diff --git a/app/legacy/api.js b/app/legacy/api.js
index f79f91af..8133fe38 100644
--- a/app/legacy/api.js
+++ b/app/legacy/api.js
@@ -159,7 +159,11 @@
         xhr.onload = () => {
           let body = {};
           try { body = JSON.parse(xhr.responseText || "{}"); } catch (_) { /* not JSON */ }
-          if (xhr.status >= 200 && xhr.status < 300) resolve(body.media && body.media[0] ? body.media[0] : body);
+          if (xhr.status >= 200 && xhr.status < 300) {
+            if (body.media && body.media[0]) resolve(body.media[0]);
+            else if (body.problems && body.problems.length) reject(new Error(body.problems.join("; ")));
+            else resolve(body);
+          }
           else reject(new Error((body.problems && body.problems.join("; ")) || body.detail || xhr.statusText || `HTTP ${xhr.status}`));
         };
         xhr.onerror = () => reject(new Error("Network error during upload"));
@@ -263,9 +267,19 @@
     },
     // null while it is still queued or running, else {error} or {videos}.
     upscaleResult: async (promptId) => {
-      const res = await fetch(`/history/${encodeURIComponent(promptId)}`);
-      const entry = res.ok ? (await res.json())[promptId] : null;
-      if (!entry) return null;
+      let entry = null;
+      try {
+        const res = await fetch(`/history/${encodeURIComponent(promptId)}`);
+        entry = res.ok ? (await res.json())[promptId] : null;
+      } catch (_) { return { retry: true }; }            // a dropped reply is not a failed job
+      if (!entry) {
+        // Not in history: still queued/running, or gone (dequeued, ComfyUI restarted).
+        try {
+          const q = await (await fetch("/queue")).json();
+          const live = [...(q.queue_running || []), ...(q.queue_pending || [])].some((r) => r[1] === promptId);
+          return live ? null : { gone: true };
+        } catch (_) { return { retry: true }; }
+      }
       const st = entry.status || {};
       if (st.status_str === "error") {
         const msg = (st.messages || []).find((m) => m[0] === "execution_error");
@@ -369,6 +383,7 @@
         // timeline trim must produce a different URL. Anything else that changes the bytes
         // (reverse) must be in the URL too, for the same reason.
         if (spec.dur != null) q.set("dur", String(spec.dur));
+        if (spec.srcIn != null) q.set("src_in", String(spec.srcIn));
         if (spec.reverse) q.set("rev", "1");
         u += "?" + q.toString();
       }
diff --git a/app/legacy/player.js b/app/legacy/player.js
index 6f50a1bf..79e092ba 100644
--- a/app/legacy/player.js
+++ b/app/legacy/player.js
@@ -177,7 +177,7 @@
         const sourceIn = sc?.source_in || 0;
         const renderIn = Math.max(0, (c.inSec || 0) - sourceIn);
         c.streamUrl = API.previewSegmentUrl(pid, c.sceneId, {
-          media: c.media, renderIn, dur: c.durationSec, reverse: wantsReverse,
+          media: c.media, renderIn, srcIn: sourceIn, dur: c.durationSec, reverse: wantsReverse,
         });
       }
     }
diff --git a/app/legacy/store.js b/app/legacy/store.js
index 1329e056..74acb57d 100644
--- a/app/legacy/store.js
+++ b/app/legacy/store.js
@@ -57,6 +57,8 @@
     // {kind:"section"|"node", id, label}. Node ids are project-scoped, which is why these
     // ride with the project rather than living in the browser alone.
     pinnedButtons: null,
+    // Post-render upscale (Settings ▸ Editor): follows the project to a new rental.
+    upscaleMode: "never", upscaleModel: "",
   };
   function _loadEditorSettings() {
     try {
@@ -3438,7 +3440,7 @@
   }
   async function upscaleMedia(media) {
     const model = getEditorSetting("upscaleModel");
-    if (!media || !media.filename) return;
+    if (!media || !media.filename || media.subfolder === "funpack_upscaled") return;   // never upscale twice
     if (!model) {
       set({ notice: "Upscale: pick a model in Settings ▸ Editor ▸ Upscale finished renders." });
       return;
@@ -3451,15 +3453,20 @@
     let notice = "";
     try {
       const promptId = await API.queueUpscale(media, model);
+      let misses = 0;
       for (;;) {
         await new Promise((res) => setTimeout(res, 2000));
         const r = await API.upscaleResult(promptId);
-        if (!r) continue;
+        if (!r) { misses = 0; continue; }
+        // A job neither queued nor in history is gone; a reply that fails to arrive is retried a while.
+        if (r.retry && ++misses < 30) continue;
+        if (r.retry) throw new Error("lost contact with ComfyUI");
+        if (r.gone && ++misses < 3) continue;
+        if (r.gone) throw new Error("the job left ComfyUI's queue without finishing (interrupted or ComfyUI restarted)");
         if (r.error) throw new Error(r.error);
         const out = { ...r.videos[0], kind: "videos" };
-        if (state.project && state.project.id === pid && !_swapRenderMedia(media, out)) {
-          notice = "Upscaled, but that render was replaced meanwhile, so nothing was swapped.";
-        }
+        if (!state.project || state.project.id !== pid) notice = `Upscaled ${media.filename} in another project: it is in output/funpack_upscaled.`;
+        else if (!_swapRenderMedia(media, out)) notice = "Upscaled, but that render was replaced meanwhile, so nothing was swapped.";
         break;
       }
     } catch (e) {
@@ -4750,8 +4757,11 @@
   // state.mediaUpload: null when idle, else { current, total, name, loaded, size } -- the
   // drop zone had no way to show this at all before, so a batch of photos/a big video
   // uploading over a slow connection just looked like nothing was happening.
+  let _uploadBatches = 0;
   async function uploadMedia(files) {
     const list = [...files];
+    const failed = [];
+    _uploadBatches++;
     for (let i = 0; i < list.length; i++) {
       const f = list[i];
       // A full notify() here (once per file) is what builds the "uploading" drop zone in the
@@ -4762,9 +4772,10 @@
         await API.uploadMedia(f, (loaded, total) => {
           updateMediaUploadProgress({ loaded, size: total || f.size });
         });
-      } catch (e) { console.error("upload failed", e); }
+      } catch (e) { console.error("upload failed", e); failed.push(`${f.name}: ${e && e.message ? e.message : e}`); }
     }
-    state.mediaUpload = null;
+    if (--_uploadBatches === 0) state.mediaUpload = null;     // a second batch drawn meanwhile keeps its bar
+    if (failed.length) set({ notice: `Not uploaded — ${failed.join(" · ")}` });
     await loadMedia();
   }
   async function deleteMedia(id) {
diff --git a/app/legacy/tour.js b/app/legacy/tour.js
index bcd5c8d3..0843c103 100644
--- a/app/legacy/tour.js
+++ b/app/legacy/tour.js
@@ -429,7 +429,7 @@
 
   function patchStore(Store) {
     const blocked = [
-      "generate", "generateMontage", "generateSelected", "renderFinal", "exportSelected",
+      "generate", "generateMontage", "generateSelected", "renderFinal", "upscaleRender", "exportSelected",
       "saveSelectedToMediaBin", "commit", "newProject", "loadProject", "deleteProject",
       "importProject", "downloadProject", "uploadMedia", "deleteMedia", "deleteMediaMany",
       "interrupt", "resetStudioSession", "syncFromPreview", "saveClipToMediaBin",
@@ -462,6 +462,7 @@
       generateMontage: "Generate",
       generateSelected: "Generate Selected",
       renderFinal: "Render",
+      upscaleRender: "Upscale",
       exportSelected: "Export",
       saveSelectedToMediaBin: "Save to media bin",
       commit: "Save project",
diff --git a/app/legacy/view_bus.js b/app/legacy/view_bus.js
index 36a9d197..947175bf 100644
--- a/app/legacy/view_bus.js
+++ b/app/legacy/view_bus.js
@@ -137,6 +137,9 @@
       // button next to Auto Montage.
       ratingSel: st.selectedSceneId,
       renders: st.sceneRenders,
+      // The Upscale button: shown by the mode setting, disabled while that render upscales.
+      upscale: [window.Store?.getEditorSetting?.("upscaleMode"),
+        st.selectedSceneId ? window.Store?.isUpscaling?.(st.selectedSceneId) : false],
       ratings: (st.project?.scenes || []).map((s) => [s.id, s.rating, s.source?.type]),
       conditioning: st.project?.conditioning_slot,
       // The Best-FaceID warning chip lives in this zone, so everything its message
diff --git a/core/media.py b/core/media.py
index d5ff4b52..01800dd4 100644
--- a/core/media.py
+++ b/core/media.py
@@ -218,7 +218,8 @@ def thumb_path_for(mid: str) -> Path | None:
         try:
             if it["kind"] == "image":
                 from PIL import Image
-                img = Image.open(src)
+                from PIL import ImageOps
+                img = ImageOps.exif_transpose(Image.open(src))      # the browser shows it turned upright
                 img.thumbnail((THUMB_MAX_DIM, THUMB_MAX_DIM))      # in place, keeps aspect, never upscales
                 (img if img.mode in ("RGB", "L") else img.convert("RGB")).save(tmp, "JPEG", quality=82)
             else:
diff --git a/core/tests/test_media.py b/core/tests/test_media.py
index bb1f19fa..c61fffdc 100644
--- a/core/tests/test_media.py
+++ b/core/tests/test_media.py
@@ -299,3 +299,15 @@ def test_rename_and_thumb_over_http(server):
     status, jpg = _request(server, "GET", f"/funpack/api/media/{mid}/thumb")
     assert status == 200 and jpg["raw"][:2] == b"\xff\xd8"
     assert _request(server, "GET", "/funpack/api/media/aaaaaaaaaaaa/thumb")[0] == 404
+
+
+def test_a_photo_thumbnail_is_turned_upright_like_the_browser_shows_it(store):
+    from PIL import Image
+    import io
+    buf = io.BytesIO()
+    img = Image.new("RGB", (400, 200), (10, 200, 10))
+    exif = img.getexif()
+    exif[274] = 6                                       # rotate 90 on display
+    img.save(buf, "JPEG", exif=exif)
+    entry = media.save_upload("p.jpg", buf.getvalue())
+    assert Image.open(media.thumb_path_for(entry["id"])).size == (160, 320)
diff --git a/modules/output/render/files.py b/modules/output/render/files.py
index da771cc6..82091048 100644
--- a/modules/output/render/files.py
+++ b/modules/output/render/files.py
@@ -24,6 +24,8 @@ from ..._core import media
 
 ISOBMFF = (".mp4", ".m4v", ".mov")          # containers where moov/mdat order applies
 
+AUDIO_RATE = 48000                          # every exported part is made at this rate, so parts can be joined
+
 FFMPEG_MISSING = "ffmpeg was not found on PATH: install it to preview, export or render clips."
 
 
@@ -146,7 +148,7 @@ def trim(src: str, out: str, start=None, dur=None, *, fast=False, reverse=False)
     cmd += ["-c:v", "libx264", "-pix_fmt", "yuv420p"]
     if fast:
         cmd += ["-preset", "veryfast"]
-    cmd += ["-c:a", "aac", "-b:a", "192k", "-movflags", "+faststart", out]
+    cmd += ["-c:a", "aac", "-b:a", "192k", "-ar", str(AUDIO_RATE), "-ac", "2", "-movflags", "+faststart", out]
     run(cmd)
 
 
@@ -161,6 +163,30 @@ def has_audio(path: str) -> bool:
     return "Audio:" in (proc.stderr or "")
 
 
+def duration(path: str) -> float | None:
+    """Seconds of picture in `path`, or None when it has none (a window past the end of the source
+    trims to a file with no streams at all) or ffprobe is not here to ask."""
+    probe = shutil.which("ffprobe")
+    if not probe:
+        return None
+    proc = subprocess.run([probe, "-v", "error", "-select_streams", "v:0", "-show_entries",
+                           "stream=duration:format=duration", "-of", "default=nw=1:nk=1", path],
+                          capture_output=True, text=True)
+    for line in proc.stdout.split():
+        try:
+            return float(line)
+        except ValueError:
+            continue
+    return 0.0 if proc.returncode == 0 else None
+
+
+def add_silence(src: str, out: str) -> None:
+    """Copy `src` with a silent stereo track added, so it can be joined to clips that have sound."""
+    run([ffmpeg(), "-y", "-i", src, "-f", "lavfi", "-i", f"anullsrc=r={AUDIO_RATE}:cl=stereo",
+         "-shortest", "-map", "0:v:0", "-map", "1:a:0", "-c:v", "copy", "-c:a", "aac", "-b:a", "192k",
+         "-movflags", "+faststart", out])
+
+
 def temp_file(name: str) -> str:
     base = comfy_dir("temp")
     if not base:
diff --git a/modules/output/render/serving.py b/modules/output/render/serving.py
index 24f354e1..17b0961d 100644
--- a/modules/output/render/serving.py
+++ b/modules/output/render/serving.py
@@ -141,8 +141,12 @@ async def result(request) -> "web.StreamResponse":
 # --- preview segments ---------------------------------------------------------
 
 
-def scene_clip(project, scene_id: str, render: dict | None = None) -> dict:
-    """The trim a scene's preview segment must show: the same window the export uses."""
+def scene_clip(project, scene_id: str, render: dict | None = None, window: dict | None = None) -> dict:
+    """The trim a scene's preview segment must show: the same window the export uses.
+
+    `window` ({dur, src_in} from the URL) wins over the saved project: the editor autosaves
+    seconds after a trim, and a segment is cached for an hour under its URL, so the bytes
+    must follow what the URL says, never a project that has not caught up."""
     scene = next((s for s in project.scenes if s.id == scene_id), None)
     if scene is None or scene.excluded:
         raise KeyError(f"scene {scene_id}")
@@ -152,9 +156,15 @@ def scene_clip(project, scene_id: str, render: dict | None = None) -> dict:
         raise KeyError(f"no render for {scene_id}")
     fps = float(scene.eff_fps(project) or 25)
     dur = float(scene.source_dur) if scene.source_dur is not None else scene.eff_frames(project) / fps
+    src_in = float(scene.source_in or 0)
+    window = window or {}
+    if window.get("dur") is not None and window["dur"] > 0:
+        dur = window["dur"]
+    if window.get("src_in") is not None and window["src_in"] >= 0:
+        src_in = window["src_in"]
     return {"filename": media["filename"], "subfolder": media.get("subfolder") or "",
             "type": media.get("type") or "output",
-            "in": float(scene.source_in or 0) + _f(render.get("inSec")), "dur": dur, "fps": fps}
+            "in": src_in + _f(render.get("inSec")), "dur": dur, "fps": fps}
 
 
 def _f(value, default=0.0):
@@ -165,6 +175,17 @@ def _f(value, default=0.0):
     return default if v != v else v
 
 
+def query_window(q) -> dict:
+    """The trim the player asked for; a missing or junk value reads as "use the project's"."""
+    def num(key):
+        try:
+            v = float(q.get(key))
+        except (TypeError, ValueError):
+            return None
+        return v if v == v and v not in (float("inf"), float("-inf")) else None
+    return {"dur": num("dur"), "src_in": num("src_in")}
+
+
 def query_render(q) -> dict | None:
     """A render named in the query string overrides the scene's saved one (a clip just made)."""
     if not q.get("filename"):
@@ -192,7 +213,7 @@ async def segment(request, project) -> "web.StreamResponse":
     q = request.query
     scene_id = request.match_info["scene_id"]
     try:
-        clip = scene_clip(project, scene_id, query_render(q))
+        clip = scene_clip(project, scene_id, query_render(q), query_window(q))
     except KeyError as exc:
         clip = ghost_clip(q)
         if clip is None:
diff --git a/modules/output/render/stitch.py b/modules/output/render/stitch.py
index 0a95427e..674ed332 100644
--- a/modules/output/render/stitch.py
+++ b/modules/output/render/stitch.py
@@ -13,6 +13,7 @@ follows the same fold, then extra tracks are delayed to their start and mixed in
 
 from __future__ import annotations
 
+import itertools
 import os
 import time
 
@@ -197,6 +198,14 @@ def has_graphics(project) -> bool:
     return bool(project.audio_tracks) or any(_f(ov.get("duration_sec")) > 0 for ov in project.overlay_tracks)
 
 
+_stamp_n = itertools.count()
+
+
+def _stamp() -> str:
+    """Unique per job: two jobs in one second must not write the same file."""
+    return f"{time.time_ns()}_{next(_stamp_n)}"
+
+
 def _clip_spec_ok(c) -> bool:
     return isinstance(c, dict) and (c.get("bin_media_ref") or c.get("filename"))
 
@@ -215,6 +224,7 @@ def render(project, clips: list[dict]) -> dict:
         raise RenderError(str(exc)) from exc
     if clips:
         cw, ch = int(_f(clips[0].get("w")) or cw), int(_f(clips[0].get("h")) or ch)
+        cw, ch = cw - cw % 2, ch - ch % 2           # yuv420p cannot be encoded at an odd size
         fps = _f(clips[0].get("fps")) or fps
         for c, p in zip(clips, paths):
             c["has_audio"] = files.has_audio(p)
@@ -264,7 +274,7 @@ def render(project, clips: list[dict]) -> dict:
     cmd += ["-filter_complex", ";".join(lines), "-map", "[vout]"]
     if has_audio:
         cmd += ["-map", "[aout]", "-c:a", "aac", "-b:a", "192k"]
-    name = f"funpack_final_{int(time.time())}.mp4"
+    name = f"funpack_final_{_stamp()}.mp4"
     out = os.path.join(tempdir, name)
     cmd += ["-c:v", "libx264", "-pix_fmt", "yuv420p", "-movflags", "+faststart", out]
     try:
@@ -281,13 +291,27 @@ def concat(clips: list[dict]) -> dict:
     clips = [c for c in clips if _clip_spec_ok(c)] if isinstance(clips, list) else []
     if not clips:
         raise RenderError("There is nothing to export.")
-    stamp = int(time.time())
+    stamp = _stamp()
+    parts = []
     try:
-        parts = []
         for i, c in enumerate(clips):
             out = files.temp_file(f"funpack_seg_{stamp}_{i}.mp4")
             files.trim(files.clip_path(c), out, c.get("in"), c.get("dur"))
             parts.append(out)
+            got, want = files.duration(out), _f(c.get("dur"))
+            if got is not None and (got <= 0 or (want > 0 and got < want - max(0.5, 0.1 * want))):
+                raise files.ClipError(
+                    f"Clip {i + 1} has {got:.1f}s of picture where the timeline expects {want:.1f}s: "
+                    f"its render is shorter than the window cut from it (or the window starts past "
+                    f"its end). Generate it again, then export.")
+        sound = [files.has_audio(p) for p in parts]
+        if any(sound) and not all(sound) and len(parts) > 1:      # the joiner keeps only the first part's streams
+            for k, p in enumerate(parts):
+                if not sound[k]:
+                    fixed = files.temp_file(f"funpack_seg_{stamp}_{k}_s.mp4")
+                    files.add_silence(p, fixed)
+                    os.remove(p)
+                    parts[k] = fixed
         name = f"funpack_export_{stamp}.mp4"
         out = files.temp_file(name)
         if len(parts) == 1:
@@ -308,5 +332,10 @@ def concat(clips: list[dict]) -> dict:
                     except OSError:
                         pass
     except files.ClipError as exc:
+        for p in parts:
+            try:
+                os.remove(p)
+            except OSError:
+                pass
         raise RenderError(str(exc)) from exc
     return {"media": {"filename": name, "subfolder": "", "type": "temp", "kind": "videos"}, "clips": len(clips)}
diff --git a/modules/output/render/tests/test_serving.py b/modules/output/render/tests/test_serving.py
index 0291a7f6..78144ebc 100644
--- a/modules/output/render/tests/test_serving.py
+++ b/modules/output/render/tests/test_serving.py
@@ -169,3 +169,16 @@ def test_the_cache_deletes_the_oldest_files_past_its_cap(comfy, monkeypatch):
         paths.append(p)
         cache.put(i, (None, str(p)))
     assert not paths[0].exists() and paths[1].exists() and paths[2].exists() and len(cache) == 2
+
+
+@needs_ffmpeg
+def test_the_url_window_wins_over_a_project_that_has_not_been_saved_yet(comfy, server):
+    moov_at_end(comfy.output / "a.mp4", 4.0)
+    proj = _project(comfy, source_in=0.0, frames=25, frames_mode="timeline")      # saved: 1 s
+    status, _h, body = get(server, f"{BASE}/projects/{proj.id}/preview-segment/s1?dur=2.5&src_in=1")
+    assert status == 200
+    (comfy.root / "seg.mp4").write_bytes(body)
+    assert probe(comfy.root / "seg.mp4")[0] == pytest.approx(2.5, abs=0.2)
+    # a different head trim is a different segment, not the cached one
+    other = get(server, f"{BASE}/projects/{proj.id}/preview-segment/s1?dur=2.5&src_in=0")[2]
+    assert other != body
diff --git a/modules/output/render/tests/test_stitch.py b/modules/output/render/tests/test_stitch.py
index bce16251..8e0b4e47 100644
--- a/modules/output/render/tests/test_stitch.py
+++ b/modules/output/render/tests/test_stitch.py
@@ -189,3 +189,29 @@ def test_a_separated_audio_lane_plays_the_clips_own_sound_from_its_file(comfy):
         {"id": "s", "kind": "separated", "scene_id": "sc1", "start_sec": 0}])
     out = stitch.render(proj, [clip("a.mp4", dur=2.0, scene_id="sc1")])
     assert probe(comfy.temp / out["media"]["filename"])[3] is True
+
+
+@needs_ffmpeg
+def test_export_keeps_the_sound_when_the_first_clip_is_silent(comfy):
+    make_clip(comfy.output / "quiet.mp4", 1.0, audio=False)
+    make_clip(comfy.output / "loud.mp4", 1.0, audio=True)
+    out = stitch.concat([{"filename": "quiet.mp4", "dur": 1.0}, {"filename": "loud.mp4", "dur": 1.0}])
+    assert files.has_audio(str(comfy.temp / out["media"]["filename"]))
+
+
+@needs_ffmpeg
+def test_export_of_a_window_past_the_end_says_so_and_leaves_nothing(comfy):
+    make_clip(comfy.output / "a.mp4", 1.0)
+    with pytest.raises(stitch.RenderError, match="shorter than the window|past"):
+        stitch.concat([{"filename": "a.mp4", "in": 5, "dur": 1.0}])
+    with pytest.raises(stitch.RenderError, match="Clip 1"):
+        stitch.concat([{"filename": "a.mp4", "in": 0, "dur": 3.0}])
+    assert not os.listdir(comfy.temp)
+
+
+@needs_ffmpeg
+def test_two_exports_in_one_second_do_not_share_a_file(comfy):
+    make_clip(comfy.output / "a.mp4", 1.0)
+    first = stitch.concat([{"filename": "a.mp4", "dur": 1.0}])["media"]["filename"]
+    second = stitch.concat([{"filename": "a.mp4", "dur": 1.0}])["media"]["filename"]
+    assert first != second and (comfy.temp / first).is_file() and (comfy.temp / second).is_file()
diff --git a/modules/output/render/upscale.py b/modules/output/render/upscale.py
index 05f41a78..1bf7e5f4 100644
--- a/modules/output/render/upscale.py
+++ b/modules/output/render/upscale.py
@@ -14,7 +14,8 @@ import subprocess
 
 from . import files
 
-CHUNK = 8                # frames per upscale call
+CHUNK = 8                # frames per upscale call, at most
+CHUNK_PIXELS = 2_000_000   # ...and at most this many input pixels per call: a big upscale of 1080p is gigabytes per frame
 SUBFOLDER = "funpack_upscaled"
 
 
@@ -51,6 +52,7 @@ def upscale_file(src, dst, upscale, interrupted=lambda: None):
     import torch
     w, h, fps, has_sound = probe(src)
     frame = w * h * 3
+    chunk = max(1, min(CHUNK, CHUNK_PIXELS // max(1, w * h)))
     ffmpeg = files.ffmpeg()
     dec = subprocess.Popen([ffmpeg, "-v", "error", "-i", src, "-f", "rawvideo", "-pix_fmt", "rgb24", "-"],
                            stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)
@@ -58,7 +60,7 @@ def upscale_file(src, dst, upscale, interrupted=lambda: None):
     try:
         while True:
             interrupted()
-            raw = _read(dec.stdout, frame * CHUNK)
+            raw = _read(dec.stdout, frame * chunk)
             n = len(raw) // frame
             if n == 0:
                 break