_path in output_dirs:
+            spelled = output_path / first
+            cache = preview_store.source_folder(output_path)
+            try:
+                if spelled.is_dir() and cache.is_dir() and spelled.samefile(cache):
+                    return True
+            except OSError:
+                continue
+        return False
+
+    @staticmethod
+    def _find_preview(output_dirs, parts, location):
+        """The preview file *parts* names in folder mode, ``"forbidden"``
+        (it resolves out of its store or through a link) or None (blocking;
+        the first root whose store holds it, in ``_select_root`` order)."""
+        for output_path in output_dirs:
+            image_path = preview_store.request_path(output_path, parts, location)
+            if image_path is None:
+                continue
+            try:
+                with preview_store.store_io():
+                    if not os.path.lexists(image_path):
+                        continue
+                    if not preview_store.owns(output_path, image_path, location):
+                        return "forbidden"
+                    if image_path.is_file():
+                        return image_path
+            except OSError:
+                return None
+        return None
+
    def _is_recorded_media(self, path) -> bool:
        """Whether the database records ``path`` as a linked image.

@@ -2961,6 +3074,9 @@ class ImageRoutesMixin:
        data, error = await _json_body_or_error(request)
        if error is not None:
            return error
+        refused = location_refusal()
+        if refused is not None:
+            return refused
        return await self._run_held(
            THUMBNAILS_JOB_KIND,
            THUMBNAIL_GENERATION_TITLE,
@@ -2980,6 +3096,7 @@ class ImageRoutesMixin:
            result = await self._run_in_executor(
                self._generate_gallery_thumbnails_sync, output_dirs
            )
+            await self._release_job_memory()
            return web.json_response(result)

        except Exception as e:
@@ -2992,6 +3109,7 @@ class ImageRoutesMixin:
        """Blocking thumbnail generation loop (run in executor)."""
        settings = writer_settings(settings)
        start = _time.monotonic()
+        thumbnails_dir = preview_store.given_store(output_path, thumbnails_dir)
        plan = self._plan_thumbnails(output_path, thumbnails_dir, settings=settings)
        payload = self._execute_thumbnail_plan(plan, settings, start)
        payload["thumbnails_path"] = _public_path(thumbnails_dir)
@@ -3004,7 +3122,8 @@ class ImageRoutesMixin:
        start = _time.monotonic()
        plan = self._plan_gallery_thumbnails(output_dirs, settings=settings)
        payload = self._execute_thumbnail_plan(plan, settings, start)
-        payload["thumbnails_path"] = _public_path(output_dirs[0] / "thumbnails")
+        store = preview_store.store_dir(output_dirs[0])
+        payload["thumbnails_path"] = None if store is None else _public_path(store)
        return payload

    def _execute_thumbnail_plan(self, plan: dict, settings, start: float) -> dict:
@@ -3047,9 +3166,12 @@ class ImageRoutesMixin:
            if stop is not None and stop():
                break
            root = Path(root)
+            store = preview_store.ensure_store(root)
+            if store is None:
+                continue  # the thumbnail folder is unavailable
            plan = self._plan_thumbnails(
                root,
-                root / "thumbnails",
+                store,
                mode=mode,
                stop=stop,
                settings=settings,
@@ -3088,6 +3210,8 @@ class ImageRoutesMixin:
                    "format": writer_settings().format,
                    # Files whose automatic preview failed this session (#249).
                    "failed": self._auto_thumbnail_failures(),
+                    # #320: where previews live (no path here, D6A).
+                    "location": self._thumbnail_location_payload(with_path=False),
                    "collection_id": hashlib.sha256(collection.encode()).hexdigest()[
                        :16
                    ],
@@ -3133,9 +3257,11 @@ class ImageRoutesMixin:
        """
        settings = writer_settings(settings)
        output_path = Path(output_path)
-        thumbnails_dir = Path(thumbnails_dir)
+        thumbnails_dir = preview_store.given_store(output_path, thumbnails_dir)
        plan = {key: 0 for key in _PLAN_COUNTS}
        plan.update(targets=[], fresh_files=[])
+        if thumbnails_dir is None:
+            return plan  # the thumbnail folder is unavailable
        folders = {}
        removed = self._removal_check_under(output_path)
        for src in _iter_media_files(output_path, MAX_GALLERY_FILES):
@@ -3225,6 +3351,9 @@ class ImageRoutesMixin:
            "dir": src.parent.name,
            "type": "video" if is_video else "image",
        }
+        # Taken when the write starts: a thumbnail location switched since
+        # then drops the write at its rename (#320).
+        guard = preview_store.write_guard(guard)
        dst = Path(dst)
        if dst.suffix != settings.extension:
            dst = dst.with_suffix(settings.extension)
@@ -3235,7 +3364,7 @@ class ImageRoutesMixin:
                return {**result, "action": "error", "error": "File no longer exists"}
            if not rebuild and _thumbnail_is_fresh(src, dst):
                return {**result, "action": "skipped", "path": str(dst)}
-            dst.parent.mkdir(parents=True, exist_ok=True)
+            preview_store.make_parent(dst)
            if is_video:
                made = self._generate_video_thumbnail(
                    src,
@@ -3440,8 +3569,12 @@ class ImageRoutesMixin:

        Invalid thumbnail directories return 400; unavailable gallery roots
        return 404, and unexpected filesystem failures return 500. Holds the
-        registry as guarded work, like generation.
+        registry as guarded work, like generation. Refused (409) while the
+        thumbnail folder is unavailable (#320).
        """
+        refused = location_refusal()
+        if refused is not None:
+            return refused
        return await self._run_held(
            THUMBNAILS_JOB_KIND,
            THUMBNAIL_CLEAR_TITLE,
@@ -3505,8 +3638,12 @@ class ImageRoutesMixin:
            self.logger.debug(f"No roots to sweep for preview temp files: {exc}")
            return 0
        for output_path in output_dirs:
-            folder = Path(output_path) / "thumbnails"
-            if folder.is_symlink() or not folder.is_dir():
+            folder = preview_store.store_dir(output_path)
+            if (
+                folder is None
+                or preview_store.store_is_link(folder)
+                or not folder.is_dir()
+            ):
                continue
            removed += sweep_stray_temps(folder)[0]
        if removed:
@@ -3524,13 +3661,16 @@ class ImageRoutesMixin:
        directories = []
        for output_path in output_dirs:
            output_path = Path(output_path)
-            thumbnails_dir = output_path / "thumbnails"
+            thumbnails_dir = preview_store.store_dir(output_path)
+            if thumbnails_dir is None:
+                continue
            if not thumbnails_dir.exists() and not thumbnails_dir.is_symlink():
                continue
+            container = preview_store.store_container(output_path)
            if (
-                thumbnails_dir.is_symlink()
-                or not _is_within(thumbnails_dir, output_path)
-                or _canonical(thumbnails_dir) == _canonical(output_path)
+                preview_store.store_is_link(thumbnails_dir)
+                or not _is_within(thumbnails_dir, container)
+                or _canonical(thumbnails_dir) == _canonical(container)
            ):
                raise ValueError(
                    "Safety check failed: invalid thumbnails directory path"
@@ -3545,7 +3685,15 @@ class ImageRoutesMixin:
            temps, temp_bytes = sweep_stray_temps(thumbnails_dir, min_age=0)
            cleared_count += temps
            cleared_size += temp_bytes
-            for root, _dirs, files in os.walk(thumbnails_dir):
+            folder_mode = preview_store.current().mode == preview_store.FOLDER_MODE
+            for root, dirs, files in os.walk(thumbnails_dir):
+                if folder_mode:
+                    # Never into a junction or reparse point (#320).
+                    dirs[:] = [
+                        d
+                        for d in dirs
+                        if not preview_store.store_is_link(Path(root) / d)
+                    ]
                for name in files:
                    path = Path(root) / name
                    if (
@@ -3553,6 +3701,7 @@ class ImageRoutesMixin:
                        or path.suffix.lower()
                        not in thumbnail_settings.THUMBNAIL_EXTENSIONS
                        or path.is_symlink()
+                        or not preview_store.may_write(path)
                    ):
                        continue
                    try:
@@ -4002,7 +4151,8 @@ class ImageRoutesMixin:
                    **observed,
                )

-            body = await self._run_in_executor(inspect)
+            # Header and text reads: the interactive image pool (#523).
+            body = await self._run_image(inspect)
            if body is None:
                return web.json_response(
                    {
@@ -4215,6 +4365,22 @@ class ImageRoutesMixin:
        # (which Windows refuses on open files) is not held up by it.
        return _CardFacts(width, height, *self._card_parse(path, records))

+    def _cached_card_facts(self, entry: tuple) -> _CardFacts | None:
+        path, mtime, root, index = entry[:4]
+        return self._workspace_card_cache.get((index, str(root)), {}).get((path, mtime))
+
+    def _card_facts_of(self, entries: list, *, parse: bool) -> list[_CardFacts]:
+        """Card facts of *entries*, in order; files not cached yet are read on
+        the interactive image pool (#523), cached ones answer here."""
+        found = [self._cached_card_facts(entry) for entry in entries]
+        missing = [i for i, facts in enumerate(found) if facts is None]
+        read = self._map_image(
+            lambda i: self._card_facts(entries[i], parse=parse), missing
+        )
+        for i, facts in zip(missing, read):
+            found[i] = facts
+        return found
+
    def _card_facts(self, entry: tuple, *, parse: bool) -> _CardFacts:
        """One listed image's card facts, read once per ``(path, mtime)``.

@@ -4223,11 +4389,11 @@ class ImageRoutesMixin:
        and drops the rest, and a roots change drops them all. Only files of
        the current scan are stored, so the cache is bounded by the listing.
        """
-        path, mtime, root, index = entry[:4]
-        root_key, key = (index, str(root)), (path, mtime)
-        cached = self._workspace_card_cache.get(root_key, {}).get(key)
+        cached = self._cached_card_facts(entry)
        if cached is not None:
            return cached
+        path, mtime, root, index = entry[:4]
+        root_key, key = (index, str(root)), (path, mtime)
        facts = self._read_card_facts(path, parse=parse)
        if facts is None:
            # Not stored: a locked or half-written file may read next time.
@@ -4253,15 +4419,17 @@ class ImageRoutesMixin:
            if linked
            else {}
        )
+        # Videos: the card reads no video metadata. Library previews show
+        # no card facts, so they skip the parse (``parse=linked``).
+        stills = [image for image in images if not image["is_video"]]
+        read = self._card_facts_of(
+            [entries[(image["root_index"], image["path"])] for image in stills],
+            parse=linked,
+        )
+        facts_of = {id(image): facts for image, facts in zip(stills, read)}
        for image in images:
            entry = entries[(image["root_index"], image["path"])]
-            # Videos: the card reads no video metadata. Library previews show
-            # no card facts, so they skip the parse (``parse=linked``).
-            facts = (
-                _NO_CARD_FACTS
-                if image["is_video"]
-                else self._card_facts(entry, parse=linked)
-            )
+            facts = facts_of.get(id(image), _NO_CARD_FACTS)
            image["width"], image["height"] = facts.width, facts.height
            if not linked:
                continue
@@ -250,7 +250,7 @@ class JobRoutesMixin:
        try:
            await response.write(_summary_event(job))
            async with contextlib.aclosing(job.events()) as events:
-                async for _payload in events:
+                async for _ in events:
                    await response.write(_summary_event(job))
            # The last event is published before the job takes its final state.
            await response.write(_summary_event(job))
@@ -204,6 +204,8 @@ class Job:
        self.total = 0
        self.counters = dict.fromkeys(groups, 0)
        self.outcomes = {group: [] for group in groups}
+        # Groups whose report lists every row, beyond MAX_OUTCOME_ROWS (#550).
+        self.complete = {}
        self.log = []
        self._cancel_requested = False
        self.last_event = None
@@ -286,42 +288,48 @@ class Job:
        index = row.get("root_index")
        if isinstance(index, bool) or not isinstance(index, int) or index < 0:
            index = None
+        shaped = {
+            "path": path,
+            "root": str(row.get("root") or ""),
+            "root_index": index,
+            "detail": str(row.get("detail") or ""),
+        }
+        if group in self.complete:  # a group kept whole for the report (#586)
+            self.complete[group].append(dict(shaped))
        if len(rows) < MAX_OUTCOME_ROWS:
-            rows.append(
-                {
-                    "path": path,
-                    "root": str(row.get("root") or ""),
-                    "root_index": index,
-                    "detail": str(row.get("detail") or ""),
-                }
-            )
+            rows.append(shaped)
        self.log_line(log_line)

-    def record_counted(self, group, count, rows=()):
+    def record_counted(self, group, count, rows=(), *, complete=False):
        """Count ``count`` outcomes in ``group`` at once, listing ``rows``.

        For outcomes that need no log line each (a thumbnail job's already
        fresh previews): the counter is exact, ``rows`` (``record``'s row
        shape) are listed up to MAX_OUTCOME_ROWS, and nothing is logged.
+        ``complete`` also keeps every row for the report (#550: a record of
+        each change that must not be cut short; the caller bounds it).
        """
        if group not in self.counters:
            raise ValueError(f"Unknown outcome group {group!r} for {self.kind}")
        self.counters[group] += max(0, int(count))
        listed = self.outcomes[group]
+        kept = self.complete.setdefault(group, []) if complete else None
        for row in rows:
-            if len(listed) >= MAX_OUTCOME_ROWS:
+            if kept is None and len(listed) >= MAX_OUTCOME_ROWS:
                break
            index = row.get("root_index")
            if isinstance(index, bool) or not isinstance(index, int) or index < 0:
                index = None
-            listed.append(
-                {
-                    "path": _relative_path(row.get("path")),
-                    "root": str(row.get("root") or ""),
-                    "root_index": index,
-                    "detail": str(row.get("detail") or ""),
-                }
-            )
+            shaped = {
+                "path": _relative_path(row.get("path")),
+                "root": str(row.get("root") or ""),
+                "root_index": index,
+                "detail": str(row.get("detail") or ""),
+            }
+            if kept is not None:
+                kept.append(shaped)
+            if len(listed) < MAX_OUTCOME_ROWS:
+                listed.append(dict(shaped))

    def finish(self, state="finished"):
        """End the job in ``state`` and release every subscriber.
@@ -406,8 +414,9 @@ class Job:
        """The downloadable report: the summary, every outcome group and the log.

        Each group carries its exact count, its listed rows (at most
-        MAX_OUTCOME_ROWS) and whether the list is cut short. Rows and log lines
-        already hold root-relative paths only.
+        MAX_OUTCOME_ROWS, or every row of a ``complete`` group) and whether
+        the list is cut short. Rows and log lines already hold root-relative
+        paths only.
        """
        summary = self.summary()
        summary.pop("listed", None)
@@ -417,16 +426,21 @@ class Job:
            "generated_at": self._clock(),
            "job": summary,
            "outcomes": {
-                group: {
-                    "count": self.counters.get(group, len(rows)),
-                    "rows": [dict(row) for row in rows],
-                    "truncated": self.counters.get(group, len(rows)) > len(rows),
-                }
+                group: self._report_group(group, rows)
                for group, rows in self.outcomes.items()
            },
            "log": list(self.log),
        }

+    def _report_group(self, group, listed):
+        rows = self.complete.get(group, listed)
+        count = self.counters.get(group, len(rows))
+        return {
+            "count": count,
+            "rows": [dict(row) for row in rows],
+            "truncated": count > len(rows),
+        }
+
    def report_filename(self):
        """The download name: prompt-manager-KIND-YYYYMMDD-HHMM.json (local time)."""
        stamp = time.strftime("%Y%m%d-%H%M", time.localtime(self._clock()))
@@ -50,6 +50,7 @@ _REFUSAL_STATUS = {
    "not-movable": 400,
    "same-folder": 400,
    "target-invalid": 400,
+    "data-dir-served": 400,
    "target-has-library": 409,
    "target-conflict": 409,
    "insufficient-space": 507,
@@ -74,6 +75,24 @@ def _failure(message, status, code):
    )


+def _thumbnail_folder():
+    """The thumbnail folder in use, or None (previews inside each source)."""
+    from . import preview_store
+
+    setting = preview_store.setting()
+    return setting.path if setting.mode == preview_store.FOLDER_MODE else None
+
+
+def _inside_thumbnail_folder(path):
+    """Whether *path* lies in the thumbnail folder in use (#320)."""
+    from . import preview_store
+
+    setting = preview_store.setting()
+    if setting.mode != preview_store.FOLDER_MODE or not setting.path:
+        return False
+    return ll._inside_any(path, [setting.path])
+
+
 def _plural(count, one, many=None):
    return f"{count:,} {one if count == 1 else (many or one + 's')}"

@@ -207,6 +226,7 @@ class LibraryLocationRoutesMixin:
        try:
            size = os.path.getsize(location.db_path)
        except OSError:
+            # no library file yet: report size 0
            pass
        return {
            "path": self._library_public_path(location.db_path),
@@ -224,6 +244,8 @@ class LibraryLocationRoutesMixin:
            ),
            "problem": location.problem or self._node_folder_risk(location),
            "size_bytes": size,
+            # #320 D201: thumbnails kept in one folder stay there (D8A).
+            "thumbnails_folder": _thumbnail_folder(),
        }

    # The node folder (tests point it at a temp tree).
@@ -271,6 +293,8 @@ class LibraryLocationRoutesMixin:
    def _plan_library_move(self):
        """The checked plan (blocking); raises MoveFailed."""
        plan = lm.plan_move(self._live_location())
+        if _inside_thumbnail_folder(plan.target_dir):
+            raise lm.MoveFailed("data-dir-served")
        if lm.space_problem(plan) is not None:
            raise lm.MoveFailed("insufficient-space")
        return plan
@@ -373,6 +397,7 @@ class LibraryLocationRoutesMixin:
        line += ". Logs move at the next restart."
        job.log_line(line)
        job.update(progress=100, status_line=line)
+        return None

    @staticmethod
    def _fail_library_move(job, code, message):
@@ -68,6 +68,23 @@ def _count(count, singular, plural):
    return f"{count} {singular if count == 1 else plural}"


+# Each kept entry's row in the job (#586), in the review's "Kept: ..." words.
+KEPT_DETAILS = {
+    "active": "Kept: the active log",
+    "link": "Kept: a link",
+    "other": "Kept: another file",
+}
+
+
+def _kept_files(rows):
+    """``{name, kind}`` of each entry the cleanup keeps, in folder order."""
+    return [
+        {"name": row["name"], "kind": row["kind"]}
+        for row in rows
+        if row["kind"] in KEPT_DETAILS
+    ]
+
+
 def _protected_reasons(rows):
    """The plan's Protected reasons: what the cleanup keeps, zero counts left out."""
    active = sum(1 for row in rows if row["kind"] == "active")
@@ -129,7 +146,7 @@ class LogCleanupMixin:
            token = store.issue(
                ROTATED_LOGS,
                json.dumps(files, sort_keys=True),
-                {"files": files, "protected": protected},
+                {"files": files, "protected": protected, "kept": _kept_files(rows)},
                (),
            )
        except ScopeTooLarge:
@@ -198,10 +215,15 @@ class LogCleanupMixin:
            job.record(
                "errors", {"path": name, "detail": detail}, f"! {name} · {detail}"
            )
-        job.record_counted("protected", plan.payload["protected"])
+        kept = [
+            {"path": row["name"], "detail": KEPT_DETAILS[row["kind"]]}
+            for row in plan.payload["kept"]
+        ]
+        job.record_counted("protected", len(kept), kept, complete=True)
        removed, failed = len(result["removed"]), len(result["failed"])
        line = f"Deleted {_count(removed, 'rotated log copy', 'rotated log copies')}"
        if failed:
            line += f", {failed} could not be deleted"
        job.log_line(line)
        job.update(processed=len(files), progress=100, status_line=line)
+        return None
@@ -436,7 +436,7 @@ class LoraImportRoutesMixin:
            job.log_line(f"{CANCELLED} {CACHE_NOTE}")
            job.update(status_line=CANCELLED)
            job.finish("cancelled")
-            return
+            return None
        except Exception:
            self.logger.exception("LoRA import staging failed")
            return _fail_job(job, "import-failed", f"{FAILED} {CACHE_NOTE}")
@@ -455,10 +455,10 @@ class LoraImportRoutesMixin:
            job.log_line(f"{CANCELLED} {CACHE_NOTE}")
            job.update(status_line=CANCELLED)
            job.finish("cancelled")
-            return
+            return None
        ok, _backup = await self._safety_backup_step(job, db, backup_on)
        if not ok:
-            return
+            return None
        # I1: the files are listed and fingerprinted again right before the
        # replace, so a file changed, removed or added while the downloads ran
        # (LoraManager refreshing its CivitAI info) aborts with nothing deleted.
@@ -466,6 +466,7 @@ class LoraImportRoutesMixin:
            return _fail_job(job, "plan-changed", f"{SOURCE_CHANGED} {CACHE_NOTE}")
        job.update(status_line="Replacing the LoRA collection", progress=95)
        await self._replace_in_job(job, db, plan, staged)
+        return None

    def _count_downloads(self, job, staged):
        downloaded = staged.stats.get("downloaded", 0)
@@ -518,3 +519,4 @@ class LoraImportRoutesMixin:
            staged.stats.get("download_errors", 0),
        )
        job.update(progress=100, processed=job.total, status_line=line)
+        return None
@@ -44,6 +44,7 @@ _FILES_CHANGED = (
    "The LoRA metadata files changed during the scan; the previous imports "
    "were kept. Run the scan again."
 )
+_LORA_SCAN_FAILED = "The LoRA import failed. Check the server log for details."
 _IMPORTS_CHANGED = (
    "The imported LoRA prompts changed during the scan; the previous imports "
    "were kept. Run the scan again."
@@ -407,10 +408,21 @@ class LoraIntegrationMixin:
            return
        if isinstance(error, PlanChanged):
            message = _IMPORTS_CHANGED
-        elif isinstance(error, (LoraFilesChanged, LoraSettingsUnusable)):
+        elif isinstance(
+            error,
+            (
+                LoraFilesChanged,
+                LoraSettingsUnusable,
+                EmptyReplacement,
+                PairDependencyError,
+            ),
+        ):
            message = str(error)
-        else:
+        elif isinstance(error, OSError):
+            # Reduced to its reason and the file's basename.
            message = self._public_error(error)
+        else:
+            message = _LORA_SCAN_FAILED
        if isinstance(
            error,
            (
@@ -536,6 +548,7 @@ class LoraIntegrationMixin:
                except asyncio.CancelledError:
                    interrupted = True
                except Exception:
+                    # the await after this loop raises it for the caller
                    pass
            if interrupted:
                raise asyncio.CancelledError
@@ -1,8 +1,9 @@
 """Maintenance routes: reviewed, read-only plans (#249 System S6).

 ``POST /prompt_manager/maintenance/preview {operation, options:{}}`` reviews
-one operation (``duplicate_prompts``, ``optimize``, ``unused_components`` or
-``missing_links``; ``database/maintenance.py``; ``duplicate_files``,
+one operation (``duplicate_prompts``, ``optimize``, ``unused_components``,
+``missing_links`` or ``pair_metadata``, #550; ``database/maintenance.py``;
+``duplicate_files``,
 ``py/api/duplicate_files.py``; ``rotated_logs``, the rotated log copies,
 ``py/api/log_cleanup.py``, which has its own apply job) off the event loop and
 answers a ``Plan``: ``{success, token, operation, expires_at, scope:{count,
@@ -97,7 +98,11 @@ MAINTENANCE_TITLES = {
    "unused_components": "Unused prompt components",
    "missing_links": "Missing-file links",
    "workflow_storage": "Store each workflow once",
+    # #550, beyond the concept: fills old Pair prompts' empty category and tags.
+    "pair_metadata": "Pair category and tags",
 }
+# Operations whose job keeps every changed row for its report (#550).
+COMPLETE_RECORD = frozenset({"pair_metadata"})
 _OPERATION_ERROR = "operation must be one of: " + ", ".join(PREVIEW_OPERATIONS)
 MAINTENANCE_GROUPS = ("changed", "protected", "errors")
 MAX_TOKEN_LENGTH = 128
@@ -281,9 +286,27 @@ def short_space_message(short):
    )


-def _changed_line(operation, count, marks=0):
+def _pair_metadata_line(result):
+    count = result["changed"]
+    noun = (
+        "prompt from its saved pairs"
+        if count == 1
+        else "prompts from their saved pairs"
+    )
+    categories = result.get("categories", 0)
+    tag_sets = result.get("tag_sets", 0)
+    return (
+        f"Filled {count:,} {noun} "
+        f"({categories:,} {'category' if categories == 1 else 'categories'}, "
+        f"{tag_sets:,} {'tag set' if tag_sets == 1 else 'tag sets'})"
+    )
+
+
+def _changed_line(operation, count, marks=0, result=None):
    if operation == "optimize":
        return "Optimized the database"
+    if operation == "pair_metadata":
+        return _pair_metadata_line(result or {"changed": count})
    if operation == "duplicate_prompts":
        noun = "duplicate prompt" if count == 1 else "duplicate prompts"
        return f"Merged {count:,} {noun}"
@@ -668,11 +691,66 @@ class MaintenanceRoutesMixin:
        rows = await self._run_in_executor(
            self._maintenance_rows, plan.operation, result["rows"]
        )
-        job.record_counted("changed", result["changed"], rows)
-        job.record_counted("protected", payload["protected"])
-        line = _changed_line(plan.operation, result["changed"], result.get("marks", 0))
+        job.record_counted(
+            "changed",
+            result["changed"],
+            rows,
+            complete=plan.operation in COMPLETE_RECORD,
+        )
+        kept = await self._run_in_executor(self._kept_rows, db, plan, result)
+        if kept is None:
+            job.record_counted("protected", payload["protected"])  # none kept
+        else:
+            # #550, #586: each kept record with its reason, like the changed
+            # ones, and every one of them in the report.
+            job.record_counted("protected", len(kept), kept, complete=True)
+        line = _changed_line(
+            plan.operation, result["changed"], result.get("marks", 0), result
+        )
        job.log_line(line)
        job.update(progress=100, status_line=f"{line} · {backup_note(backup)}")
+        return None
+
+    def _kept_rows(self, db, plan, result):
+        """Outcome rows for the records the apply kept (blocking), or None.
+
+        Prompts are records (no path); a missing-links plan's kept links
+        name their file, relative to its output root, so Activity can open
+        and locate it (#586); one under a source that is gone keeps its path
+        under that source's label. None for an operation that keeps nothing
+        (Optimize).
+        """
+        if plan.operation == "missing_links":
+            roots = _scan_roots(self._get_all_output_dirs())
+            judged = plan.payload["roots"]
+            rows = []
+            for item in db.kept_links(judged):
+                path, label, index = _scan_location(item["image_path"], roots)
+                if index is None and item["owner"] is not None:
+                    # A source that is gone is not listed: name the file
+                    # under it, with no listing index to open it by.
+                    source = judged[item["owner"]]
+                    where = [(os.path.abspath(source), self._public_path(source), None)]
+                    path, label, index = _scan_location(item["image_path"], where)
+                rows.append(
+                    {
+                        "path": path,
+                        "root": label,
+                        "root_index": index,
+                        "detail": f"Kept: {item['reason']}",
+                    }
+                )
+            return rows
+        if "kept" not in result:
+            return None
+        return [
+            {
+                "path": "",
+                "detail": f"Prompt {item['prompt_id']}: kept, "
+                + "; ".join(item["reasons"]),
+            }
+            for item in result["kept"]
+        ]

    def _maintenance_rows(self, operation, described):
        """Outcome rows for the changed records (root-relative paths only)."""
@@ -690,6 +768,8 @@ class MaintenanceRoutesMixin:
                    }
                )
            return rows
+        if operation == "pair_metadata":
+            return [{"path": "", "detail": _filled_detail(item)} for item in described]
        if operation == "duplicate_prompts":
            return [
                {
@@ -707,6 +787,16 @@ class MaintenanceRoutesMixin:
        ]


+def _filled_detail(item):
+    """``Prompt 12: category “portrait”; tags a, b``: one filled prompt (#550)."""
+    parts = []
+    if "category" in item:
+        parts.append(f"category “{item['category']}”")
+    if item.get("tags"):
+        parts.append("tags " + ", ".join(item["tags"]))
+    return f"Prompt {item['prompt_id']}: " + "; ".join(parts)
+
+
 def backup_note(backup):
    """The status line's backup part: the file name, or that there is none."""
    return f"Safety backup {backup}" if backup else NO_BACKUP
@@ -0,0 +1,728 @@
+"""The thumbnail location setting (#320): parsing, validation, source keys
+and the thumbnail folder's marker.
+
+``preview_store`` holds the runtime state and maps paths; this module holds
+the rules it applies. Nothing here keeps state.
+
+Schema (config.json ``thumbnails.location``)::
+
+    {"mode": "folder", "path": "D:\\\\Thumbs", "id": "<uuid4>",
+     "install": "<uuid4>", "cleanup": []}
+
+The default (and a missing key) is ``{"mode": "source"}``: previews inside
+each source. An invalid value never falls back to the sources: it parses as
+a folder location with problem ``invalid``, so nothing is written anywhere.
+
+Layout in folder mode: ``<folder>/<source key>/<rel dir>/<stem>_thumb<ext>``.
+A source key is a readable slug plus a short hash of the source's identity
+(``output-3f9a2c1b``), assigned once and stored in the marker
+``.promptmanager-thumbnails.json`` with the identity it belongs to.
+"""
+
+import errno
+import hashlib
+import json
+import logging
+import ntpath
+import os
+import posixpath
+import re
+import stat as stat_module
+import threading
+import time
+import unicodedata
+import uuid
+from contextlib import contextmanager
+from dataclasses import dataclass, field
+
+try:
+    from ...utils import library_location
+except ImportError:  # tests import the package top-level
+    from utils import library_location
+
+logger = logging.getLogger("prompt_manager.thumbnails")
+
+SOURCE_MODE = "source"
+FOLDER_MODE = "folder"
+MARKER_NAME = ".promptmanager-thumbnails.json"
+MARKER_VERSION = 1
+# Beside the marker while one process re-reads, changes and replaces it.
+MARKER_LOCK_NAME = ".promptmanager-thumbnails.lock"
+MARKER_LOCK_TIMEOUT = 1.5  # a writer waits this long (under preview_store.IO_BUDGET)
+MARKER_LOCK_STALE = 30.0  # a lock this old was left by a writer that died
+MARKER_LOCK_POLL = 0.02
+# A source key: one folder name, a slug and a 8-16 hex hash (``source_key``).
+KEY_PATTERN = re.compile(r"^[a-z0-9_-]{1,24}-[0-9a-f]{8,16}$")
+# A marker is a few keys; anything larger is not ours.
+MAX_MARKER_BYTES = 4 * 2**20
+# OS metadata files a folder may hold and still count as empty.
+OS_METADATA = frozenset({"thumbs.db", "desktop.ini", ".ds_store"})
+KEY_HASH_LENGTHS = (8, 12, 16)
+SLUG_LENGTH = 24
+# Folder + the longest key (24 + 1 + 16) + this margin must fit (Windows).
+WINDOWS_FOLDER_LIMIT = 247
+LONGEST_KEY = SLUG_LENGTH + 1 + KEY_HASH_LENGTHS[-1]
+PATH_MARGIN = 40
+# A validation stat on a share that does not answer in time is unavailable.
+VALIDATION_TIMEOUT = 5.0
+FILE_ATTRIBUTE_REPARSE_POINT = 0x400
+
+_RESERVED = re.compile(r"^(con|prn|aux|nul|com[1-9]|lpt[1-9])(\..*)?$", re.IGNORECASE)
+_BAD_CHARS = re.compile(r'[<>:"|?*\x00-\x1f]')
+
+# Problem codes, their HTTP status and the text the UI shows (no path).
+MESSAGES = {
+    "location-not-absolute": (
+        400,
+        "Enter a full folder path, such as D:\\Thumbnails or /mnt/fast/thumbnails.",
+    ),
+    "location-device-path": (
+        400,
+        "Enter the folder as a drive letter or \\\\server\\share path, "
+        "without \\\\?\\.",
+    ),
+    "location-invalid-name": (
+        400,
+        "This folder name can't be used on Windows. Choose another name.",
+    ),
+    "location-too-broad": (
+        400,
+        "Choose a folder inside a drive or share, not the drive itself.",
+    ),
+    "location-served": (
+        400,
+        "Choose a folder outside your image sources and ComfyUI's output, input "
+        "and temp folders.",
+    ),
+    "location-node-folder": (
+        400,
+        "Choose a folder outside the Prompt Manager node folder.",
+    ),
+    "location-contains-source": (
+        400,
+        "This folder contains an image source. Choose a folder beside it instead.",
+    ),
+    "location-same": (400, "Thumbnails are already stored here."),
+    "location-inside-current": (
+        400,
+        "This folder is inside the thumbnail folder in use. Choose a folder "
+        "outside it.",
+    ),
+    "location-parent-missing": (
+        400,
+        "The folder that would hold it doesn't exist. Check the path and that its "
+        "drive is connected.",
+    ),
+    "location-unavailable": (
+        409,
+        "This folder can't be reached right now. Check that its drive or share is "
+        "connected.",
+    ),
+    "location-not-empty": (
+        409,
+        "This folder already holds other files. Choose an empty folder or one "
+        "Prompt Manager used before.",
+    ),
+    "location-not-writable": (
+        409,
+        "Prompt Manager can't write to this folder. Check its permissions.",
+    ),
+    "location-path-too-long": (
+        400,
+        "This path is too long for Windows. Choose a shorter folder path.",
+    ),
+    "insufficient-space": (
+        507,
+        "There is not enough space for the thumbnails. Free some space or choose "
+        "another folder.",
+    ),
+    "location-needs-move": (
+        409,
+        "Use Move thumbnails in System › Sources & scans.",
+    ),
+}
+HOLDS_THUMBNAILS_REASON = "This folder holds Prompt Manager's thumbnails."
+
+
+def message(code):
+    """``(status, text)`` of a problem code."""
+    return MESSAGES[code]
+
+
+# ── parsing ──────────────────────────────────────────────────────────
+
+
+@dataclass(frozen=True)
+class ParsedLocation:
+    """A ``thumbnails.location`` value, checked as data (no filesystem)."""
+
+    mode: str = SOURCE_MODE
+    path: str | None = None
+    id: str | None = None
+    install: str | None = None
+    cleanup: tuple = field(default_factory=tuple)
+    problem: str | None = None
+
+    def to_config(self):
+        """The config.json form (``invalid`` values are never written)."""
+        if self.mode == SOURCE_MODE:
+            value = {"mode": SOURCE_MODE}
+        else:
+            value = {"mode": FOLDER_MODE, "path": self.path, "id": self.id}
+        if self.install:
+            value["install"] = self.install
+        value["cleanup"] = list(self.cleanup)
+        return value
+
+
+def _cleanup(value):
+    if not isinstance(value, list):
+        return ()
+    return tuple(item for item in value if isinstance(item, dict))
+
+
+def parse_location(value, *, flavor=os.path):
+    """The location a ``thumbnails.location`` value names.
+
+    Missing: inside each source. Anything else that is not a well-formed
+    location (an unknown mode, a relative path, a missing id) becomes a
+    folder location with problem ``invalid``: never a silent fall-back.
+    """
+    if value is None:
+        return ParsedLocation()
+    if not isinstance(value, dict):
+        return ParsedLocation(mode=FOLDER_MODE, problem="invalid")
+    mode = value.get("mode", SOURCE_MODE)
+    install = value.get("install") if isinstance(value.get("install"), str) else None
+    cleanup = _cleanup(value.get("cleanup"))
+    if mode == SOURCE_MODE:
+        return ParsedLocation(install=install, cleanup=cleanup)
+    if mode != FOLDER_MODE:
+        return ParsedLocation(mode=FOLDER_MODE, problem="invalid", cleanup=cleanup)
+    path, marker_id = value.get("path"), value.get("id")
+    if (
+        not isinstance(path, str)
+        or form_problem(path, flavor=flavor) is not None
+        or not isinstance(marker_id, str)
+        or not marker_id.strip()
+    ):
+        return ParsedLocation(
+            mode=FOLDER_MODE,
+            path=path if isinstance(path, str) else None,
+            problem="invalid",
+            cleanup=cleanup,
+        )
+    return ParsedLocation(
+        mode=FOLDER_MODE,
+        path=flavor.abspath(path),
+        id=marker_id,
+        install=install,
+        cleanup=cleanup,
+    )
+
+
+# ── form (text only) ─────────────────────────────────────────────────
+
+
+def _is_windows(flavor):
+    return flavor is ntpath or getattr(flavor, "__name__", "") == "ntpath"
+
+
+def form_problem(path, *, flavor=os.path):
+    """The text-only problem of *path*, or None (no filesystem access).
+
+    ``\\\\?\\`` and ``\\\\.\\`` prefixes, relative, drive-relative (``C:x``)
+    and root-relative (``\\x``) spellings, and names Windows cannot hold
+    (checked on every OS: the folder may be moved to Windows).
+    """
+    if not isinstance(path, str) or not path.strip() or path != path.lstrip():
+        return "location-not-absolute"
+    if path.replace("/", "\\").startswith(("\\\\?\\", "\\\\.\\")):
+        return "location-device-path"
+    if _is_windows(flavor):
+        drive, rest = ntpath.splitdrive(path)
+        if not drive or not rest.startswith(("\\", "/")):
+            return "location-not-absolute"
+    elif not posixpath.isabs(path):
+        return "location-not-absolute"
+    drive, rest = flavor.splitdrive(path)
+    for part in re.split(r"[\\/]+", rest):
+        if not part:
+            continue
+        if (
+            _RESERVED.match(part)
+            or part.endswith((".", " "))
+            or _BAD_CHARS.search(part)
+        ):
+            return "location-invalid-name"
+    return None
+
+
+def is_too_broad(path, *, home=None, flavor=os.path):
+    """A filesystem or share root, or the home folder itself."""
+    normalized = flavor.normpath(path)
+    drive, rest = flavor.splitdrive(normalized)
+    if rest in ("", "\\", "/"):
+        return True
+    home = home if home is not None else os.path.expanduser("~")
+    return bool(home) and flavor.normcase(normalized) == flavor.normcase(
+        flavor.normpath(home)
+    )
+
+
+def too_long_for_windows(path, long_paths=None):
+    """Folder + the longest key + a margin over the folder limit (Windows
+    without long paths; *long_paths* injects the registry answer)."""
+    if long_paths is None:
+        long_paths = long_paths_enabled()
+    if long_paths:
+        return False
+    return len(path) + 1 + LONGEST_KEY + PATH_MARGIN > WINDOWS_FOLDER_LIMIT
+
+
+def long_paths_enabled():
+    """``LongPathsEnabled`` on Windows (True on other systems)."""
+    if os.name != "nt":
+        return True
+    try:
+        import winreg
+
+        with winreg.OpenKey(
+            winreg.HKEY_LOCAL_MACHINE,
+            r"SYSTEM\CurrentControlSet\Control\FileSystem",
+        ) as key:
+            return winreg.QueryValueEx(key, "LongPathsEnabled")[0] == 1
+    except OSError:
+        return False
+
+
+# ── links ────────────────────────────────────────────────────────────
+
+
+def is_link_like(path):
+    """A symlink, a junction or any reparse point (one lstat), or missing.
+
+    Raises OSError other than "not found" (an unreachable share).
+    """
+    try:
+        info = os.lstat(path)
+    except FileNotFoundError:
+        return False
+    if stat_module.S_ISLNK(info.st_mode):
+        return True
+    attributes = getattr(info, "st_file_attributes", 0)
+    if attributes & FILE_ATTRIBUTE_REPARSE_POINT:
+        return True
+    is_junction = getattr(os.path, "isjunction", None)
+    return bool(is_junction and is_junction(path))
+
+
+# ── source keys ──────────────────────────────────────────────────────
+
+
+def slug(name):
+    """``NFKD`` to ASCII, lower case, runs outside ``[a-z0-9_]`` as ``-``,
+    trimmed and cut to 24 characters; empty becomes ``source``."""
+    text = unicodedata.normalize("NFKD", str(name))
+    text = text.encode("ascii", "ignore").decode("ascii").lower()
+    text = re.sub(r"[^a-z0-9_]+", "-", text).strip("-")
+    text = text[:SLUG_LENGTH].strip("-")
+    return text or "source"
+
+
+def source_key(spelling, identity, taken):
+    """The key of a source: ``slug(basename) + "-" + sha256(identity)[:n]``.
+
+    *taken* maps existing keys to their identity; a key taken by another
+    identity grows its hash to 12, then 16 characters.
+    """
+    base = slug(ntpath.basename(str(spelling).rstrip("\\/")))
+    digest = hashlib.sha256(str(identity).encode("utf-8")).hexdigest()
+    for length in KEY_HASH_LENGTHS:
+        key = f"{base}-{digest[:length]}"
+        owner = taken.get(key)
+        if owner is None or owner == identity:
+            return key
+    raise ValueError("no free source key")
+
+
+def file_identity(path):
+    """``[st_dev, st_ino]`` of an existing folder, or None (no file ids)."""
+    try:
+        info = os.stat(path)
+    except (OSError, ValueError):
+        return None
+    if not info.st_ino:
+        return None
+    return [info.st_dev, info.st_ino]
+
+
+def find_key(keys, spelling, identity, dev_ino):
+    """The marker key of a source: the same configured spelling, then the
+    same identity text, then the same file id; or None."""
+    keys = {k: v for k, v in keys.items() if valid_key(k) and isinstance(v, dict)}
+    for key, entry in keys.items():
+        if entry.get("path") == spelling:
+            return key
+    for key, entry in keys.items():
+        if entry.get("identity") == identity:
+            return key
+    if dev_ino:
+        for key, entry in keys.items():
+            if entry.get("dev_ino") == list(dev_ino):
+                return key
+    return None
+
+
+# ── the marker ───────────────────────────────────────────────────────
+
+
+def marker_path(folder):
+    return os.path.join(folder, MARKER_NAME)
+
+
+def read_marker(folder):
+    """The marker in *folder* as a dict, or None (absent or unreadable as
+    ours). OSError other than "not found" propagates (an unreachable share)."""
+    try:
+        with open(marker_path(folder), "r", encoding="utf-8") as handle:
+            text = handle.read(MAX_MARKER_BYTES + 1)
+    except FileNotFoundError:
+        return None
+    except (ValueError, UnicodeDecodeError):
+        return None
+    if len(text) > MAX_MARKER_BYTES:
+        return None
+    try:
+        data = json.loads(text)
+    except ValueError:
+        return None
+    if not isinstance(data, dict) or not isinstance(data.get("id"), str):
+        return None
+    data["keys"] = valid_keys(data.get("keys"))
+    return data
+
+
+def valid_key(key):
+    """Whether *key* can name a source's folder: one folder name of the
+    ``source_key`` form, never a separator, ``..`` or a drive."""
+    return isinstance(key, str) and KEY_PATTERN.fullmatch(key) is not None
+
+
+def valid_keys(keys):
+    """The marker's keys that are safe to join onto the folder; a hand-edited
+    or foreign entry that is not is dropped (and logged), never followed."""
+    if not isinstance(keys, dict):
+        return {}
+    kept = {}
+    for key, entry in keys.items():
+        if valid_key(key) and isinstance(entry, dict):
+            kept[key] = entry
+        else:
+            logger.warning(
+                "Ignoring a thumbnail folder marker entry that is not a source " "key"
+            )
+    return kept
+
+
+@contextmanager
+def _marker_lock(folder):
+    """Hold the folder's marker lock: a file made with ``O_CREAT | O_EXCL``
+    (atomic on local disks and SMB/NFS shares, unlike ``flock``), so installs
+    sharing the folder change the marker one at a time. A lock older than
+    MARKER_LOCK_STALE was left by a writer that died and is taken over;
+    waiting longer than MARKER_LOCK_TIMEOUT raises TimeoutError."""
+    lock = os.path.join(folder, MARKER_LOCK_NAME)
+    deadline = time.monotonic() + MARKER_LOCK_TIMEOUT
+    while True:
+        try:
+            handle = os.open(lock, os.O_CREAT | os.O_EXCL | os.O_WRONLY, 0o644)
+        except FileExistsError:
+            _break_stale_lock(lock)
+            if time.monotonic() >= deadline:
+                raise TimeoutError(
+                    errno.ETIMEDOUT, "the thumbnail folder marker is locked", lock
+                )
+            time.sleep(MARKER_LOCK_POLL)
+            continue
+        try:
+            os.write(handle, f"{os.getpid()}\n".encode("ascii"))
+        finally:
+            os.close(handle)  # closed before any unlink (Windows)
+        break
+    try:
+        yield
+    finally:
+        try:
+            os.unlink(lock)
+        except FileNotFoundError:
+            pass  # taken over as stale by another writer: nothing to release
+
+
+def _break_stale_lock(lock):
+    """Remove *lock* when it is older than MARKER_LOCK_STALE (its writer
+    died); a lock that changed since it was looked at is left alone."""
+    try:
+        before = os.stat(lock)
+    except FileNotFoundError:
+        return
+    if time.time() - before.st_mtime < MARKER_LOCK_STALE:
+        return
+    logger.warning(f"Taking over a stale thumbnail folder lock: {lock}")
+    try:
+        after = os.stat(lock)
+        if (after.st_ino, after.st_mtime_ns) == (before.st_ino, before.st_mtime_ns):
+            os.unlink(lock)
+    except FileNotFoundError:
+        pass  # another writer took it over first
+
+
+def write_marker(folder, mutate):
+    """Re-read the marker, apply ``mutate(marker)`` and write it atomically
+    (a temp sibling renamed over it), all under the folder's marker lock so a
+    second install sharing the folder never drops this one's change (and
+    the other way round). Callers hold ``preview_store.write_lock`` (threads
+    of this process). Returns the marker written; TimeoutError when another
+    writer holds the lock too long."""
+    with _marker_lock(folder):
+        return _write_marker_locked(folder, mutate)
+
+
+def _write_marker_locked(folder, mutate):
+    current = read_marker(folder) or {}
+    marker = {
+        "version": MARKER_VERSION,
+        "id": current.get("id"),
+        "created_by_pm": bool(current.get("created_by_pm", False)),
+        "keys": dict(current.get("keys") or {}),
+    }
+    mutate(marker)
+    if not marker.get("id"):
+        raise ValueError("a marker needs an id")
+    target = marker_path(folder)
+    temp = os.path.join(
+        folder, f".{MARKER_NAME}.{os.getpid()}-{threading.get_ident()}.tmp"
+    )
+    try:
+        with open(temp, "w", encoding="utf-8") as handle:
+            json.dump(marker, handle, indent=2, sort_keys=True)
+            handle.flush()
+            os.fsync(handle.fileno())
+        os.replace(temp, target)
+    finally:
+        try:
+            os.unlink(temp)
+        except OSError:
+            pass  # gone with the rename; a leftover is swept with the temps
+    return marker
+
+
+def new_id():
+    return str(uuid.uuid4())
+
+
+def init_folder(folder, *, created_by_pm=False):
+    """The marker id of *folder*: an existing marker is adopted; a folder
+    without one gets a new marker (new id, no keys)."""
+    existing = read_marker(folder)
+    if existing is not None:
+        return existing["id"]
+
+    def create(marker):
+        if not marker.get("id"):
+            marker["id"] = new_id()
+            marker["created_by_pm"] = created_by_pm
+
+    return write_marker(folder, create)["id"]
+
+
+def folder_state(path, expected_id):
+    """``(available, problem, marker)`` of a configured thumbnail folder.
+
+    Available: the folder exists, is a directory and not a link, junction or
+    reparse point, and holds our marker with *expected_id*. Raises OSError
+    when the folder cannot be reached (an I/O error other than not found).
+    """
+    try:
+        info = os.lstat(path)
+    except FileNotFoundError:
+        return False, "missing", None
+    except OSError as error:
+        if error.errno in (errno.ENOENT, errno.ENOTDIR):
+            return False, "missing", None
+        raise
+    if is_link_like(path):
+        return False, "invalid", None
+    if not stat_module.S_ISDIR(info.st_mode):
+        return False, "invalid", None
+    marker = read_marker(path)
+    if marker is None:
+        return False, "missing", None
+    if marker["id"] != expected_id:
+        return False, "marker-mismatch", marker
+    return True, None, marker
+
+
+def holds_only_metadata(path):
+    """Whether an existing folder is empty but for OS metadata files."""
+    with os.scandir(path) as entries:
+        for entry in entries:
+            name = entry.name.lower()
+            if name in OS_METADATA or name.startswith("._"):
+                continue
+            return False
+    return True
+
+
+# ── validation ───────────────────────────────────────────────────────
+
+
+@dataclass(frozen=True)
+class Context:
+    """What a location is checked against (gathered by the caller)."""
+
+    roots: tuple = ()  # every image source of every root list
+    contained: tuple = ()  # ComfyUI output/input/temp and the library folder
+    node_folder: str | None = None
+    default_path: str | None = None
+    current_path: str | None = None  # the folder in use (folder mode)
+    home: str | None = None
+    flavor: object = os.path
+    long_paths: bool | None = None
+    environ: object = None
+    # ComfyUI's folder_paths module (None: none; unset: imported).
+    folder_paths: object = library_location._UNSET
+
+
+def _timed(func, timeout):
+    """``func()`` on a daemon thread; raises TimeoutError past *timeout*.
+    A stuck call is left to finish on its own thread."""
+    result = {}
+    done = threading.Event()
+
+    def run():
+        try:
+            result["value"] = func()
+        except BaseException as error:  # _timed() re-raises it in the caller
+            result["error"] = error
+        finally:
+            done.set()
+
+    threading.Thread(target=run, name="pm-preview-stat", daemon=True).start()
+    if not done.wait(timeout):
+        raise TimeoutError("the folder did not answer in time")
+    if "error" in result:
+        raise result["error"]
+    return result.get("value")
+
+
+def _inside(path, folders):
+    return library_location._inside_any(path, folders)
+
+
+def _same(first, second):
+    return library_location.same_folder(first, second) or os.path.normcase(
+        os.path.realpath(first)
+    ) == os.path.normcase(os.path.realpath(second))
+
+
+def _served(path, context):
+    environ = os.environ if context.environ is None else context.environ
+    return (
+        library_location.data_dir_problem(
+            path,
+            folder_paths=context.folder_paths,
+            environ=environ,
+            gallery_roots=list(context.roots),
+        )
+        == "data-dir-served"
+    )
+
+
+def _probe_write(path):
+    """Create and delete a probe file in *path*; False when refused."""
+    probe = os.path.join(path, f".pm-probe-{uuid.uuid4().hex[:8]}.tmp")
+    try:
+        with open(probe, "wb") as handle:
+            handle.write(b"")
+    except OSError:
+        return False
+    try:
+        os.unlink(probe)
+    except OSError:
+        return False
+    return True
+
+
+def location_problem(path, *, purpose, context, timeout=VALIDATION_TIMEOUT):
+    """Why *path* cannot be the thumbnail folder, as a code, or None.
+
+    *purpose*: ``move`` (every rule), ``startup`` (no ``same``, ``empty``,
+    ``writable`` or parent rules: availability covers them) or ``recreate``
+    (the folder is missing and is made again).
+    """
+    flavor = context.flavor
+    code = form_problem(path, flavor=flavor)
+    if code is not None:
+        return code
+    path = flavor.abspath(path)
+    default = bool(context.default_path) and flavor.normcase(path) == flavor.normcase(
+        flavor.abspath(context.default_path)
+    )
+    if is_too_broad(path, home=context.home, flavor=flavor):
+        return "location-too-broad"
+    try:
+        return _timed(
+            lambda: _filesystem_problem(path, purpose, context, default), timeout
+        )
+    except (TimeoutError, OSError):
+        return "location-unavailable"
+
+
+def _filesystem_problem(path, purpose, context, default):
+    if _served(path, context):
+        return "location-served"
+    if context.node_folder and not default and _inside(path, [context.node_folder]):
+        return "location-node-folder"
+    inner = list(context.roots) + list(context.contained)
+    if any(folder and _inside(folder, [path]) for folder in inner):
+        if not default:
+            return "location-contains-source"
+    if (
+        purpose == "move"
+        and context.current_path
+        and (
+            os.path.normcase(path) == os.path.normcase(context.current_path)
+            or (os.path.isdir(path) and _same(path, context.current_path))
+        )
+    ):
+        return "location-same"
+    if (
+        purpose == "move"
+        and context.current_path
+        and _inside(path, [context.current_path])
+    ):
+        # The old key folders are removed after the move, and with them a
+        # target nested inside one of them.
+        return "location-inside-current"
+    # Windows, or a test injecting its limit (``long_paths=False``).
+    if os.name == "nt" or context.long_paths is False:
+        if too_long_for_windows(path, context.long_paths):
+            return "location-path-too-long"
+    if purpose == "startup":
+        return None
+    if is_link_like(path):
+        # Never through a link: the folder itself must be a real folder.
+        return "location-not-empty"
+    exists = os.path.isdir(path)
+    if not exists:
+        if os.path.lexists(path):
+            return "location-not-empty"
+        if not default and not os.path.isdir(os.path.dirname(path)):
+            return "location-parent-missing"
+        return None
+    if read_marker(path) is None and not holds_only_metadata(path):
+        return "location-not-empty"
+    if not _probe_write(path):
+        return "location-not-writable"
+    return None
@@ -0,0 +1,728 @@
+"""Where previews live on disk (#320): the one resolver.
+
+Every mapping between an image source (a "root"), one of its media files and
+that file's preview on disk goes through this module. URL text stays in
+``thumbnail_settings`` (``thumbnail_rel``: ``thumbnails/<rel>_thumb<ext>``,
+the shape the serve route, ``inspection-state.mjs`` and ``admin.js`` share);
+this module answers where such a preview is on disk.
+
+The store of a source is where its previews live. With the default location
+(mode ``source``, "Inside each source") it is ``<source>/thumbnails``, exactly
+the folder every caller joined by hand before, so nothing moves.
+
+Writes and the switch: every preview writer takes ``write_guard`` when it
+starts (it records the location's ``generation``); the final rename runs
+under ``write_lock`` and only when the generation is unchanged and no hold
+applies (``thumbnail_encode.replace_unless_held``). Changing the location
+bumps the generation under the same lock, so no write that began before can
+land in the old store afterwards. Nothing reads or commits config while
+``write_lock`` is held. The hold check runs under it too, so hold checks take
+no lock (the job registry's ``running()`` is a lock-free snapshot) and
+``bump_generation`` is never called with a registry or config lock held.
+
+All functions are blocking: call them off the event loop.
+"""
+
+import errno
+import logging
+import os
+import threading
+import time
+from contextlib import contextmanager
+from dataclasses import dataclass, replace
+from pathlib import Path
+
+from . import preview_location, thumbnail_settings
+
+try:
+    from ...utils.media_folders import PREVIEW_FOLDER
+except ImportError:  # tests import the package top-level
+    from utils.media_folders import PREVIEW_FOLDER
+
+logger = logging.getLogger("prompt_manager.thumbnails")
+
+SOURCE_MODE = preview_location.SOURCE_MODE
+FOLDER_MODE = preview_location.FOLDER_MODE
+# The probe checks the folder this often, and a check (or a store call)
+# taking longer than the budget marks it unreachable.
+PROBE_INTERVAL = 5.0
+IO_BUDGET = 2.0
+PROBE_THREAD = "pm-preview-probe"
+
+
+@dataclass(frozen=True)
+class Location:
+    """One snapshot of the thumbnail location (take one per request or job)."""
+
+    mode: str = SOURCE_MODE
+    path: str | None = None
+    available: bool = True
+    problem: str | None = None
+    generation: int = 0
+
+
+write_lock = threading.Lock()
+_generation = 0
+# The runtime location: the parsed setting, availability and the marker keys
+# last read. Swapped as a whole; readers take one snapshot.
+_state_lock = threading.Lock()
+_parsed = preview_location.ParsedLocation()
+_available = True
+_problem = None
+# The newest check whose answer was published.
+_published_order = 0
+_keys = {}
+_key_cache = {}
+_clock = time.monotonic
+
+
+def current():
+    """The thumbnail location now."""
+    with _state_lock:
+        parsed, available, problem, generation_now = (
+            _parsed,
+            _available,
+            _problem,
+            _generation,
+        )
+    if parsed.mode == SOURCE_MODE:
+        return Location(generation=generation_now)
+    return Location(FOLDER_MODE, parsed.path, available, problem, generation_now)
+
+
+def setting():
+    """The parsed setting in use (``preview_location.ParsedLocation``)."""
+    return _parsed
+
+
+def generation():
+    return _generation
+
+
+def bump_generation():
+    """Invalidate every write that started before (under ``write_lock``)."""
+    global _generation
+    with write_lock:
+        _generation += 1
+        return _generation
+
+
+def _canonical(path):
+    """Resolved and case-folded, so paths compare on every OS."""
+    return Path(os.path.normcase(os.path.realpath(str(path))))
+
+
+def _within(path, folder):
+    return _canonical(path).is_relative_to(_canonical(folder))
+
+
+# ── the setting and availability ─────────────────────────────────────
+
+
+def configure(value, *, context=None, check=True):
+    """Use the ``thumbnails.location`` *value* (config.json) from now on.
+
+    A folder location is validated against *context* (``startup`` rules: a
+    problem other than an unreachable folder makes it ``invalid``), then
+    checked once; the probe keeps checking it. Swapped under ``write_lock``
+    with a generation bump, so no write that started before lands.
+    """
+    global _parsed, _available, _problem, _generation
+    parsed = preview_location.parse_location(value)
+    problem = parsed.problem
+    if parsed.mode == FOLDER_MODE and problem is None and context is not None:
+        code = preview_location.location_problem(
+            parsed.path, purpose="startup", context=context
+        )
+        if code == "location-unavailable":
+            problem = "unreachable"
+        elif code is not None:
+            problem = "invalid"
+            parsed = preview_location.ParsedLocation(
+                mode=FOLDER_MODE,
+                path=parsed.path,
+                id=parsed.id,
+                install=parsed.install,
+                cleanup=parsed.cleanup,
+                problem="invalid",
+            )
+    with write_lock:
+        with _state_lock:
+            _parsed = parsed
+            _available = parsed.mode == SOURCE_MODE
+            _problem = problem if parsed.mode == FOLDER_MODE else None
+            _keys.clear()
+            _key_cache.clear()
+        _generation += 1
+    if parsed.mode == FOLDER_MODE:
+        if check and parsed.problem is None:
+            refresh()
+        _probe.start()
+    else:
+        _probe.stop()
+    return current()
+
+
+def refresh():
+    """Check the folder now (bounded by IO_BUDGET); returns availability."""
+    parsed = _parsed
+    if parsed.mode != FOLDER_MODE or parsed.problem is not None:
+        return parsed.mode == SOURCE_MODE
+    try:
+        (available, problem, marker), order = _probe.ordered_check(
+            parsed.path, parsed.id
+        )
+    except (OSError, TimeoutError, RuntimeError):
+        available, problem, marker = False, "unreachable", None
+        order = _probe.latest_order()
+    _set_state(parsed, available, problem, marker, order)
+    return available
+
+
+def _set_keys(parsed, marker):
+    """Take the keys of a marker just written (availability unchanged)."""
+    with _state_lock:
+        if _parsed is not parsed:
+            return
+        keys = dict((marker or {}).get("keys") or {})
+        if keys != _keys:
+            _keys.clear()
+            _keys.update(keys)
+            _key_cache.clear()
+
+
+def set_cleanup(entries):
+    """The setting's ``cleanup`` after a removal was committed."""
+    global _parsed
+    with _state_lock:
+        _parsed = replace(_parsed, cleanup=tuple(entries))
+
+
+def mark_invalid():
+    """The setting cannot be used (a startup check that failed): folder
+    mode stays in force, unavailable, so nothing is written anywhere."""
+    global _parsed, _available, _problem
+    with _state_lock:
+        if _parsed.mode != FOLDER_MODE:
+            _parsed = preview_location.ParsedLocation(
+                mode=FOLDER_MODE, problem="invalid"
+            )
+        else:
+            _parsed = replace(_parsed, problem="invalid")
+        _available, _problem = False, "invalid"
+
+
+def _set_state(parsed, available, problem, marker, order):
+    """Publish a check's answer, unless a check that started later already
+    published (two callers can finish out of order, #611)."""
+    global _available, _problem, _published_order
+    with _state_lock:
+        if _parsed is not parsed:
+            return  # the setting changed meanwhile
+        if order < _published_order:
+            return
+        _published_order = order
+        _available, _problem = available, problem
+        keys = dict((marker or {}).get("keys") or {})
+        if keys != _keys:
+            _keys.clear()
+            _keys.update(keys)
+            _key_cache.clear()
+
+
+def note_failure():
+    """A store call failed or stalled: unreachable until the probe finds the
+    folder again (requests do no store I/O meanwhile)."""
+    global _available, _problem
+    if _parsed.mode != FOLDER_MODE:
+        return
+    with _state_lock:
+        _available, _problem = False, "unreachable"
+    _probe.wake()
+
+
+@contextmanager
+def store_io():
+    """Around a store call in folder mode: an I/O error (other than a file
+    that is not there) or a call over IO_BUDGET marks the folder
+    unreachable."""
+    if _parsed.mode != FOLDER_MODE:
+        yield
+        return
+    started = _clock()
+    try:
+        yield
+    except OSError as error:
+        if not isinstance(error, (FileNotFoundError, NotADirectoryError)):
+            note_failure()
+        raise
+    finally:
+        if _clock() - started > IO_BUDGET:
+            note_failure()
+
+
+class _Probe:
+    """The background check of the thumbnail folder (one thread, one check
+    at a time; a stuck check is left to finish on its own thread)."""
+
+    def __init__(self):
+        self._lock = threading.Lock()
+        self._wake = threading.Event()
+        self._stop = threading.Event()
+        self._thread = None
+        self._checking = None
+        self._order = 0
+
+    def check(self, path, expected_id):
+        """``folder_state`` within IO_BUDGET; see :meth:`ordered_check`."""
+        return self.ordered_check(path, expected_id)[0]
+
+    def latest_order(self):
+        """The order number of the check started last."""
+        with self._lock:
+            return self._order
+
+    def ordered_check(self, path, expected_id):
+        """``(folder_state, order)`` within IO_BUDGET; raises TimeoutError.
+
+        ``order`` grows with each check started, so answers can be published
+        in the order they looked. The answer comes from a check that started
+        after this call: one already running may have looked before what the
+        caller just did, so it is waited for (never run twice at once; a stuck
+        one times out here) and followed by a new one."""
+        key = (path, expected_id)
+        with self._lock:
+            earlier = self._running(key)
+            pending = None if earlier else self._start_check(path, expected_id)
+        if earlier:
+            self._wait(earlier)
+            with self._lock:
+                # One another caller started meanwhile is new enough to join.
+                pending = self._running(key) or self._start_check(path, expected_id)
+        self._wait(pending)
+        with self._lock:
+            if self._checking is pending:
+                self._checking = None
+        if "error" in pending[2]:
+            raise pending[2]["error"]
+        return pending[2]["value"], pending[2]["order"]
+
+    def _running(self, key):
+        """The check of *key* still running (lock held), else None."""
+        pending = self._checking
+        if pending is None or pending[0] != key or pending[1].is_set():
+            return None
+        return pending
+
+    @staticmethod
+    def _wait(pending):
+        if not pending[1].wait(IO_BUDGET):
+            raise TimeoutError("the thumbnail folder did not answer in time")
+
+    def _start_check(self, path, expected_id):
+        """Start one check on its own thread (lock held)."""
+        self._order += 1
+        result = {"order": self._order}
+        done = threading.Event()
+
+        def run():
+            try:
+                result["value"] = preview_location.folder_state(path, expected_id)
+            except BaseException as error:  # check() re-raises it in the caller
+                result["error"] = error
+            finally:
+                done.set()
+
+        pending = ((path, expected_id), done, result)
+        self._checking = pending
+        threading.Thread(target=run, name=PROBE_THREAD + "-check", daemon=True).start()
+        return pending
+
+    def start(self):
+        with self._lock:
+            if self._thread is not None and self._thread.is_alive():
+                return
+            # Each thread has its own stop: a stopped one never resumes.
+            stop = self._stop = threading.Event()
+            thread = threading.Thread(
+                target=self._run, args=(stop,), name=PROBE_THREAD, daemon=True
+            )
+            try:
+                thread.start()
+            except RuntimeError:
+                return  # refused at interpreter exit: no probe
+            self._thread = thread
+
+    def _run(self, stop):
+        while not stop.is_set():
+            self._wake.wait(PROBE_INTERVAL)
+            self._wake.clear()
+            if stop.is_set():
+                return
+            try:
+                refresh()
+            except Exception:  # one failed check never stops the probe
+                logger.debug("Thumbnail folder check failed", exc_info=True)
+
+    def wake(self):
+        self._wake.set()
+
+    def stop(self, timeout=2.0):
+        """Stop the probe; True when its thread ended."""
+        with self._lock:
+            thread, self._thread = self._thread, None
+        self._stop.set()
+        self._wake.set()
+        if thread is None or thread is threading.current_thread():
+            return True
+        thread.join(timeout)
+        return not thread.is_alive()
+
+
+_probe = _Probe()
+
+
+def stop_probe(timeout=2.0):
+    """Stop the folder probe (the package teardown, tests)."""
+    return _probe.stop(timeout)
+
+
+# ── stores ───────────────────────────────────────────────────────────
+
+
+def source_folder(root):
+    """``<source>/thumbnails``: the store in source mode, a leftover in
+    folder mode."""
+    return Path(root) / PREVIEW_FOLDER
+
+
+def store_container(root, location=None):
+    """The folder a store of *root* must stay inside: the source itself, or
+    the thumbnail folder in folder mode."""
+    location = location or current()
+    if location.mode == FOLDER_MODE:
+        return Path(location.path) if location.path else None
+    return Path(root)
+
+
+def _identity(root):
+    return os.path.normcase(os.path.realpath(str(root)))
+
+
+def _lookup_key(root):
+    spelling = str(root)
+    with _state_lock:
+        if spelling in _key_cache:
+            return _key_cache[spelling]
+        keys = dict(_keys)
+    key = preview_location.find_key(
+        keys,
+        spelling,
+        _identity(root),
+        preview_location.file_identity(root),
+    )
+    if key is not None:
+        with _state_lock:
+            _key_cache[spelling] = key
+    return key
+
+
+def store_dir(root, location=None):
+    """The store of *root*: ``<source>/thumbnails``, or in folder mode
+    ``<folder>/<key>`` (None while the folder is unavailable or before the
+    source has a key: a reader then finds no preview)."""
+    location = location or current()
+    if location.mode == SOURCE_MODE:
+        return Path(root) / PREVIEW_FOLDER
+    if not location.available or not location.path:
+        return None
+    key = _lookup_key(root)
+    return None if key is None else _key_folder(location.path, key)
+
+
+def _key_folder(folder, key):
+    """``<folder>/<key>``, only for a key that is one folder name directly
+    below the thumbnail folder (a marker is data, never a path)."""
+    if not preview_location.valid_key(key):
+        return None
+    store = Path(folder) / key
+    if store.parent != Path(folder) or store.name != key:
+        return None
+    return store
+
+
+def ensure_store(root, location=None, *, create=False):
+    """``store_dir`` for a writer: in folder mode a source without a key gets
+    one (recorded in the marker); with *create* its key folder is made (never
+    the thumbnail folder itself). None while the folder is unavailable, and
+    for a key folder that is a link, junction or reparse point: nothing is
+    planned, written or removed through it."""
+    location = location or current()
+    store = store_dir(root, location)
+    if location.mode == SOURCE_MODE or (store is None and not location.available):
+        return store
+    if store is None:
+        store = _assign_key(root, location)
+        if store is None:
+            return None
+    try:
+        with store_io():
+            linked = preview_location.is_link_like(store)
+    except OSError:
+        return None
+    if linked:
+        logger.warning(f"Skipping the thumbnail folder {store}: it is a link")
+        return None
+    if create:
+        try:
+            with store_io():
+                os.mkdir(store)
+        except FileExistsError:
+            pass  # already there: another writer made the key folder
+        except OSError:
+            return None
+    return store
+
+
+def _assign_key(root, location):
+    parsed = _parsed
+    if location.path != parsed.path:
+        return None
+    spelling = str(root)
+    identity = _identity(root)
+    dev_ino = preview_location.file_identity(root)
+    assigned = {}
+
+    def add(marker):
+        if marker.get("id") != parsed.id:
+            raise ValueError("another folder's marker")  # marker-mismatch
+        keys = marker["keys"]
+        key = preview_location.find_key(keys, spelling, identity, dev_ino)
+        if key is None:
+            taken = {k: v.get("identity") for k, v in keys.items()}
+            key = preview_location.source_key(spelling, identity, taken)
+            keys[key] = {
+                "path": spelling,
+                "identity": identity,
+                "dev_ino": dev_ino,
+                "install": parsed.install,
+            }
+        assigned["key"] = key
+
+    try:
+        with write_lock, store_io():
+            marker = preview_location.write_marker(location.path, add)
+    except (OSError, ValueError):
+        return None
+    _set_keys(parsed, marker)
+    return _key_folder(location.path, assigned["key"])
+
+
+def may_write(path, location=None):
+    """The one ownership check every preview write and delete passes.
+
+    Source mode: True (the callers' own root rules apply, as before). Folder
+    mode: *path* lies below a source key folder of the thumbnail folder,
+    lexically and resolved, and no link, junction or reparse point sits
+    anywhere from the key folder down to it (the file itself included).
+    """
+    location = location or current()
+    if location.mode == SOURCE_MODE:
+        return True
+    if not location.path:
+        return False
+    folder = Path(os.path.abspath(location.path))
+    path = Path(os.path.abspath(path))
+    try:
+        relative = path.relative_to(folder)
+    except ValueError:
+        return False
+    if len(relative.parts) < 2 or ".." in relative.parts:
+        return False
+    store = _key_folder(folder, relative.parts[0])
+    if store is None or not _within(path, folder):
+        return False
+    try:
+        return _no_link_below(store, path)
+    except OSError:
+        note_failure()
+        return False
+
+
+def make_parent(dst, location=None):
+    """Make the folders a preview *dst* is written into. In folder mode only
+    folders below the thumbnail folder are made, never the folder itself,
+    and only while it holds this install's marker (an unplugged drive or an
+    unmounted mount point raises FileNotFoundError); a *dst* that does not
+    pass ``may_write`` raises PermissionError."""
+    location = location or current()
+    dst = Path(dst)
+    if location.mode == SOURCE_MODE or not location.path:
+        if location.mode != SOURCE_MODE:
+            raise FileNotFoundError(errno.ENOENT, "thumbnail folder unavailable")
+        dst.parent.mkdir(parents=True, exist_ok=True)
+        return
+    folder = Path(os.path.abspath(location.path))
+    with store_io():
+        if not location.available or not folder.is_dir():
+            raise FileNotFoundError(errno.ENOENT, "thumbnail folder unavailable")
+        marker = preview_location.read_marker(str(folder))
+        if marker is None or marker.get("id") != _parsed.id:
+            note_failure()
+            raise FileNotFoundError(errno.ENOENT, "thumbnail folder unavailable")
+        if not may_write(dst, location):
+            raise PermissionError(errno.EACCES, "outside the thumbnail folder")
+        current_folder = folder
+        for part in Path(os.path.abspath(dst.parent)).relative_to(folder).parts:
+            current_folder = current_folder / part
+            try:
+                os.mkdir(current_folder)
+            except FileExistsError:
+                pass  # already there: another writer made this folder
+            if preview_location.is_link_like(current_folder):
+                raise PermissionError(errno.EACCES, "a link in the thumbnail folder")
+
+
+def store_is_link(store, location=None):
+    """Whether a store folder is a link (a junction or reparse point too in
+    folder mode): it is skipped by sweeps and refused by clears."""
+    location = location or current()
+    if location.mode == SOURCE_MODE:
+        return Path(store).is_symlink()
+    return preview_location.is_link_like(store)
+
+
+def given_store(root, store):
+    """A caller's explicit store argument: the default spelling
+    (``<root>/thumbnails``) means the resolver's store; another folder (only
+    tests pass one) is used as given."""
+    store = Path(store)
+    if store == Path(root) / PREVIEW_FOLDER:
+        return store_dir(root)
+    return store
+
+
+def preview_path(root, media_rel, ext=None, location=None, *, create=False):
+    """Where the preview of *media_rel* (relative to *root*) is, or is to be
+    written (*create*: a writer, which gives a new source its key), in *ext*
+    (the extension written now when None)."""
+    if create:
+        store = ensure_store(root, location)
+    else:
+        store = store_dir(root, location)
+    if store is None:
+        return None
+    if ext is None:
+        from .thumbnail_encode import writer_settings
+
+        ext = writer_settings().extension
+    return store / (thumbnail_settings.preview_stem(media_rel) + ext)
+
+
+def request_path(root, parts, location=None):
+    """The disk path of the URL parts ``("thumbnails", ...)``, or None when
+    *parts* is not under an exact ``thumbnails`` first part or the store has
+    no place for it. The text is checked before (``is_preview_text``)."""
+    parts = tuple(parts)
+    if len(parts) < 2 or parts[0] != PREVIEW_FOLDER:
+        return None
+    store = store_dir(root, location)
+    if store is None:
+        return None
+    return store.joinpath(*parts[1:])
+
+
+def _no_link_below(store, path):
+    """No folder from *store* down to *path* (and *store* itself) is a link,
+    junction or reparse point (lexical walk, one lstat each)."""
+    store = Path(os.path.abspath(store))
+    path = Path(os.path.abspath(path))
+    try:
+        relative = path.relative_to(store)
+    except ValueError:
+        return False
+    current = store
+    for part in ("",) + relative.parts:
+        current = current / part if part else current
+        if preview_location.is_link_like(current):
+            return False
+    return True
+
+
+def owns(root, path, location=None):
+    """Whether *path* lies inside the store of *root*, resolved: the store
+    stays inside its container and no link takes *path* out of the store.
+    In folder mode no link, junction or reparse point may sit anywhere from
+    the store down to *path*."""
+    location = location or current()
+    store = store_dir(root, location)
+    if store is None:
+        return False
+    container = store_container(root, location)
+    if not (_within(store, container) and _within(path, store)):
+        return False
+    if location.mode == SOURCE_MODE:
+        return True
+    return may_write(path, location)
+
+
+# ── preview text ─────────────────────────────────────────────────────
+
+
+def is_preview_text(filepath):
+    """URL text naming a preview: ``thumbnails/<...>/<name>_thumb<ext>``.
+
+    Text only, before any join: no backslash, drive or stream colon, and no
+    empty, ``.`` or ``..`` segment; ``thumbnails`` exactly as the first part
+    and nowhere else among the folders; the extension, in any case, one a
+    preview may carry (``X_thumb.JPG`` of an older release included).
+    """
+    if not filepath or "\\" in filepath or ":" in filepath:
+        return False
+    parts = filepath.split("/")
+    if len(parts) < 2 or parts[0] != PREVIEW_FOLDER:
+        return False
+    if any(part in ("", ".", "..") for part in parts):
+        return False
+    if PREVIEW_FOLDER in parts[1:-1]:
+        return False
+    stem, extension = os.path.splitext(parts[-1])
+    return (
+        stem.endswith(thumbnail_settings.THUMB_SUFFIX)
+        and len(stem) > len(thumbnail_settings.THUMB_SUFFIX)
+        and extension.lower() in thumbnail_settings.THUMBNAIL_EXTENSIONS
+    )
+
+
+# ── writes ───────────────────────────────────────────────────────────
+
+
+class _WriteGuard:
+    """``guard()`` for one preview write: true while the location has not
+    changed since the write started and *hold* (if any) allows it."""
+
+    __slots__ = ("generation", "_hold")
+
+    def __init__(self, hold=None):
+        self.generation = _generation
+        self._hold = hold
+
+    def __call__(self):
+        if self.generation != _generation:
+            return False
+        return self._hold is None or bool(self._hold())
+
+
+def write_guard(hold=None):
+    """Take when a preview write starts; hand to its final rename."""
+    if isinstance(hold, _WriteGuard):
+        return hold
+    return _WriteGuard(hold)
+
+
+@contextmanager
+def committed(guard=None):
+    """Around a preview's final rename: holds ``write_lock`` and yields
+    whether the write may land (``guard()``, re-checked under the lock)."""
+    with write_lock:
+        yield guard is None or bool(guard())
@@ -30,6 +30,7 @@ from . import thumbnail_settings
 from .admin import _current_image_monitor
 from .job_routes import busy_response
 from .jobs import THUMBNAILS_JOB_KIND, JobBusy
+from .thumbnail_location import needs_move_response

 try:
    from ...utils.validators import validate_result_timeout, validate_worker_threads
@@ -54,9 +55,25 @@ _SETTINGS_FILE_KEYS = {
    "AUTOTAG_EXISTING": ("autotag", "defaults", "existing"),
    "AUTOTAG_GENERAL_THRESHOLD": ("autotag", "defaults", "general_threshold"),
    "AUTOTAG_CHARACTER_THRESHOLD": ("autotag", "defaults", "character_threshold"),
-    "AUTOTAG_TEMPLATE": ("autotag", "defaults", "template"),
    "AUTOTAG_SUGGESTION_LIMIT": ("autotag", "defaults", "suggestion_limit"),
+    "AUTOTAG_SKIPPED_TAGS": ("autotag", "defaults", "skipped_tags"),
+    # #431: the saved instructions and each engine's default, always written
+    # together (server-side pairing).
+    "AUTOTAG_INSTRUCTIONS": ("autotag", "defaults", "instructions"),
+    "AUTOTAG_DEFAULT_INSTRUCTIONS": ("autotag", "defaults", "default_instructions"),
 }
+# The old single template: written only as the GGUF default's mirror for a
+# downgrade (#431 B1.1), deleted when that default is Built-in.
+_TEMPLATE_MIRROR_KEY = ("autotag", "defaults", "template")
+TEMPLATE_REPLACED_ERROR = (
+    "LLM tag template was replaced by Saved instructions. Reload the page."
+)
+# Whole-list settings (#431): a save without ``expected_revision`` would merge
+# a stale copy over a list changed elsewhere, so it is refused.
+_REVISION_REQUIRED = frozenset(
+    {"autotag_skipped_tags", "autotag_instructions", "autotag_default_instructions"}
+)
+REVISION_REQUIRED_ERROR = "Reload the page and try again."
 # The thumbnail settings a running Convert outdated job fixes (#317).
 _THUMBNAIL_SETTINGS = ("THUMBNAIL_FORMAT", "THUMBNAIL_QUALITY", "THUMBNAIL_EDGE")
 # Attributes that live on GalleryConfig; the others on PromptManagerConfig.
@@ -137,13 +154,20 @@ def _settings_mutation(updates, new_roots):
    """The config commit for a settings save: only the submitted keys change.

    Every other section and key (integrations and the CivitAI key, database,
-    unknown sections) is kept as it is on disk.
+    unknown sections) is kept as it is on disk. A save of the instructions
+    also writes the old ``template`` key as the GGUF default's mirror.
    """

    def mutate(config):
        for name, value in updates.items():
            *sections, key = _SETTINGS_FILE_KEYS[name]
-            _set_nested(config, sections, key, value)
+            _set_nested(config, sections, key, _jsonable(value))
+        if "AUTOTAG_INSTRUCTIONS" in updates:
+            *sections, key = _TEMPLATE_MIRROR_KEY
+            mirror = _mirror_text(
+                updates["AUTOTAG_INSTRUCTIONS"], updates["AUTOTAG_DEFAULT_INSTRUCTIONS"]
+            )
+            _set_nested(config, sections, key, _DELETE if mirror is None else mirror)
        if new_roots is not None:
            gallery = _section(config, "gallery")
            monitoring = _section(gallery, "monitoring")
@@ -155,10 +179,37 @@ def _settings_mutation(updates, new_roots):
    return mutate


+# ``_set_nested``'s value that removes the key instead of setting it.
+_DELETE = object()
+
+
+def _jsonable(value):
+    """A runtime value as config.json holds it (tuples become lists)."""
+    if isinstance(value, (list, tuple)):
+        return [_jsonable(item) for item in value]
+    if isinstance(value, dict):
+        return {key: _jsonable(item) for key, item in value.items()}
+    return value
+
+
+def _mirror_text(entries, defaults):
+    """The GGUF default's text, or None when it is Built-in (#431 B1.1)."""
+    from ..tagging_defaults import BUILTIN_INSTRUCTIONS_ID
+
+    for item in entries:
+        if item["id"] == defaults["gguf"] != BUILTIN_INSTRUCTIONS_ID:
+            return item["text"]
+    return None
+
+
 def _set_nested(config, sections, key, value):
-    """``config[s1][s2]...[key] = value``, each section a fresh dict."""
+    """``config[s1][s2]...[key] = value``, each section a fresh dict;
+    ``_DELETE`` removes the key."""
    if not sections:
-        config[key] = value
+        if value is _DELETE:
+            config.pop(key, None)
+        else:
+            config[key] = value
        return
    merged = _section(config, sections[0])
    _set_nested(merged, sections[1:], key, value)
@@ -176,7 +227,7 @@ def _validate_autotag_settings(data):
        MAX_SUGGESTION_LIMIT,
        MODEL_TYPES,
        validate_saved_threshold,
-        validate_template,
+        validate_skipped_tags,
    )

    updates = {}
@@ -205,12 +256,7 @@ def _validate_autotag_settings(data):
                raise ValueError(f"{error}.") from None
            updates[key.upper()] = value
    if "autotag_template" in data:
-        try:
-            updates["AUTOTAG_TEMPLATE"] = validate_template(
-                data["autotag_template"], "LLM tag template"
-            )
-        except ValueError as error:
-            raise ValueError(f"{error}.") from None
+        raise ValueError(TEMPLATE_REPLACED_ERROR)
    if "autotag_suggestion_limit" in data:
        value = data["autotag_suggestion_limit"]
        if type(value) is not int or not 1 <= value <= MAX_SUGGESTION_LIMIT:
@@ -219,9 +265,41 @@ def _validate_autotag_settings(data):
                f"{MAX_SUGGESTION_LIMIT}."
            )
        updates["AUTOTAG_SUGGESTION_LIMIT"] = value
+    if "autotag_skipped_tags" in data:
+        updates["AUTOTAG_SKIPPED_TAGS"] = tuple(
+            validate_skipped_tags(data["autotag_skipped_tags"])
+        )
+    updates.update(_validate_instruction_settings(data))
    return updates


+def _validate_instruction_settings(data):
+    """Server-side pairing (#431): a save that carries either instruction key
+    gets the other from the running configuration (which holds the migrated
+    list), the defaults are checked against the merged list, and both are
+    written. Empty when the save carries neither."""
+    from ..config import AutotagConfig
+    from ..tagging_defaults import (
+        validate_default_instructions,
+        validate_instructions,
+    )
+
+    if not {"autotag_instructions", "autotag_default_instructions"} & set(data):
+        return {}
+    if "autotag_instructions" in data:
+        entries = validate_instructions(data["autotag_instructions"])
+    else:
+        entries = [dict(item) for item in AutotagConfig.INSTRUCTIONS]
+    defaults = data.get(
+        "autotag_default_instructions", dict(AutotagConfig.DEFAULT_INSTRUCTIONS)
+    )
+    defaults = validate_default_instructions(defaults, entries)
+    return {
+        "AUTOTAG_INSTRUCTIONS": tuple(entries),
+        "AUTOTAG_DEFAULT_INSTRUCTIONS": defaults,
+    }
+
+
 async def _read_json(request):
    """Parse a JSON object body through the package's capped reader."""
    from . import _read_json_body
@@ -249,6 +327,7 @@ class SettingsRoutesMixin:
        """Get current settings."""
        try:
            from ..config import AutotagConfig, PromptManagerConfig, GalleryConfig
+            from ..tagging_defaults import DEFAULT_TAG_TEMPLATE

            root_paths = [
                self._public_path(d) for d in GalleryConfig.MONITORING_DIRECTORIES
@@ -264,6 +343,12 @@ class SettingsRoutesMixin:
                    "sources": source_status,
                    "monitor": monitor,
                    "thumbnail_encoders": encoders,
+                    # #320: the full path only here (D6A).
+                    "thumbnail_location": await self._run_in_executor(
+                        functools.partial(
+                            self._thumbnail_location_payload, with_path=True
+                        )
+                    ),
                    "settings": {
                        "monitoring_enabled": GalleryConfig.MONITORING_ENABLED,
                        "save_foreign_runs": GalleryConfig.SAVE_FOREIGN_RUNS,
@@ -281,8 +366,21 @@ class SettingsRoutesMixin:
                        "autotag_character_threshold": (
                            AutotagConfig.CHARACTER_THRESHOLD
                        ),
-                        "autotag_template": AutotagConfig.TEMPLATE,
+                        # Read-only for one release (#431): a page cached
+                        # from before the upgrade still renders.
+                        "autotag_template": AutotagConfig.default_instructions_text(
+                            "gguf"
+                        ),
+                        "autotag_instructions": [
+                            dict(item) for item in AutotagConfig.INSTRUCTIONS
+                        ],
+                        "autotag_default_instructions": dict(
+                            AutotagConfig.DEFAULT_INSTRUCTIONS
+                        ),
+                        # Built-in's text, which System shows read-only.
+                        "autotag_builtin_instructions": DEFAULT_TAG_TEMPLATE,
                        "autotag_suggestion_limit": AutotagConfig.SUGGESTION_LIMIT,
+                        "autotag_skipped_tags": list(AutotagConfig.SKIPPED_TAGS),
                        "cpu_count": PromptManagerConfig.max_worker_threads(),
                        "gallery_root_paths": root_paths,
                        "gallery_root_path": root_paths[0] if root_paths else "",
@@ -377,12 +475,19 @@ class SettingsRoutesMixin:
            if error_response is not None:
                return error_response

+            if "thumbnail_location" in data:
+                # #320: only the Move thumbnails job changes the location.
+                return needs_move_response()
            expected_revision = data.get("expected_revision")
            if expected_revision is not None and not isinstance(expected_revision, str):
                return web.json_response(
                    {"success": False, "error": "expected_revision must be a string"},
                    status=400,
                )
+            if expected_revision is None and _REVISION_REQUIRED & set(data):
+                return web.json_response(
+                    {"success": False, "error": REVISION_REQUIRED_ERROR}, status=400
+                )
            try:
                updates = self._validate_settings(data)
            except ValueError as ve:
@@ -481,7 +586,8 @@ class SettingsRoutesMixin:
            for key in _THUMBNAIL_SETTINGS
        )
        job = self._jobs.active(THUMBNAILS_JOB_KIND) if changed else None
-        if job is None or job.scope.get("mode") != "convert":
+        # A move copies previews of the current settings (#320).
+        if job is None or job.scope.get("mode") not in ("convert", "move"):
            return None
        return web.json_response(
            {
@@ -511,6 +617,12 @@ class SettingsRoutesMixin:
            if name in _AUTOTAG_SETTINGS:
                setattr(AutotagConfig, name[len(_AUTOTAG_PREFIX) :], value)
                continue
+        if "AUTOTAG_INSTRUCTIONS" in updates:
+            # What config.json now holds as the old key (the mirror).
+            AutotagConfig._LEGACY_TEMPLATE = AutotagConfig.mirror_template()
+        for name, value in updates.items():
+            if name in _AUTOTAG_SETTINGS:
+                continue
            owner = GalleryConfig if name in _GALLERY_SETTINGS else PromptManagerConfig
            setattr(owner, name, value)
        restart_fields = []
@@ -30,6 +30,8 @@ import ntpath
 import os
 import re

+from .preview_location import HOLDS_THUMBNAILS_REASON
+
 logger = logging.getLogger("prompt_manager.api")

 MAX_SOURCE_PATH = 4096  # characters
@@ -114,7 +116,26 @@ def source_problem(text):
    code = source_form_error(text)
    if code is not None:
        return code, FORM_REASONS[code]
-    return GalleryConfig.gallery_root_problem(text)
+    code, reason = GalleryConfig.gallery_root_problem(text)
+    if code is None and _holds_thumbnails(GalleryConfig.resolve_gallery_root(text)):
+        return "holds-thumbnails", HOLDS_THUMBNAILS_REASON
+    return code, reason
+
+
+def _holds_thumbnails(path):
+    """Whether *path* is inside or around the thumbnail folder in use (#320):
+    a source there would list Prompt Manager's own previews."""
+    from . import preview_store
+
+    try:
+        from ...utils.library_location import _inside_any
+    except ImportError:  # tests import the package top-level
+        from utils.library_location import _inside_any
+
+    setting = preview_store.setting()
+    if setting.mode != preview_store.FOLDER_MODE or not setting.path:
+        return False
+    return _inside_any(path, [setting.path]) or _inside_any(setting.path, [path])


 def public_spelling(text):
@@ -8,7 +8,8 @@ previews behind those URLs are made here, in three ways:
 - **On first view.** ``GET /prompt_manager/images/serve/thumbnails/<rel>_thumb
  <ext>`` for a preview that does not exist yet is admitted on the event loop
  (``_PreviewGate``): at most ``ON_DEMAND_LIMIT`` previews are written at once,
-  on this API's own small pool (never the default executor), one flight runs
+  on this API's interactive image pool (``IMAGE_POOL_SIZE`` threads, shared
+  with card facts and inspector reads; never the default executor), one flight runs
  per file, and the requests waiting are capped (``MAX_WAITING``); past the
  cap a request gets its fallback at once. Inside the admission the preview is
  mapped back to its media file under the same root (the request text is
@@ -24,7 +25,8 @@ previews behind those URLs are made here, in three ways:
 - **On capture.** The image monitor hands every new output it settles to
  ``queue_capture_thumbnail``, which queues its preview for one background
  worker thread (``AutoThumbnailer``). Each wake takes at most Worker threads
-  (``WORKER_THREADS``) files and writes them on that many threads; enqueuing
+  (``WORKER_THREADS``) files and writes them on the long-lived job pool
+  (``utils.parallel``, shared with scans and thumbnail jobs); enqueuing
  is O(1), so the monitor and ComfyUI's queue never wait. A file already
  queued is not queued again, the queue is bounded (``MAX_QUEUED``) and a
  preview left out is made on its first view instead.
@@ -49,7 +51,7 @@ write starts (after its slot) and again just before its rename.

 Shutdown: ``close_auto_thumbnails`` stops the worker at a file boundary,
 kills a running ffmpeg, waits a bounded time (and logs when the wait ran
-out) and shuts the view pool down; after the app's cleanup
+out) and shuts the image pool down; after the app's cleanup
 (``final=True``) nothing starts a worker again. Importing this module again
 (a package reload) stops the workers the previous import left.
 """
@@ -60,12 +62,12 @@ import functools
 import io
 import os
 import threading
-from concurrent.futures import ThreadPoolExecutor
+from concurrent.futures import CancelledError, ThreadPoolExecutor
 from pathlib import Path

 from aiohttp import web

-from . import thumbnail_settings
+from . import preview_store, thumbnail_settings
 from .images import (
    in_trash_below_roots,
    MEDIA_EXTENSIONS,
@@ -76,7 +78,7 @@ from .images import (
    _thumbnail_is_fresh,
    _video_placeholder_image,
    _worker_threads,
-    media_thumbnail_rel,
+    media_preview_path,
 )
 from .jobs import (
    DUPLICATE_CLEANUP_JOB_KIND,
@@ -104,8 +106,11 @@ PLACEHOLDER_SIZE = (thumbnail_settings.DEFAULT_EDGE, thumbnail_settings.DEFAULT_
 PLACEHOLDER_QUALITY = 85
 # Source extensions in the order a shared preview name looks for them (R2).
 _SOURCE_ORDER = thumbnail_settings.IMAGE_SOURCE_ORDER + tuple(sorted(VIDEO_EXTENSIONS))
-# Previews views may write at once (the size of the view pool).
-ON_DEMAND_LIMIT = 3
+# Threads of the interactive image pool (#523): view previews, card facts and
+# inspector reads. Fixed, so image buffers stay in a few threads' arenas.
+IMAGE_POOL_SIZE = 3
+# Previews views may write at once (the whole image pool).
+ON_DEMAND_LIMIT = IMAGE_POOL_SIZE
 # View requests that may wait on the gate; one more gets its fallback at once.
 MAX_WAITING = 64
 # How long a pool thread waits for the capture worker's flight of the same file.
@@ -124,7 +129,7 @@ AUTO_REFUSED_KINDS = frozenset(
    {RESTORE_JOB_KIND, DUPLICATE_CLEANUP_JOB_KIND, SOURCE_CHANGE_JOB_KIND}
 )
 WORKER_NAME = "PromptManagerThumbnailWorker"
-POOL_PREFIX = "pm-preview"
+POOL_PREFIX = "pm-image"
 # Identifies this import's workers: a reload stops the ones it did not start.
 _MODULE_TOKEN = object()

@@ -153,6 +158,36 @@ def _dst_key(dst):
    return flight_key(Path(dst).parent, (Path(dst).name,))


+class DeferredPreview:
+    """The preview of *rel* under *root*, resolved when its write starts
+    (#320): a queued capture follows the thumbnail location at write time,
+    not the one when it was queued."""
+
+    __slots__ = ("root", "rel", "strict")
+
+    def __init__(self, root, rel, *, strict=True):
+        self.root = Path(root)
+        self.rel = Path(rel)
+        # A capture refuses a store linked out of its container (the serve
+        # route's rule); a planned target keeps the plan's rule: inside the
+        # store, as the thumbnail job writes it.
+        self.strict = strict
+
+    def resolve(self):
+        """The preview's path now, or None when nothing may be written."""
+        dst = media_preview_path(self.root, self.rel, create=True)
+        if dst is None:
+            return None
+        if self.strict:
+            return dst if preview_store.owns(self.root, dst) else None
+        store = preview_store.store_dir(self.root)
+        return dst if _is_within(dst, store) else None
+
+
+def _resolved(dst):
+    return dst.resolve() if isinstance(dst, DeferredPreview) else Path(dst)
+
+
@functools.lru_cache(maxsize=1)
 def video_placeholder_jpeg():
    """The placeholder frame as JPEG bytes (a video whose preview is missing)."""
@@ -210,10 +245,19 @@ def _candidates(parts):
 def _current_preview(root, parts):
    """The preview *parts* names, in the format written now (#317): a request
    for an older name (``_thumb.png`` before a conversion) is answered with
-    the current file."""
+    the current file. None when the store of *root* has no place for it."""
    _folder, base, _wanted = _candidates(parts)
    name = base + thumbnail_settings.THUMB_SUFFIX + writer_settings().extension
-    return Path(root).joinpath(*parts[:-1], name)
+    return preview_store.request_path(root, (*parts[:-1], name))
+
+
+def _request_key(root, parts):
+    """The flight key of the preview *parts* under *root*: the key of its
+    disk path (so the serve and history routes share one flight)."""
+    path = preview_store.request_path(root, parts)
+    if path is None:
+        return flight_key(root, parts)
+    return _dst_key(path)


 def _quick_source(root, parts):
@@ -254,12 +298,14 @@ def _thumbnail_source(root, parts):
    if in_trash_below_roots(found, [root]):
        return None
    rel = Path(*folder_parts, found.name)
-    dst = root / media_thumbnail_rel(rel)
+    dst = media_preview_path(root, rel, create=True)
+    if dst is None:
+        # Nowhere to write (the thumbnail folder is unavailable): the
+        # original is served and nothing is written.
+        return found, None, found.suffix.lower() in VIDEO_EXTENSIONS
    if dst != _current_preview(root, parts):
        return None
-    if not _is_within(root / "thumbnails", root) or not _is_within(
-        dst, root / "thumbnails"
-    ):
+    if not preview_store.owns(root, dst):
        dst = None
    return found, dst, found.suffix.lower() in VIDEO_EXTENSIONS

@@ -279,6 +325,21 @@ def _scan_folder(folder, base, extensions):
    return None


+def _deferred(roots, src, dst):
+    """The ``DeferredPreview`` of a planned ``(src, dst)``: the root whose
+    store the plan wrote *dst* into (nested roots plan one each); *dst* as
+    planned when none matches."""
+    src = Path(src)
+    for root in roots:
+        root = Path(root)
+        if not src.is_relative_to(root):
+            continue
+        rel = src.relative_to(root)
+        if media_preview_path(root, rel) == Path(dst):
+            return DeferredPreview(root, rel, strict=False)
+    return dst
+
+
 def _stop_stale_workers():
    """Stop capture workers a previous import of this module started."""
    for thread in threading.enumerate():
@@ -294,7 +355,7 @@ class AutoThumbnailer:
    ``generate(src, dst, is_video, *, stop, guard, track)`` writes one
    preview and returns ``_generate_one``'s result dict; ``may_write()``
    says whether automatic previews may be written now. Views call
-    ``ensure`` on the view pool, the monitor calls ``enqueue`` from its
+    ``ensure`` on the image pool, the monitor calls ``enqueue`` from its
    thread.
    """

@@ -420,16 +481,23 @@ class AutoThumbnailer:

    def enqueue(self, src, dst, is_video):
        """Queue *dst*'s preview for the worker; False when already queued,
-        full, closed or its worker is refused at interpreter exit. Never
-        blocks on a write."""
-        key = _dst_key(dst)
+        full, closed, nowhere to write it or its worker is refused at
+        interpreter exit. Never blocks on a write. *dst* may be a
+        ``DeferredPreview``: its path is resolved again when the write
+        starts."""
+        now = _resolved(dst)
+        if now is None:
+            return False
+        key = _dst_key(now)
+        if not isinstance(dst, DeferredPreview):
+            dst = now
        with self._changed:
            if self._closed or key in self._queued:
                return False
            if len(self._queue) >= self._max_queued:
                return False
            self._queued.add(key)
-            self._queue.append((key, Path(src), Path(dst), bool(is_video)))
+            self._queue.append((key, Path(src), dst, bool(is_video)))
            self._busy = True
            started = True
            if self._start_worker and not self._worker_running:
@@ -491,12 +559,15 @@ class AutoThumbnailer:
                    self._worker_running = False
                    self._changed.notify_all()
                    return
-                take = min(len(self._queue), max(1, int(self._workers() or 1)))
+                workers = max(1, int(self._workers() or 1))
+                take = min(len(self._queue), workers)
                batch = [self._queue.popleft() for _ in range(take)]
                self._batch = len(batch)
                self._changed.notify_all()
            try:
-                map_parallel(self._write_queued, batch, len(batch))
+                # The job pool's size is the setting; a smaller batch uses
+                # fewer of its threads (#523: one long-lived pool).
+                map_parallel(self._write_queued, batch, workers)
            finally:
                with self._changed:
                    self._batch = 0
@@ -506,6 +577,9 @@ class AutoThumbnailer:
    def _write_queued(self, item):
        _key, src, dst, is_video = item
        try:
+            dst = _resolved(dst)
+            if dst is None:
+                return  # nowhere to write it now: made on its first view
            self.ensure(src, dst, is_video)
        except Exception:  # one file never stops the worker
            self._logger.warning(
@@ -533,6 +607,7 @@ class AutoThumbnailer:
            try:
                process.kill()
            except OSError:
+                # the process has already exited
                pass
        if worker is None:
            return True
@@ -566,7 +641,7 @@ class _PreviewGate:
    """Admission of view requests on the event loop (#249 I2).

    Waiters are coroutines: at most ``limit`` previews are written at once
-    on the view pool, one flight runs per key, and past ``MAX_WAITING``
+    on the image pool, one flight runs per key, and past ``MAX_WAITING``
    waiting requests ``run`` answers ``OVER`` at once.
    """

@@ -621,13 +696,17 @@ class _PreviewGate:
                flight.set_result(result)


+def _on_image_thread():
+    return threading.current_thread().name.startswith(POOL_PREFIX + "_")
+
+
 class AutoThumbnailMixin:
    """Automatic previews on the API: views, the monitor's queue, scans."""

    _auto_thumbnailer = None
    _auto_thumbnails_shut = False
    _preview_gate_obj = None
-    _preview_pool_obj = None
+    _image_pool_obj = None
    _auto_thumbnailer_lock = threading.Lock()

    def _auto_thumbnails(self):
@@ -650,7 +729,7 @@ class AutoThumbnailMixin:
            self._auto_thumbnails_shut = True

    def close_auto_thumbnails(self, final=False, timeout=None):
-        """Stop the capture worker and the view pool, and forget them.
+        """Stop the capture worker and the image pool, and forget them.

        Bounded by ``timeout`` (see AutoThumbnailer.close). ``final`` (the
        package teardown) also keeps a late monitor event from starting a
@@ -661,7 +740,7 @@ class AutoThumbnailMixin:
            if final:
                self._auto_thumbnails_shut = True
            thumbnailer, self._auto_thumbnailer = self._auto_thumbnailer, None
-            pool, self._preview_pool_obj = self._preview_pool_obj, None
+            pool, self._image_pool_obj = self._image_pool_obj, None
            self._preview_gate_obj = None
        closed = True
        if thumbnailer is not None:
@@ -670,6 +749,8 @@ class AutoThumbnailMixin:
            pool.shutdown(wait=False, cancel_futures=True)
        if final:
            shutdown_encoders()  # kill JPEG XL / ffmpeg encoders still running
+            # The thumbnail folder's probe (#320), bounded like the rest.
+            closed = preview_store.stop_probe() and closed
        return closed

    def _auto_thumbnail_failures(self):
@@ -694,6 +775,9 @@ class AutoThumbnailMixin:
                return job
            if job.kind == THUMBNAILS_JOB_KIND and job.title == THUMBNAIL_CLEAR_TITLE:
                return job
+            # Move thumbnails holds automatic previews for its whole run (D2A).
+            if job.kind == THUMBNAILS_JOB_KIND and job.scope.get("mode") == "move":
+                return job
        return None

    # ── the view admission ────────────────────────────────────────────
@@ -705,16 +789,67 @@ class AutoThumbnailMixin:
            gate = self._preview_gate_obj = _PreviewGate(ON_DEMAND_LIMIT, self.logger)
        return gate

-    def _preview_pool(self):
-        with AutoThumbnailMixin._auto_thumbnailer_lock:
-            if self._preview_pool_obj is None:
-                self._preview_pool_obj = ThreadPoolExecutor(
-                    ON_DEMAND_LIMIT, thread_name_prefix=POOL_PREFIX
-                )
-            return self._preview_pool_obj
+    def _image_pool(self):
+        """The interactive image pool (#523): IMAGE_POOL_SIZE threads for view
+        previews (behind their gate), card facts and inspector reads, so
+        image buffers never spread over the default executor's threads.

-    def _preview_pool_threads(self):
-        pool = self._preview_pool_obj
+        None after the package teardown (``close_auto_thumbnails(final=True)``):
+        a late request then runs on the default executor (``run_in_executor``
+        with None) and starts no thread the teardown no longer stops.
+        """
+        with AutoThumbnailMixin._auto_thumbnailer_lock:
+            if self._image_pool_obj is None and not self._auto_thumbnails_shut:
+                self._image_pool_obj = ThreadPoolExecutor(
+                    IMAGE_POOL_SIZE, thread_name_prefix=POOL_PREFIX
+                )
+            return self._image_pool_obj
+
+    async def _run_image(self, func, *args, **kwargs):
+        """``_run_in_executor`` for interactive image work: the image pool.
+
+        After the teardown, or with the pool shut down in between (a test
+        reset), the call runs on the default executor as before.
+        """
+        call = functools.partial(func, *args, **kwargs)
+        loop = asyncio.get_running_loop()
+        try:
+            future = loop.run_in_executor(self._image_pool(), call)
+        except RuntimeError:  # submit refused: the pool was shut down
+            future = loop.run_in_executor(None, call)
+        return await future
+
+    def _map_image(self, func, items):
+        """``func`` over *items* on the image pool, in order (blocking).
+
+        Called from an image pool thread, after the teardown, or with the
+        pool shut down in between (its queued items are cancelled), the
+        items it did not run run on the calling thread.
+        """
+        items = list(items)
+        pool = None if not items or _on_image_thread() else self._image_pool()
+        if pool is None:
+            return [func(item) for item in items]
+        futures = []
+        try:
+            for item in items:
+                futures.append(pool.submit(func, item))
+        except RuntimeError:
+            pass  # shut down in between: the rest run here
+        results = []
+        for index, item in enumerate(items):
+            future = futures[index] if index < len(futures) else None
+            if future is None or future.cancelled():
+                results.append(func(item))
+                continue
+            try:
+                results.append(future.result())
+            except CancelledError:  # cancelled while this caller waited
+                results.append(func(item))
+        return results
+
+    def _image_pool_threads(self):
+        pool = self._image_pool_obj
        return [] if pool is None else list(getattr(pool, "_threads", ()))

    def _video_placeholder_bytes(self):
@@ -729,7 +864,7 @@ class AutoThumbnailMixin:
        return await self._preview_gate().run(
            flight_key(Path(dst).parent, (Path(dst).name,)),
            functools.partial(self._ensure_view, src, dst, is_video),
-            self._preview_pool(),
+            self._image_pool(),
        )

    def _ensure_view(self, src, dst, is_video):
@@ -773,17 +908,17 @@ class AutoThumbnailMixin:
        The flight answers only the outcome (a history flight may be the one
        joined); the file it previews is derived here: the preview path is
        the request's own, and a fallback looks its source up again on the
-        view pool (bounded by it, never the default executor).
+        image pool (bounded by it, never the default executor).
        """
        if _has_traversal(filepath) or not _is_preview_request(filepath):
            return None
        parts = tuple(filepath.split("/"))
        gate = self._preview_gate()
-        pool = self._preview_pool()
+        pool = self._image_pool()
        for root in output_dirs:
            root = Path(root)
            outcome = await gate.run(
-                flight_key(root, parts),
+                _request_key(root, parts),
                functools.partial(self._preview_on_demand, root, parts),
                pool,
            )
@@ -796,7 +931,7 @@ class AutoThumbnailMixin:
                    continue
                return self._preview_response(BUSY, quick[0], None, quick[1])
            dst = _current_preview(root, parts)
-            if outcome == READY:
+            if outcome == READY and dst is not None:
                return self._file_response(dst)
            located = await gate.loop.run_in_executor(
                pool, _thumbnail_source, root, parts
@@ -819,17 +954,31 @@ class AutoThumbnailMixin:
        """
        if self._auto_thumbnails_shut:
            return "skipped"
-        located = self._capture_target(image_path)
+        located = self._capture_source(image_path)
        if located is None:
            return "skipped"
-        src, dst, is_video = located
+        src, root, rel, is_video = located
+        dst = DeferredPreview(root, rel).resolve()
+        if dst is None:
+            return "skipped"
        if _thumbnail_is_fresh(src, dst):
            return "fresh"
-        if self._auto_thumbnails().enqueue(src, dst, is_video):
+        if self._auto_thumbnails().enqueue(src, DeferredPreview(root, rel), is_video):
            return "queued"
        return "skipped"

    def _capture_target(self, image_path):
+        """``(src, dst, is_video)`` of a new output's preview now, or None."""
+        located = self._capture_source(image_path)
+        if located is None:
+            return None
+        src, root, rel, is_video = located
+        dst = DeferredPreview(root, rel).resolve()
+        return None if dst is None else (src, dst, is_video)
+
+    def _capture_source(self, image_path):
+        """``(src, root, rel, is_video)`` of a media file under a current
+        root (not a preview, a link or in a trash folder), or None."""
        path = Path(os.path.abspath(str(image_path)))
        if path.suffix.lower() not in MEDIA_EXTENSIONS or not _regular_file(path):
            return None
@@ -842,12 +991,7 @@ class AutoThumbnailMixin:
            rel = Path(os.path.relpath(path, root))
            if "thumbnails" in rel.parts[:-1] or in_trash_below_roots(path, [root]):
                return None
-            dst = root / media_thumbnail_rel(rel)
-            if not _is_within(root / "thumbnails", root) or not _is_within(
-                dst, root / "thumbnails"
-            ):
-                return None
-            return path, dst, path.suffix.lower() in VIDEO_EXTENSIONS
+            return path, root, rel, path.suffix.lower() in VIDEO_EXTENSIONS
        return None

    # ── after a scan ──────────────────────────────────────────────────
@@ -889,7 +1033,7 @@ class AutoThumbnailMixin:
            return "none"
        thumbnailer = self._auto_thumbnails()
        for src, dst, is_video in plan["targets"]:
-            thumbnailer.enqueue(src, dst, is_video)
+            thumbnailer.enqueue(src, _deferred(output_dirs, src, dst), is_video)
        self.logger.info(f"{missing:,} previews missing after the scan; queued")
        return "queued"

@@ -44,7 +44,7 @@ import os
 import time
 from pathlib import Path

-from . import thumbnail_settings
+from . import preview_store, thumbnail_settings
 from .thumbnail_encode import ThumbnailVerifyError, verify_thumbnail, writer_settings
 from .admin import _plural, _scan_location, _scan_roots, _scan_status_line
 from .images import _thumbnail_is_fresh, _worker_threads, _thumbnail_batch_size
@@ -153,6 +153,7 @@ class ThumbnailConvertMixin:
            job.log_line("Conversion failed · internal error")
            state = "failed"
        job.finish(state)
+        await self._release_job_memory()

    async def _convert_job_body(self, job, options):
        output_dirs = await self._run_in_executor(self._get_all_output_dirs)
@@ -392,6 +393,12 @@ class ThumbnailConvertMixin:
        removed, with no bytes (another run or a sibling removed it)."""
        removed, kept = 0, []
        for path, size in old:
+            if not preview_store.may_write(path):
+                # Folder mode: never a file outside a key folder, or one
+                # reached through a link (checked at the moment of the delete).
+                self.logger.warning(f"Not removing {path}: outside the thumbnails")
+                kept.append(path)
+                continue
            try:
                os.remove(path)
            except FileNotFoundError:
@@ -46,7 +46,7 @@ from pathlib import Path

 from PIL import Image

-from . import thumbnail_settings
+from . import preview_location, preview_store, thumbnail_settings

 try:
    from ...utils.logging_config import get_logger
@@ -101,14 +101,20 @@ def temp_sibling(dst, tag="part"):


 def replace_unless_held(tmp, dst, guard=None):
-    """Rename *tmp* over *dst*, unless ``guard()`` is false (PreviewWriteHeld)."""
-    if guard is not None and not guard():
-        raise PreviewWriteHeld(PREVIEW_HELD)
-    os.replace(tmp, dst)
+    """Rename *tmp* over *dst*, unless ``guard()`` is false (PreviewWriteHeld).
+
+    The check and the rename run under ``preview_store.write_lock`` (#320): a
+    guard from ``preview_store.write_guard`` also refuses a write that started
+    before the thumbnail location changed."""
+    with preview_store.committed(guard) as allowed:
+        if not allowed:
+            raise PreviewWriteHeld(PREVIEW_HELD)
+        os.replace(tmp, dst)


 # ``temp_sibling``'s names: ``.<stem>.<tag>-<pid>-<thread id><ext>``.
 _TEMP_NAME = re.compile(r"^\..+\.(?:part|src)-(\d+)-\d+\.[A-Za-z0-9]+$")
+_MOVE_TEMP_NAME = re.compile(r"\.pm-move-[0-9a-f]{8}\.tmp$")
 # A temp at least this old (seconds) outlived its write: no encode runs longer.
 STRAY_TEMP_AGE = 4 * ENCODE_TIMEOUT
 # When this process started (this module's import): a temp carrying its PID
@@ -120,7 +126,10 @@ def sweep_stray_temps(folder, min_age=None):
    """Remove the temp files a crashed write left under *folder* (a preview
    folder, walked without following links); returns ``(count, bytes)``.

-    Only ``temp_sibling`` names are touched, never a link. With *min_age*
+    Only ``temp_sibling`` names are touched, never a link: a folder that is a
+    link, junction or reparse point is not walked into (Windows walks into a
+    junction even without ``followlinks``), and each file passes
+    ``preview_store.may_write`` before it goes. With *min_age*
    (seconds, the startup sweep) a temp younger than that, or one this
    process wrote since it started (it may still be writing it), is left;
    ``min_age=0`` (the clear, which holds every preview write) removes them
@@ -130,19 +139,39 @@ def sweep_stray_temps(folder, min_age=None):
    now = time.time()
    own = str(os.getpid())
    count = size = 0
-    for root, _dirs, files in os.walk(folder):
+    try:
+        if preview_location.is_link_like(folder):
+            return count, size
+    except OSError as exc:
+        logger.debug(f"Not sweeping {folder}: {exc}")
+        return count, size
+    for root, dirs, files in os.walk(folder):
+        dirs[:] = [d for d in dirs if not _link_like(Path(root) / d)]
        for name in files:
            match = _TEMP_NAME.match(name)
-            if match is None:
+            # A move's copy temp (#320): ``<name>.pm-move-<8 hex>.tmp``.
+            move_temp = match is None and _MOVE_TEMP_NAME.search(name)
+            if match is None and not move_temp:
                continue
            path = Path(root) / name
            try:
                stat = path.lstat()
-                if path.is_symlink() or not path.is_file():
+                if (
+                    path.is_symlink()
+                    or not path.is_file()
+                    or _link_like(path)
+                    or not preview_store.may_write(path)
+                ):
                    continue
                if min_age and (
                    now - stat.st_mtime < min_age
-                    or (match.group(1) == own and stat.st_mtime >= PROCESS_STARTED)
+                    or move_temp
+                    and stat.st_mtime >= PROCESS_STARTED
+                    or (
+                        match is not None
+                        and match.group(1) == own
+                        and stat.st_mtime >= PROCESS_STARTED
+                    )
                ):
                    continue
                path.unlink()
@@ -154,10 +183,19 @@ def sweep_stray_temps(folder, min_age=None):
    return count, size


+def _link_like(path):
+    """``is_link_like``, with a path that cannot be checked counted as one."""
+    try:
+        return preview_location.is_link_like(path)
+    except OSError:
+        return True
+
+
 def _unlink_quietly(path):
    try:
        Path(path).unlink()
    except FileNotFoundError:
+        # already gone, which is what was wanted
        pass
    except OSError as exc:
        logger.debug(f"Could not remove temp file {Path(path).name}: {exc}")
@@ -221,6 +259,7 @@ def shutdown_encoders():
        try:
            process.kill()
        except OSError:
+            # the process has already exited
            pass


@@ -359,10 +398,12 @@ def thumbnail_frame(img, edge):
    try:
        img.seek(0)
    except (EOFError, AttributeError, ValueError):
+        # not seekable or a single frame: use the current one
        pass
    try:
        img.draft("RGB", (edge, edge))  # JPEG: decode at a reduced scale
    except (AttributeError, ValueError, OSError):
+        # draft is only a speedup; the full decode below still works
        pass
    frame = img.convert("RGB") if img.mode != "RGB" else img.copy()
    frame.thumbnail((edge, edge), Image.Resampling.LANCZOS)
@@ -49,6 +49,7 @@ from .images import (
    _worker_threads,
 )
 from .job_routes import busy_response
+from .thumbnail_location import location_refusal
 from .jobs import THUMBNAIL_GROUP_NAMES, THUMBNAILS_JOB_KIND, JobBusy
 from .thumbnail_convert import CONVERT_JOB_TITLE
 from .thumbnail_encode import writer_settings
@@ -131,7 +132,10 @@ class ThumbnailJobsMixin:
    """The thumbnail plan, the thumbnail job and the legacy stream on it."""

    async def get_thumbnail_plan(self, request):
-        """What a thumbnail run would do (read-only; capped like a run)."""
+        """What a thumbnail run would do (read-only; capped like a run).
+        ``mode=prune`` lists the removed sources' thumbnails (#320)."""
+        if request.query.get("mode") == "prune":
+            return await self.get_prune_plan()
        options, error = thumbnail_options(request.query, from_query=True)
        if error:
            return _invalid(error)
@@ -179,15 +183,39 @@ class ThumbnailJobsMixin:
                )
            except (ValueError, UnicodeDecodeError):
                return _invalid(_OPTIONS_ERROR)
+        if isinstance(body, dict) and body.get("mode") in ("move", "prune"):
+            return await self._start_location_job(body)
        options, error = thumbnail_options(body)
        if error:
            return _invalid(error)
+        refused = location_refusal()
+        if refused is not None:
+            return refused
        try:
            job = self._start_thumbnail_job(options)
        except JobBusy as busy:
            return busy_response(busy)
        return web.json_response({"success": True, "job": job.summary()}, status=202)

+    async def _start_location_job(self, body):
+        """Move thumbnails or Remove thumbnails of removed sources (#320)."""
+        if body["mode"] == "prune":
+            refused = location_refusal()
+            if refused is not None:
+                return refused
+        try:
+            if body["mode"] == "move":
+                started = self.start_thumbnail_move(body)
+            else:
+                started = self.start_thumbnail_prune()
+        except JobBusy as busy:
+            return busy_response(busy)
+        if isinstance(started, web.Response):
+            return started
+        return web.json_response(
+            {"success": True, "job": started.summary()}, status=202
+        )
+
    def _start_thumbnail_job(self, options):
        """Register the thumbnail job synchronously; raises JobBusy.

@@ -226,6 +254,7 @@ class ThumbnailJobsMixin:
            )
            state = "failed"
        job.finish(state)
+        await self._release_job_memory()

    async def _thumbnail_job_body(self, job, options):
        """Plan, then generate in worker batches; returns the final state.
@@ -458,8 +487,12 @@ class ThumbnailJobsMixin:
        or attaches to the running thumbnail job, and streams its frames. A
        legacy hold (the blocking generate or clear) or a record-changing
        job refuses it with the stream's error frame. The job goes on when
-        the client goes away.
+        the client goes away. Refused (409) while the thumbnail folder is
+        unavailable (#320).
        """
+        refused = location_refusal()
+        if refused is not None:
+            return refused
        response = web.StreamResponse(
            status=200,
            headers={
@@ -506,8 +539,12 @@ class ThumbnailJobsMixin:
        the way.
        """
        running = self._jobs.active(THUMBNAILS_JOB_KIND)
-        if running is not None and running.scope.get("mode") == "convert":
-            return None, False, running  # no legacy frames to follow (#317)
+        if running is not None and running.scope.get("mode") in (
+            "convert",
+            "move",
+            "prune",
+        ):
+            return None, False, running  # no legacy frames to follow (#317, #320)
        if running is not None and running.cancellable:
            return running, False, None
        busy = self._jobs.blocker(THUMBNAILS_JOB_KIND, admission="guarded")
@@ -0,0 +1,162 @@
+"""The thumbnail location on the API (#320): startup, the settings payload
+and the refusals while the thumbnail folder is unavailable.
+
+The setting itself is config.json ``thumbnails.location``
+(``preview_location``); the runtime state is ``preview_store``. POST
+``/settings`` never changes it (409 ``location-needs-move``): the Move
+thumbnails job is its only writer.
+"""
+
+import os
+
+from aiohttp import web
+
+from . import preview_location, preview_store
+
+try:
+    from ...utils import library_location
+except ImportError:  # tests import the package top-level
+    from utils import library_location
+
+# The node folder (its web/ is served and a reinstall wipes it).
+NODE_FOLDER = os.path.dirname(
+    os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+)
+
+
+def default_path():
+    """``<data folder>/data/thumbnails`` (D7B), or None when unknown."""
+    try:
+        return library_location.cache_dir("thumbnails")
+    except Exception:  # no data folder can be decided: no default
+        return None
+
+
+def location_refusal(location=None):
+    """The 409 ``location-unavailable`` response while the thumbnail folder
+    is unavailable, else None (thumbnail generate, convert, clear, prune)."""
+    location = location or preview_store.current()
+    if location.mode != preview_store.FOLDER_MODE or location.available:
+        return None
+    status, text = preview_location.message("location-unavailable")
+    return web.json_response(
+        {"success": False, "code": "location-unavailable", "error": text},
+        status=status,
+    )
+
+
+def needs_move_response():
+    status, text = preview_location.message("location-needs-move")
+    return web.json_response(
+        {"success": False, "code": "location-needs-move", "error": text},
+        status=status,
+    )
+
+
+class ThumbnailLocationMixin:
+    """Startup check and payloads of the thumbnail location."""
+
+    def _all_source_roots(self):
+        """Every image source of every root list: the Images roots, the
+        configured sources and the extra gallery roots (as strings)."""
+        from ..config import GalleryConfig, _extra_gallery_roots
+
+        roots = [str(root) for root in self._get_all_output_dirs()]
+        roots += [str(root) for root in GalleryConfig.MONITORING_DIRECTORIES]
+        roots += list(_extra_gallery_roots())
+        return tuple(dict.fromkeys(root for root in roots if root))
+
+    def _thumbnail_location_context(self):
+        """What a thumbnail folder is validated against (blocking)."""
+        contained = []
+        try:
+            import folder_paths
+
+            for name in (
+                "get_output_directory",
+                "get_input_directory",
+                "get_temp_directory",
+            ):
+                getter = getattr(folder_paths, name, None)
+                folder = getter() if getter is not None else None
+                if folder:
+                    contained.append(str(folder))
+        except ImportError:
+            pass  # folder_paths exists only inside ComfyUI (tests run without it)
+        try:
+            contained.append(library_location.config_location()[1])
+        except Exception:  # no data folder can be decided
+            self.logger.debug("No library folder for the thumbnail check")
+        setting = preview_store.setting()
+        return preview_location.Context(
+            roots=self._all_source_roots(),
+            contained=tuple(contained),
+            node_folder=NODE_FOLDER,
+            default_path=default_path(),
+            current_path=(
+                setting.path if setting.mode == preview_store.FOLDER_MODE else None
+            ),
+        )
+
+    def use_preview_location(self):
+        """Put the configured location in force at once, unchecked (the
+        package's import, before any request): folder mode is unavailable
+        until ``start_preview_location`` has checked it, so nothing is ever
+        written to the sources meanwhile. No filesystem access."""
+        from ..config import PromptManagerConfig
+
+        try:
+            return preview_store.configure(
+                PromptManagerConfig.THUMBNAIL_LOCATION, check=False
+            )
+        except Exception:
+            self.logger.warning("The thumbnail location is unusable", exc_info=True)
+            preview_store.mark_invalid()
+            return preview_store.current()
+
+    def start_preview_location(self):
+        """Parse and check the configured location once (startup thread);
+        the probe takes over. Never raises; a check that fails leaves a
+        folder location unavailable (``invalid``), never the sources."""
+        from ..config import PromptManagerConfig
+
+        try:
+            value = PromptManagerConfig.THUMBNAIL_LOCATION
+            parsed = preview_location.parse_location(value)
+            context = None
+            if parsed.mode == preview_store.FOLDER_MODE:
+                context = self._thumbnail_location_context()
+            location = preview_store.configure(value, context=context)
+        except Exception:
+            self.logger.warning("The thumbnail location check failed", exc_info=True)
+            if (
+                preview_location.parse_location(
+                    PromptManagerConfig.THUMBNAIL_LOCATION
+                ).mode
+                == preview_store.FOLDER_MODE
+            ):
+                preview_store.mark_invalid()
+            return preview_store.current()
+        if location.mode == preview_store.FOLDER_MODE and not location.available:
+            self.logger.warning(
+                "The thumbnail folder is unavailable "
+                f"({location.problem or 'checking'}): originals are shown and "
+                "no thumbnails are written until it is back"
+            )
+        return location
+
+    def _thumbnail_location_payload(self, *, with_path):
+        """``{mode, available, problem}`` plus, for the settings GET only,
+        ``path`` and ``default_path`` (D6A)."""
+        location = preview_store.current()
+        payload = {
+            "mode": location.mode,
+            "available": location.available,
+            "problem": location.problem,
+        }
+        if with_path:
+            payload["path"] = location.path
+            payload["default_path"] = default_path()
+            # Old copies a move still has to remove (#320 Part 3).
+            payload["cleanup_pending"] = len(preview_store.setting().cleanup)
+        return payload
@@ -0,0 +1,579 @@
+"""Move thumbnails (#320 Part 3): the reviewed job that changes where previews
+live, the removal of old copies after it, recovery at startup and the
+"Remove thumbnails of removed sources" scope (Part 5).
+
+Kind ``thumbnails`` with ``mode: "move"`` (D1A): admission ``guarded``, so
+scans, deletes, tagging, source changes and every other thumbnail job wait
+for it, while the monitor's Needs review recording runs beside it.
+Automatic previews are held for the whole job (D2A, ``_auto_thumbnail_blocker``).
+
+Phases: review (``POST /images/thumbnails/plan``, no writes but the
+validation probe), start (a plan token), hold (generation bump, journal,
+target folder), copy (cancellable at every file boundary, on the job pool
+in small chunks, D3A), switch (one config commit sets the location and
+records the old stores under ``cleanup``; not cancellable from here),
+remove old copies, end. Per-file errors switch anyway (D10A); a folder-wide
+error or a cancel before the switch removes what the job wrote and changes
+nothing. The move is the only writer of the setting (D4B).
+
+Moving away from a thumbnail folder also removes the previews of this
+install's sources that are no longer listed (Q320-8: remove).
+"""
+
+import functools
+import os
+import time
+from pathlib import Path
+
+from aiohttp import web
+
+from . import preview_location, preview_store
+from . import thumbnail_move_files as files
+from .jobs import THUMBNAILS_JOB_KIND
+from .thumbnail_move_plan import (
+    MOVE_GROUPS,
+    MOVE_TITLE,
+    PLAN_TTL,
+    _number,
+    _plural,
+    _remove,
+    _roots_revision,
+    _volume,
+    _is_network,
+    _write_json,
+)
+from . import thumbnail_move_plan as move_plan
+
+try:
+    from ...utils import exit_signal
+    from ...utils.parallel import map_parallel
+except ImportError:  # tests import the package top-level
+    from utils import exit_signal
+    from utils.parallel import map_parallel
+
+
+class ThumbnailMoveMixin:
+    """Start and run the move job; the removal of old copies."""
+
+    # ── start ─────────────────────────────────────────────────────────
+
+    def _take_move_plan(self, body):
+        """The plan a start names, or ``(status, code)``."""
+        token = body.get("token")
+        plan = (self._move_plans or {}).get(token) if isinstance(token, str) else None
+        if plan is None or time.monotonic() - plan.created > PLAN_TTL:
+            return 409, "plan-stale"
+        roots = [str(root) for root in self._get_all_output_dirs()]
+        if _roots_revision(roots) != plan.revision:
+            return 409, "plan-stale"
+        if preview_store.setting() != plan.old:
+            return 409, "plan-stale"
+        if plan.confirm_required and body.get("confirmed") is not True:
+            return 400, "confirmation-required"
+        return plan
+
+    def start_thumbnail_move(self, body):
+        """Start the move job (sync, on the loop); raises JobBusy. Returns
+        the job or a refusal response."""
+        if not self._move_recovered:
+            blocker = self._jobs.active(THUMBNAILS_JOB_KIND)
+            return web.json_response(
+                {
+                    "success": False,
+                    "code": "busy",
+                    "error": "Prompt Manager is still checking an earlier move. "
+                    "Try again in a moment.",
+                    "running": None if blocker is None else {"id": blocker.id},
+                },
+                status=409,
+            )
+        taken = self._take_move_plan(body)
+        if isinstance(taken, tuple):
+            status, code = taken
+            text = {
+                "plan-stale": "The review is out of date. Review the move again.",
+                "confirmation-required": "Confirm that Prompt Manager may "
+                "create its folders there.",
+            }[code]
+            return web.json_response(
+                {"success": False, "code": code, "error": text}, status=status
+            )
+        plan = taken
+        self._move_plans.pop(plan.token, None)
+        return self._jobs.start(
+            THUMBNAILS_JOB_KIND,
+            MOVE_TITLE,
+            admission="guarded",
+            cancellable=True,
+            scope={
+                "mode": "move",
+                "from": plan.old.mode,
+                "to": plan.target["mode"],
+                "to_path": plan.target["path"],
+            },
+            groups=MOVE_GROUPS,
+            runner=functools.partial(self._run_thumbnail_move, plan=plan),
+        )
+
+    # ── the job ───────────────────────────────────────────────────────
+
+    async def _run_thumbnail_move(self, job, *, plan):
+        state = {"written": [], "created": [], "created_folder": False}
+        try:
+            await self._run_in_executor(self._move_hold, job, plan, state)
+        except (OSError, ValueError) as error:
+            await self._run_in_executor(self._move_rollback, plan, state)
+            self._end_move(
+                job, "failed", "The new folder could not be made; nothing changed."
+            )
+            self.logger.warning(f"Move thumbnails could not start: {error}")
+            return
+        left = [
+            {
+                "path": "/".join(item),
+                "root": s.label,
+                "detail": "Not a thumbnail; left in place",
+            }
+            for s in plan.sources
+            if s.scan is not None
+            for item in s.scan.left
+        ]
+        if left:
+            job.record_counted("left", len(left), left)
+        items = [
+            (source, item)
+            for source in plan.sources
+            if source.scan is not None
+            for item in source.scan.copy
+        ]
+        total = len(items)
+        job.update(total=total, processed=0, progress=0)
+        chunk = await self._run_in_executor(self._move_chunk, plan)
+        workers = self._move_workers()
+        done = 0
+        for start in range(0, total, chunk):
+            if job.cancelled:
+                await self._move_cancelled(job, plan, state)
+                return
+            batch = items[start : start + chunk]
+            try:
+                results = await self._run_in_executor(
+                    map_parallel,
+                    functools.partial(self._move_copy_one, state=state),
+                    batch,
+                    workers,
+                )
+            except exit_signal.ExitRequested:
+                return  # exiting: the next start undoes the copies (journal)
+            except files.FolderGone as error:
+                self.logger.warning(f"Move thumbnails stopped: {error}")
+                await self._run_in_executor(self._move_rollback, plan, state)
+                self._end_move(
+                    job,
+                    "failed",
+                    "The new folder could not be reached or is full; nothing changed.",
+                )
+                return
+            except Exception:
+                # Anything else before the switch: undo, never half a move.
+                self.logger.exception("Move thumbnails failed while copying")
+                await self._run_in_executor(self._move_rollback, plan, state)
+                self._end_move(job, "failed", "The copy failed; nothing changed.")
+                return
+            for (source, item), (outcome, detail) in zip(batch, results):
+                row = {
+                    "path": "/".join(item[0]),
+                    "root": source.label,
+                    "detail": detail,
+                }
+                job.record(
+                    "moved" if outcome == "moved" else outcome,
+                    row,
+                    f"{outcome}: {source.label} · {'/'.join(item[0])}",
+                )
+            done += len(batch)
+            label = batch[-1][0].label
+            job.update(
+                processed=done,
+                progress=int(done * 90 / total) if total else 90,
+                status_line=(
+                    f"Copying {_number(done)} of {_number(total)} previews · {label}"
+                ),
+            )
+            job.publish({"type": "progress", "summary": job.summary()})
+        if job.cancelled:
+            await self._move_cancelled(job, plan, state)
+            return
+        # The switch: not cancellable from here (an exit still stops between
+        # files and leaves the cleanup to the next start).
+        job.cancellable = False
+        job.update(status_line="Switching to the new location", progress=92)
+        job.publish({"type": "progress", "summary": job.summary()})
+        try:
+            await self._run_in_executor(self._move_switch, plan)
+        except Exception:
+            self.logger.exception("Move thumbnails could not switch")
+            await self._run_in_executor(self._move_rollback, plan, state)
+            self._end_move(
+                job, "failed", "The setting could not be saved; nothing changed."
+            )
+            return
+        await self._remove_old_copies(job, plan)
+        moved = job.counters.get("moved", 0) + job.counters.get("skipped", 0)
+        errors = job.counters.get("errors", 0)
+        where = plan.target["path"] or "inside each source"
+        parts = [f"{_number(moved)} moved"]
+        if errors:
+            parts.append(_plural(errors, "error"))
+        parts.append(
+            "old copies removed"
+            if not job.scope.get("cleanup_left")
+            else "some old copies are removed at the next start"
+        )
+        self._end_move(
+            job, "finished", f"Thumbnails moved to {where}: " + " · ".join(parts) + "."
+        )
+
+    def _end_move(self, job, state, line):
+        job.update(status_line=line, progress=100)
+        job.log_line(line)
+        job.publish({"type": "complete", "summary": job.summary()})
+        job.finish(state)
+
+    def _move_workers(self):
+        from .images import _worker_threads
+
+        return max(1, int(_worker_threads() or 1))
+
+    def _move_chunk(self, plan):
+        """2 files at a time across volumes or to/from a share, else 4, never
+        more than Worker threads (D3A: the pool keeps its size)."""
+        sides = [plan.target["path"] or ""] + [s.old_store or "" for s in plan.sources]
+        sides += [s.new_store for s in plan.sources]
+        network = any(_is_network(side) for side in sides if side)
+        volumes = {_volume(side) for side in sides if side}
+        size = 2 if network or len(volumes) > 1 else 4
+        return max(1, min(size, self._move_workers()))
+
+    def _move_hold(self, job, plan, state):
+        """Phase 3: bump the generation, write the journal, make the target."""
+        preview_store.bump_generation()
+        if plan.to_folder:
+            folder = plan.target["path"]
+            if not os.path.isdir(folder):
+                if plan.target_default:
+                    os.makedirs(folder, exist_ok=True)
+                else:
+                    os.mkdir(folder)
+                state["created_folder"] = True
+            plan.target_id = preview_location.init_folder(
+                folder, created_by_pm=state["created_folder"]
+            )
+            install = plan.install
+
+            def add_keys(marker):
+                for source in plan.sources:
+                    if source.key and source.key not in marker["keys"]:
+                        marker["keys"][source.key] = {
+                            "path": source.root,
+                            "identity": os.path.normcase(os.path.realpath(source.root)),
+                            "dev_ino": preview_location.file_identity(source.root),
+                            "install": install,
+                        }
+
+            with preview_store.write_lock:
+                preview_location.write_marker(folder, add_keys)
+        _write_json(
+            move_plan.journal_path(),
+            {
+                "state": "copying",
+                "from": plan.old.to_config(),
+                "to": plan.target,
+                "stores": [s.new_store for s in plan.sources],
+                # Stores that do not exist yet are made by this job only:
+                # after a crash everything in them goes (B4).
+                "created_dirs": [
+                    s.new_store for s in plan.sources if not os.path.isdir(s.new_store)
+                ],
+                "created_folder": state["created_folder"],
+                "install": plan.install,
+            },
+        )
+        job.log_line(
+            f"Move thumbnails started: {plan.old.path or 'inside each source'} → "
+            f"{plan.target['path'] or 'inside each source'}"
+        )
+
+    def _move_copy_one(self, pair, *, state):
+        """Copy one preview (a pool thread); ``(group, detail)``."""
+        source, (relative, size, mtime_ns) = pair
+        destination = Path(source.new_store).joinpath(*relative)
+        try:
+            if not os.path.isdir(destination.parent):
+                base = Path(source.new_store)
+                if not base.is_dir():
+                    if plan_parent_missing(base):
+                        raise files.FolderGone("the new folder is gone")
+                    created = []
+                    files._make_folders(base.parent, (base.name,), created)
+                    state["created"].extend(created)
+                created = []
+                files._make_folders(base, relative[:-1], created)
+                state["created"].extend(created)
+            # Also when the folders already exist (Codex P1 on #592).
+            files.refuse_links(source.new_store, relative[:-1])
+            outcome = files.copy_one(
+                Path(source.old_store).joinpath(*relative),
+                destination,
+                size,
+                mtime_ns,
+                state["created"],
+            )
+        except files.CopyFailed as error:
+            return "errors", str(error)
+        if outcome == "moved":
+            state["written"].append(str(destination))
+            return "moved", "Copied and checked"
+        return "skipped", "Already there"
+
+    async def _move_cancelled(self, job, plan, state):
+        if exit_signal.requested():
+            return  # the next start removes the partial copies (journal)
+        await self._run_in_executor(self._move_rollback, plan, state)
+        self._end_move(job, "cancelled", "Move cancelled: nothing changed.")
+
+    def _move_rollback(self, plan, state):
+        """Remove what this job wrote (files, folders it made, a folder and
+        marker it created) and the journal: nothing changed."""
+        for path in state["written"]:
+            files.remove_file(path)
+        for folder in reversed(state["created"]):
+            files.remove_empty_folders(folder)
+        if plan.to_folder and state.get("created_folder"):
+            folder = plan.target["path"]
+            try:
+                names = os.listdir(folder)
+            except OSError:
+                names = None
+            if names is not None and set(names) <= {preview_location.MARKER_NAME}:
+                _remove(preview_location.marker_path(folder))
+                files.remove_empty_folders(folder)
+        _remove(move_plan.journal_path())
+
+    def _move_switch(self, plan):
+        """Phase 5: one config commit sets the location and records the old
+        stores under ``cleanup``; the runtime follows under the write lock."""
+        from ..config import PromptManagerConfig
+        from ..config_store import get_config_store
+
+        entry = {
+            "from": plan.old.mode,
+            "folder": plan.old.path if plan.from_folder else None,
+            "stores": [s.old_store for s in plan.sources if s.old_store],
+            "drop_keys": self._old_keys_to_drop(plan),
+            "install": plan.install,
+        }
+        # An older entry never removes a store the move just filled (a move
+        # back while old copies still waited).
+        filled = {os.path.normcase(s.new_store) for s in plan.sources}
+        cleanup = []
+        for old_entry in plan.old.cleanup:
+            stores = [
+                store
+                for store in old_entry.get("stores") or []
+                if isinstance(store, str) and os.path.normcase(store) not in filled
+            ]
+            folder = old_entry.get("folder")
+            drop = [
+                key
+                for key in old_entry.get("drop_keys") or []
+                if not folder
+                or os.path.normcase(os.path.join(folder, key)) not in filled
+            ]
+            cleanup.append({**old_entry, "stores": stores, "drop_keys": drop})
+        cleanup.append(entry)
+        if plan.to_folder:
+            value = {
+                "mode": preview_store.FOLDER_MODE,
+                "path": plan.target["path"],
+                "id": plan.target_id,
+                "install": plan.install,
+                "cleanup": cleanup,
+            }
+        else:
+            value = {
+                "mode": preview_store.SOURCE_MODE,
+                "install": plan.install,
+                "cleanup": cleanup,
+            }
+
+        def mutate(config):
+            section = config.get("thumbnails")
+            if not isinstance(section, dict):
+                section = {}
+            section["location"] = value
+            config["thumbnails"] = section
+            return config
+
+        def publish(_config):
+            PromptManagerConfig.THUMBNAIL_LOCATION = value
+            preview_store.configure(value, check=False)
+
+        get_config_store().commit(mutate, expected_revision=None, publish=publish)
+        # The switch is made: what follows never undoes it.
+        try:
+            preview_store.refresh()
+            _remove(move_plan.journal_path())
+        except OSError as error:
+            self.logger.warning(
+                f"The thumbnail move journal stays until the next start: {error}"
+            )
+
+    def _old_keys_to_drop(self, plan):
+        if not plan.from_folder:
+            return []
+        keys = [s.old_store and os.path.basename(s.old_store) for s in plan.sources]
+        keys = [key for key in keys if key]
+        if plan.to_folder and os.path.normcase(plan.old.path or "") == os.path.normcase(
+            plan.target["path"] or ""
+        ):
+            return []
+        return keys + [key for key, _store, _scan in plan.unlisted]
+
+    async def _remove_old_copies(self, job, plan):
+        """Phase 6: run the cleanup the switch recorded (and earlier ones)."""
+        job.update(status_line="Removing old copies", progress=95)
+        job.publish({"type": "progress", "summary": job.summary()})
+        left = await self._run_in_executor(self._run_cleanup, job)
+        if left:
+            job.scope["cleanup_left"] = True
+
+    def _run_cleanup(self, job=None):
+        """Remove every recorded old store's previews, temps and empty
+        folders; keep in ``cleanup`` what could not go. Returns how many
+        entries are left (blocking)."""
+        setting = preview_store.setting()
+        remaining = []
+        for entry in setting.cleanup:
+            if not self._cleanup_entry(entry, job):
+                remaining.append(entry)
+        if list(setting.cleanup) != remaining:
+            self._commit_cleanup(remaining)
+        return len(remaining)
+
+    def _cleanup_entry(self, entry, job):
+        """One recorded removal; True when it is complete."""
+        folder = entry.get("folder")
+        stores = [
+            store for store in entry.get("stores") or [] if isinstance(store, str)
+        ]
+        if folder:
+            if not os.path.isdir(folder):
+                return False  # the old folder is not reachable: kept for later
+            folder_marker = preview_location.read_marker(folder) or {}
+            keys = folder_marker.get("keys") or {}
+            stores += [
+                os.path.join(folder, key)
+                for key in entry.get("drop_keys") or []
+                if preview_location.valid_key(key) and key in keys
+            ]
+        complete = True
+        for store in dict.fromkeys(stores):
+            if not self._remove_store(store, folder, job):
+                complete = False
+        if folder and complete:
+            drop = set(entry.get("drop_keys") or [])
+
+            def forget(marker):
+                for key in drop:
+                    marker["keys"].pop(key, None)
+
+            try:
+                with preview_store.write_lock:
+                    marker = preview_location.write_marker(folder, forget)
+            except (OSError, ValueError):
+                return False
+            if not marker["keys"] and marker.get("created_by_pm"):
+                names = set(os.listdir(folder))
+                rest = {n for n in names if not files.is_os_metadata(n)}
+                if rest <= {preview_location.MARKER_NAME}:
+                    _remove(preview_location.marker_path(folder))
+                    files.remove_empty_folders(folder)
+        return complete
+
+    def _remove_store(self, store, folder, job):
+        """Remove the previews and temps of one old store; True when done."""
+        store = Path(store)
+        if folder:
+            # A key folder directly in the old thumbnail folder, nothing else.
+            if not preview_location.valid_key(store.name) or os.path.normcase(
+                str(store.parent)
+            ) != os.path.normcase(str(folder)):
+                return True
+        elif store.name != "thumbnails":
+            return True  # a hand-edited entry never names another folder
+        if not store.exists():
+            return True
+        if preview_location.is_link_like(store):
+            return True  # never through a link; nothing of ours there
+        complete = True
+        removed = 0
+        for current, dirs, names in os.walk(store):
+            dirs[:] = [
+                d for d in dirs if not preview_location.is_link_like(Path(current) / d)
+            ]
+            for name in names:
+                path = Path(current) / name
+                if files.is_temp_name(name) or files._preview_parts(name):
+                    if preview_location.is_link_like(path):
+                        continue
+                    if exit_signal.requested():
+                        return False  # exiting: the next start finishes it
+                    if files.remove_file(path):
+                        removed += 1
+                    else:
+                        complete = False
+                        relative = path.relative_to(store).as_posix()
+                        self.logger.warning(
+                            f"Could not remove the old thumbnail {path}; it is "
+                            "removed at the next start"
+                        )
+                        if job is not None:
+                            # D10A: a removal that failed is an error the job lists.
+                            job.record(
+                                "errors",
+                                {
+                                    "path": relative,
+                                    "root": store.name,
+                                    "detail": "In use by another program; removed "
+                                    "at the next start",
+                                },
+                                f"In use by another program; removed at the next "
+                                f"start: {store.name}/{relative}",
+                            )
+        files.remove_empty_folders(store)
+        if job is not None and removed:
+            job.log_line(f"Removed {_number(removed)} old files from {store.name}")
+        return complete
+
+    def _commit_cleanup(self, remaining):
+        from ..config import PromptManagerConfig
+        from ..config_store import get_config_store
+
+        def mutate(config):
+            section = config.get("thumbnails")
+            if isinstance(section, dict) and isinstance(section.get("location"), dict):
+                section["location"]["cleanup"] = remaining
+            return config
+
+        def publish(config):
+            value = (config.get("thumbnails") or {}).get("location")
+            PromptManagerConfig.THUMBNAIL_LOCATION = value
+            preview_store.set_cleanup(remaining)
+
+        get_config_store().commit(mutate, expected_revision=None, publish=publish)
+
+
+def plan_parent_missing(store):
+    """A key folder's parent (the thumbnail folder) is gone mid-copy."""
+    return not Path(store).parent.is_dir()
@@ -0,0 +1,348 @@
+"""The file side of Move thumbnails (#320 Part 3): what is copied, how a
+copy is made and checked, and how old copies are removed.
+
+No job, HTTP or config code lives here; ``thumbnail_move`` drives it.
+
+Copy set (B5): each old store is walked with ``os.scandir``, never through a
+symlink, junction or reparse point (counted as "skipped link"). A regular
+file is
+
+- copied when it has the preview grammar (``<name>_thumb<ext>``, any written
+  or legacy extension) and its original still exists in the source;
+- removed with the old copies, not copied, when it is an orphan (no
+  original), lies under a trash folder, or is a temp sibling of a write
+  (``.<stem>.part-…``) or of a move (``….pm-move-<8 hex>.tmp``);
+- left in place otherwise ("Left in place"). OS metadata files (``Thumbs.db``,
+  ``desktop.ini``, ``.DS_Store``, ``._*``) are removed only when they alone
+  keep a preview folder from being removed.
+
+A copy goes to ``<name>.pm-move-<8 hex>.tmp`` beside its destination, its
+size is compared, its mtime is set to the source preview's rounded up to the
+next 2-second step (FAT/exFAT keep it fresh, a stale preview stays stale),
+then it is renamed into place. Every handle is closed before a rename or an
+unlink (Windows).
+"""
+
+import errno
+import logging
+import os
+import re
+import secrets
+import shutil
+import stat as stat_module
+import time
+from dataclasses import dataclass, field
+from pathlib import Path
+
+from . import preview_location, thumbnail_settings
+from .thumbnail_encode import _TEMP_NAME
+
+try:
+    from ...utils.media_folders import in_trash_folder
+except ImportError:  # tests import the package top-level
+    from utils.media_folders import in_trash_folder
+
+logger = logging.getLogger("prompt_manager.thumbnails")
+
+MOVE_TEMP = re.compile(r"\.pm-move-[0-9a-f]{8}\.tmp$")
+MOVE_TEMP_SUFFIX = ".pm-move-{token}.tmp"
+# The temp name adds this much to a destination path (".pm-move-xxxxxxxx.tmp").
+TEMP_EXTRA = 21
+WINDOWS_FILE_LIMIT = 259
+MTIME_STEP_NS = 2_000_000_000
+# A file another program holds open (Windows) is retried this often.
+REMOVE_RETRIES = (0.5, 1.0, 2.0)
+_WINDOWS_IN_USE = {32, 33}  # ERROR_SHARING_VIOLATION, ERROR_LOCK_VIOLATION
+
+
+def is_os_metadata(name):
+    folded = name.lower()
+    return folded in preview_location.OS_METADATA or folded.startswith("._")
+
+
+def is_temp_name(name):
+    return bool(_TEMP_NAME.match(name) or MOVE_TEMP.search(name))
+
+
+def _preview_parts(name):
+    """``(base, extension)`` of a preview file name, or None."""
+    stem, extension = os.path.splitext(name)
+    suffix = thumbnail_settings.THUMB_SUFFIX
+    if not stem.endswith(suffix) or len(stem) <= len(suffix):
+        return None
+    if extension.lower() not in thumbnail_settings.THUMBNAIL_EXTENSIONS:
+        return None
+    return stem[: -len(suffix)], extension
+
+
+def _has_original(root, rel_dir, base, extension):
+    """Whether a media file in ``<root>/<rel_dir>`` owns this preview."""
+    folder = Path(root).joinpath(*rel_dir)
+    try:
+        with os.scandir(folder) as entries:
+            for entry in entries:
+                stem, source_ext = os.path.splitext(entry.name)
+                if stem != base or not source_ext:
+                    continue
+                if not thumbnail_settings.owns(extension, source_ext):
+                    continue
+                if entry.is_file(follow_symlinks=False):
+                    return True
+    except OSError:
+        return False
+    return False
+
+
+@dataclass
+class StoreScan:
+    """One old store's files, sorted into what the move does with them."""
+
+    store: Path
+    copy: list = field(default_factory=list)  # (relative parts, size, mtime_ns)
+    orphans: list = field(default_factory=list)  # relative parts
+    temps: list = field(default_factory=list)
+    left: list = field(default_factory=list)
+    links: int = 0
+    bytes: int = 0
+
+    @property
+    def removable(self):
+        return [item[0] for item in self.copy] + self.orphans + self.temps
+
+
+def scan_store(store, root, *, stop=None):
+    """Sort the files of *store* (the previews of the source *root*).
+
+    A store that does not exist, or is itself a link, scans empty (a link
+    counts once).
+    """
+    store = Path(store)
+    scan = StoreScan(store)
+    try:
+        if preview_location.is_link_like(store):
+            scan.links += 1
+            return scan
+        if not store.is_dir():
+            return scan
+    except OSError:
+        return scan
+    _walk(scan, store, (), root, stop)
+    return scan
+
+
+def _walk(scan, folder, rel_dir, root, stop):
+    try:
+        with os.scandir(folder) as iterator:
+            entries = list(iterator)
+    except OSError:
+        return
+    for entry in entries:
+        if stop is not None and stop():
+            return
+        relative = rel_dir + (entry.name,)
+        path = Path(entry.path)
+        try:
+            if preview_location.is_link_like(path):
+                scan.links += 1
+                continue
+            info = entry.stat(follow_symlinks=False)
+        except OSError:
+            continue
+        if stat_module.S_ISDIR(info.st_mode):
+            _walk(scan, path, relative, root, stop)
+            continue
+        if not stat_module.S_ISREG(info.st_mode):
+            scan.left.append(relative)
+            continue
+        if is_temp_name(entry.name):
+            scan.temps.append(relative)
+            continue
+        if is_os_metadata(entry.name):
+            continue  # removed only when it alone keeps a folder (rmdir)
+        parts = _preview_parts(entry.name)
+        if parts is None:
+            scan.left.append(relative)
+            continue
+        if in_trash_folder("/".join(relative)) or not _has_original(
+            root, rel_dir, *parts
+        ):
+            scan.orphans.append(relative)
+            continue
+        scan.copy.append((relative, info.st_size, info.st_mtime_ns))
+        scan.bytes += info.st_size
+
+
+# ── copying ──────────────────────────────────────────────────────────
+
+
+def rounded_mtime_ns(mtime_ns):
+    """*mtime_ns* rounded up to the next 2-second step (FAT/exFAT)."""
+    return -(-mtime_ns // MTIME_STEP_NS) * MTIME_STEP_NS
+
+
+def too_long(path, long_paths=None):
+    """A destination (with its temp name) over Windows' file limit."""
+    if os.name != "nt" and long_paths is not False:
+        return False
+    if long_paths is None:
+        long_paths = preview_location.long_paths_enabled()
+    if long_paths:
+        return False
+    return len(str(path)) + TEMP_EXTRA > WINDOWS_FILE_LIMIT
+
+
+class CopyFailed(Exception):
+    """One preview could not be copied (a per-file error, D10A)."""
+
+
+class FolderGone(Exception):
+    """The destination cannot take writes any more (abort the move)."""
+
+
+def _make_folders(base, relative_dir, created):
+    """Make ``base/relative_dir`` one folder at a time (*base* must exist);
+    every folder made is added to *created*."""
+    current = Path(base)
+    for part in relative_dir:
+        current = current / part
+        try:
+            os.mkdir(current)
+            created.append(str(current))
+        except FileExistsError:
+            pass  # already there: made by an earlier copy into this folder
+        except OSError as error:
+            if error.errno in (errno.ENOSPC, errno.EDQUOT, errno.EROFS):
+                raise FolderGone(str(error)) from error
+            raise CopyFailed(
+                "Its folder could not be made; made again on view"
+            ) from error
+        if preview_location.is_link_like(current):
+            raise CopyFailed("a link in the destination")
+
+
+def refuse_links(base, relative_dir):
+    """Raise CopyFailed when *base* or an existing folder on the way to
+    ``base/relative_dir`` is a link (never copy through one)."""
+    current = Path(base)
+    for part in (None, *relative_dir):
+        if part is not None:
+            current = current / part
+        if preview_location.is_link_like(current):
+            raise CopyFailed("a link in the destination")
+
+
+def copy_one(source, destination, size, mtime_ns, created, *, long_paths=None):
+    """Copy one preview; returns ``"moved"`` or ``"skipped"`` (already
+    there). Raises CopyFailed (this file) or FolderGone (the destination)."""
+    destination = Path(destination)
+    if too_long(destination, long_paths):
+        raise CopyFailed("Path too long for Windows; the original is shown")
+    wanted = rounded_mtime_ns(mtime_ns)
+    try:
+        existing = os.stat(destination, follow_symlinks=False)
+    except FileNotFoundError:
+        existing = None
+    except OSError as error:
+        raise FolderGone(str(error)) from error
+    if (
+        existing is not None
+        and stat_module.S_ISREG(existing.st_mode)
+        and existing.st_size == size
+        and existing.st_mtime_ns == wanted
+    ):
+        return "skipped"
+    temp = destination.with_name(
+        destination.name + MOVE_TEMP_SUFFIX.format(token=secrets.token_hex(4))
+    )
+    try:
+        shutil.copyfile(source, temp)
+        if os.stat(temp).st_size != size:
+            raise CopyFailed("The copy did not match; made again on view")
+        os.utime(temp, ns=(wanted, wanted))
+        os.replace(temp, destination)
+    except CopyFailed:
+        _unlink(temp)
+        raise
+    except FileNotFoundError as error:
+        _unlink(temp)
+        if not Path(source).exists():
+            raise CopyFailed("Could not be read; made again on view") from error
+        raise FolderGone(str(error)) from error
+    except OSError as error:
+        _unlink(temp)
+        if error.errno in (errno.ENOSPC, errno.EDQUOT, errno.EROFS):
+            raise FolderGone(str(error)) from error
+        raise CopyFailed("Could not be copied; made again on view") from error
+    return "moved"
+
+
+def _unlink(path):
+    """Remove a copy's temp file after a failed copy; True when it is gone.
+
+    One that cannot go (a Windows lock, permissions) is logged with its path;
+    the next start's temp sweep removes it (``.pm-move-*.tmp``)."""
+    try:
+        os.unlink(path)
+        return True
+    except FileNotFoundError:
+        return True  # never written, or already renamed into place
+    except OSError as error:
+        logger.warning(f"Could not remove the move's temp file {path}: {error}")
+        return False
+
+
+# ── removing ─────────────────────────────────────────────────────────
+
+
+def _in_use(error):
+    return getattr(error, "winerror", None) in _WINDOWS_IN_USE
+
+
+def remove_file(path, *, sleep=time.sleep):
+    """Remove one file; a file another program holds open (Windows) is
+    retried 3 times. Returns True when it is gone."""
+    for wait in (0.0,) + REMOVE_RETRIES:
+        if wait:
+            sleep(wait)
+        try:
+            os.unlink(path)
+            return True
+        except FileNotFoundError:
+            return True
+        except OSError as error:
+            if not _in_use(error):
+                return False
+    return False
+
+
+def remove_empty_folders(top, *, keep_top=False):
+    """``rmdir`` the empty folders below *top* (and *top*), bottom-up, never
+    through a link. A folder holding only OS metadata files loses them first.
+    Returns the folders that could not be removed."""
+    top = Path(top)
+    left = []
+    if not top.is_dir() or preview_location.is_link_like(top):
+        return left
+    # Top-down, pruning every link, junction or reparse point, then bottom-up:
+    # never into a folder outside *top* (Windows junctions included).
+    folders = []
+    for folder, dirs, _files in os.walk(top):
+        folder = Path(folder)
+        dirs[:] = [d for d in dirs if not preview_location.is_link_like(folder / d)]
+        folders.append(folder)
+    for folder in reversed(folders):
+        if folder == top and keep_top:
+            continue
+        try:
+            names = os.listdir(folder)
+        except OSError:
+            left.append(folder)
+            continue
+        if names and all(is_os_metadata(name) for name in names):
+            for name in names:
+                remove_file(folder / name)
+        try:
+            os.rmdir(folder)
+        except OSError:
+            left.append(folder)
+    return left
@@ -0,0 +1,492 @@
+"""Move thumbnails, the review (#320 Part 3 phase 1): what a move would copy,
+remove and leave, checked before anything is written."""
+
+import hashlib
+import json
+import os
+import secrets
+import shutil
+import time
+import uuid
+from dataclasses import dataclass, field
+from pathlib import Path
+
+from aiohttp import web
+
+from . import preview_location, preview_store
+from . import thumbnail_move_files as files
+from .job_routes import busy_response
+from .jobs import THUMBNAILS_JOB_KIND, JobBusy
+from .thumbnail_location import default_path
+
+try:
+    from ...utils import library_location
+except ImportError:  # tests import the package top-level
+    from utils import library_location
+
+MOVE_TITLE = "Move thumbnails"
+FINISHING_TITLE = "Move thumbnails (finishing)"
+PRUNE_TITLE = "Remove thumbnails of removed sources"
+MOVE_GROUPS = ("moved", "skipped", "left", "errors")
+PRUNE_GROUPS = ("removed", "left", "errors")
+PLAN_TTL = 600.0
+JOURNAL_NAME = "thumbnail-move.json"
+SPACE_MARGIN = 64 * 2**20
+SPACE_SHARE = 0.05
+LISTED = 5
+SENTENCE = (
+    "Every thumbnail is copied and checked before Prompt Manager switches. "
+    "Scans, deletes and tagging wait until it finishes; closing this page does "
+    "not stop it."
+)
+
+
+def _number(value):
+    return f"{value:,}"
+
+
+def _plural(count, one, many=None):
+    return f"{_number(count)} {one if count == 1 else (many or one + 's')}"
+
+
+def _size(value):
+    size = float(value)
+    for unit in ("B", "KB", "MB", "GB"):
+        if size < 1024 or unit == "GB":
+            return f"{size:.1f} {unit}" if unit != "B" else f"{int(size)} B"
+        size /= 1024
+    return f"{size:.1f} GB"
+
+
+def _refusal(code, status=None, **extra):
+    known_status, text = preview_location.MESSAGES.get(code, (400, code))
+    return web.json_response(
+        {"success": False, "code": code, "error": text, **extra},
+        status=status or known_status,
+    )
+
+
+def journal_path():
+    """``<data folder>/data/thumbnail-move.json`` (only while a move copies)."""
+    return library_location.cache_dir(JOURNAL_NAME)
+
+
+def _read_json(path):
+    try:
+        with open(path, "r", encoding="utf-8") as handle:
+            data = json.load(handle)
+    except (OSError, ValueError):
+        return None
+    return data if isinstance(data, dict) else None
+
+
+def _write_json(path, data):
+    os.makedirs(os.path.dirname(path), exist_ok=True)
+    temp = f"{path}.{os.getpid()}.tmp"
+    with open(temp, "w", encoding="utf-8") as handle:
+        json.dump(data, handle, indent=2)
+        handle.flush()
+        os.fsync(handle.fileno())
+    os.replace(temp, path)
+
+
+def _remove(path):
+    try:
+        os.unlink(path)
+    except FileNotFoundError:
+        pass  # already gone: removing it is the goal
+
+
+def _is_network(path):
+    text = str(path)
+    if text.startswith(("\\\\", "//")):
+        return True
+    if os.name == "nt":
+        try:
+            import ctypes
+
+            drive = os.path.splitdrive(os.path.abspath(text))[0] + "\\"
+            return ctypes.windll.kernel32.GetDriveTypeW(drive) == 4  # DRIVE_REMOTE
+        except (AttributeError, OSError):
+            return False
+    return False
+
+
+def _volume(path):
+    current = Path(os.path.abspath(path))
+    while not current.exists() and current.parent != current:
+        current = current.parent
+    try:
+        return os.stat(current).st_dev
+    except OSError:
+        return None
+
+
+def _free(path):
+    current = Path(os.path.abspath(path))
+    while not current.exists() and current.parent != current:
+        current = current.parent
+    try:
+        return shutil.disk_usage(current).free
+    except OSError:
+        return None
+
+
+# ── the plan ─────────────────────────────────────────────────────────
+
+
+@dataclass
+class SourcePlan:
+    """One listed source: its old store, its new store and what moves."""
+
+    root: str
+    label: str
+    key: str | None
+    old_store: str | None
+    new_store: str
+    scan: files.StoreScan | None
+    available: bool = True
+    too_long: list = field(default_factory=list)
+
+
+@dataclass
+class MovePlan:
+    """A reviewed move: from, to, the sources and the removals."""
+
+    token: str
+    created: float
+    revision: str
+    old: preview_location.ParsedLocation
+    target: dict  # {"mode", "path"}
+    target_id: str | None
+    target_exists: bool
+    target_default: bool
+    install: str
+    sources: list
+    unlisted: list  # (key, store path, scan)
+    needs_bytes: int
+    confirm_required: bool
+
+    @property
+    def to_folder(self):
+        return self.target["mode"] == preview_store.FOLDER_MODE
+
+    @property
+    def from_folder(self):
+        return self.old.mode == preview_store.FOLDER_MODE
+
+
+def _roots_revision(roots):
+    text = json.dumps(sorted(str(root) for root in roots))
+    return hashlib.sha256(text.encode("utf-8")).hexdigest()[:16]
+
+
+class ThumbnailMovePlanMixin:
+    """The move's review and its routes."""
+
+    _move_plans = None
+
+    # ── routes ────────────────────────────────────────────────────────
+
+    def _register_thumbnail_move_routes(self, routes):
+        @routes.post("/prompt_manager/images/thumbnails/plan")
+        async def thumbnail_move_plan_route(request):
+            return await self.plan_thumbnail_move(request)
+
+        @routes.post("/prompt_manager/images/thumbnails/location/recreate")
+        async def thumbnail_location_recreate_route(request):
+            return await self.recreate_thumbnail_folder(request)
+
+        @routes.post("/prompt_manager/images/thumbnails/location/adopt")
+        async def thumbnail_location_adopt_route(request):
+            return await self.adopt_thumbnail_folder(request)
+
+    # ── review ────────────────────────────────────────────────────────
+
+    async def plan_thumbnail_move(self, request):
+        try:
+            body = await request.json()
+        except (ValueError, UnicodeDecodeError):
+            body = None
+        if not isinstance(body, dict) or body.get("mode") != "move":
+            return web.json_response(
+                {
+                    "success": False,
+                    "code": "invalid-request",
+                    "error": "mode must be move",
+                },
+                status=400,
+            )
+        target = body.get("location")
+        if not isinstance(target, dict) or target.get("mode") not in (
+            preview_store.SOURCE_MODE,
+            preview_store.FOLDER_MODE,
+        ):
+            return web.json_response(
+                {
+                    "success": False,
+                    "code": "invalid-request",
+                    "error": "location must name a mode",
+                },
+                status=400,
+            )
+        blocker = self._jobs.blocker(THUMBNAILS_JOB_KIND, admission="guarded")
+        if blocker is not None:
+            return busy_response(JobBusy(blocker))
+        try:
+            outcome = await self._run_in_executor(self._build_move_plan, target)
+        except Exception:
+            self.logger.exception("The thumbnail move could not be planned")
+            return web.json_response(
+                {
+                    "success": False,
+                    "code": None,
+                    "error": "The move could not be planned",
+                },
+                status=500,
+            )
+        if isinstance(outcome, str):
+            return _refusal(outcome)
+        plan, payload = outcome
+        if payload.get("insufficient"):
+            return _refusal(
+                "insufficient-space",
+                status=507,
+                error_detail=payload["insufficient"],
+                plan=payload,
+            )
+        self._store_move_plan(plan)
+        return web.json_response({"success": True, **payload})
+
+    def _store_move_plan(self, plan):
+        if self._move_plans is None:
+            self._move_plans = {}
+        now = time.monotonic()
+        self._move_plans = {
+            token: kept
+            for token, kept in self._move_plans.items()
+            if now - kept.created < PLAN_TTL
+        }
+        self._move_plans[plan.token] = plan
+
+    def _build_move_plan(self, target):
+        """``(plan, payload)`` or a refusal code (blocking)."""
+        old = preview_store.setting()
+        location = preview_store.current()
+        install = old.install or str(uuid.uuid4())
+        target_path = None
+        default = default_path()
+        if target["mode"] == preview_store.FOLDER_MODE:
+            raw = target.get("path")
+            if not isinstance(raw, str):
+                return "location-not-absolute"
+            context = self._thumbnail_location_context()
+            code = preview_location.location_problem(
+                raw, purpose="move", context=context
+            )
+            if code is not None:
+                return code
+            target_path = os.path.abspath(raw)
+        elif old.mode == preview_store.SOURCE_MODE and not old.problem:
+            return "location-same"
+        target_default = bool(default) and os.path.normcase(
+            target_path or ""
+        ) == os.path.normcase(os.path.abspath(default))
+        target_exists = bool(target_path) and os.path.isdir(target_path)
+        target_marker = (
+            preview_location.read_marker(target_path) if target_exists else None
+        )
+        roots = [str(root) for root in self._get_all_output_dirs()]
+        labels = self._source_labels(roots)
+        old_keys = {}
+        if old.mode == preview_store.FOLDER_MODE and location.available:
+            marker = preview_location.read_marker(old.path) or {}
+            old_keys = marker.get("keys") or {}
+        new_keys = dict((target_marker or {}).get("keys") or {})
+        taken = {key: entry.get("identity") for key, entry in new_keys.items()}
+        sources = []
+        for root in roots:
+            identity = os.path.normcase(os.path.realpath(root))
+            dev_ino = preview_location.file_identity(root)
+            old_key = None
+            old_store = None
+            available = True
+            if old.mode == preview_store.SOURCE_MODE:
+                old_store = str(preview_store.source_folder(root))
+            elif location.available:
+                old_key = preview_location.find_key(old_keys, root, identity, dev_ino)
+                if old_key:
+                    old_store = os.path.join(old.path, old_key)
+            else:
+                available = False
+            key = None
+            if target_path:
+                key = old_key or preview_location.find_key(
+                    new_keys, root, identity, dev_ino
+                )
+                if key is None or taken.get(key, identity) != identity:
+                    key = preview_location.source_key(root, identity, taken)
+                taken[key] = identity
+                new_store = os.path.join(target_path, key)
+            else:
+                new_store = str(preview_store.source_folder(root))
+            scan = None
+            if old_store:
+                scan = files.scan_store(old_store, root)
+            plan = SourcePlan(
+                root, labels.get(root, root), key, old_store, new_store, scan, available
+            )
+            if scan is not None and target_path:
+                plan.too_long = [
+                    item[0]
+                    for item in scan.copy
+                    if files.too_long(Path(new_store).joinpath(*item[0]))
+                ]
+            sources.append(plan)
+        unlisted = self._unlisted_keys(old, location, old_keys, install)
+        needs = sum(source.scan.bytes for source in sources if source.scan is not None)
+        plan = MovePlan(
+            token=secrets.token_urlsafe(16),
+            created=time.monotonic(),
+            revision=_roots_revision(roots),
+            old=old,
+            target={"mode": target["mode"], "path": target_path},
+            target_id=(target_marker or {}).get("id"),
+            target_exists=target_exists,
+            target_default=target_default,
+            install=install,
+            sources=sources,
+            unlisted=unlisted,
+            needs_bytes=needs,
+            confirm_required=bool(target_path) and not target_default,
+        )
+        return plan, self._plan_payload(plan, location)
+
+    def _unlisted_keys(self, old, location, keys, install):
+        """This install's keys whose source no longer is in any root list
+        (``(key, store, scan)``), in the folder in use."""
+        if old.mode != preview_store.FOLDER_MODE or not location.available:
+            return []
+        listed = {
+            os.path.normcase(os.path.realpath(root))
+            for root in self._all_source_roots()
+        }
+        found = []
+        for key, entry in sorted(keys.items()):
+            if not preview_location.valid_key(key) or not isinstance(entry, dict):
+                continue  # a marker is data: never a path out of the folder
+            if entry.get("install") not in (install, None):
+                continue
+            if entry.get("identity") in listed:
+                continue
+            store = os.path.join(old.path, key)
+            found.append(
+                (key, store, files.scan_store(store, entry.get("path") or store))
+            )
+        return found
+
+    def _source_labels(self, roots):
+        from . import sources
+
+        labels = sources._comfyui_labels()
+        return {root: sources.source_label(root, labels) for root in roots}
+
+    def _plan_payload(self, plan, location):
+        sources = plan.sources
+        copies = sum(len(s.scan.copy) for s in sources if s.scan)
+        orphans = sum(len(s.scan.orphans) for s in sources if s.scan)
+        temps = sum(len(s.scan.temps) for s in sources if s.scan)
+        links = sum(s.scan.links for s in sources if s.scan)
+        left = [
+            f"{s.label} · {'/'.join(item)}"
+            for s in sources
+            if s.scan
+            for item in s.scan.left
+        ]
+        too_long = [
+            f"{s.label} · {'/'.join(item)}" for s in sources for item in s.too_long
+        ]
+        unlisted_count = sum(
+            len(scan.copy) + len(scan.orphans) for _k, _s, scan in plan.unlisted
+        )
+        free = None
+        insufficient = None
+        if plan.needs_bytes:
+            volumes = {}
+            for source in sources:
+                if source.scan is None or not source.scan.bytes:
+                    continue
+                volume = _volume(source.new_store)
+                entry = volumes.setdefault(volume, [source.new_store, 0])
+                entry[1] += source.scan.bytes
+            for where, needed in volumes.values():
+                available = _free(where)
+                if available is None:
+                    continue
+                free = available if free is None else min(free, available)
+                margin = max(SPACE_MARGIN, int(needed * SPACE_SHARE))
+                if needed + margin > available:
+                    insufficient = {
+                        "needed": needed + margin,
+                        "free": available,
+                        "text": (
+                            f"There is not enough space for the thumbnails: "
+                            f"{_size(available)} free, {_size(needed + margin)} "
+                            "needed. Free some space or choose another folder."
+                        ),
+                    }
+        payload = {
+            "mode": "move",
+            "from": {
+                "mode": plan.old.mode,
+                "path": plan.old.path,
+                "available": location.available,
+            },
+            "to": {
+                "mode": plan.target["mode"],
+                "path": plan.target["path"],
+                "exists": plan.target_exists,
+                "will_create": bool(plan.target["path"]) and not plan.target_exists,
+                "default": plan.target_default,
+            },
+            "sources": [
+                {
+                    "label": s.label,
+                    "key": s.key,
+                    "files": len(s.scan.copy) if s.scan else 0,
+                    "bytes": s.scan.bytes if s.scan else 0,
+                    "too_long": len(s.too_long),
+                    "links": s.scan.links if s.scan else 0,
+                    "orphans": len(s.scan.orphans) if s.scan else 0,
+                    "left_in_place": len(s.scan.left) if s.scan else 0,
+                    "available": s.available,
+                }
+                for s in sources
+            ],
+            "totals": {
+                "sources": len(sources),
+                "files": copies,
+                "bytes": plan.needs_bytes,
+                "orphans": orphans,
+                "temps": temps,
+                "links": links,
+                "left_in_place": len(left),
+                "too_long": len(too_long),
+                "unlisted_sources": len(plan.unlisted),
+                "unlisted_files": unlisted_count,
+            },
+            "too_long_listed": too_long[:LISTED],
+            "left_listed": left[:LISTED],
+            "unlisted": [
+                {"key": key, "files": len(scan.copy) + len(scan.orphans)}
+                for key, _store, scan in plan.unlisted
+            ],
+            "needs_bytes": plan.needs_bytes,
+            "free_bytes": free,
+            "confirm_required": plan.confirm_required,
+            "token": plan.token,
+            "sentence": SENTENCE,
+        }
+        if insufficient:
+            payload["insufficient"] = insufficient
+        return payload
@@ -0,0 +1,246 @@
+"""Move thumbnails after a restart and the unavailable folder's actions
+(#320 Parts 3 and 4): undo an interrupted copy, finish a removal that
+waited, Recreate folder and Use this folder."""
+
+import os
+import threading
+from pathlib import Path
+
+from aiohttp import web
+
+from . import preview_location, preview_store
+from . import thumbnail_move_files as files
+from .job_routes import busy_response
+from .jobs import THUMBNAILS_JOB_KIND, JobBusy
+from .thumbnail_move_plan import (
+    FINISHING_TITLE,
+    MOVE_GROUPS,
+    _read_json,
+    _refusal,
+    _remove,
+)
+from . import thumbnail_move_plan as move_plan
+
+
+class ThumbnailMoveRecoveryMixin:
+    """Startup recovery, the finishing job, Recreate and Use this folder."""
+
+    _move_recover_lock = threading.Lock()
+    # Per API: set once recover_thumbnail_move has run (a move waits for it).
+    _move_recovered = False
+
+    # ── startup ───────────────────────────────────────────────────────
+
+    def recover_thumbnail_move(self):
+        """Startup (B4): undo an interrupted copy, or forget a journal the
+        switch already made true. Idempotent; the move start waits for it."""
+        with self._move_recover_lock:
+            if self._move_recovered:
+                return
+            try:
+                self._recover_journal()
+            except Exception:
+                self.logger.warning(
+                    "The interrupted thumbnail move check failed", exc_info=True
+                )
+            self._move_recovered = True
+
+    def _recover_journal(self):
+        path = move_plan.journal_path()
+        journal = _read_json(path)
+        if journal is None:
+            return
+        setting = preview_store.setting()
+        target = journal.get("to") or {}
+        now = setting.path if setting.mode == preview_store.FOLDER_MODE else None
+        if setting.mode == target.get("mode") and (
+            now is None
+            or os.path.normcase(now) == os.path.normcase(target.get("path") or "")
+        ):
+            _remove(path)  # the switch happened; only the journal was left
+            return
+        for store in journal.get("stores") or []:
+            if not isinstance(store, str) or not os.path.isdir(store):
+                continue
+            for current, dirs, names in os.walk(store):
+                dirs[:] = [
+                    d
+                    for d in dirs
+                    if not preview_location.is_link_like(Path(current) / d)
+                ]
+                for name in names:
+                    if files.MOVE_TEMP.search(name):
+                        files.remove_file(Path(current) / name)
+        for folder in reversed(journal.get("created_dirs") or []):
+            if not isinstance(folder, str) or not os.path.isdir(folder):
+                continue
+            for current, dirs, names in os.walk(folder):
+                dirs[:] = [
+                    d
+                    for d in dirs
+                    if not preview_location.is_link_like(Path(current) / d)
+                ]
+                for name in names:
+                    if files._preview_parts(name) or files.is_temp_name(name):
+                        files.remove_file(Path(current) / name)
+            files.remove_empty_folders(folder)
+        folder = target.get("path")
+        if journal.get("created_folder") and folder and os.path.isdir(folder):
+            names = set(os.listdir(folder))
+            if names <= {preview_location.MARKER_NAME}:
+                _remove(preview_location.marker_path(folder))
+                files.remove_empty_folders(folder)
+        _remove(path)
+        self.logger.info("An interrupted thumbnail move was undone; nothing changed")
+
+    def _cleanup_reachable(self, entry):
+        folder = entry.get("folder")
+        if folder:
+            return os.path.isdir(folder)
+        return True
+
+    async def finish_thumbnail_move(self, _app=None):
+        """Startup: recover, then start "Move thumbnails (finishing)" when old
+        copies wait and every one is reachable (on the server's loop)."""
+        await self._run_in_executor(self.recover_thumbnail_move)
+        cleanup = list(preview_store.setting().cleanup)
+        if not cleanup:
+            return None
+        reachable = await self._run_in_executor(
+            lambda: all(self._cleanup_reachable(entry) for entry in cleanup)
+        )
+        if not reachable:
+            return None
+        try:
+            return self._jobs.start(
+                THUMBNAILS_JOB_KIND,
+                FINISHING_TITLE,
+                admission="guarded",
+                cancellable=False,
+                scope={"mode": "move", "phase": "remove"},
+                groups=MOVE_GROUPS,
+                runner=self._run_finishing,
+            )
+        except JobBusy:
+            return None
+
+    async def _run_finishing(self, job):
+        await self._remove_old_copies(job, None)
+        left = len(preview_store.setting().cleanup)
+        self._end_move(
+            job,
+            "finished",
+            (
+                "Old thumbnails removed."
+                if not left
+                else (
+                    "Some old thumbnails are still in use; they are removed at "
+                    "the next start."
+                )
+            ),
+        )
+
+    # ── Recreate and Use this folder (Part 4) ─────────────────────────
+
+    async def recreate_thumbnail_folder(self, _request):
+        blocker = self._jobs.blocker(THUMBNAILS_JOB_KIND, admission="guarded")
+        if blocker is not None:
+            return busy_response(JobBusy(blocker))
+        code = await self._run_in_executor(self._recreate_folder)
+        if code is not None:
+            status = (
+                409 if code in ("location-has-marker", "location-not-empty") else 400
+            )
+            if code == "location-has-marker":
+                return web.json_response(
+                    {
+                        "success": False,
+                        "code": code,
+                        "error": "The folder is back with its thumbnails. Nothing "
+                        "was recreated.",
+                    },
+                    status=status,
+                )
+            return _refusal(code, status=status)
+        return web.json_response(
+            {
+                "success": True,
+                "location": self._thumbnail_location_payload(with_path=True),
+            }
+        )
+
+    def _recreate_folder(self):
+        setting = preview_store.setting()
+        if setting.mode != preview_store.FOLDER_MODE or not setting.path:
+            return "location-same"
+        folder = setting.path
+        if os.path.isdir(folder):
+            if preview_location.read_marker(folder) is not None:
+                return "location-has-marker"
+            if not preview_location.holds_only_metadata(folder):
+                return "location-not-empty"
+        elif not os.path.isdir(os.path.dirname(folder)):
+            return "location-parent-missing"
+        else:
+            try:
+                os.mkdir(folder)
+            except OSError:
+                return "location-not-writable"
+        try:
+            marker_id = preview_location.init_folder(folder, created_by_pm=True)
+        except OSError:
+            return "location-not-writable"
+        return self._commit_location_id(marker_id)
+
+    async def adopt_thumbnail_folder(self, _request):
+        blocker = self._jobs.blocker(THUMBNAILS_JOB_KIND, admission="guarded")
+        if blocker is not None:
+            return busy_response(JobBusy(blocker))
+        code = await self._run_in_executor(self._adopt_folder)
+        if code is not None:
+            return _refusal(code)
+        return web.json_response(
+            {
+                "success": True,
+                "location": self._thumbnail_location_payload(with_path=True),
+            }
+        )
+
+    def _adopt_folder(self):
+        setting = preview_store.setting()
+        if setting.mode != preview_store.FOLDER_MODE or not setting.path:
+            return "location-same"
+        try:
+            marker = preview_location.read_marker(setting.path)
+        except OSError:
+            return "location-unavailable"
+        if marker is None:
+            return "location-unavailable"
+        return self._commit_location_id(marker["id"])
+
+    def _commit_location_id(self, marker_id):
+        from ..config import PromptManagerConfig
+        from ..config_store import get_config_store
+
+        value = dict(preview_store.setting().to_config())
+        value["id"] = marker_id
+
+        def mutate(config):
+            section = config.get("thumbnails")
+            if not isinstance(section, dict):
+                section = {}
+            section["location"] = value
+            config["thumbnails"] = section
+            return config
+
+        def publish(_config):
+            PromptManagerConfig.THUMBNAIL_LOCATION = value
+            preview_store.configure(value, check=False)
+
+        try:
+            get_config_store().commit(mutate, expected_revision=None, publish=publish)
+        except Exception:
+            self.logger.exception("The thumbnail folder could not be saved")
+            return "location-not-writable"
+        preview_store.refresh()
+        return None
@@ -0,0 +1,175 @@
+"""Remove thumbnails of removed sources (#320 Part 5, D200): a Thumbnail
+maintenance scope, offered only in folder mode (31A).
+
+*Removed* means a key of this install in the thumbnail folder's marker whose
+identity matches no root in any root list. The job removes the
+preview-grammar files and temps of those key folders, ``rmdir``s the empty
+folders, drops the keys from the marker and lists anything else as "Left in
+place". Kind ``thumbnails``, ``mode: "prune"``.
+"""
+
+import functools
+import os
+from pathlib import Path
+
+from aiohttp import web
+
+from . import preview_location, preview_store
+from . import thumbnail_move_files as files
+from .jobs import THUMBNAILS_JOB_KIND
+from .thumbnail_location import location_refusal
+from .thumbnail_move_plan import _number, _plural, _size
+
+PRUNE_TITLE = "Remove thumbnails of removed sources"
+PRUNE_GROUPS = ("removed", "left", "errors")
+
+
+def _prune_line(count, files_count, size):
+    if not count:
+        return "No sources were removed: nothing to remove."
+    return (
+        f"{_plural(count, 'source')} no longer listed: "
+        f"{_plural(files_count, 'thumbnail')} ({_size(size)}) are removed."
+    )
+
+
+class ThumbnailPruneMixin:
+    """The prune plan and job."""
+
+    def _prune_targets(self):
+        """``[(key, store, scan)]`` of this install's unlisted keys (blocking)."""
+        setting = preview_store.setting()
+        location = preview_store.current()
+        if setting.mode != preview_store.FOLDER_MODE or not location.available:
+            return []
+        marker = preview_location.read_marker(setting.path) or {}
+        install = setting.install
+        return self._unlisted_keys(setting, location, marker.get("keys") or {}, install)
+
+    def _prune_payload(self, targets):
+        files_count = sum(
+            len(scan.copy) + len(scan.orphans) for _k, _s, scan in targets
+        )
+        size = sum(scan.bytes for _k, _s, scan in targets)
+        return {
+            "success": True,
+            "mode": "prune",
+            "sources": [
+                {
+                    "key": key,
+                    "files": len(scan.copy) + len(scan.orphans),
+                    "bytes": scan.bytes,
+                    "left_in_place": len(scan.left),
+                }
+                for key, _store, scan in targets
+            ],
+            "targets": files_count,
+            "bytes": size,
+            "line": _prune_line(len(targets), files_count, size),
+            "folder": preview_store.setting().path,
+        }
+
+    async def get_prune_plan(self):
+        refused = location_refusal()
+        if refused is not None:
+            return refused
+        if preview_store.current().mode != preview_store.FOLDER_MODE:
+            return web.json_response(
+                {
+                    "success": False,
+                    "code": "invalid-request",
+                    "error": "Thumbnails are kept inside each source: no removed "
+                    "source has thumbnails here.",
+                },
+                status=400,
+            )
+        targets = await self._run_in_executor(self._prune_targets)
+        return web.json_response(
+            self._prune_payload(targets), headers={"Cache-Control": "no-store"}
+        )
+
+    def start_thumbnail_prune(self):
+        """Start the prune job (sync, on the loop); raises JobBusy."""
+        return self._jobs.start(
+            THUMBNAILS_JOB_KIND,
+            PRUNE_TITLE,
+            admission="guarded",
+            cancellable=True,
+            scope={"mode": "prune"},
+            groups=PRUNE_GROUPS,
+            runner=self._run_thumbnail_prune,
+        )
+
+    async def _run_thumbnail_prune(self, job):
+        targets = await self._run_in_executor(self._prune_targets)
+        job.update(total=len(targets), processed=0)
+        setting = preview_store.setting()
+        for done, (key, store, scan) in enumerate(targets, 1):
+            if job.cancelled:
+                break
+            removed, failed = await self._run_in_executor(
+                functools.partial(self._prune_store, store)
+            )
+            job.record_counted(
+                "removed", removed, [{"path": key, "detail": "Thumbnails removed"}]
+            )
+            if failed:
+                job.record_counted("errors", failed)
+            if scan.left:
+                job.record_counted(
+                    "left",
+                    len(scan.left),
+                    [{"path": f"{key}/{'/'.join(item)}"} for item in scan.left],
+                )
+            await self._run_in_executor(
+                functools.partial(self._forget_key, setting.path, key, store)
+            )
+            job.update(
+                processed=done,
+                progress=int(done * 100 / len(targets)),
+                status_line=f"Removing thumbnails of {_number(done)} of "
+                f"{_number(len(targets))} removed sources",
+            )
+            job.publish({"type": "progress", "summary": job.summary()})
+        line = f"{_number(job.counters.get('removed', 0))} thumbnails removed"
+        if job.counters.get("errors"):
+            line += f" · {_plural(job.counters['errors'], 'error')}"
+        job.update(status_line=line, progress=100)
+        job.log_line(line)
+        job.finish("cancelled" if job.cancelled else "finished")
+
+    @staticmethod
+    def _prune_store(store):
+        """Remove the previews and temps of one key folder; ``(removed, failed)``."""
+        removed = failed = 0
+        store = Path(store)
+        if not store.is_dir() or preview_location.is_link_like(store):
+            return 0, 0
+        for current, dirs, names in os.walk(store):
+            dirs[:] = [
+                d for d in dirs if not preview_location.is_link_like(Path(current) / d)
+            ]
+            for name in names:
+                path = Path(current) / name
+                if not (files.is_temp_name(name) or files._preview_parts(name)):
+                    continue
+                if preview_location.is_link_like(path):
+                    continue
+                if files.remove_file(path):
+                    removed += 1
+                else:
+                    failed += 1
+        files.remove_empty_folders(store)
+        return removed, failed
+
+    @staticmethod
+    def _forget_key(folder, key, store):
+        """Drop *key* from the marker once its folder is gone."""
+        if os.path.exists(store):
+            return
+
+        def forget(marker):
+            marker["keys"].pop(key, None)
+
+        with preview_store.write_lock:
+            preview_location.write_marker(folder, forget)
@@ -114,9 +114,16 @@ def validate_edge(value):
 # ── names ────────────────────────────────────────────────────────────


+def preview_stem(rel_path):
+    """``<rel without extension>_thumb`` (POSIX): a preview's name inside the
+    store of its source (``preview_store``)."""
+    return f"{Path(rel_path).with_suffix('').as_posix()}{THUMB_SUFFIX}"
+
+
 def thumbnail_stem_rel(rel_path):
-    """``thumbnails/<rel without extension>_thumb`` (POSIX)."""
-    return f"thumbnails/{Path(rel_path).with_suffix('').as_posix()}{THUMB_SUFFIX}"
+    """``thumbnails/<rel without extension>_thumb`` (POSIX): URL text only.
+    Where the preview is on disk is ``preview_store``'s answer."""
+    return f"thumbnails/{preview_stem(rel_path)}"


 def thumbnail_rel(rel_path, extension=None):
@@ -207,9 +214,20 @@ def owned_in_folder(folder, stem, source_extension, preferred=None):


 def _owned(root, rel_path, preferred):
+    from . import preview_store
+
    rel_path = Path(rel_path)
-    stem = Path(root) / thumbnail_stem_rel(rel_path)
-    return owned_in_folder(stem.parent, stem.name, rel_path.suffix, preferred)
+    store = preview_store.store_dir(root)
+    if store is None:
+        return iter(())
+    stem = store / preview_stem(rel_path)
+    found = owned_in_folder(stem.parent, stem.name, rel_path.suffix, preferred)
+    if preview_store.current().mode == preview_store.SOURCE_MODE:
+        return found
+    # Folder mode: timed, so a stalled share marks the folder unreachable,
+    # and only previews no link takes out of the key folder (deletes use it).
+    with preview_store.store_io():
+        return iter([path for path in found if preview_store.may_write(path)])


 def owned_thumbnails(root, rel_path, preferred=None):
@@ -59,6 +59,9 @@ REWRITE_FAILED = (
 )
 RECLAIM_FAILED = "Reclaim space failed; the database is unchanged."
 ROW_KEPT = "could not be rewritten; it keeps its inline text and reads as before"
+# A protected value's row (#586), in the review's "not text; kept as is".
+VALUE_KEPT = "stored value not text; kept as is"
+KEPT_COLUMNS = {"workflow_data": "workflow", "prompt_metadata": "prompt graph"}


 NOTHING_LEFT = "Every image record already stores its workflow once"
@@ -177,7 +180,19 @@ class WorkflowStorageRoutesMixin:
            protected += batch["protected"]
            errors += len(batch["errors"])
            job.record_counted("changed", batch["rows"])
-            job.record_counted("protected", batch["protected"])
+            job.record_counted(
+                "protected",
+                batch["protected"],
+                [
+                    {
+                        "path": "",
+                        "detail": f"Image record {image_id}: "
+                        f"{KEPT_COLUMNS.get(column, column)}, {VALUE_KEPT}",
+                    }
+                    for image_id, column in batch["kept"]
+                ],
+                complete=True,
+            )
            for image_id in batch["errors"]:
                job.record(
                    "errors",
@@ -275,3 +290,4 @@ class WorkflowStorageRoutesMixin:
        job.record_counted("changed", 1)
        job.log_line(line)
        job.update(progress=100, status_line=line)
+        return None
@@ -30,9 +30,9 @@ except ImportError:
 # The tag template and thresholds live with the saved tagging defaults
 # (#328), so config.py never imports PIL.
 try:
-    from .tagging_defaults import DEFAULT_TAG_TEMPLATE
+    from .tagging_defaults import DEFAULT_TAG_TEMPLATE, read_wd14_label_rows
 except ImportError:
-    from py.tagging_defaults import DEFAULT_TAG_TEMPLATE
+    from py.tagging_defaults import DEFAULT_TAG_TEMPLATE, read_wd14_label_rows

 try:
    from ..utils import exit_signal
@@ -559,7 +559,6 @@ class AutoTagService:
        # A missing onnxruntime is refused by load_model before this runs
        # (#424); a ModuleNotFoundError here becomes the same refusal.
        import onnxruntime as ort
-        import csv

        config = MODELS[model_type]
        model_dir = self.models_dir / config["subdir"]
@@ -576,12 +575,8 @@ class AutoTagService:

        session = ort.InferenceSession(str(model_path), providers=providers)

-        # Read tag list from CSV
-        tags_list = []
-        with open(tags_path, "r", encoding="utf-8") as f:
-            reader = csv.DictReader(f)
-            for row in reader:
-                tags_list.append(row)
+        # Read tag list from CSV (the reader the Skipped tags preview shares)
+        tags_list = read_wd14_label_rows(tags_path)

        self.logger.info(
            f"WD14 model loaded ({len(tags_list)} tags, "
@@ -992,6 +987,7 @@ class AutoTagService:
        prompt: Optional[str] = None,
        general_threshold: Optional[float] = None,
        character_threshold: Optional[float] = None,
+        skip: Any = None,
    ) -> List[Tuple[str, Optional[float]]]:
        """The top ``limit`` suggestions as ``(name, confidence)`` pairs.

@@ -1000,7 +996,9 @@ class AutoTagService:
        ``None``. Names are distinct case-insensitively (first one wins).
        A name Save would reject (over 50 characters, a control character
        such as a newline, a comma) is skipped before the dedupe and the
-        ``limit`` count. ``prompt`` is used for this call only;
+        ``limit`` count. A name ``skip`` matches (a ``SkipMatcher``, the
+        Skipped tags compiled for this request or job, #431) is dropped next,
+        so it uses up no slot. ``prompt`` is used for this call only;
        ``custom_prompt`` is never changed.
        """
        if type(limit) is not int or not 1 <= limit <= MAX_SUGGESTION_LIMIT:
@@ -1017,6 +1015,8 @@ class AutoTagService:
                name = validate_vocabulary_tag_name(raw)
            except ValueError:
                continue
+            if skip is not None and skip.matches(name):
+                continue
            key = name.casefold()
            if key in seen:
                continue
@@ -30,6 +30,7 @@ routes = server_instance.routes
 # Extension info
 extension_uri = None  # Will be set in __init__.py

+import hashlib  # noqa: E402
 import os  # noqa: E402
 from typing import Any, Dict, List, Optional, Tuple  # noqa: E402

@@ -587,8 +588,15 @@ try:
        MODEL_TYPES,
        WD14_MODEL_TYPES,
        validate_saved_threshold,
+        validate_skipped_tags,
        validate_template,
        validate_threshold,
+        BUILTIN_INSTRUCTIONS_ID,
+        INSTRUCTION_ENGINES,
+        MAX_SAVED_INSTRUCTIONS,
+        builtin_instructions,
+        validate_default_instructions,
+        validate_instructions,
    )
 except ImportError:
    from py.tagging_defaults import (  # noqa: F401 - re-exported
@@ -600,8 +608,15 @@ except ImportError:
        MODEL_TYPES,
        WD14_MODEL_TYPES,
        validate_saved_threshold,
+        validate_skipped_tags,
        validate_template,
        validate_threshold,
+        BUILTIN_INSTRUCTIONS_ID,
+        INSTRUCTION_ENGINES,
+        MAX_SAVED_INSTRUCTIONS,
+        builtin_instructions,
+        validate_default_instructions,
+        validate_instructions,
    )


@@ -617,6 +632,31 @@ def _valid_existing(value: Any) -> str:
    return value


+def _valid_skipped_tags(value: Any) -> Tuple[str, ...]:
+    return tuple(validate_skipped_tags(value))
+
+
+def _reason(error: ValueError) -> str:
+    """A settings sentence as a load warning's reason ("entry 2 is empty")."""
+    text = str(error).rstrip(".")
+    for prefix in ("Skipped tags", "Saved instructions"):
+        if text.startswith(prefix):
+            return text.removeprefix(prefix).lstrip(": ")
+    return text
+
+
+def _text_id(text: str) -> str:
+    """A migrated entry's id: deterministic, so every load gives the same."""
+    return hashlib.sha256(text.encode("utf-8")).hexdigest()[:12]
+
+
+def _fallback_warning(key: str, error: ValueError, default: Any) -> str:
+    """The one load warning of a saved tagging default that fails its check."""
+    if key == "skipped_tags":
+        return f"autotag.defaults.skipped_tags {_reason(error)}; using no skipped tags"
+    return f"autotag.defaults.{key} {error}; using {default!r}"
+
+
 def _valid_suggestion_limit(value: Any) -> int:
    if type(value) is not int or not 1 <= value <= MAX_SUGGESTION_LIMIT:
        raise ValueError(f"must be an integer from 1 to {MAX_SUGGESTION_LIMIT}")
@@ -637,8 +677,18 @@ class AutotagConfig:
    EXISTING = "skip"
    GENERAL_THRESHOLD = 0.35
    CHARACTER_THRESHOLD = 0.85
-    TEMPLATE = DEFAULT_TAG_TEMPLATE
    SUGGESTION_LIMIT = DEFAULT_SUGGESTION_LIMIT
+    SKIPPED_TAGS: Tuple[str, ...] = ()
+    # #431: the saved instructions (Built-in is never stored) and the default
+    # of each language-model engine, by id.
+    INSTRUCTIONS: Tuple[Dict[str, str], ...] = ()
+    DEFAULT_INSTRUCTIONS: Dict[str, str] = {
+        "gguf": BUILTIN_INSTRUCTIONS_ID,
+        "hf": BUILTIN_INSTRUCTIONS_ID,
+    }
+    # The old single template as read at load (None when absent or invalid);
+    # only the migration reads it. Saves keep it as the GGUF default's mirror.
+    _LEGACY_TEMPLATE: Optional[str] = None

    # config.json key -> (attribute, validator, default)
    _KEYS = {
@@ -654,12 +704,13 @@ class AutotagConfig:
            lambda v: validate_saved_threshold("value", v),
            0.85,
        ),
-        "template": ("TEMPLATE", validate_template, DEFAULT_TAG_TEMPLATE),
        "suggestion_limit": (
            "SUGGESTION_LIMIT",
            _valid_suggestion_limit,
            DEFAULT_SUGGESTION_LIMIT,
        ),
+        # #431: words whose suggested tags are never offered.
+        "skipped_tags": ("SKIPPED_TAGS", _valid_skipped_tags, ()),
    }

    @classmethod
@@ -672,17 +723,142 @@ class AutotagConfig:
            type(value) is int and 1 <= value <= MAX_SUGGESTION_LIMIT
        )  # bool, float and str are rejected

+    @classmethod
+    def all_instructions(cls) -> List[Dict[str, str]]:
+        """Built-in first, then the saved entries (copies)."""
+        return [builtin_instructions()] + [dict(item) for item in cls.INSTRUCTIONS]
+
+    @classmethod
+    def default_instructions_text(cls, engine: str) -> str:
+        """The text of ``engine``'s (``gguf`` or ``hf``) default instructions."""
+        if engine not in INSTRUCTION_ENGINES:
+            raise ValueError(f"{engine} takes no instructions")
+        wanted = cls.DEFAULT_INSTRUCTIONS.get(engine, BUILTIN_INSTRUCTIONS_ID)
+        for item in cls.INSTRUCTIONS:
+            if item["id"] == wanted:
+                return item["text"]
+        return DEFAULT_TAG_TEMPLATE
+
+    @classmethod
+    def mirror_template(cls) -> Optional[str]:
+        """What an older build reads as its one template (#431 B1.1): the
+        GGUF default's text, or None (no key) when that default is Built-in."""
+        if cls.DEFAULT_INSTRUCTIONS.get("gguf") == BUILTIN_INSTRUCTIONS_ID:
+            return None
+        return cls.default_instructions_text("gguf")
+
    @classmethod
    def get_config(cls) -> Dict[str, Any]:
-        """The saved defaults; the template only when it is not the built-in
-        one, so a later built-in template still reaches who never set one."""
+        """The saved defaults; ``template`` only as the GGUF default's mirror."""
        defaults = {
            key: getattr(cls, attr) for key, (attr, _v, _d) in cls._KEYS.items()
        }
-        if defaults["template"] == DEFAULT_TAG_TEMPLATE:
-            del defaults["template"]
+        defaults["skipped_tags"] = list(defaults["skipped_tags"])
+        defaults["instructions"] = [dict(item) for item in cls.INSTRUCTIONS]
+        defaults["default_instructions"] = dict(cls.DEFAULT_INSTRUCTIONS)
+        mirror = cls.mirror_template()
+        if mirror is not None:
+            defaults["template"] = mirror
        return {"defaults": defaults}

+    @classmethod
+    def _load_instructions(cls, defaults: Dict[str, Any]) -> None:
+        """Each instruction key alone, then the cross-key default check, then
+        the in-memory migration of the old template (#431). Nothing is
+        written here, so the revision never changes at load."""
+        cls._LEGACY_TEMPLATE = None
+        if "template" in defaults:
+            try:
+                cls._LEGACY_TEMPLATE = validate_template(defaults["template"])
+            except ValueError as error:
+                config_logger.warning(
+                    f"autotag.defaults.template {error}; using the built-in one"
+                )
+        entries: List[Dict[str, str]] = []
+        damaged = False
+        if "instructions" in defaults:
+            try:
+                entries = validate_instructions(defaults["instructions"])
+            except ValueError as error:
+                damaged = True
+                config_logger.warning(
+                    f"autotag.defaults.instructions {_reason(error)}; "
+                    "using Built-in only"
+                )
+        chosen = {engine: BUILTIN_INSTRUCTIONS_ID for engine in INSTRUCTION_ENGINES}
+        stored = defaults.get("default_instructions")
+        if damaged:
+            # Both defaults fall back with the list (its one warning says so);
+            # the old template is migrated as on a first upgrade.
+            pass
+        elif "default_instructions" in defaults and (
+            not isinstance(stored, dict) or set(stored) != set(INSTRUCTION_ENGINES)
+        ):
+            config_logger.warning(
+                "autotag.defaults.default_instructions must name gguf and hf; "
+                "using Built-in"
+            )
+        elif isinstance(stored, dict):
+            ids = {item["id"] for item in entries}
+            for engine in INSTRUCTION_ENGINES:
+                value = stored[engine]
+                if isinstance(value, str) and (
+                    value == BUILTIN_INSTRUCTIONS_ID or value in ids
+                ):
+                    chosen[engine] = value
+                else:
+                    config_logger.warning(
+                        f"autotag.defaults.default_instructions.{engine} names no "
+                        "saved instructions; using Built-in"
+                    )
+        cls._migrate_template(
+            entries,
+            chosen,
+            first=damaged or "instructions" not in defaults,
+            keep_defaults=not damaged and "default_instructions" in defaults,
+        )
+        cls.INSTRUCTIONS = tuple(entries)
+        cls.DEFAULT_INSTRUCTIONS = chosen
+
+    @classmethod
+    def _migrate_template(cls, entries, chosen, *, first, keep_defaults) -> None:
+        """Bring a template saved by an older build in as a named entry."""
+        legacy = cls._LEGACY_TEMPLATE
+        if legacy is None or legacy == DEFAULT_TAG_TEMPLATE:
+            return
+        if first:
+            # The first upgrade: it becomes "Custom template", the default for
+            # both engines unless defaults are stored already (20A).
+            entries.append(
+                {"id": _text_id(legacy), "name": "Custom template", "text": legacy}
+            )
+            if not keep_defaults:
+                for engine in INSTRUCTION_ENGINES:
+                    chosen[engine] = entries[-1]["id"]
+            return
+        if any(item["text"] == legacy for item in entries):
+            return  # the mirror of a saved default
+        # Edited on an older build after an upgrade (B1.2): import it.
+        if len(entries) >= MAX_SAVED_INSTRUCTIONS:
+            config_logger.warning(
+                "The tagging template edited on an older version was not imported: "
+                f"the saved instructions are full ({MAX_SAVED_INSTRUCTIONS})"
+            )
+            return
+        names = {item["name"].casefold() for item in entries}
+        number = 2
+        while f"custom template ({number})" in names:
+            number += 1
+        name = f"Custom template ({number})"
+        ids = {item["id"] for item in entries}
+        new_id, n = _text_id(legacy), 2
+        while new_id in ids:
+            new_id, n = _text_id(f"{legacy}\n{n}"), n + 1
+        entries.append({"id": new_id, "name": name, "text": legacy})
+        config_logger.info(
+            "Imported the tagging template edited on an older version as " f"'{name}'"
+        )
+
    @classmethod
    def update_config(cls, new_config: Any) -> None:
        if not isinstance(new_config, dict):
@@ -698,12 +874,9 @@ class AutotagConfig:
            try:
                setattr(cls, attr, validate(defaults[key]))
            except ValueError as error:
-                config_logger.warning(
-                    f"autotag.defaults.{key} {error}; using {default!r}"
-                    if key != "template"
-                    else f"autotag.defaults.template {error}; using the built-in one"
-                )
+                config_logger.warning(_fallback_warning(key, error, default))
                setattr(cls, attr, default)
+        cls._load_instructions(defaults)


 class PromptManagerConfig:
@@ -767,6 +940,8 @@ class PromptManagerConfig:
    THUMBNAIL_QUALITY = 80
    THUMBNAIL_EDGE = 512
    THUMBNAIL_EDGE_RANGE = (128, 2048)
+    # #320 thumbnail location (config.json ``thumbnails.location``), as read.
+    THUMBNAIL_LOCATION = None

    @classmethod
    def max_worker_threads(cls) -> int:
@@ -828,6 +1003,12 @@ class PromptManagerConfig:
                "format": cls.THUMBNAIL_FORMAT,
                "quality": cls.THUMBNAIL_QUALITY,
                "edge": cls.THUMBNAIL_EDGE,
+                # #320: as read; only the Move thumbnails job writes it.
+                **(
+                    {"location": cls.THUMBNAIL_LOCATION}
+                    if cls.THUMBNAIL_LOCATION is not None
+                    else {}
+                ),
            },
            "gallery": GalleryConfig.get_config(),
            "integrations": IntegrationConfig.get_config(),
@@ -1002,6 +1183,11 @@ class PromptManagerConfig:
        low, high = cls.THUMBNAIL_EDGE_RANGE
        if type(edge) is int and low <= edge <= high:
            cls.THUMBNAIL_EDGE = edge
+        # #320: kept as read (``preview_location.parse_location`` checks it;
+        # a bad value becomes an unavailable ``invalid`` location, never a
+        # silent fall-back to the sources).
+        if "location" in section:
+            cls.THUMBNAIL_LOCATION = section["location"]


 # Load configuration on import
@@ -109,6 +109,7 @@ def _write_atomically(path: str, payload: bytes) -> None:
        try:
            os.unlink(temp_path)
        except OSError:
+            # nothing to clean up; the original error is raised below
            pass
        raise

@@ -642,6 +642,7 @@ def layout_summary(layout: LoraManagerLayout, home: Path) -> Dict:
            relative = Path(settings_file).relative_to(home)
            settings_file = os.path.join("~", str(relative))
        except ValueError:
+            # outside the home folder: show the full path
            pass
    return {
        "source": layout.source,
@@ -585,6 +585,7 @@ def _read_capped(resp, cap: int) -> Optional[bytes]:
            if int(declared) > cap:
                return None
        except ValueError:
+            # a bad header says nothing; the read below enforces the cap
            pass

    chunks = []
@@ -707,6 +708,7 @@ def _save_atomically(image, local_path: Path) -> None:
        try:
            os.remove(temp)
        except OSError:
+            # nothing to clean up; the original error is raised below
            pass
        raise

@@ -4,8 +4,13 @@ Server-free on purpose: ``py.api`` must import without ComfyUI's ``server``
 module, which ``py/config.py`` needs; config re-exports all of this.
 """

+import csv
 import math
-from typing import Any
+import os
+import re
+import threading
+import unicodedata
+from typing import Any, Dict, Iterable, List, Set, Tuple

 # The tagging engines (``py/autotag.py`` MODELS) and the options they take.
 WD14_MODEL_TYPES = frozenset({"wd14-swinv2", "wd14-vit"})
@@ -88,3 +93,230 @@ def validate_template(value: Any, name: str = "instructions") -> str:
    if len(encoded) > MAX_INSTRUCTION_BYTES:
        raise ValueError(f"{name} {'are' if name == 'instructions' else 'is'} too long")
    return value
+
+
+# Skipped tags (#431): words whose suggested tags are never offered.
+MAX_SKIPPED_TAGS = 200
+MAX_SKIPPED_TAG_CHARS = 50
+_WORD_SEPARATORS = re.compile(r"[ _-]+")
+_FORBIDDEN_IN_ENTRY = re.compile(r"[,\x00-\x1f\x7f-\x9f\u2028\u2029]")
+
+
+def tag_words(text: str) -> Tuple[str, ...]:
+    """The words of a tag or a skipped entry: NFC, case-folded, split on runs
+    of space, ``_`` and ``-``. Every other character belongs to a word."""
+    folded = unicodedata.normalize("NFC", text).casefold()
+    return tuple(word for word in _WORD_SEPARATORS.split(folded) if word)
+
+
+def validate_skipped_tags(value: Any) -> List[str]:
+    """The Skipped tags list, each entry trimmed, or ValueError with the
+    sentence the System page shows (entries are numbered from 1)."""
+    if not isinstance(value, list):
+        raise ValueError("Skipped tags must be a list of words.")
+    if len(value) > MAX_SKIPPED_TAGS:
+        raise ValueError(f"Skipped tags: at most {MAX_SKIPPED_TAGS} entries.")
+    entries: List[str] = []
+    seen: Dict[Tuple[str, ...], int] = {}
+    for number, raw in enumerate(value, 1):
+        if not isinstance(raw, str):
+            raise ValueError(f"Skipped tags: entry {number} must be text.")
+        entry = raw.strip()
+        if not entry:
+            raise ValueError(f"Skipped tags: entry {number} is empty.")
+        if len(entry) > MAX_SKIPPED_TAG_CHARS:
+            raise ValueError(
+                f"Skipped tags: entry {number} must be at most "
+                f"{MAX_SKIPPED_TAG_CHARS} characters."
+            )
+        if _FORBIDDEN_IN_ENTRY.search(entry):
+            raise ValueError(
+                f"Skipped tags: entry {number} must not contain a comma "
+                "or a line break."
+            )
+        words = tag_words(entry)
+        if not words:
+            raise ValueError(f"Skipped tags: entry {number} is empty.")
+        if words in seen:
+            raise ValueError(
+                f"Skipped tags: entry {number} repeats entry {seen[words]}."
+            )
+        seen[words] = number
+        entries.append(entry)
+    return entries
+
+
+class SkipMatcher:
+    """Whether a suggested tag contains a skipped entry's words, consecutive
+    and whole (#431, 17B). Compiled once per request or job; the cost of a
+    check depends on the tag's words, not on the number of entries."""
+
+    def __init__(self, entries: Iterable[str] = ()):
+        self._entries = frozenset(filter(None, (tag_words(e) for e in entries)))
+        self._longest = max((len(words) for words in self._entries), default=0)
+
+    def __bool__(self) -> bool:
+        return bool(self._entries)
+
+    def matches(self, name: str) -> bool:
+        if not self._entries:
+            return False
+        words = tag_words(name)
+        for start in range(len(words)):
+            stop = min(len(words), start + self._longest)
+            for end in range(start + 1, stop + 1):
+                if words[start:end] in self._entries:
+                    return True
+        return False
+
+    def counting(self) -> "CountingSkip":
+        """A per-request view that also remembers which names it hid."""
+        return CountingSkip(self)
+
+
+class CountingSkip:
+    """A :class:`SkipMatcher` that records the distinct names it hid, so the
+    Tag image dialog can say how many skipped tags were not suggested."""
+
+    def __init__(self, matcher: SkipMatcher):
+        self._matcher = matcher
+        self.hidden: Set[str] = set()
+
+    def matches(self, name: str) -> bool:
+        if self._matcher.matches(name):
+            self.hidden.add(name.casefold())
+            return True
+        return False
+
+
+# A WD14 label list's tags the engine can suggest: general (0) and character (4).
+WD14_SUGGESTED_CATEGORIES = frozenset({"0", "4"})
+_label_cache: Dict[str, Tuple[Tuple[int, int], Tuple[str, ...]]] = {}
+_label_cache_lock = threading.Lock()
+
+
+def read_wd14_label_rows(path) -> List[Dict[str, str]]:
+    """Every row of a WD14 ``selected_tags.csv``, read as UTF-8 and closed
+    before returning (the handle never outlives the call, for Windows)."""
+    with open(path, "r", encoding="utf-8", newline="") as handle:
+        return list(csv.DictReader(handle))
+
+
+def wd14_label_names(path) -> Tuple[str, ...]:
+    """The names a WD14 label list can suggest (categories 0 and 4), cached
+    by ``(mtime_ns, size)``. OSError (missing) and ValueError (unreadable)
+    propagate; the caller skips that list."""
+    key = os.fspath(path)
+    stat = os.stat(key)
+    stamp = (stat.st_mtime_ns, stat.st_size)
+    with _label_cache_lock:
+        cached = _label_cache.get(key)
+    if cached is not None and cached[0] == stamp:
+        return cached[1]
+    try:
+        rows = read_wd14_label_rows(key)
+    except csv.Error as exc:  # a damaged list (a NUL byte, an oversized field)
+        raise ValueError(f"unreadable label list: {exc}") from None
+    names = tuple(
+        name
+        for row in rows
+        if row.get("category", "0") in WD14_SUGGESTED_CATEGORIES
+        and (name := (row.get("name") or "").strip())
+    )
+    with _label_cache_lock:
+        _label_cache[key] = (stamp, names)
+    return names
+
+
+# Saved instructions (#431): named language-model instructions with a default
+# per engine. Built-in is never stored; readers put it first.
+BUILTIN_INSTRUCTIONS_ID = "builtin"
+BUILTIN_INSTRUCTIONS_NAME = "Built-in"
+MAX_SAVED_INSTRUCTIONS = 20
+MAX_INSTRUCTION_NAME_CHARS = 60
+INSTRUCTION_ENGINES = ("gguf", "hf")
+ENGINE_LABELS = {"gguf": "GGUF JoyCaption", "hf": "HuggingFace JoyCaption"}
+_INSTRUCTION_ID = re.compile(r"[0-9a-f]{12}")
+_CONTROL = re.compile(r"[\x00-\x1f\x7f-\x9f  ]")
+
+
+def builtin_instructions() -> Dict[str, str]:
+    """The read-only Built-in entry, always the shipped template."""
+    return {
+        "id": BUILTIN_INSTRUCTIONS_ID,
+        "name": BUILTIN_INSTRUCTIONS_NAME,
+        "text": DEFAULT_TAG_TEMPLATE,
+    }
+
+
+def _instruction_entry(raw: Any, number: int) -> Dict[str, str]:
+    prefix = f"Saved instructions: entry {number}"
+    if (
+        not isinstance(raw, dict)
+        or set(raw) != {"id", "name", "text"}
+        or not isinstance(raw["id"], str)
+        or _INSTRUCTION_ID.fullmatch(raw["id"]) is None
+    ):
+        raise ValueError(f"{prefix} has an invalid id.")
+    name = raw["name"].strip() if isinstance(raw["name"], str) else ""
+    if not name:
+        raise ValueError(f"{prefix} needs a name.")
+    if len(name) > MAX_INSTRUCTION_NAME_CHARS:
+        raise ValueError(
+            f"{prefix} name must be at most {MAX_INSTRUCTION_NAME_CHARS} characters."
+        )
+    if _CONTROL.search(name):
+        raise ValueError(f"{prefix} name must not contain a line break.")
+    if name.casefold() == BUILTIN_INSTRUCTIONS_NAME.casefold():
+        raise ValueError("Saved instructions: the name “Built-in” is reserved.")
+    try:
+        text = validate_template(raw["text"], f"{prefix} text")
+    except ValueError as error:
+        raise ValueError(f"{error}.") from None
+    return {"id": raw["id"], "name": name, "text": text}
+
+
+def validate_instructions(value: Any) -> List[Dict[str, str]]:
+    """The saved entries ``[{id, name, text}]`` in order (names trimmed), or
+    ValueError with the sentence System shows (Built-in is not counted)."""
+    if not isinstance(value, list):
+        raise ValueError("Saved instructions must be a list.")
+    if len(value) > MAX_SAVED_INSTRUCTIONS:
+        raise ValueError(
+            f"Saved instructions: at most {MAX_SAVED_INSTRUCTIONS} entries besides "
+            "Built-in."
+        )
+    entries: List[Dict[str, str]] = []
+    ids: Dict[str, int] = {}
+    names: Dict[str, int] = {}
+    for number, raw in enumerate(value, 1):
+        item = _instruction_entry(raw, number)
+        if item["id"] in ids:
+            raise ValueError(
+                f"Saved instructions: entry {number} repeats the id of entry "
+                f"{ids[item['id']]}."
+            )
+        key = item["name"].casefold()
+        if key in names:
+            raise ValueError(
+                f"Saved instructions: entry {number} name “{item['name']}” is "
+                "already used."
+            )
+        ids[item["id"]] = number
+        names[key] = number
+        entries.append(item)
+    return entries
+
+
+def validate_default_instructions(value: Any, entries) -> Dict[str, str]:
+    """``{gguf: id, hf: id}``, each Built-in or an id of ``entries``."""
+    if not isinstance(value, dict) or set(value) != set(INSTRUCTION_ENGINES):
+        raise ValueError("Default instructions must name GGUF and HuggingFace.")
+    ids = {BUILTIN_INSTRUCTIONS_ID} | {item["id"] for item in entries}
+    for engine in INSTRUCTION_ENGINES:
+        if not isinstance(value[engine], str) or value[engine] not in ids:
+            raise ValueError(
+                f"Default for {ENGINE_LABELS[engine]} must be one of the saved "
+                "instructions."
+            )
+    return {engine: value[engine] for engine in INSTRUCTION_ENGINES}
@@ -1,10 +1,10 @@
 [project]
 name = "promptmanager"
 description = "A powerful ComfyUI custom node that extends the standard text encoder with persistent prompt storage, advanced search capabilities, and an automatic image gallery system using SQLite."
-version = "3.3.1"
+version = "3.5.0"
 license = {file = "LICENSE"}
 requires-python = ">=3.12"
-dependencies = ["watchdog>=2.1.0", "Pillow>=8.0.0"]
+dependencies = ["watchdog>=2.1.0", "Pillow>=10.1.0"]

 [build-system]
 requires = ["setuptools>=84.2.1"]
@@ -1,11 +1,11 @@
-# Runtime dependencies
+# Runtime dependencies (Pillow, aiohttp and numpy floors match ComfyUI requirements.txt)
 watchdog>=6.0.0
-Pillow>=12.3.0
-aiohttp>=3.14.5
+Pillow>=10.1.0
+aiohttp>=3.11.8

 # Tests and coverage
 coverage>=7.16.2
-numpy>=2.2.6  # WD14 engine tests
+numpy>=1.25.0  # WD14 engine tests

 # Code quality
 black==26.10.1
@@ -1,4 +1,4 @@
 # Runtime dependencies for PromptManager.
 # aiohttp, numpy and torch come from ComfyUI itself and are not listed here.
-watchdog>=2.1.0              # Output directory monitoring
-Pillow>=8.0.0                # Image metadata extraction and thumbnails
+watchdog>=2.1.0               # Output directory monitoring
+Pillow>=10.1.0               # Image metadata extraction and thumbnails
@@ -6,7 +6,6 @@ import { THEMES, seedConcept, openConcept, openProduction, diffInventory, mutate
 // app.js 1428–1432) and its backup box with the concept's System `.notice`; the differences are D55. The job view
 // has no concept counterpart: it is compared with the approved mockup `activity-scan.html` (a local, ignored file),
 // whose structure and CSS values are restated below (D56). Each comparison is shown to notice a mutation.
-const workspace = '/prompt_manager/workspace';

 test.beforeEach(async ({ page, request, browserName }) => {
    await startCoverage(page, browserName);
@@ -320,3 +320,44 @@ test('copy toast and fallback dialog',async({page})=>{
    await expect(fallback).toContainText('Automatic clipboard access requires a secure browser context.');
    await page.keyboard.press('Escape');await expect(fallback).toBeHidden();await expect(copy).toBeFocused();
 });
+
+// #542 D191: "All N eligible nodes" previews every node, sends one after another and names each refusal.
+test('All eligible nodes previews each node, sends in node id order and names a refusal',async({page,context},testInfo)=>{
+    const host=await context.newPage();await host.goto('/prompt_manager/workspace#/overview');
+    await host.evaluate(async()=>{
+        const {createBridgeHost}=await import('/prompt_manager/js/shared/toolkit/prompt-bridge.js');
+        const targets=['12','3','7'].map(id=>({id,label:id==='7'?'Edited in ComfyUI':'Prompt Manager (+/-)',type:'PromptManagerPair',roles:['positive','negative']}));
+        window.hostValues=Object.fromEntries(targets.map(target=>[target.id,{positive:`Existing ${target.id}`,negative:'Existing negative'}]));window.applied=[];
+        window.fixtureHost=createBridgeHost({origin:location.origin,namespace:'/',label:'Test ComfyUI',adapter:{
+            listTargets:()=>targets,
+            preview:(id,roles)=>{const target=targets.find(item=>item.id===id);return{preview:{target,fields:Object.entries(roles).map(([role,after])=>({role,before:window.hostValues[id][role],after}))},snapshot:{id,roles}};},
+            apply:({id,roles})=>{if(id==='7')throw new Error('Workflow or prompt changed. Preview again.');Object.assign(window.hostValues[id],roles);window.applied.push(id);return{targetId:id,values:roles};},
+        }});
+    });
+    try {
+        await page.goto(workspace);await select(page,'0:shared/same.png');await details(page).getByRole('button',{name:/^Send prompt pair to ComfyUI: /}).click();
+        const sender=dialog(page);const nodes=sender.getByRole('combobox',{name:'Destination node',exact:true});
+        await sender.getByRole('combobox',{name:'ComfyUI window',exact:true}).selectOption({label:'Test ComfyUI'});
+        await expect(nodes.locator('option')).toHaveText(['Choose a destination node','#12 Prompt Manager (+/-)','#3 Prompt Manager (+/-)','#7 Edited in ComfyUI','All 3 eligible nodes']);
+        await expect(nodes).toHaveValue('');
+        await nodes.selectOption({label:'All 3 eligible nodes'});
+        await expect(sender.getByRole('status')).toHaveText('Sending to all 3 eligible nodes in Test ComfyUI. Apply to send it, or preview the changes first.');
+        await page.screenshot({path:testInfo.outputPath('send-all-option.png')});
+        await sender.getByRole('button',{name:'Preview changes',exact:true}).click();
+        const reviews=sender.locator('section.prompt-sender-node');
+        await expect(reviews.locator('> h4')).toHaveText(['#3 Prompt Manager (+/-)','#7 Edited in ComfyUI','#12 Prompt Manager (+/-)']);
+        await expect(sender.getByRole('region',{name:'#12 Prompt Manager (+/-)',exact:true})).toContainText('Existing 12');
+        expect(await host.evaluate(()=>window.applied)).toEqual([]);
+        await sender.getByRole('button',{name:'Apply to ComfyUI',exact:true}).click();
+        await expect(sender.getByRole('alert')).toHaveText('Sent to 2 of 3 nodes in Test ComfyUI. #7 Edited in ComfyUI: Workflow or prompt changed. Preview again.');
+        expect(await host.evaluate(()=>window.applied)).toEqual(['3','12']);
+        expect(await host.evaluate(()=>window.hostValues['7'].positive)).toBe('Existing 7');
+        await page.screenshot({path:testInfo.outputPath('send-all-result.png')});
+        await page.setViewportSize({width:390,height:844});
+        await sender.getByRole('button',{name:'Preview changes',exact:true}).click();await expect(reviews).toHaveCount(3);
+        await reviews.last().scrollIntoViewIfNeeded();
+        expect(await page.evaluate(()=>document.querySelector('dialog.prompt-sender').scrollWidth<=document.querySelector('dialog.prompt-sender').clientWidth+1)).toBe(true);
+        await page.screenshot({path:testInfo.outputPath('send-all-mobile.png')});
+        const apply=sender.getByRole('button',{name:'Apply to ComfyUI',exact:true});await apply.focus();await expect(apply).toBeFocused();
+    } finally {await host.evaluate(()=>window.fixtureHost.dispose());await host.close();}
+});
@@ -22,6 +22,9 @@ from PIL.PngImagePlugin import PngInfo
 from tests.browser.folder_trash import close_trash, replace_folder
 from tests.browser.malloc_tuning import pin_mmap_threshold
 from tests.browser.request_hold import register_request_holds
+from tests.browser.thumbnail_location_fixture import (
+    register_thumbnail_location_commands,
+)
 from tests.browser import slow_reset_watch
 from tests.browser.fast_reset import SEED_ON_LIVE_ENV, ScratchSeeder
 from tests.browser.workspace_activity_fixture import register_activity_commands
@@ -85,6 +88,9 @@ class TestModel:
    suggestions: list | None = None
    # The engine's model table (``py/autotag.py`` MODELS), set at startup.
    models_config: dict = {}
+    # Where the WD14 label lists live (the Skipped tags preview, #431), set at
+    # startup; the tagging fixture writes or removes a small list there.
+    models_dir = None

    def get_models_status(self) -> dict:
        from py.autotag import package_fields
@@ -115,21 +121,26 @@ class TestModel:
        return ["generated", Path(image_path).parent.parent.name]

    def generate_tag_suggestions(
-        self, image_path: str, *, limit: int, **kwargs: object
+        self, image_path: str, *, limit: int, skip=None, **kwargs: object
    ) -> list[tuple[str, float | None]]:
-        """Fixed scored suggestions (WD14) or unscored ones (language models)."""
+        """Fixed scored suggestions (WD14) or unscored ones (language models),
+        without the ones ``skip`` hides before the limit, as the engine does
+        (#431)."""
        scored = self.loaded is not None and self.loaded.startswith("wd14")
        if self.suggestions is not None:
-            return [
+            pairs = [
                (name, confidence if scored else None)
-                for name, confidence in self.suggestions[:limit]
+                for name, confidence in self.suggestions
            ]
-        names = ["sandstone", "desert", "arch", "sky", "rock", "dune", "canyon"]
-        names += [f"tag_{index:02d}" for index in range(100)]
-        return [
-            (name, round(0.98 - index * 0.008, 3) if scored else None)
-            for index, name in enumerate(names[:limit])
-        ]
+        else:
+            names = ["sandstone", "desert", "arch", "sky", "rock", "dune", "canyon"]
+            names += [f"tag_{index:02d}" for index in range(100)]
+            pairs = [
+                (name, round(0.98 - index * 0.008, 3) if scored else None)
+                for index, name in enumerate(names)
+            ]
+        kept = [pair for pair in pairs if skip is None or not skip.matches(pair[0])]
+        return kept[:limit]

    def download_model(self, model_type: str, progress_callback=None) -> bool:
        raise AssertionError("browser tests never download a model")
@@ -233,6 +244,7 @@ def create_app(root: Path) -> web.Application:

    TestModel.models_config = autotag.MODELS
    model = TestModel()
+    model.models_dir = root / "models"
    autotag.get_autotag_service = lambda: model
    api = PromptManagerAPI()
    api.add_routes(routes)
@@ -240,6 +252,7 @@ def create_app(root: Path) -> web.Application:
    library_editor_commands = register_library_editor_commands(routes, api, root)
    register_vocabulary_commands(routes, api, root)
    restore_sources = register_source_change_commands(routes, api)
+    reset_thumbnail_location = register_thumbnail_location_commands(routes, api, root)
    register_tagging_commands(routes, api, root, model, on_reset=restore_sources)
    register_review_commands(routes, api, root)
    register_collections_commands(routes, api, root)
@@ -451,6 +464,8 @@ def create_app(root: Path) -> web.Application:
        restore_sources()
        # No preview queued by the last test may land in the new fixture.
        await api._run_in_executor(api.close_auto_thumbnails)
+        # Previews inside each source again (#320).
+        await api._run_in_executor(reset_thumbnail_location)
        library_editor_commands.reset()
        await api._run_in_executor(reset_logs)
        data = await request.json() if request.can_read_body else {}
@@ -595,6 +610,7 @@ def create_app(root: Path) -> web.Application:
        history_commands.reset()
        library_editor_commands.reset()
        reveal_stub.reset()
+        await api._run_in_executor(reset_thumbnail_location)
        history_fixture = None
        manifest = await api._run_in_executor(
            seeder.run,
@@ -109,6 +109,7 @@ class ResetWatch:
            stream.write(text)
            stream.flush()
        except (OSError, ValueError):
+            # the stream closed; a watcher must not fail the server
            pass


@@ -162,13 +162,15 @@ async function serverJson(request, url) {
 }

 const number = value => value.toLocaleString('en-US');
+// The sidebar's Images count (state.mjs), which System's Images metric shows (#555).
+const IMAGES_COUNT_URL = '/prompt_manager/images/output?mode=workspace&limit=1';

 /** The concept's shell and Overview with the recorded deviations applied, given the server's real overview. */
-function mapOverviewConcept(reference, overview) {
+function mapOverviewConcept(reference, overview, images) {
    // D165: the discreet legacy-pages line follows the settings layout.
    reference = { ...reference, tree: [...reference.tree, 'p.legacy-pages.small'] };
    const relabel = { 'Database integrity': 'Not checked', 'Positive prompts': number(overview.library.positive_prompts),
-        'Negative variants': number(overview.library.negative_variants), Images: number(overview.images.indexed) };
+        'Negative variants': number(overview.library.negative_variants), Images: number(images) };
    const rows = {
        // D93: the real pending count; Review metadata opens Needs review (the concept's go-review).
        '3 ambiguous image links': row => ({ ...row,
@@ -179,8 +181,9 @@ function mapOverviewConcept(reference, overview) {
        'One display configuration': row => ({ ...row, description: 'Grid and density settings are shared across views.' }),
        // D93: the real sources, not samples.
        '2 sample output sources': row => ({ ...row, title: `${number(overview.sources.effective)} output sources` }),
-        // D96: the dialog shows runs by category and library totals, not prompt, tag or date usage (D153: no ratings).
-        Statistics: row => ({ ...row, description: 'Runs by category, with library totals.' }),
+        // D96: the dialog shows runs by category and database record counts, not prompt, tag or date usage (D153: no
+        // ratings; #555: the counts are labelled as records, not as the Library or Images page counts).
+        Statistics: row => ({ ...row, description: 'Runs by category, with database record counts.' }),
    };
    const surfaces = reference.columns.surfaces.map(surface => ({ ...surface,
        rows: surface.rows.map(row => (rows[row.title] ?? (value => value))(row)) }));
@@ -218,6 +221,8 @@ async function conceptOverview(page, theme) {
 async function productionOverview(page, theme) {
    await openProduction(page, 'system/overview', theme);
    await expect(page.locator('#workspace-main .summary-metrics')).toBeVisible();
+    // #555: the Images metric is the shell's Images count: compare once it was read.
+    await expect(page.locator('#workspace-main .summary-metrics > .metric:nth-child(3) strong')).toHaveText(/^[\d,]+$/);
    // The thumbnail row is its own read (I2): compare once it answered.
    await expect(page.locator('#workspace-main .operation h3').filter({ hasText: 'thumbnails' })).toHaveText('No missing thumbnails');
    // So is the backup row (S9).
@@ -231,6 +236,7 @@ for (const theme of THEMES) for (const [width, height] of SIZES) {
    test(`system shell and overview match the concept ${theme} ${width}x${height}`, async ({ page, request }, testInfo) => {
        await page.setViewportSize({ width, height });
        const overview = await serverJson(request, '/prompt_manager/system/overview');
+        const images = (await serverJson(request, IMAGES_COUNT_URL)).total;
        // The fixture's thumbnails all exist, so the concept's "No missing thumbnails" is also the real title.
        expect((await serverJson(request, '/prompt_manager/images/thumbnails/status')).pending).toBe(0);
        const concept = await conceptOverview(page, theme);
@@ -239,7 +245,7 @@ for (const theme of THEMES) for (const [width, height] of SIZES) {
        await page.screenshot({ path: testInfo.outputPath(`concept-system-${theme}-${width}.png`), fullPage: true });
        const production = await productionOverview(page, theme);
        await page.screenshot({ path: testInfo.outputPath(`production-system-${theme}-${width}.png`), fullPage: true });
-        expect(diffInventory(mapOverviewConcept(concept, overview), production)).toEqual([]);
+        expect(diffInventory(mapOverviewConcept(concept, overview, images), production)).toEqual([]);
        expect(production.pageScroll).toBe(false);
    });
 }
@@ -265,8 +271,9 @@ const UNMAPPED_PATHS = [
 test('system comparison detects mutations', async ({ page, request }) => {
    await page.setViewportSize({ width: 1600, height: 1100 });
    const overview = await serverJson(request, '/prompt_manager/system/overview');
+    const images = (await serverJson(request, IMAGES_COUNT_URL)).total;
    const concept = await conceptOverview(page, 'dark');
-    const expected = mapOverviewConcept(concept, overview);
+    const expected = mapOverviewConcept(concept, overview, images);
    const production = await productionOverview(page, 'dark');
    expect(diffInventory(expected, production)).toEqual([]);
    // Unmapped, the concept differs exactly where a deviation is recorded, and nowhere else.
@@ -290,7 +297,7 @@ test('system comparison detects mutations', async ({ page, request }) => {
 });

 /**
- * D96: the concept's table, its rows the real ones; then "Library totals" in the same table markup. D153 (#447): the
+ * D96: the concept's table, its rows the real ones; then "Database records" (#555) in the same table markup. D153 (#447): the
 * concept's "Avg. rating" column and a "Rated images" total are not drawn.
 */
 function mapStatisticsConcept(reference, statistics) {
@@ -302,9 +309,10 @@ function mapStatisticsConcept(reference, statistics) {
        tables: [
            { ...runs, head: runs.head.filter(([, , text]) => text !== 'Avg. rating'),
                rows: statistics.by_category.map(row => [row.category ?? 'Uncategorized', number(row.runs)]) },
-            { caption: 'Library totals', head: [['th', 'col', 'Total'], ['th', 'col', 'Count']],
-                rows: [['Prompts', number(statistics.totals.total_prompts)], ['Tags', number(statistics.totals.total_tags)],
-                    ['Images', number(statistics.totals.total_images)]] },
+            { caption: 'Database records', head: [['th', 'col', 'Total'], ['th', 'col', 'Count']],
+                rows: [['Prompt records', number(statistics.totals.total_prompts)],
+                    ['Tags on prompts', number(statistics.totals.total_tags)],
+                    ['Image records', number(statistics.totals.total_images)]] },
        ],
    };
 }
@@ -420,7 +428,7 @@ for (const theme of THEMES) test(`statistics and health dialogs match the concep
    expect(diffInventory(mapHealthConcept(concept.health), await page.evaluate(measureDialog)).map(item => item.path))
        .toEqual(['operations.rows.0.title']);
    await page.evaluate(() => { document.querySelector('#modal .operation h3').textContent = 'Integrity check'; });
-    // And a removed "Library totals" table and a changed caption in the statistics dialog.
+    // And a removed "Database records" table and a changed caption in the statistics dialog.
    await page.keyboard.press('Escape');
    await page.locator('#workspace-main .section-nav').getByRole('button', { name: 'Overview', exact: true }).click();
    await page.locator('#workspace-main').getByRole('button', { name: 'Explore', exact: true }).click();
@@ -648,9 +656,10 @@ function mapSourcesConcept(reference, { settings, sources }) {
            // D113: the range ends at the server's core count (the concept's fixed 16) and shows the real worker count.
            return [{ ...row, control: { ...row.control, max: String(settings.cpu_count), value: String(settings.worker_threads) } }];
        }),
-        // D158: the inserted row after the first setting row; D98: "Refresh files" closes the surface.
+        // D158: the inserted row after the first setting row; D196 (#320): the Thumbnail location block after
+        // "Thumbnail generation"; D98: "Refresh files" closes the surface.
        surface: { ...reference.surface, tree: [...reference.surface.tree.slice(0, rowAt + 1), 'div.setting-row',
-            ...reference.surface.tree.slice(rowAt + 1), 'div.operation'] },
+            ...reference.surface.tree.slice(rowAt + 1), 'div.setting-block', 'div.operation'] },
        operations: [...reference.operations, { ...reference.operations[0], title: REFRESH_FILES.title,
            description: REFRESH_FILES.description, actions: [{ ...reference.operations[0].actions[0], text: REFRESH_FILES.label }] }],
    };
@@ -64,11 +64,31 @@ function measureMaintenance(mainSelector) {
    };
 }

-/** D102: the Metadata cache row says why its review is unavailable and its button is aria-disabled (D93's dimmed style). */
-function mapMaintenanceConcept(reference) {
+/**
+ * D192 (#550, beyond the concept): Database adds "Pair category and tags" after "Unused prompt components", shaped like
+ * the concept's plain Review plan row (Optimize database's).
+ */
+function mapPairRow(reference) {
    return {
        ...reference,
-        surfaces: reference.surfaces.map(surface => ({ ...surface, rows: surface.rows.map(row => row.title !== 'Metadata cache' ? row : {
+        surfaces: reference.surfaces.map(surface => {
+            const plain = surface.rows.find(row => row.title === 'Optimize database');
+            const at = surface.rows.findIndex(row => row.title === 'Unused prompt components');
+            if (!plain || at < 0) return surface;
+            return { ...surface, tree: [...surface.tree, 'div.operation'], rows: [...surface.rows.slice(0, at + 1),
+                { ...plain, title: 'Pair category and tags', description: 'Fill an empty category or tags on prompts older ' +
+                    'Pair node runs saved, from their saved pairs. Only empty fields of never-edited prompts.' },
+                ...surface.rows.slice(at + 1)] };
+        }),
+    };
+}
+
+/** D102: the Metadata cache row says why its review is unavailable and its button is aria-disabled (D93's dimmed style). */
+function mapMaintenanceConcept(reference) {
+    const mapped = mapPairRow(reference);
+    return {
+        ...mapped,
+        surfaces: mapped.surfaces.map(surface => ({ ...surface, rows: surface.rows.map(row => row.title !== 'Metadata cache' ? row : {
            ...row, description: `${row.description} Nothing is cached in this browser.`,
            actions: row.actions.map(action => ({ ...action, opacity: '0.55', cursor: 'not-allowed' })) }) })),
    };
@@ -209,8 +229,8 @@ test('maintenance comparison detects mutations', async ({ page, request }) => {
    const expected = mapMaintenanceConcept(concept);
    const production = await productionMaintenance(page, 'dark');
    expect(diffInventory(expected, production)).toEqual([]);
-    // Unmapped, the section differs only on the D102 row.
-    expect(diffInventory(concept, production).map(item => item.path).sort()).toEqual([
+    // Mapped only for the D192 row, the section differs only on the D102 row.
+    expect(diffInventory(mapPairRow(concept), production).map(item => item.path).sort()).toEqual([
        'surfaces.1.rows.3.actions.0.cursor', 'surfaces.1.rows.3.actions.0.opacity', 'surfaces.1.rows.3.description']);
    const measure = () => page.evaluate(measureMaintenance, '#workspace-main');
    const paths = async () => diffInventory(expected, await measure()).map(item => item.path);
@@ -33,6 +33,10 @@ test.afterEach(async ({ page, request, browserName }) => {
 const PREVIEW_URL = '/prompt_manager/autotag/batch/preview';
 const MODEL_OPTIONS = ['WD14 SwinV2 · ~400 MB', 'WD14 ViT · ~400 MB', 'GGUF JoyCaption · ~4.5 GB', 'HuggingFace JoyCaption · ~16 GB'];
 const SUGGESTIONS = 'From 1 to 100: the most suggestions Generate shows for one image.';
+const SKIPPED_DESCRIPTION = 'Suggested tags that contain one of these words are hidden. Words are separated by spaces, _ or -; '
+    + 'other characters such as ( ) belong to the word.';
+const DEFAULT_DESCRIPTION = 'The Tag image dialog and batches start from this.';
+const INSTRUCTIONS_DESCRIPTION = 'Instructions for the language-model engines. Built-in can’t be changed; duplicate it to make your own.';
 const BATCH = 'Tag each output image from its own pixels with the model above. Prompts are not changed. Review the scope first.';

 /** Runs in the page: Auto-tagging's surface under `mainSelector`: rows, field, actions, operation, geometry and tokens. */
@@ -62,7 +66,7 @@ function measureTagging(mainSelector) {
            text: [...row.firstElementChild.children].map(node => [name(node), text(node), node.localName === 'label' ? node.htmlFor : null]),
            control: control(row), flexWrap: getComputedStyle(row).flexWrap,
            controlBelow: row.lastElementChild.getBoundingClientRect().top >= row.firstElementChild.getBoundingClientRect().bottom - 0.5 })),
-        field: { tree: [...field.children].map(name), label: [text(field.querySelector('label')), field.querySelector('label').htmlFor],
+        field: field && { tree: [...field.children].map(name), label: [text(field.querySelector('label')), field.querySelector('label').htmlFor],
            textarea: { id: field.querySelector('textarea').id, value: field.querySelector('textarea').value,
                ...css(field.querySelector('textarea'), 'fontSize', 'minHeight', 'backgroundColor', 'color', 'borderTopColor') },
            ...css(field, 'display', 'rowGap', 'fontSize', 'marginTop', 'marginBottom') },
@@ -70,6 +74,31 @@ function measureTagging(mainSelector) {
            ...css(actions, 'display', 'flexWrap', 'columnGap', 'justifyContent'),
            primary: css(actions.querySelector('.ca-primary'), 'backgroundColor', 'color', 'fontSize', 'paddingTop', 'paddingLeft'),
            plain: css(actions.querySelector('button:not(.ca-primary)'), 'backgroundColor', 'color', 'fontSize', 'borderTopColor') },
+        // D202 (#431): the Skipped tags block (the concept has none).
+        skipped: (block => block && { tree: [...block.children].map(name), key: block.dataset.key,
+            text: [...block.firstElementChild.children].map(node => [node.localName, text(node), node.localName === 'label' ? node.htmlFor : null]),
+            add: [...block.querySelector('.skip-add').children].map(node => [name(node), node.id, node.getAttribute('placeholder'), text(node)]),
+            preview: [text(block.querySelector('.skip-preview')), block.querySelector('.skip-preview').getAttribute('role')],
+            ...css(block, 'paddingTop', 'paddingBottom', 'borderTopWidth', 'borderTopColor'),
+            label: css(block.querySelector('label'), 'fontSize', 'fontWeight', 'color'),
+            description: css(block.querySelector('.setting-block-text p'), 'fontSize', 'color', 'marginTop'),
+            input: css(block.querySelector('input'), 'fontSize', 'backgroundColor', 'color', 'borderTopColor') })(
+            surface.querySelector(':scope > .setting-block[data-setting="tag-skipped"]')),
+        // D203 (#431): Saved instructions (the concept has a template field instead).
+        instructions: (block => block && { tree: [...block.children].map(name), key: block.dataset.key,
+            text: [...block.firstElementChild.children].map(node => [node.localName, text(node)]),
+            list: [...block.querySelectorAll('[role="option"]')].map(option => [text(option.firstElementChild),
+                [...option.querySelectorAll('.badges > .chip')].map(chip => [text(chip), chip.className]), option.getAttribute('aria-selected')]),
+            listRole: block.querySelector('.instruction-list').getAttribute('role'),
+            actions: [...block.querySelectorAll('.instruction-actions > button')].map(item => [text(item), item.className, item.disabled]),
+            editor: [...block.querySelectorAll('.instruction-editor .field')].map(item => [text(item.querySelector('label > span')),
+                item.querySelector('input, textarea').value, item.querySelector('input, textarea').readOnly]),
+            note: text(block.querySelector('#instruction-note')),
+            layout: getComputedStyle(block.querySelector('.instructions-layout')).gridTemplateColumns.split(' ').length,
+            ...css(block, 'paddingTop', 'paddingBottom', 'borderTopWidth', 'borderTopColor'),
+            label: css(block.querySelector('label'), 'fontSize', 'fontWeight', 'color'),
+            textarea: css(block.querySelector('textarea'), 'fontSize', 'backgroundColor', 'borderTopColor') })(
+            surface.querySelector(':scope > .setting-block[data-setting="tag-instructions"]')),
        operations: [...surface.querySelectorAll(':scope > .operation')].map(row => ({ tree: [...row.children].map(name),
            title: text(row.querySelector('h3')), description: text(row.querySelector('p')),
            actions: [...row.querySelectorAll('.row-actions > button')].map(item => [text(item), item.className]) })),
@@ -103,13 +132,21 @@ function measureTagging(mainSelector) {
 * The concept's Auto-tagging with the recorded deviations applied, for the fixture (all engines on disk, none loaded).
 * `phone` is a viewport at the concept's 700px breakpoint or below.
 */
-function mapTaggingConcept(reference, { template, phone }) {
+function mapTaggingConcept(reference, { builtin, saved, phone }) {
    const [model, existing, general, character] = reference.rows;
    const [preview] = reference.actions.buttons;
+    // D203: Built-in first, then the saved entries, in each default select.
+    const names = ['Built-in', ...saved.map(entry => entry.name)];
+    const defaultRow = (engine, long) => ({ ...existing,
+        text: [['label', `Default for ${long}`, `instruction-default-${engine}`], ['p', DEFAULT_DESCRIPTION, null]],
+        control: { ...existing.control, id: `instruction-default-${engine}`, options: names.map(label => [label, false]),
+            selected: names[1] } });
    return {
        ...reference,
-        // D133 adds a row after the thresholds; D134 adds the operation after the actions.
-        tree: [...reference.tree.slice(0, 6), 'div.setting-row', ...reference.tree.slice(6), 'div.operation'],
+        // D133 adds a row after the thresholds, D202 the Skipped tags block after it; D203 replaces the template field
+        // with Saved instructions, the two default rows and their note; D134 adds the operation after the actions.
+        tree: [...reference.tree.slice(0, 6), 'div.setting-row', 'div.setting-block', 'div.setting-block', 'div.setting-row',
+            'div.setting-row', 'p.instruction-reset.small', reference.tree[7], 'div.operation'],
        rows: [
            // D132 (OQ5, OQ6): the four real engines with their download size, and the chosen one's live status.
            { ...model, text: [model.text[0], ['p', 'Downloaded. Not loaded.', null]],
@@ -120,16 +157,49 @@ function mapTaggingConcept(reference, { template, phone }) {
            // D133: the persisted suggestion count, on the concept's number row.
            { ...general, text: [['label', 'Suggestions per image', 'tag-suggestions'], ['p', SUGGESTIONS, null]],
                control: { ...general.control, id: 'tag-suggestions', value: '10' } },
+            // D203: the default of each language-model engine (the fixture's saved entry is both), on the concept's
+            // select row.
+            defaultRow('gguf', 'GGUF JoyCaption'), defaultRow('hf', 'HuggingFace JoyCaption'),
        ],
-        // The saved template (the server's default until one is saved) replaces the concept's sample text.
-        field: { ...reference.field, textarea: { ...reference.field.textarea, value: template } },
+        // D203: Saved instructions in the concept's setting-row tokens (as D202), Built-in selected and read-only.
+        instructions: { tree: ['div.setting-block-text', 'div.instructions-layout'], key: 'autotag_instructions',
+            text: [['label', 'Saved instructions'], ['p', `${INSTRUCTIONS_DESCRIPTION} ${saved.length} of 20 saved · Built\u2011in is not counted.`]],
+            list: [['Built-in', [['Read-only', 'chip']], 'true'],
+                ...saved.map((entry, index) => [entry.name, index === 0
+                    ? [['Default for GGUF', 'chip blue'], ['Default for HuggingFace', 'chip blue']] : [], 'false'])],
+            listRole: 'listbox',
+            actions: [['+ New', '', false], ['Duplicate', '', false], ['Delete', 'danger', true]],
+            editor: [['Name', 'Built-in', true], ['Text', builtin, true]],
+            note: 'Built-in instructions can’t be changed. Duplicate them to make your own.',
+            layout: phone ? 1 : 2,
+            paddingTop: reference.row.paddingTop, paddingBottom: reference.row.paddingBottom,
+            borderTopWidth: reference.row.borderTopWidth, borderTopColor: reference.row.borderTopColor,
+            label: reference.label,
+            textarea: { fontSize: reference.field.textarea.fontSize, backgroundColor: reference.field.textarea.backgroundColor,
+                borderTopColor: reference.field.textarea.borderTopColor } },
+        // D202 (#431): the Skipped tags block in the concept's setting-row tokens: its label and description as a row's,
+        // the row's padding and rule above, the concept's field input; an empty list says so.
+        skipped: { tree: ['div.setting-block-text', 'div.skip-add', 'p.skip-problem.small', 'div.skip-chips.tags', 'p.skip-preview.small'],
+            key: 'autotag_skipped_tags',
+            text: [['label', 'Skipped tags', 'tag-skipped-input'], ['p', SKIPPED_DESCRIPTION, null]],
+            add: [['input', 'tag-skipped-input', 'Add a word or words', ''], ['button', 'tag-skipped-add', null, 'Add']],
+            preview: ['No tags are skipped.', 'status'],
+            paddingTop: reference.row.paddingTop, paddingBottom: reference.row.paddingBottom,
+            borderTopWidth: reference.row.borderTopWidth, borderTopColor: reference.row.borderTopColor,
+            label: reference.label,
+            description: { fontSize: reference.description.fontSize, color: reference.description.color,
+                marginTop: reference.description.marginTop },
+            input: { fontSize: '12px', backgroundColor: reference.field.textarea.backgroundColor, color: reference.field.textarea.color,
+                borderTopColor: reference.field.textarea.borderTopColor } },
+        // D203: no template field.
+        field: null,
        // D132: Download (for an engine already on disk, "Download again") and Unload replace the two simulated jobs.
        actions: { ...reference.actions, buttons: [preview, ['Download again', ''], ['Unload', '']] },
        // D134: the prompt-tag batch, reviewed first.
        operations: [{ tree: ['div', 'div.row-actions'], title: 'Tag output images', description: BATCH, actions: [['Review', '']] }],
        // D132 (#398): every select shows its whole chosen option at every width (at 390 the concept's 120px cap cuts
        // them; production lets each grow past it).
-        selectsFit: reference.selectsFit.map(() => true),
+        selectsFit: [...reference.selectsFit, true, true].map(() => true),
    };
 }

@@ -153,7 +223,9 @@ async function productionTagging(page, theme) {
 async function savedTemplate(request, page) {
    const response = await request.get('/prompt_manager/settings');
    await expect(response).toBeOK();
-    return { template: (await response.json()).settings.autotag_template, phone: page.viewportSize().width <= 700 };
+    const { settings } = await response.json();
+    return { builtin: settings.autotag_builtin_instructions, saved: settings.autotag_instructions,
+        phone: page.viewportSize().width <= 700 };
 }

 for (const theme of THEMES) for (const [width, height] of SIZES) {
@@ -177,14 +249,15 @@ for (const theme of THEMES) for (const width of [390, 320]) {
        await page.locator('#workspace-main #tag-existing').selectOption('replace_after_review');
        await page.locator('#workspace-main section.surface').screenshot({ path: testInfo.outputPath(`production-tagging-selects-${theme}-${width}.png`) });
        const selects = page.locator('#workspace-main section.surface > .setting-row > select');
-        await expect(selects).toHaveCount(2);
-        for (let index = 0; index < 2; index += 1) {
+        // D203 adds the two per-engine default selects.
+        await expect(selects).toHaveCount(4);
+        for (let index = 0; index < 4; index += 1) {
            const select = selects.nth(index);
            const values = await select.evaluate(node => [...node.options].map(option => option.value));
            for (const value of values) {
                await select.selectOption(value);
                const measured = await page.evaluate(measureTagging, '#workspace-main');
-                expect(measured.selectsFit, `${await select.getAttribute('id')}=${value}`).toEqual([true, true]);
+                expect(measured.selectsFit, `${await select.getAttribute('id')}=${value}`).toEqual([true, true, true, true]);
                expect(measured.pageScroll, value).toBe(false);
            }
        }
@@ -198,12 +271,16 @@ test('auto-tagging comparison detects mutations', async ({ page, request }) => {
    const expected = mapTaggingConcept(concept, saved);
    const production = await productionTagging(page, 'dark');
    expect(diffInventory(expected, production)).toEqual([]);
-    // Unmapped, the section differs only where D132, D133 and D134 are recorded (and the saved template's text).
-    expect(diffInventory(concept, production).map(item => item.path.split('.').slice(0, 3).join('.'))
+    // Unmapped, the section differs only where D132, D133, D134, D202 and D203 are recorded (and the saved template's text).
+    // (The concept has no Skipped tags block, so every path under it is one D202 difference.)
+    expect(diffInventory(concept, production).map(item => (/^(skipped|instructions|field)\b/.test(item.path) ? item.path.split('.')[0]
+        : item.path.split('.').slice(0, 3).join('.')))
        .filter((path, index, all) => all.indexOf(path) === index).sort()).toEqual([
-        'actions.buttons.1', 'actions.buttons.2', 'field.textarea.value', 'operations.0.actions', 'operations.0.description',
-        'operations.0.title', 'operations.0.tree', 'operations.length', 'rows.0.control', 'rows.0.text', 'rows.4.control', 'rows.4.controlBelow',
-        'rows.4.flexWrap', 'rows.4.text', 'rows.4.tree', 'rows.length', 'tree.6', 'tree.7', 'tree.8', 'tree.9', 'tree.length'].sort());
+        'actions.buttons.1', 'actions.buttons.2', 'field', 'instructions', 'operations.0.actions', 'operations.0.description',
+        'operations.0.title', 'operations.0.tree', 'operations.length', 'rows.0.control', 'rows.0.text',
+        ...[4, 5, 6].flatMap(row => ['control', 'controlBelow', 'flexWrap', 'text', 'tree'].map(key => `rows.${row}.${key}`)),
+        'rows.length', 'selectsFit.2', 'selectsFit.3', 'selectsFit.length', 'skipped',
+        ...Array.from({ length: 8 }, (_, index) => `tree.${index + 6}`), 'tree.length'].sort());
    const measure = () => page.evaluate(measureTagging, '#workspace-main');
    const paths = async () => diffInventory(expected, await measure()).map(item => item.path);
    // A removed row.
@@ -254,8 +331,8 @@ test('auto-tagging at 390 wraps only the engine row', async ({ page, request })
    const concept = await conceptTagging(page, 'dark');
    const production = await productionTagging(page, 'dark');
    expect(diffInventory(mapTaggingConcept(concept, await savedTemplate(request, page)), production)).toEqual([]);
-    expect(production.rows.map(row => row.flexWrap)).toEqual(['wrap', 'nowrap', 'nowrap', 'nowrap', 'nowrap']);
-    expect(production.selectsFit).toEqual([true, true]);
+    expect(production.rows.map(row => row.flexWrap)).toEqual(['wrap', 'nowrap', 'nowrap', 'nowrap', 'nowrap', 'nowrap', 'nowrap']);
+    expect(production.selectsFit).toEqual([true, true, true, true]);
 });

 /** Runs in the page: the open review dialog: its title, body and the concept's tokens. */
@@ -92,6 +92,8 @@ export function cardActionsInventory(card) {
    };
 }

+// #431: the fixture's saved "Describe the image" entry, the default of both engines (workspace_tagging_fixture.py).
+export const FIXTURE_INSTRUCTIONS_ID='d35c71be0a1e';
 // D84 (plan D61): the legacy engines' values, labels and sizes, GGUF JoyCaption in the concept's Ollama slot.
 const MODEL_LABELS=Object.freeze({'wd14-swinv2':['wd14-swinv2','WD14 SwinV2 · ~400 MB'],'wd14-vit':['wd14-vit','WD14 ViT · ~400 MB'],
    ollama:['gguf','GGUF JoyCaption (Recommended) · ~4.5 GB'],huggingface:['hf','HuggingFace JoyCaption · ~16 GB']});
@@ -106,17 +108,24 @@ const CONCEPT_LABELS=Object.freeze({'WD14 SwinV2 · fast classifier':'WD14 SwinV
 *   (`chip`: a concept `.chip` inventory, the heading's size chip) around the row's own text (12px) in the checked
 *   row's colours (accent border, `--soft-blue`);
 * - D84 (plan D61): the legacy engine labels and values, and the server's default instructions (`instructions`);
+ * - D204 (#431): a "Saved instructions" select (`picker`: its value and options) before the instructions, on the
+ *   concept's select field tokens;
 * - D91 (plan D68): a Suggestions count field after the model's own fields, on the concept's number field tokens
 *   (`numberField`: the concept's General confidence field) with the configured count (`limit`);
 * - D29: the prototype's "Sample suggestions from …" status reads "Suggestions from …".
 * The opened state is compared unmapped: both show the concept's on-screen "Generate suggestions with the selected
 * model before approving." (its renderTagModelOptions, a1062–1076, replaces the markup's sentence at once).
 */
-export function mapConceptTagging(reference,{instructions,limit=10,chip,numberField}) {
+export function mapConceptTagging(reference,{instructions,limit=10,chip,numberField,
+    picker={value:FIXTURE_INSTRUCTIONS_ID,options:[['builtin','Built-in'],[FIXTURE_INSTRUCTIONS_ID,`${instructions} · default`]]}}) {
    const [select,...own]=reference.modelPanel.fields;
+    // D204 (#431): a "Saved instructions" select on the concept's select field, before the instructions.
+    const pickField={...select,label:'Saved instructions',control:{...select.control,id:'image-tag-instructions-pick',
+        value:picker.value,options:picker.options}};
    const suggestionsField={...numberField,label:'Suggestions',control:{...numberField.control,id:'image-suggestion-limit',
        value:String(limit),min:'1',max:'100',step:'1'}};
-    const mappedOwn=own.map(field=>field.control.id==='image-tag-instructions'?{...field,control:{...field.control,value:instructions}}:field);
+    const mappedOwn=own.flatMap(field=>field.control.id==='image-tag-instructions'
+        ?[pickField,{...field,control:{...field.control,value:instructions}}]:[field]);
    const rows=reference.suggestions.rows.map(row=>({...row,
        control:row.control?.kind==='checkbox'&&row.control.checked?{kind:'remove',label:`Remove ${row.name}`}:row.control,
        borderTopLeftRadius:chip.borderTopLeftRadius}));
@@ -0,0 +1,170 @@
+"""The thumbnail location on the test server (#320), undone by every reset.
+
+Folder mode is reachable from config.json and tests only until the Move
+thumbnails job lands, so page tests set it here, inside the server's root:
+
+- ``POST /__test__/thumbnail-location`` ``{"mode": "folder"}`` (or
+  ``"source"``): previews live in ``<root>/thumbs/<key>`` from now on (a new
+  folder with Prompt Manager's marker).
+- ``GET /__test__/thumbnail-files``: the preview files in the thumbnail
+  folder and whether any source grew a ``thumbnails/`` folder.
+- ``POST /__test__/thumbnail-folder/remove``: the thumbnail folder goes, as
+  when its drive is unplugged; the server notices it on its next check.
+"""
+
+from __future__ import annotations
+
+import shutil
+from pathlib import Path
+from typing import TYPE_CHECKING, Callable
+
+from aiohttp import web
+
+if TYPE_CHECKING:
+    from py.api import PromptManagerAPI
+
+FOLDER_NAME = "thumbs"
+
+
+def register_thumbnail_location_commands(
+    routes: web.RouteTableDef, api: PromptManagerAPI, root: Path
+) -> Callable[[], None]:
+    """Register the commands; returns the reset every reset runs."""
+    from py.api import preview_location, preview_store
+    from py.api import thumbnail_location, thumbnail_move_plan
+    from py.config import PromptManagerConfig
+    from py.config_store import get_config_store
+
+    folder = root / FOLDER_NAME
+    default = root / "default-thumbs"
+    custom = root / "custom-thumbs"  # a folder a page types in
+    journal = root / "data" / "thumbnail-move.json"
+    # The move's journal and default folder live in this server's root, never
+    # in the checkout's data folder.
+    thumbnail_move_plan.journal_path = lambda: str(journal)
+    thumbnail_move_plan.default_path = lambda: str(default)
+    thumbnail_location.default_path = lambda: str(default)
+    api.recover_thumbnail_move()
+
+    def forget_config(config: dict) -> dict:
+        section = config.get("thumbnails")
+        if isinstance(section, dict):
+            section.pop("location", None)
+        return config
+
+    real_free = thumbnail_move_plan._free
+
+    def reset() -> None:
+        thumbnail_move_plan._free = real_free
+        preview_store.configure(None)
+        PromptManagerConfig.THUMBNAIL_LOCATION = None
+        store = get_config_store()
+        config, _revision = store.read()
+        if (
+            isinstance(config.get("thumbnails"), dict)
+            and "location" in config["thumbnails"]
+        ):
+            store.commit(forget_config, expected_revision=None)
+        for path in (folder, default, custom):
+            shutil.rmtree(path, ignore_errors=True)
+        journal.unlink(missing_ok=True)
+
+    def use(mode: str) -> dict:
+        reset()
+        if mode == "source":
+            return {"mode": "source"}
+        folder.mkdir()
+        marker_id = preview_location.init_folder(str(folder), created_by_pm=True)
+        location = preview_store.configure(
+            {
+                "mode": "folder",
+                "path": str(folder),
+                "id": marker_id,
+                "install": "browser-tests",
+            }
+        )
+        return {"mode": location.mode, "available": location.available}
+
+    @routes.post("/__test__/thumbnail-location")
+    async def set_location(request: web.Request) -> web.Response:
+        data = await request.json()
+        mode = data.get("mode") if isinstance(data, dict) else None
+        if mode not in ("source", "folder"):
+            raise web.HTTPBadRequest()
+        return web.json_response(await api._run_in_executor(use, mode))
+
+    def files() -> dict:
+        setting = preview_store.setting()
+        where = Path(setting.path) if setting.path else folder
+        previews = sorted(
+            path.relative_to(where).as_posix()
+            for path in where.rglob("*_thumb.*")
+            if path.is_file()
+        )
+        sources = [str(path) for path in api._get_all_output_dirs()]
+        return {
+            "folder": previews,
+            "folder_exists": folder.exists() or default.exists() or custom.exists(),
+            "custom_path": str(custom),
+            "source_thumbnails": any(
+                (Path(source) / "thumbnails").exists() for source in sources
+            ),
+        }
+
+    @routes.get("/__test__/thumbnail-files")
+    async def thumbnail_files(_request: web.Request) -> web.Response:
+        return web.json_response(await api._run_in_executor(files))
+
+    def remove() -> bool:
+        setting = preview_store.setting()
+        shutil.rmtree(setting.path or folder, ignore_errors=True)
+        return preview_store.refresh()
+
+    @routes.post("/__test__/thumbnail-folder/remove")
+    async def remove_folder(_request: web.Request) -> web.Response:
+        available = await api._run_in_executor(remove)
+        return web.json_response({"available": available})
+
+    def foreign() -> bool:
+        """Another install recreated the folder: its marker has another id."""
+        setting = preview_store.setting()
+
+        def other(marker: dict) -> None:
+            marker["id"] = "another-install"
+
+        preview_location.write_marker(setting.path, other)
+        return preview_store.refresh()
+
+    @routes.post("/__test__/thumbnail-folder/foreign")
+    async def foreign_folder(_request: web.Request) -> web.Response:
+        return web.json_response({"available": await api._run_in_executor(foreign)})
+
+    def unlisted() -> None:
+        """A source this install no longer lists left its thumbnails here."""
+        setting = preview_store.setting()
+
+        def add(marker: dict) -> None:
+            marker["keys"]["gone-0123abcd"] = {
+                "path": "/gone",
+                "identity": "/gone",
+                "install": setting.install,
+            }
+
+        preview_location.write_marker(setting.path, add)
+        gone = Path(setting.path) / "gone-0123abcd"
+        gone.mkdir()
+        (gone / "x_thumb.webp").write_bytes(b"preview")
+        preview_store.refresh()
+
+    @routes.post("/__test__/thumbnail-folder/unlisted")
+    async def unlisted_source(_request: web.Request) -> web.Response:
+        await api._run_in_executor(unlisted)
+        return web.json_response({"success": True})
+
+    @routes.post("/__test__/thumbnail-space/full")
+    async def space_full(_request: web.Request) -> web.Response:
+        """Every target disk reports 1 byte free until the next reset."""
+        thumbnail_move_plan._free = lambda _path: 1
+        return web.json_response({"success": True})
+
+    return reset
@@ -261,3 +261,20 @@ test('prompt deletion requires confirmation and can retry after a network failur
        await expect(await request.get(url)).toBeOK();
    }
 });
+
+// #320: with previews in one folder, the legacy gallery still shows them, made
+// and served from that folder (the fixture's own previews inside the sources
+// are never served then).
+test('the legacy gallery shows thumbnails kept in one folder', async ({ page, request }) => {
+    await expect(await request.post('/__test__/thumbnail-location', { data: { mode: 'folder' } })).toBeOK();
+    const served = page.waitForResponse(response =>
+        response.url().includes('/prompt_manager/images/serve/thumbnails/') && response.status() === 200);
+    await page.goto('/prompt_manager/gallery');
+    await expect(page.locator('#galleryGrid .image-item')).toHaveCount(2);
+    const response = await served; // made in the folder before it was served
+    const name = decodeURIComponent(new URL(response.url()).pathname.split('/serve/thumbnails/')[1]);
+    const files = await (await request.get('/__test__/thumbnail-files')).json();
+    const stem = name.replace(/\.[^.]+$/, '');
+    expect(files.folder.some(file => /^[a-z0-9_-]+-[0-9a-f]{8}\//.test(file)
+        && file.slice(file.indexOf('/') + 1).replace(/\.[^.]+$/, '') === stem)).toBe(true);
+});
@@ -156,8 +156,9 @@ test('at 390px the window fits the screen, actions stay reachable and the page s
    expect(frame.bottom-frame.top).toBeLessThan(844);
    expect(frame.bottom-frame.top).toBeGreaterThanOrEqual(280);
    expect(await page.evaluate(()=>document.documentElement.scrollWidth)).toBeLessThanOrEqual(390);
-    // The last row's actions can be scrolled to inside the window and fit its width.
-    const last=rows(page).last().getByRole('button',{name:'Rename / merge',exact:true});
+    // The first page's last row's actions can be scrolled to inside the window and fit its width.
+    // Pinned to row 100: reaching it loads the next page (D183), and last() would then follow row 200.
+    const last=rows(page).nth(99).getByRole('button',{name:'Rename / merge',exact:true});
    await last.scrollIntoViewIfNeeded();await expect(last).toBeInViewport();
    const [button]=await boxes(last);const [after]=await boxes(tagWindow(page));
    expect(button.right).toBeLessThanOrEqual(after.right);
--- a/Show More
+++ b/Show More