[misc]: drop .agents/exploration journals added by #1453

AGENTS.md bans experiment journals and branch-state snapshots under
.agents/.

.buildkite/performance-benchmarks/tests/wan-t2v-1.3b.json

@@ -1,5 +1,9 @@
 {
   "benchmark_id": "wan-t2v-1.3b-2gpu",
+  "config_schema_version": 2,
+  "workload_id": "wan-t2v-1.3b",
+  "variant_id": "canonical",
+  "benchmark_version": 1,
   "description": "Wan2.1 T2V 1.3B inference performance",
   "model": {
     "model_path": "Wan-AI/Wan2.1-T2V-1.3B-Diffusers",

.buildkite/pipeline.yml

@@ -114,6 +114,17 @@ steps:
             limit: 2
       agents:
         queue: "default"
+    - label: ":test_tube: LoRA Extraction Tests"
+      if: build.env("TEST_SCOPE") == "direct" && build.env("TEST_TYPE") == "lora_extraction"
+      command: "timeout 90m .buildkite/scripts/pr_test.sh"
+      retry:
+        automatic:
+          - exit_status: 128
+            limit: 3
+          - exit_status: -1
+            limit: 2
+      agents:
+        queue: "default"
     - label: ":test_tube: Training Tests"
       if: build.env("TEST_SCOPE") == "direct" && build.env("TEST_TYPE") == "training"
       command: "timeout 90m .buildkite/scripts/pr_test.sh"
@@ -371,6 +382,21 @@ steps:
                   - TEST_TYPE=inference_lora
                 agents:
                   queue: "default"
+            - path:
+                - "scripts/lora_extraction/**"
+                - "fastvideo/tests/lora_extraction/**"
+                - "fastvideo/models/loader/**"
+                - "fastvideo/training/training_utils.py"
+                - "fastvideo/layers/lora/**"
+                - "pyproject.toml"
+                - "docker/Dockerfile"
+              config:
+                command: "timeout 90m .buildkite/scripts/pr_test.sh"
+                label: ":test_tube: LoRA Extraction Tests"
+                env:
+                  - TEST_TYPE=lora_extraction
+                agents:
+                  queue: "default"
             - path:
                 - "fastvideo/**"
                 - "pyproject.toml"

.github/workflows/ci-slash-commands.yml

@@ -125,7 +125,7 @@ jobs:
           set -euo pipefail
           TEST_NAME=$(echo "$COMMENT" | grep -oP '(?<=/test\s)\S+' | head -1 || true)
 
-          VALID="encoder vae transformer kernel unit dreamverse ssim training lora-inference lora-training distillation self-forcing vsa vmoba performance api train-framework eval full fastcheck pre-commit"
+          VALID="encoder vae transformer kernel unit dreamverse ssim training lora-inference lora-training lora-extraction distillation self-forcing vsa vmoba performance api train-framework eval full fastcheck pre-commit"
           if [ -z "$TEST_NAME" ] || ! echo "$VALID" | grep -qw "$TEST_NAME"; then
             echo "Unknown test: '$TEST_NAME'. Valid: $VALID"
             exit 1
@@ -136,6 +136,7 @@ jobs:
             [kernel]=kernel_tests [unit]=unit_test [dreamverse]=dreamverse_app
             [ssim]=ssim [training]=training
             [lora-inference]=inference_lora [lora-training]=training_lora
+            [lora-extraction]=lora_extraction
             [distillation]=distillation_dmd [self-forcing]=self_forcing
             [vsa]=training_vsa [vmoba]=inference_vmoba
             [performance]=performance [api]=api_server

.github/workflows/infra-build-image.yml

@@ -13,12 +13,33 @@ on:
         required: false
         default: false
         type: boolean
+  # Auto-rebuild the CUDA images when their Dockerfile changes on main. The CUDA
+  # matrix is the only lane that builds from docker/Dockerfile, so a path-scoped
+  # push trigger is a sufficient change detector on its own -- no separate
+  # detect-changes/paths-filter job is needed now that there is a single
+  # in-scope Dockerfile. Dreamverse (apps/dreamverse/docker/Dockerfile) and the
+  # rocm Dockerfile stay manual-dispatch only.
+  push:
+    branches: [main]
+    paths:
+      - 'docker/Dockerfile'
 
 
 permissions:
   contents: read
   packages: write
 
+# One static group, no cancellation: every run of this workflow writes the same
+# mutable registry tags (latest, py3.12-latest, ...), so runs must serialize —
+# concurrent push/dispatch runs would race on those tags, and cancelling a run
+# mid-publish can strand the cu126/cu130 tag families at different commits. An
+# in-flight superseded build wastes its runner time, but its tags are then
+# overwritten by the newer queued run. GitHub keeps a single pending run per
+# group: the newest queued run replaces any older queued one.
+concurrency:
+  group: infra-build-image
+  cancel-in-progress: false
+
 jobs:
   # CUDA matrix: Python 3.12 x {12.6.3, 13.0.0} x {amd64, arm64}. Each architecture
   # builds natively and pushes only by digest; publish-cuda-manifests is the sole
@@ -28,7 +49,11 @@ jobs:
   # aliases; 13.0.0/cu130 is published under explicit versioned tags. Flash-attn
   # 2.8.3 comes from the architecture-specific prebuilt releases.
   build-cuda-images:
-    if: ${{ github.event.inputs.build_cuda_matrix == 'true' }}
+    # Runs on a manual dispatch when build_cuda_matrix is set, or automatically
+    # on a push that changed docker/Dockerfile (inputs are null on push). The
+    # repository guard keeps fork syncs from auto-building; manual dispatch
+    # still works in forks.
+    if: ${{ (github.event_name == 'push' && github.repository == 'hao-ai-lab/FastVideo') || github.event.inputs.build_cuda_matrix == 'true' }}
     strategy:
       fail-fast: false
       matrix:
@@ -75,10 +100,10 @@ jobs:
     secrets: inherit
 
   publish-cuda-manifests:
-    # !cancelled(): a failed sibling build leg must not skip the manifests for a
-    # CUDA lane whose own digests all exist; the digest-count check below fails
-    # the incomplete lane loudly instead.
-    if: ${{ !cancelled() && github.event.inputs.build_cuda_matrix == 'true' }}
+    # !cancelled(): publish lanes whose digests exist even if a sibling build
+    # leg failed (the digest-count check fails incomplete lanes); it also
+    # bypasses skipped-needs propagation, hence the explicit skipped check.
+    if: ${{ !cancelled() && needs.build-cuda-images.result != 'skipped' }}
     needs: build-cuda-images
     runs-on: ubuntu-latest
     permissions:

apps/dreamverse/docker/Dockerfile

@@ -84,9 +84,12 @@ RUN source /opt/venv/bin/activate \
        FFMPEG_NATIVE_CXX=/usr/bin/g++ \
        bash /opt/FastVideo/apps/dreamverse/scripts/install_native_ffmpeg.sh
 
+# FASTVIDEO_FA4: FA4 (flash_attn.cute) is opt-in; this image installs it via
+# the dreamverse extra and is validated with it, so enable it here.
 ENV FASTVIDEO_DREAMVERSE_HOME=/var/lib/dreamverse \
     STREAM_MODE=av_fmp4 \
     FASTVIDEO_ENABLE_PROMPT_SAFETY=0 \
+    FASTVIDEO_FA4=1 \
     HF_HOME=/root/.cache/huggingface
 
 RUN mkdir -p /var/lib/dreamverse

apps/performance_dashboard/README.md

@@ -12,13 +12,17 @@ Defaults:
 
 - `HF_REPO_ID=FastVideo/performance-tracking`
 - `PERFORMANCE_TRACKING_ROOT=/tmp/fastvideo-perf-dashboard`
-- `PERF_MAX_REGRESSION=0.05`
 
-Records can include source metadata:
+Records can include source metadata and rolling-baseline policy context:
 
 - `run_source`: `pr`, `local`, `scheduled_main`, or `unknown`
 - `baseline_eligible`: only successful scheduled-main records should be true
 - Buildkite metadata such as branch, PR number, build URL, build ID, and job ID
+- `regression_thresholds`: per-metric rolling-baseline percent and absolute
+  floors used for recomputed status context
+
+Dashboard/API metric payloads expose `threshold_exceeded` for raw threshold
+crossings; `regressed` remains the gated CI-failure signal.
 
 Set one of `HF_API_KEY`, `HUGGINGFACE_HUB_TOKEN`, or `HF_TOKEN` if the
 configured dataset repo requires authenticated access:
@@ -89,7 +93,8 @@ Trend charts show metric-specific axes and exact point details on hover/focus:
 - PR number, branch, and Buildkite URL when present
 
 The latest status table uses the stored JSON `success` value. Recomputed
-baseline context is shown separately and does not override stored status.
+baseline context applies each metric's percent and absolute regression floors
+and does not override stored status.
 
 ## API
 

apps/performance_dashboard/frontend/src/App.tsx

@@ -440,6 +440,8 @@ export default function App() {
                   <th>Throughput</th>
                   <th>Memory</th>
                   <th>Worst</th>
+                  <th>Exceeded</th>
+                  <th>Failing</th>
                 </tr>
               </thead>
               <tbody>
@@ -465,6 +467,12 @@ export default function App() {
                     <td>{formatNumber(row.metrics.throughput?.current, 3)}</td>
                     <td>{formatNumber(row.metrics.memory?.current, 1)}</td>
                     <td>{formatNumber(row.worst_regression_pct, 1)}%</td>
+                    <td>
+                      {row.threshold_exceeded_metrics.length
+                        ? row.threshold_exceeded_metrics.join(", ")
+                        : "none"}
+                    </td>
+                    <td>{row.failing_metrics.length ? row.failing_metrics.join(", ") : "none"}</td>
                   </tr>
                 ))}
               </tbody>

apps/performance_dashboard/frontend/src/api.ts

@@ -2,6 +2,12 @@ export type MetricValue = {
   current: number | null;
   baseline: number | null;
   regression_pct: number | null;
+  absolute_delta: number | null;
+  threshold_percent: number;
+  threshold_absolute: number;
+  gated: boolean;
+  threshold_exceeded: boolean;
+  regressed: boolean;
   label: string;
   lower_is_better: boolean;
   precision: number;
@@ -15,7 +21,8 @@ export type SummaryRow = {
   success: boolean;
   baseline_n: number;
   worst_regression_pct: number | null;
-  regression_threshold_pct: number;
+  threshold_exceeded_metrics: string[];
+  failing_metrics: string[];
   computed_regression_status: "pass" | "fail";
   status: "pass" | "fail";
   run_source: RunSource;

docker/Dockerfile

@@ -170,12 +170,14 @@ RUN --mount=type=cache,target=/opt/uv/cache \
 # rmtree clears the wheel's stale cute files first to avoid an install conflict.
 # Then verify both survive so a broken overlay fails the build instead of shipping
 # an FA2-less image. x86 only: the FA4 stack (quack-kernels etc.) is unvalidated on
-# arm64 / GB10 (sm_121), so there we skip the overlay and FA4 falls back to FA2.
+# arm64 / GB10 (sm_121), so there we skip the overlay; FA4 is opt-in
+# (FASTVIDEO_FA4=1) and errors if set without the overlay, so leave it unset on
+# arm64 and the image runs FA3/FA2 as usual.
 RUN --mount=type=cache,target=/opt/uv/cache \
     source $HOME/.local/bin/env && \
     source /opt/venv/bin/activate && \
     if [ "${TARGETARCH}" = "arm64" ]; then \
-        echo "Skipping FA4 cute overlay on arm64 (FA4 stack unvalidated there; FA4 falls back to FA2)"; \
+        echo "Skipping FA4 cute overlay on arm64 (FA4 stack unvalidated there; do not set FASTVIDEO_FA4)"; \
     else \
         python -c "import glob, shutil; [shutil.rmtree(d, ignore_errors=True) for d in glob.glob('/opt/venv/lib/python*/site-packages/flash_attn/cute')]" && \
         uv pip install "flash-attn-4 @ git+https://github.com/Dao-AILab/flash-attention.git@${FA4_CUTE_REF}#subdirectory=flash_attn/cute" && \

docs/contributing/ci_architecture.md

@@ -103,6 +103,7 @@ can merge a PR.
 |---|---|---|
 | SSIM Tests | `ssim` | `fastvideo/**/*.py`, `pyproject.toml`, `docker/Dockerfile` |
 | LoRA Inference Tests | `inference_lora` | LoRA tests, loader, transformer tests, pipelines, LoRA layers |
+| LoRA Extraction Tests | `lora_extraction` | LoRA extraction scripts/tests, loader, training utilities, LoRA layers |
 | Training Tests | `training` | `fastvideo/**`, `pyproject.toml`, `docker/Dockerfile` |
 | Distillation DMD Tests | `distillation_dmd` | `fastvideo/training/*distillation_pipeline.py` |
 | Self-Forcing Tests | `self_forcing` | self-forcing distillation pipeline and tests |
@@ -144,6 +145,7 @@ Valid direct test names:
 | `/test training` | `training` |
 | `/test lora-inference` | `inference_lora` |
 | `/test lora-training` | `training_lora` |
+| `/test lora-extraction` | `lora_extraction` |
 | `/test distillation` | `distillation_dmd` |
 | `/test self-forcing` | `self_forcing` |
 | `/test vsa` | `training_vsa` |

docs/contributing/performance_benchmarks.md

@@ -72,7 +72,10 @@ fastvideo/tests/performance/
     │           writes Markdown summary + (optionally) uploads new records
     ├── dashboard.py
     │       └── builds time-series Plotly HTML from HF history
-    └── hf_store.py               # shared HF I/O + DataFrame helpers
+
+fastvideo/performance/
+    ├── hf_store.py               # shared HF I/O + DataFrame helpers
+    └── metric_policy.py          # shared rolling-baseline threshold policy
 ```
 
 The HF dataset (`FastVideo/performance-tracking` by default) holds one
@@ -92,16 +95,18 @@ and recipe changes instead of treating all records for a model as equivalent.
 
 ## Metrics
 
-Each benchmark records six metrics:
+Each benchmark records six metrics. The rolling-baseline comparator also has a
+per-metric policy with direction, percent threshold, absolute threshold, and a
+`gated` flag.
 
-| Metric | Raw key | Normalized key | Direction |
-|---|---|---|---|
-| End-to-end generation latency | `avg_generation_time_s` | `latency` | Lower is better |
-| Video throughput | `throughput_fps` | `throughput` | Higher is better |
-| Peak GPU memory | `max_peak_memory_mb` | `memory` | Lower is better |
-| Text encoder time | `text_encoder_time_s` | `text_encoder_time_s` | Lower is better |
-| DiT denoising time | `dit_time_s` | `dit_time_s` | Lower is better |
-| VAE decode time | `vae_decode_time_s` | `vae_decode_time_s` | Lower is better |
+| Metric | Raw key | Normalized key | Direction | Default rolling policy |
+|---|---|---|---|---|
+| End-to-end generation latency | `avg_generation_time_s` | `latency` | Lower is better | 8% and 0.5 s |
+| Video throughput | `throughput_fps` | `throughput` | Higher is better | 8% and 0.05 FPS |
+| Peak GPU memory | `max_peak_memory_mb` | `memory` | Lower is better | 5% and 256 MB |
+| Text encoder time | `text_encoder_time_s` | `text_encoder_time_s` | Lower is better | 5% and 0.25 s |
+| DiT denoising time | `dit_time_s` | `dit_time_s` | Lower is better | 5% and 0.25 s |
+| VAE decode time | `vae_decode_time_s` | `vae_decode_time_s` | Lower is better | 5% and 0.25 s |
 
 `test_inference_performance.py` temporarily sets `FASTVIDEO_STAGE_LOGGING=1`
 while it runs so pipeline stage execution times are available in
@@ -156,9 +161,22 @@ headroom and almost never need touching.
 
 `compare_baseline.py` loads the last 5 successful, baseline-eligible records
 for the same `(model_id, gpu_type)` from the HF dataset, computes the median
-for each available metric, and fails if the current run regresses by more than
-`PERF_MAX_REGRESSION` (default 5%). For latency, memory, and component times,
-higher values are regressions. For throughput, lower values are regressions.
+for each available metric, and evaluates the current run with the metric's
+rolling regression policy. For latency, memory, and component times, higher
+values are regressions. For throughput, lower values are regressions.
+
+A metric exceeds its rolling threshold when both of these are true:
+
+```text
+percent_delta > threshold_percent
+absolute_delta > threshold_absolute
+```
+
+Gated metrics fail CI when that threshold crossing happens. Set `gated: false`
+for metrics that should remain visible in reports and the dashboard without
+failing CI. Dashboard/API payloads expose `threshold_exceeded` separately from
+`regressed`, where `regressed` means a gated CI failure. Missing or `null`
+metrics are skipped.
 
 This is the **drift detector** — it catches sub-threshold regressions that
 slowly add up. Only scheduled-main successful records are baseline eligible.
@@ -172,6 +190,45 @@ agent skill to advance the rolling median.
 
 ## Schemas
 
+### Benchmark config (`.buildkite/performance-benchmarks/tests/*.json`)
+
+Benchmark configs without `config_schema_version` are treated as legacy v1
+configs and remain loadable. New or migrated configs should use
+`config_schema_version: 2` and include explicit comparable identity fields:
+
+```jsonc
+{
+  "benchmark_id": "wan-t2v-1.3b-2gpu",
+  "config_schema_version": 2,
+  "workload_id": "wan-t2v-1.3b",
+  "variant_id": "canonical",
+  "benchmark_version": 1
+}
+```
+
+`benchmark_id` is still required in this phase because raw artifact names,
+generated-video directories, normalized record paths, and the current rolling
+baseline comparator still depend on it. The v2 identity fields are config
+metadata that make the measured workload explicit:
+
+| Field | Purpose |
+|---|---|
+| `workload_id` | Stable benchmark family, such as `wan-t2v-1.3b`. |
+| `variant_id` | Intentional recipe family, such as `canonical`. |
+| `benchmark_version` | Version of the measurement protocol and comparison policy. |
+
+If a config declares `config_schema_version: 2`, loading fails clearly when any
+required v2 identity field is missing. If v2 identity or metadata fields are
+added without `config_schema_version: 2`, loading also fails so partial
+migrations do not silently run as v1 configs. Optional v2 metadata fields
+reserved for follow-up work, such as `recipe`, `metric_threshold_policy`, and
+`quality_metadata`, must be JSON objects when present.
+
+Recipe fingerprinting, hardware/software profile IDs, exact-identity
+comparison, metric-specific threshold policy behavior, promoted baselines, and
+dashboard regrouping are separate follow-up changes. Until those land, rolling
+baseline comparison remains keyed by `(model_id, gpu_type)`.
+
 ### Raw record (`results/perf_*.json`)
 
 Written by `test_inference_performance.py`. One file per benchmark run.
@@ -179,6 +236,10 @@ Written by `test_inference_performance.py`. One file per benchmark run.
 ```jsonc
 {
   "benchmark_id": "wan-t2v-1.3b-2gpu",
+  "config_schema_version": 2,
+  "workload_id": "wan-t2v-1.3b",
+  "variant_id": "canonical",
+  "benchmark_version": 1,
   "model_short_name": "Wan2.1-T2V-1.3B-Diffusers",
   "device": "NVIDIA L40S",
   "num_gpus": 2,
@@ -196,6 +257,13 @@ Written by `test_inference_performance.py`. One file per benchmark run.
     "max_dit_time_s": 10.0,
     "max_vae_decode_time_s": 10.0
   },
+  "regression_thresholds": {
+    "latency": {
+      "threshold_percent": 0.10,
+      "threshold_absolute": 1.0,
+      "gated": true
+    }
+  },
   "commit": "<full sha>",
   "pr_number": "1234",
   "timestamp": "2026-05-08T22:00:00+00:00",
@@ -222,6 +290,13 @@ result, used as the rolling-baseline source of truth.
   "text_encoder_time_s": 2.141,
   "dit_time_s": 8.437,
   "vae_decode_time_s": 3.208,
+  "regression_thresholds": {
+    "latency": {
+      "threshold_percent": 0.08,
+      "threshold_absolute": 0.5,
+      "gated": true
+    }
+  },
   "success": true
 }
 ```
@@ -238,18 +313,17 @@ successful main/full-suite uploads and remain eligible for rolling baselines.
 
 | Variable | Default | Used by | Purpose |
 |---|---|---|---|
-| `PERF_MAX_REGRESSION` | `0.05` | `compare_baseline.py` | Per-metric regression fraction that fails the build. |
 | `PERFORMANCE_TRACKING_ROOT` | `/tmp/perf-tracking` | `compare_baseline.py`, `dashboard.py` | Local directory the HF dataset is synced to. |
 | `PERF_REPORTS_DIR` | `/root/data/perf_reports` | `compare_baseline.py`, `dashboard.py` | Where the Markdown summary and Plotly HTML get written for Buildkite to pick up. |
-| `HF_REPO_ID` | `FastVideo/performance-tracking` | `hf_store.py` | HF dataset repo holding rolling-baseline records. |
-| `HF_API_KEY`, `HUGGINGFACE_HUB_TOKEN`, `HF_TOKEN` | unset | `hf_store.py` | Required for upload or private dataset reads. |
+| `HF_REPO_ID` | `FastVideo/performance-tracking` | `fastvideo/performance/hf_store.py` | HF dataset repo holding rolling-baseline records. |
+| `HF_API_KEY`, `HUGGINGFACE_HUB_TOKEN`, `HF_TOKEN` | unset | `fastvideo/performance/hf_store.py` | Required for upload or private dataset reads. |
 | `PERF_RUN_SOURCE` | inferred | `compare_baseline.py` | Source metadata for uploaded records: `pr`, `local`, `scheduled_main`, or `unknown`. |
 | `PERF_UPLOAD_POLICY` | `never` | `compare_baseline.py` | Upload policy: `never`, `pass`, or `always`. |
 | `PERF_PYTEST_RC` | unset | `compare_baseline.py` | Static-threshold pytest exit code, used so scheduled-main failures can be uploaded with `success=false`. |
 | `TEST_SCOPE` | unset | `compare_baseline.py` | CI context used to infer scheduled-main runs together with `BUILDKITE_BRANCH=main`. |
 | `BUILDKITE_BRANCH`, `BUILDKITE_COMMIT`, `BUILDKITE_PULL_REQUEST` | unset | `compare_baseline.py`, `test_inference_performance.py` | CI metadata stamped into records. |
 | `DASHBOARD_DAYS` | `30` | `dashboard.py` | Lookback window for the Plotly trend pages. |
-| `PERFORMANCE_TRACKING_SYNC_REUSE_TTL_SECONDS` | `3600` | `hf_store.py` | Freshness window for reusing an existing HF sync when requested by dashboard consumers. |
+| `PERFORMANCE_TRACKING_SYNC_REUSE_TTL_SECONDS` | `3600` | `fastvideo/performance/hf_store.py` | Freshness window for reusing an existing HF sync when requested by dashboard consumers. |
 | `FASTVIDEO_STAGE_LOGGING` | set by the pytest test | `test_inference_performance.py` | Enables pipeline stage timing capture for component metrics during benchmark runs. |
 
 ## CI integration
@@ -261,9 +335,11 @@ Buildkite artifact upload is in
 `.buildkite/scripts/pr_test.sh:upload_performance_artifacts`.
 
 Each performance build runs pytest first. If that fixed-threshold phase fails,
-`compare_baseline.py` is skipped, so Markdown summaries and normalized JSON
-artifacts are not emitted. The dashboard still runs best-effort for
-observability. When pytest passes, the rolling-baseline phase emits:
+PR/direct runs skip `compare_baseline.py` because they only upload passing
+records. Scheduled-main runs still execute `compare_baseline.py` with
+`PERF_PYTEST_RC` set so the failed canonical attempt is visible in normalized
+JSON and dashboard history. The dashboard runs best-effort for observability.
+When the rolling-baseline phase runs, it emits:
 
 * **Markdown summary** — appended to `$GITHUB_STEP_SUMMARY` when that variable
   is set, and written as `perf_<sha>_<ts>.md` for Buildkite upload. Contains a
@@ -279,11 +355,16 @@ observability. When pytest passes, the rolling-baseline phase emits:
 ## Adding a new benchmark
 
 1. Drop a new JSON config into
-   `.buildkite/performance-benchmarks/tests/<name>.json`. Required keys:
+   `.buildkite/performance-benchmarks/tests/<name>.json`. New configs should
+   use v2 identity fields:
 
    ```json
    {
      "benchmark_id": "<unique-id>",
+     "config_schema_version": 2,
+     "workload_id": "<stable-workload-id>",
+     "variant_id": "canonical",
+     "benchmark_version": 1,
      "model": { "model_path": "...", "model_short_name": "..." },
      "init_kwargs": { "num_gpus": 1, ... },
      "generation_kwargs": { "num_frames": 45, ... },
@@ -299,9 +380,17 @@ observability. When pytest passes, the rolling-baseline phase emits:
          "max_vae_decode_time_s": 10.0
        },
        "default": { "max_generation_time_s": 120.0, "max_peak_memory_mb": 30000.0 }
+     },
+     "regression_thresholds": {
+       "latency": { "threshold_percent": 0.10, "threshold_absolute": 1.0, "gated": true }
      }
-   }
-   ```
+  }
+
+  ```
+
+   Legacy v1 configs without `config_schema_version` still load, but should not
+   gain v2 identity or metadata fields until they are migrated to
+   `config_schema_version: 2`.
 
 2. The pytest test auto-discovers all configs — no test code needed. CI
    picks it up on the next `/test performance` run.
@@ -320,6 +409,13 @@ observability. When pytest passes, the rolling-baseline phase emits:
    a useful fixed gate. The rolling baseline will still track component times
    when static component thresholds are omitted.
 
+6. Omit `regression_thresholds` to use the default rolling-baseline policy, or
+   include only benchmark-specific deviations. Tune these independently from
+   the fixed thresholds when a metric is noisy or should be informational. The
+   fixed `thresholds` block is an absolute pytest ceiling. The
+   `regression_thresholds` block controls rolling-baseline comparisons against
+   recent scheduled-main records.
+
 ## Troubleshooting
 
 **"No baseline for ... Initializing"** — first run for this `(model_id,

docs/design/inference_schema_parity_inventory.yaml

@@ -41,6 +41,11 @@ surfaces:
       disable_autocast: generator.engine.disable_autocast
       enable_stage_verification: generator.engine.enable_stage_verification
       prompt_txt: request.inputs.prompt_path
+      batching_mode: generator.engine.batching.mode
+      batching_max_size: generator.engine.batching.max_size
+      batching_delay_ms: generator.engine.batching.delay_ms
+      batching_config: generator.engine.batching.config_path
+      enable_batching_metrics: generator.engine.batching.enable_metrics
       override_text_encoder_safetensors: generator.pipeline.components.text_encoder_weights
       override_text_encoder_quant: generator.engine.quantization.text_encoder_quant
       transformer_quant: generator.engine.quantization.transformer_quant

docs/inference/optimizations.md

@@ -74,6 +74,23 @@ uv pip install ninja
 python setup.py install
 ```
 
+### Flash Attention 4 (opt-in)
+
+FastVideo never auto-selects FlashAttention-4 (`flash_attn.cute`) just because it
+is installed: its CuTeDSL kernels JIT-compile per shape family and can fail at
+runtime on some GPU/shape combinations. To use FA4, install the pinned
+`flash-attn-4` build (see the `flash-attn-4` source in `pyproject.toml`) and set:
+
+```bash
+export FASTVIDEO_FA4=1
+```
+
+On GPUs below sm90 a capability gate routes to FlashAttention-2 the calls FA4
+cannot serve there: grad-enabled (training) attention (FA4's backward requires
+sm90+) and GQA attention (FA4's `pack_gqa` fails to JIT-compile below sm90).
+On sm90+ both run on FA4. If FA4 is unusable while `FASTVIDEO_FA4=1` is set,
+FastVideo fails loudly instead of silently falling back.
+
 ### FP4 Flash Attention 4 (Blackwell only)
 
 **`FLASH_ATTN`** with **`--nvfp4_fa4`**

fastvideo-kernel/CMakeLists.txt

@@ -12,6 +12,9 @@ set(_FASTVIDEO_USER_CUDA_ARCH "${CMAKE_CUDA_ARCHITECTURES}")
 if(NOT DEFINED GPU_BACKEND AND DEFINED ENV{GPU_BACKEND})
     set(GPU_BACKEND "$ENV{GPU_BACKEND}")
 endif()
+if(NOT GPU_BACKEND)
+    set(GPU_BACKEND "CUDA")
+endif()
 
 if(GPU_BACKEND STREQUAL "ROCM")
     enable_language(HIP)
@@ -50,7 +53,16 @@ if(NOT GPU_BACKEND STREQUAL "ROCM")
         if(_FASTVIDEO_USER_CUDA_ARCH)
             # Caller pinned -DCMAKE_CUDA_ARCHITECTURES (which torch ignores); translate it
             # to the TORCH_CUDA_ARCH_LIST spelling: "121" -> "12.1", "90a" -> "9.0a".
+            # Only numeric spellings translate; keywords like "native"/"all" would
+            # otherwise be mangled into nonsense ("nativ.e").
             foreach(_fv_arch IN LISTS _FASTVIDEO_USER_CUDA_ARCH)
+                if(NOT _fv_arch MATCHES "^[0-9]+[af]?$")
+                    message(FATAL_ERROR
+                        "fastvideo-kernel: CMAKE_CUDA_ARCHITECTURES='${_fv_arch}' is not "
+                        "supported. Use a numeric arch (e.g. 90a, 121), set "
+                        "TORCH_CUDA_ARCH_LIST directly (e.g. 9.0a), or unset both to "
+                        "auto-detect from the visible GPU.")
+                endif()
                 string(REGEX MATCH "[af]$" _fv_suffix "${_fv_arch}")
                 string(REGEX REPLACE "[af]$" "" _fv_num "${_fv_arch}")
                 string(REGEX REPLACE "(.)$" ".\\1" _fv_num "${_fv_num}")    # dot before the last digit
@@ -173,6 +185,14 @@ else()
     endif()
 endif()
 
+# ThunderKittens headers don't compile on aarch64 hosts: plain char is unsigned
+# there, and tk's base_types.cuh brace-initializes signed-char vector members
+# from char (narrowing error). Skip TK until upstream is aarch64-clean.
+if(ENABLE_TK_KERNELS AND CMAKE_SYSTEM_PROCESSOR MATCHES "^(aarch64|arm64)$")
+    message(STATUS "ThunderKittens kernels: forced OFF on ${CMAKE_SYSTEM_PROCESSOR} (tk headers are not aarch64-clean)")
+    set(ENABLE_TK_KERNELS OFF)
+endif()
+
 if(ENABLE_TK_KERNELS)
     message(STATUS "ThunderKittens kernels: ENABLED")
 else()
@@ -263,11 +283,6 @@ set(CUDA_FLAGS
     "--expt-relaxed-constexpr"
     "-Xcompiler=-fno-strict-aliasing"
     "-Xcompiler=-fPIC"
-    # ARM/aarch64 defaults `char` to unsigned, but ThunderKittens headers assume the
-    # x86 signed-char behavior (else base_types.cuh hits "narrowing conversion from
-    # char to signed char"). Force signed char so TK compiles on Grace Hopper; this
-    # is a no-op on x86_64, where char is already signed.
-    "-Xcompiler=-fsigned-char"
     "-DTORCH_COMPILE"
     "-Xnvlink=--verbose"
     "-Xptxas=--verbose"
@@ -426,3 +441,14 @@ if(ENABLE_ATTN_QAT_INFER)
     install(TARGETS fp4attn_cuda LIBRARY DESTINATION .)
     install(TARGETS fp4quant_cuda LIBRARY DESTINATION .)
 endif()
+
+# One-look answer to "what is this build producing?" — kept last so it is the
+# final thing configure prints. The per-kernel matrix lives in README.md.
+message(STATUS "============== fastvideo-kernel build summary ==============")
+message(STATUS "host / backend:       ${CMAKE_SYSTEM_PROCESSOR} / ${GPU_BACKEND}")
+message(STATUS "TORCH_CUDA_ARCH_LIST: ${TORCH_CUDA_ARCH_LIST}")
+message(STATUS "fastvideo_kernel_ops: ON  (turbodiffusion int8-gemm/quant/rmsnorm/layernorm, all listed archs)")
+message(STATUS "  + TK sta/block_sparse (sm_90a only):          ${ENABLE_TK_KERNELS}")
+message(STATUS "fp4attn/fp4quant (sm_120a only, CUDA >= 12.8):  ${ENABLE_ATTN_QAT_INFER}")
+message(STATUS "Triton fallbacks ship in python/fastvideo_kernel/triton_kernels regardless.")
+message(STATUS "============================================================")

fastvideo-kernel/README.md

@@ -2,6 +2,42 @@
 
 CUDA kernels for FastVideo video generation.
 
+## Kernel inventory
+
+Compiled CUDA extensions (CMake, see the build summary printed at the end of every configure):
+
+| Extension | Kernels | Sources | GPU arch | Build gate |
+|---|---|---|---|---|
+| `fastvideo_kernel._C.fastvideo_kernel_ops` | TurboDiffusion INT8 GEMM, quant, RMSNorm, LayerNorm | `csrc/turbodiffusion/` | every arch in `TORCH_CUDA_ARCH_LIST` | always built |
+| same extension, optional part | ThunderKittens sliding-tile attention (`sta_fwd`) and VSA block-sparse (`block_sparse_fwd/bwd`) | `csrc/attention/*_h100.cu` | Hopper `sm_90a` only | `FASTVIDEO_KERNEL_BUILD_TK` (AUTO = ON iff `9.0a` is in the arch list; always OFF on aarch64 hosts — TK headers don't compile there) |
+| `fp4attn_cuda`, `fp4quant_cuda` | FP4 attention + quantization ("attn_qat_infer", modified SageAttention3) | `attn_qat_infer/` | consumer Blackwell `sm_120a` only, CUDA ≥ 12.8 | `FASTVIDEO_KERNEL_BUILD_ATTN_QAT_INFER` (AUTO = ON iff `12.0a` is in the arch list) |
+
+Runtime-JIT kernels (no build step, ship in every wheel/image):
+
+| Kernels | Where | Used when |
+|---|---|---|
+| Triton: STA, VSA block-sparse, SLA, fused compress+topk, FP4 QAT training, quant/norm utils | `python/fastvideo_kernel/triton_kernels/` | automatic fallback when the matching C++ op is absent (`ops.py`, `turbodiffusion_ops.py`) |
+| FA4 CuTe-DSL block-sparse (VSA-256 fastpath on `sm_100`) | `block_sparse_attn_cute_fwd.py` | optional `flash_attn.cute` dependency, see below |
+| VMoBA `moba_attn_varlen` | `vmoba.py` | wraps flash-attn varlen |
+
+## What gets built where, and when
+
+| Surface | Trigger | Leg | `TORCH_CUDA_ARCH_LIST` | TK | FP4 |
+|---|---|---|---|---|---|
+| PyPI wheels (`.github/workflows/publish-kernel.yml`) | version bump in `fastvideo-kernel/pyproject.toml` on main, or manual dispatch | x86_64 cu126 | `9.0a` | ON | — (CUDA < 12.8) |
+| | | x86_64 cu130 | `9.0a;12.0a` | ON | ON |
+| | | aarch64 cu130 | `10.0a;12.0a` | — | ON |
+| Docker images `ghcr.io/hao-ai-lab/fastvideo/fastvideo-dev` (`.github/workflows/infra-build-image.yml`) | `docker/Dockerfile` changes on main, or manual dispatch | amd64 cuda12.6.3 + cuda13.0.0 | `9.0a` | ON | — |
+| | | arm64 cuda12.6.3 (GH200) | `9.0a` | — (aarch64) | — |
+| | | arm64 cuda13.0.0 (GB10 / DGX Spark) | `12.1` | — | — |
+| Local `./build.sh` | manual | probes the visible GPU via torch | detected | ON iff sm_90 (non-aarch64 host) | ON iff sm_120 |
+
+Notes:
+
+- No Docker image ships the FP4 kernels; only the x86_64/aarch64 cu130 wheels do.
+- On arm64 images (GH200 included) STA/VSA run on the Triton fallbacks, since TK never builds on aarch64.
+- Kernel tests run on Buildkite GPU CI for PRs touching `fastvideo-kernel/**` (see `.buildkite/pipeline.yml`).
+
 ## Installation
 
 ### Standard Installation (Local Development)

fastvideo-kernel/build.sh

@@ -46,6 +46,23 @@ fi
 if git rev-parse --git-dir >/dev/null 2>&1; then
     git submodule update --init --recursive include/cutlass include/tk
 fi
+# Fail fast with a clear message if the headers are still missing (e.g. a
+# Docker context that excluded .git AND the submodule contents) instead of
+# dying later in a wall of nvcc include errors. CUTLASS is consumed by the
+# always-built turbodiffusion sources, so it is a hard error; ThunderKittens
+# only feeds the TK-gated Hopper kernels, so a missing tree just warns (the
+# TK gate resolves later, and non-SM90/ROCm builds never touch it).
+if [ ! -d include/cutlass/include ]; then
+    echo "ERROR: include/cutlass/include is missing. Outside a git checkout the" >&2
+    echo "       CUTLASS sources must already be present (run" >&2
+    echo "       'git submodule update --init --recursive include/cutlass include/tk'" >&2
+    echo "       in the source checkout, or include them in the build context)." >&2
+    exit 1
+fi
+if [ ! -d include/tk/include ]; then
+    echo "WARNING: include/tk/include is missing; ThunderKittens (Hopper sm_90a)" >&2
+    echo "         kernels cannot be built. Fine for non-SM90/ROCm targets." >&2
+fi
 
 # Install build dependencies
 uv pip install scikit-build-core cmake ninja

fastvideo/api/compat.py

@@ -159,6 +159,16 @@ def legacy_from_pretrained_to_config(
             preset_refine["guidance_scale"] = value
         elif key in {"enable_stage_verification", "use_fsdp_inference", "disable_autocast"}:
             engine[key] = value
+        elif key == "batching_mode":
+            engine.setdefault("batching", {})["mode"] = value
+        elif key == "batching_max_size":
+            engine.setdefault("batching", {})["max_size"] = value
+        elif key == "batching_delay_ms":
+            engine.setdefault("batching", {})["delay_ms"] = value
+        elif key == "batching_config":
+            engine.setdefault("batching", {})["config_path"] = value
+        elif key == "enable_batching_metrics":
+            engine.setdefault("batching", {})["enable_metrics"] = value
         elif key == "override_text_encoder_quant":
             quantization["text_encoder_quant"] = value
         elif key == "workload_type":
@@ -244,6 +254,11 @@ def generator_config_to_fastvideo_args(config: GeneratorConfig | Mapping[str, An
         "enable_stage_verification": engine.enable_stage_verification,
         "use_fsdp_inference": engine.use_fsdp_inference,
         "disable_autocast": engine.disable_autocast,
+        "batching_mode": engine.batching.mode,
+        "batching_max_size": engine.batching.max_size,
+        "batching_delay_ms": engine.batching.delay_ms,
+        "batching_config": engine.batching.config_path,
+        "enable_batching_metrics": engine.batching.enable_metrics,
     }
     if normalized.pipeline.workload_type is not None:
         kwargs["workload_type"] = normalized.pipeline.workload_type

fastvideo/api/schema.py

@@ -71,6 +71,15 @@ class QuantizationConfig:
     transformer_quant: str | None = None
 
 
+@dataclass
+class BatchingConfig:
+    mode: Literal["disabled", "dynamic"] = "disabled"
+    max_size: int = 1
+    delay_ms: float = 0.0
+    config_path: str | None = None
+    enable_metrics: bool = False
+
+
 @dataclass
 class EngineConfig:
     num_gpus: int = 1
@@ -82,6 +91,7 @@ class EngineConfig:
     use_fsdp_inference: bool = False
     disable_autocast: bool = False
     quantization: QuantizationConfig | None = None
+    batching: BatchingConfig = field(default_factory=BatchingConfig)
 
 
 @dataclass
@@ -280,6 +290,7 @@ class ServeConfig:
 
 
 __all__ = [
+    "BatchingConfig",
     "CompileConfig",
     "ComponentConfig",
     "ContinuationState",

fastvideo/attention/backends/flash_attn.py

@@ -1,15 +1,39 @@
 # SPDX-License-Identifier: Apache-2.0
 
+import importlib.util
 import os
+
 import torch
 import torch.nn.functional as F
 from dataclasses import dataclass
 
-try:
-    from fastvideo.attention.utils.flash_attn_cute import flash_attn_func
+from fastvideo import envs
+from fastvideo.attention.backends.abstract import (
+    AttentionBackend,
+    AttentionImpl,
+    AttentionMetadata,
+    AttentionMetadataBuilder,
+)
+from fastvideo.logger import init_logger
 
+logger = init_logger(__name__)
+
+# FA4 (flash_attn.cute) is explicit opt-in via FASTVIDEO_FA4=1, mirroring the
+# kernel package's FASTVIDEO_VSA_CUTEDSL: its CuTeDSL kernels JIT-compile per
+# shape family and can fail at runtime on some arch/shape combinations, so it
+# is never auto-selected just because it is installed. Below sm90 a capability
+# gate in flash_attn_cute routes to FA2 the calls FA4 cannot serve there:
+# grad-enabled (its backward asserts sm90+) and GQA (pack_gqa fails CuTeDSL
+# JIT, observed on sm_89).
+if envs.FASTVIDEO_FA4:
+    try:
+        from fastvideo.attention.utils.flash_attn_cute import flash_attn_func
+    except ImportError as e:
+        raise RuntimeError(f"FASTVIDEO_FA4=1 but flash_attn.cute (FA4) is not usable ({e}); "
+                           "fix the FA4 install (see the flash-attn-4 pin in pyproject.toml) "
+                           "or unset FASTVIDEO_FA4.") from e
     fa_version = "4"
-except ImportError:
+else:
     try:
         from flash_attn_interface import flash_attn_func as flash_attn_3_func
 
@@ -21,6 +45,12 @@ except ImportError:
         from flash_attn import flash_attn_func as flash_attn_2_func
         flash_attn_func = flash_attn_2_func
         fa_version = "2"
+    try:
+        if importlib.util.find_spec("flash_attn.cute") is not None:
+            logger.info("flash_attn.cute (FA4) is installed but not enabled; "
+                        "set FASTVIDEO_FA4=1 to use it for inference.")
+    except ImportError:
+        pass
 
 # torch.compile traceability: the FA4/cute path (fa_version=="4") is
 # already a registered torch.library custom op, so dynamo treats it as a
@@ -87,9 +117,10 @@ if fa_version in ("2", "3"):
             return _fa_default(q, k, v, softmax_scale=softmax_scale, causal=causal)
         return torch.ops.fastvideo._flash_attn_default_forward(q, k, v, softmax_scale, causal)
 elif fa_version == "4":
-    # FA4 path: `flash_attn_func` is already a torch.library custom op
-    # (registered in `fastvideo.attention.utils.flash_attn_cute`), so a
-    # passthrough is enough — no extra registration needed.
+    # FA4 path: `flash_attn_func` (from `flash_attn_cute`) goes through a
+    # registered torch.library custom op (with an FA4 backward on sm90+;
+    # grad-enabled and GQA calls below sm90 route to FA2), so a passthrough
+    # is enough — no extra registration needed.
     def flash_attn_func_compilable(q, k, v, softmax_scale=None, causal=False):
         return flash_attn_func(q, k, v, softmax_scale=softmax_scale, causal=causal)
 else:
@@ -99,17 +130,6 @@ else:
     raise RuntimeError(f"Unsupported FlashAttention version: {fa_version!r} — expected "
                        f"'2', '3', or '4' from the import probe above.")
 
-from fastvideo.attention.backends.abstract import (
-    AttentionBackend,
-    AttentionImpl,
-    AttentionMetadata,
-    AttentionMetadataBuilder,
-)
-from fastvideo.logger import init_logger
-
-logger = init_logger(__name__)
-
-_WARNED_NON_FA_DTYPE = False
 logger.info("Using FlashAttention-%s backend", fa_version)
 
 # FP4 FA4 support: quantize Q/K to NVFP4 E2M1 for block-scaled MMA on Blackwell.
@@ -271,12 +291,8 @@ class FlashAttentionImpl(AttentionImpl):
         # SP). Cast through bf16 and restore, matching TORCH_SDPA's tolerance.
         orig_dtype = query.dtype
         if orig_dtype not in (torch.float16, torch.bfloat16):
-            global _WARNED_NON_FA_DTYPE
-            if not _WARNED_NON_FA_DTYPE:
-                _WARNED_NON_FA_DTYPE = True
-                logger.warning(
-                    "FLASH_ATTN received %s inputs; casting to bfloat16 for the "
-                    "kernel and restoring on output.", orig_dtype)
+            logger.warning_once(f"FLASH_ATTN received {orig_dtype} inputs; casting to "
+                                f"bfloat16 for the kernel and restoring on output.")
             query = query.to(torch.bfloat16)
             key = key.to(torch.bfloat16)
             value = value.to(torch.bfloat16)

fastvideo/attention/utils/flash_attn_cute.py

@@ -4,10 +4,9 @@ import functools
 from collections.abc import Callable
 
 import torch
-from flash_attn import flash_attn_func as _flash_attn_2_func
-from flash_attn import flash_attn_varlen_func as _flash_attn_2_varlen_func
 
 from fastvideo.logger import init_logger
+from fastvideo.platforms import current_platform
 
 logger = init_logger(__name__)
 
@@ -16,7 +15,8 @@ if torch.cuda.is_available():
         from flash_attn.cute.interface import _flash_attn_bwd, _flash_attn_fwd
     except ImportError:
         # flash_attn.cute (FA4) is simply not installed -- expected on builds
-        # without it; callers fall back to FA3/FA2 quietly.
+        # without it; callers handle the ImportError (the FASTVIDEO_FA4 gate in
+        # flash_attn.py raises, the FP4 probe treats FA4 as unavailable).
         raise
     except Exception as e:
         # flash_attn.cute IS installed but failed to import -- almost always an
@@ -24,23 +24,57 @@ if torch.cuda.is_available():
         # 'cutlass.cute.core' has no attribute 'ThrMma'" (an AttributeError, not
         # ImportError). This is fixable by pinning a compatible
         # nvidia-cutlass-dsl, so warn loudly, then re-raise as ImportError so
-        # callers fall back to FA3/FA2 instead of crashing worker init.
+        # callers can handle it uniformly.
         logger.warning(
-            "flash_attn.cute (FA4) is installed but failed to import (%r); "
-            "falling back to FA3/FA2. This is usually an nvidia-cutlass-dsl "
-            "version mismatch -- pin a compatible nvidia-cutlass-dsl to "
-            "restore FA4.", e)
+            "flash_attn.cute (FA4) is installed but failed to import (%r). "
+            "This is usually an nvidia-cutlass-dsl version mismatch -- pin a "
+            "compatible nvidia-cutlass-dsl to restore FA4.", e)
         raise ImportError(f"flash_attn.cute (FA4) import failed: {e!r}") from e
 else:
     # This error will be caught in flash_attn.py or flash_attn_no_pad.py
     raise ImportError("flash_attn.cute is only available on CUDA devices; this error must be handled internally")
 
+try:
+    # FA2 serves the calls FA4 cute cannot on pre-sm90 GPUs (backward, GQA).
+    # Optional so FA4-only installs can still import this module.
+    from flash_attn import flash_attn_func as _flash_attn_2_func
+    from flash_attn import flash_attn_varlen_func as _flash_attn_2_varlen_func
+except ImportError:
+    _flash_attn_2_func = None
+    _flash_attn_2_varlen_func = None
+
 
 def _check_dropout(dropout_p: float) -> None:
     if dropout_p != 0.0:
         raise NotImplementedError(f"flash_attn.cute does not support dropout (got dropout_p={dropout_p})")
 
 
+@functools.cache
+def _sm90_or_newer() -> bool:
+    return current_platform.has_device_capability(90)
+
+
+def _use_fa2(q: torch.Tensor, k: torch.Tensor, v: torch.Tensor) -> bool:
+    if _sm90_or_newer():
+        return False
+    # Pre-sm90 FA4 cute limitations, both served by FA2 (deterministic
+    # capability gate, not a runtime fallback):
+    #   * the backward asserts sm90+ (L40S/sm_89 dies on its arch check);
+    #   * GQA fails CuTeDSL JIT in pack_gqa ("ValueError: Operation creation
+    #     failed", observed on sm_89 with HunyuanGameCraft/LTX2).
+    if q.shape[-2] != k.shape[-2]:
+        return True
+    return torch.is_grad_enabled() and any(t.requires_grad for t in (q, k, v))
+
+
+def _fa2_or_raise(fa2_func: Callable | None) -> Callable:
+    if fa2_func is None:
+        raise RuntimeError("this attention call cannot run on FA4 cute below sm90 (its backward and "
+                           "GQA support require sm90+) and flash-attn 2, which serves it there, is "
+                           "not installed.")
+    return fa2_func
+
+
 @torch.library.custom_op(
     "fastvideo::_flash_attn_cute_forward",
     mutates_args=(),
@@ -243,70 +277,6 @@ torch.library.register_autograd(
 )
 
 
-# FA4's CuTeDSL kernels JIT-compile per shape family, and some configurations
-# fail MLIR op creation at runtime even though the import succeeded (observed:
-# GQA models on sm_89 dying in pack_gqa with "ValueError: Operation creation
-# failed"). Degrade to FA2 once, process-wide, instead of crashing inference.
-class _FA4Policy:
-    """Per-call gate for the FA4 cute fast path, with FA2 as the fallback.
-
-    FA4 is skipped when:
-      * a previous call failed at runtime -- CuTeDSL JIT compilation is
-        shape-dependent, so the first failure disables FA4 for the rest of
-        the process instead of retrying a broken JIT on every call; or
-      * the call needs autograd -- FA4's backward asserts sm90+ (L40S/sm_89
-        dies on its arch check) and is unvalidated for training in this repo
-        (its lse is not even allocated through our inference-shaped custom
-        op), so training keeps the pre-FA4 behavior: FA2 on every device.
-    """
-
-    def __init__(self) -> None:
-        self.broken = False
-
-    def use_fa4(self, *tensors: torch.Tensor) -> bool:
-        if self.broken:
-            return False
-        return not (torch.is_grad_enabled() and any(t.requires_grad for t in tensors))
-
-    def mark_broken(self, error: Exception) -> None:
-        if not self.broken:
-            self.broken = True
-            logger.warning(
-                "flash_attn.cute (FA4) failed at runtime (%r); falling back "
-                "to FA2 for the rest of this process.", error)
-
-
-_FA4 = _FA4Policy()
-
-
-def _with_fa2_fallback(fa2_func: Callable) -> Callable:
-    """Pair an FA4 cute wrapper with its FA2 twin of the same signature.
-
-    The decorated body runs only when ``_FA4`` allows it; otherwise (or after
-    the first FA4 runtime failure) the call is served by ``fa2_func``.
-    ``NotImplementedError`` is a contract error (e.g. dropout), not a JIT
-    failure, so it propagates without disabling FA4.
-    """
-
-    def decorator(fa4_func: Callable) -> Callable:
-
-        @functools.wraps(fa4_func)
-        def wrapper(q: torch.Tensor, k: torch.Tensor, v: torch.Tensor, *args, **kwargs) -> torch.Tensor:
-            if _FA4.use_fa4(q, k, v):
-                try:
-                    return fa4_func(q, k, v, *args, **kwargs)
-                except NotImplementedError:
-                    raise
-                except Exception as e:  # CuTeDSL compile errors surface as ValueError
-                    _FA4.mark_broken(e)
-            return fa2_func(q, k, v, *args, **kwargs)
-
-        return wrapper
-
-    return decorator
-
-
-@_with_fa2_fallback(_flash_attn_2_func)
 def flash_attn_func(
     q: torch.Tensor,
     k: torch.Tensor,
@@ -317,6 +287,16 @@ def flash_attn_func(
     deterministic: bool = False,
 ) -> torch.Tensor:
     """Only returns the output, not the lse."""
+    if _use_fa2(q, k, v):
+        return _fa2_or_raise(_flash_attn_2_func)(
+            q,
+            k,
+            v,
+            dropout_p=dropout_p,
+            softmax_scale=softmax_scale,
+            causal=causal,
+            deterministic=deterministic,
+        )
     _check_dropout(dropout_p)
     out, _ = torch.ops.fastvideo._flash_attn_cute_forward(q, k, v, softmax_scale, causal, deterministic)
     return out
@@ -392,7 +372,6 @@ def flash_attn_fp4_func(
     return torch.ops.fastvideo._flash_attn_cute_fp4_forward(q, k, v, sfq, sfk, softmax_scale, causal)
 
 
-@_with_fa2_fallback(_flash_attn_2_varlen_func)
 def flash_attn_varlen_func(
     q: torch.Tensor,
     k: torch.Tensor,
@@ -407,6 +386,20 @@ def flash_attn_varlen_func(
     deterministic: bool = False,
 ) -> torch.Tensor:
     """Only returns the output, not the lse."""
+    if _use_fa2(q, k, v):
+        return _fa2_or_raise(_flash_attn_2_varlen_func)(
+            q,
+            k,
+            v,
+            cu_seqlens_q,
+            cu_seqlens_k,
+            max_seqlen_q,
+            max_seqlen_k,
+            dropout_p=dropout_p,
+            softmax_scale=softmax_scale,
+            causal=causal,
+            deterministic=deterministic,
+        )
     _check_dropout(dropout_p)
     out, _ = torch.ops.fastvideo._flash_attn_cute_varlen_forward(
         q,

fastvideo/attention/utils/flash_attn_no_pad.py

@@ -21,24 +21,35 @@ from einops import rearrange
 from flash_attn import flash_attn_varlen_qkvpacked_func
 from flash_attn.bert_padding import pad_input, unpad_input
 
+from fastvideo import envs
+
 
 def _resolve_flash_attn_varlen_func() -> Any:
-    try:
-        from fastvideo.attention.utils.flash_attn_cute import (
-            flash_attn_varlen_func as flash_attn_varlen_func_cute, )
+    if envs.FASTVIDEO_FA4:
+        # FA4 cute is explicit opt-in (see fastvideo/attention/backends/
+        # flash_attn.py); with FASTVIDEO_FA4=1 an unimportable FA4 build must
+        # fail loudly here rather than fall through to FA3/FA2. RuntimeError,
+        # not ImportError: importers like bsa_attn.py treat ImportError as
+        # "flash-attn not installed" and silently degrade to reference kernels.
+        try:
+            from fastvideo.attention.utils.flash_attn_cute import (
+                flash_attn_varlen_func as flash_attn_varlen_func_cute, )
+        except ImportError as e:
+            raise RuntimeError(f"FASTVIDEO_FA4=1 but flash_attn.cute (FA4) is not usable ({e}); "
+                               "fix the FA4 install (see the flash-attn-4 pin in pyproject.toml) "
+                               "or unset FASTVIDEO_FA4.") from e
 
         return flash_attn_varlen_func_cute
+    try:
+        from flash_attn_interface import (
+            flash_attn_varlen_func as flash_attn_varlen_func_interface, )
+
+        return flash_attn_varlen_func_interface
     except ImportError:
-        try:
-            from flash_attn_interface import (
-                flash_attn_varlen_func as flash_attn_varlen_func_interface, )
+        from flash_attn import (
+            flash_attn_varlen_func as flash_attn_varlen_func_flash, )
 
-            return flash_attn_varlen_func_interface
-        except ImportError:
-            from flash_attn import (
-                flash_attn_varlen_func as flash_attn_varlen_func_flash, )
-
-            return flash_attn_varlen_func_flash
+        return flash_attn_varlen_func_flash
 
 
 flash_attn_varlen_func_impl = _resolve_flash_attn_varlen_func()

fastvideo/batching/__init__.py

@@ -0,0 +1,26 @@
+# SPDX-License-Identifier: Apache-2.0
+"""Dynamic generation batching helpers."""
+
+from fastvideo.batching.admission import (
+    AdmissionLimit,
+    BatchAdmissionController,
+    BatchingRule,
+    load_batching_config,
+)
+from fastvideo.batching.signature import (
+    BatchCompatibility,
+    can_dynamic_batch,
+    dynamic_batch_signature,
+    resolution_key,
+)
+
+__all__ = [
+    "AdmissionLimit",
+    "BatchAdmissionController",
+    "BatchCompatibility",
+    "BatchingRule",
+    "can_dynamic_batch",
+    "dynamic_batch_signature",
+    "load_batching_config",
+    "resolution_key",
+]

fastvideo/batching/admission.py

@@ -0,0 +1,297 @@
+# SPDX-License-Identifier: Apache-2.0
+from __future__ import annotations
+
+import json
+import os
+from dataclasses import dataclass
+from difflib import get_close_matches
+from typing import Any
+
+from fastvideo.batching.signature import resolution_key
+from fastvideo.fastvideo_args import FastVideoArgs
+from fastvideo.logger import init_logger
+
+logger = init_logger(__name__)
+
+_BYTES_PER_GB = 1024**3
+_BATCHING_RULE_KEYS = frozenset({
+    "model",
+    "model_contains",
+    "resolution",
+    "device_memory_gb_min",
+    "device_memory_gb_max",
+    "offload",
+    "max_batch_size",
+    "max_cost",
+    "calibration",
+})
+
+
+@dataclass(frozen=True)
+class AdmissionLimit:
+    max_batch_size: int
+    max_cost: float | None = None
+    cap_reason: str | None = None
+
+    def reject_reason(self, *, batch_size: int, batch_cost: float) -> str | None:
+        if batch_size > self.max_batch_size:
+            return self.cap_reason or f"config_cap:{self.max_batch_size}"
+        if self.max_cost is not None and batch_cost > self.max_cost:
+            return f"cost_budget:{batch_cost:.0f}>{self.max_cost:.0f}"
+        return None
+
+    def stop_reason_for_next_cost(self, next_batch_cost: float) -> str | None:
+        if self.max_cost is not None and next_batch_cost > self.max_cost:
+            return f"cost_budget_next:{next_batch_cost:.0f}>{self.max_cost:.0f}"
+        return None
+
+
+@dataclass(frozen=True)
+class BatchingRule:
+    model: str | None = None
+    model_contains: str | None = None
+    resolution: str | None = None
+    device_memory_gb_min: float | None = None
+    device_memory_gb_max: float | None = None
+    offload: bool | None = None
+    max_batch_size: int = 1
+    max_cost: float | None = None
+    source: str = "user"
+
+    @classmethod
+    def from_dict(cls, data: dict[str, Any], *, source: str) -> BatchingRule:
+        if not isinstance(data, dict):
+            raise ValueError(f"batching config rule from {source} must be an object, got {type(data).__name__}")
+        _validate_rule_keys(data, source=source)
+        if "max_batch_size" not in data:
+            raise ValueError("batching config rule requires max_batch_size")
+
+        rule = cls(
+            model=_optional_str(data.get("model")),
+            model_contains=_optional_str(data.get("model_contains")),
+            resolution=_optional_str(data.get("resolution")),
+            device_memory_gb_min=_optional_float(data.get("device_memory_gb_min")),
+            device_memory_gb_max=_optional_float(data.get("device_memory_gb_max")),
+            offload=_optional_bool(data.get("offload")),
+            max_batch_size=int(data["max_batch_size"]),
+            max_cost=_optional_float(data.get("max_cost")),
+            source=source,
+        )
+        rule.validate()
+        return rule
+
+    def validate(self) -> None:
+        if self.model is not None and self.model_contains is not None:
+            raise ValueError("batching config rule cannot set both model and model_contains")
+        if self.model is None and self.model_contains is None:
+            raise ValueError("batching config rule requires model or model_contains")
+        if self.max_batch_size < 1:
+            raise ValueError("batching config rule max_batch_size must be >= 1")
+        if self.max_cost is not None and self.max_cost <= 0.0:
+            raise ValueError("batching config rule max_cost must be > 0")
+        if (self.device_memory_gb_min is not None and self.device_memory_gb_max is not None
+                and self.device_memory_gb_min > self.device_memory_gb_max):
+            raise ValueError("batching config rule device_memory_gb_min must be <= device_memory_gb_max")
+
+    def matches(
+        self,
+        *,
+        model_path: str,
+        resolution: str | None,
+        device_memory_gb: float | None,
+        offload: bool,
+    ) -> bool:
+        if self.model is not None and self.model != model_path:
+            return False
+        if self.model_contains is not None and self.model_contains not in model_path:
+            return False
+        if self.resolution not in (None, "*") and self.resolution != resolution:
+            return False
+        if self.offload is not None and self.offload != offload:
+            return False
+        if device_memory_gb is None:
+            return True
+        if self.device_memory_gb_min is not None and device_memory_gb < self.device_memory_gb_min:
+            return False
+        return not (self.device_memory_gb_max is not None and device_memory_gb > self.device_memory_gb_max)
+
+
+class BatchAdmissionController:
+
+    def __init__(self, fastvideo_args: FastVideoArgs, *, gpu_id: int = 0):
+        self._mode = fastvideo_args.batching_mode
+        self._user_max_batch_size = max(1, int(fastvideo_args.batching_max_size))
+        self._model_path = fastvideo_args.model_path
+        self._offload = bool(fastvideo_args.dit_cpu_offload or fastvideo_args.dit_layerwise_offload)
+        self._device_memory_gb = self._get_device_memory_gb(gpu_id)
+        self._rules = load_batching_config(fastvideo_args.batching_config)
+        self._pipeline_config = fastvideo_args.pipeline_config
+
+        if self.enabled:
+            logger.info(
+                "Batch admission enabled: user_max=%d, device_memory=%.1fGiB, rules=%d",
+                self._user_max_batch_size,
+                self._device_memory_gb or 0.0,
+                len(self._rules),
+            )
+
+    @property
+    def enabled(self) -> bool:
+        return self._mode == "dynamic" and self._user_max_batch_size > 1
+
+    def reject_reason_for_candidate(self, current_requests: list[Any], candidate_request: Any) -> str | None:
+        if not self.enabled:
+            return None
+        proposed = current_requests + [candidate_request]
+        limit = self.limit_for(proposed[0])
+        return limit.reject_reason(
+            batch_size=len(proposed),
+            batch_cost=self.estimate_batch_cost(proposed),
+        )
+
+    def batch_is_full(self, requests: list[Any]) -> bool:
+        if not self.enabled or not requests:
+            return len(requests) >= self._user_max_batch_size
+
+        limit = self.limit_for(requests[0])
+        if len(requests) >= limit.max_batch_size:
+            return True
+
+        next_cost = self.estimate_batch_cost(requests + [requests[0]])
+        return limit.max_cost is not None and next_cost > limit.max_cost
+
+    def limit_reason_for_batch(self, requests: list[Any]) -> str | None:
+        if not self.enabled or not requests:
+            return None
+
+        limit = self.limit_for(requests[0])
+        if len(requests) >= limit.max_batch_size:
+            return limit.cap_reason or f"config_cap:{limit.max_batch_size}"
+
+        next_cost = self.estimate_batch_cost(requests + [requests[0]])
+        return limit.stop_reason_for_next_cost(next_cost)
+
+    def max_admissible_batch_size(self, request: Any) -> int:
+        return self.limit_for(request).max_batch_size
+
+    def limit_for(self, request: Any) -> AdmissionLimit:
+        rules = self._matching_rules(request)
+        if not rules:
+            return AdmissionLimit(max_batch_size=self._user_max_batch_size)
+
+        config_cap = min(rule.max_batch_size for rule in rules)
+        max_batch_size = min(self._user_max_batch_size, config_cap)
+        cap_reason = f"config_cap:{max_batch_size}" if max_batch_size < self._user_max_batch_size else None
+        costs = [rule.max_cost for rule in rules if rule.max_cost is not None]
+        return AdmissionLimit(
+            max_batch_size=max(1, max_batch_size),
+            max_cost=min(costs) if costs else None,
+            cap_reason=cap_reason,
+        )
+
+    def estimate_batch_cost(self, requests: list[Any]) -> float:
+        return sum(float(self._pipeline_config.estimate_request_cost(request)) for request in requests)
+
+    def _matching_rules(self, request: Any) -> list[BatchingRule]:
+        return [
+            rule for rule in self._rules if rule.matches(
+                model_path=self._model_path,
+                resolution=resolution_key(request),
+                device_memory_gb=self._device_memory_gb,
+                offload=self._offload,
+            )
+        ]
+
+    @staticmethod
+    def _get_device_memory_gb(gpu_id: int) -> float | None:
+        try:
+            from fastvideo.platforms import current_platform
+
+            return current_platform.get_device_total_memory(gpu_id) / _BYTES_PER_GB
+        except Exception:
+            return None
+
+
+def load_batching_config(path: str | None) -> list[BatchingRule]:
+    if path is None:
+        return []
+
+    with open(path, encoding="utf-8") as f:
+        payload = json.load(f)
+
+    source = os.path.abspath(path)
+    entries = _config_entries(payload)
+    rules = [BatchingRule.from_dict(entry, source=source) for entry in entries]
+    if not rules:
+        raise ValueError(f"batching config {source} does not contain any rules")
+    return rules
+
+
+def _config_entries(payload: Any) -> list[dict[str, Any]]:
+    if isinstance(payload, dict) and payload.get("schema_version") not in (None, 1):
+        raise ValueError("batching config schema_version must be 1")
+    if isinstance(payload, dict) and isinstance(payload.get("rules"), list):
+        return payload["rules"]
+    if isinstance(payload, list):
+        return payload
+    if isinstance(payload, dict):
+        entries: list[dict[str, Any]] = []
+        for key, value in payload.items():
+            if key == "schema_version" or not isinstance(value, dict):
+                continue
+            model, _sep, resolution = key.partition("|")
+            entry = dict(value)
+            if model:
+                entry.setdefault("model", model)
+            if resolution:
+                entry.setdefault("resolution", resolution)
+            entries.append(entry)
+        return entries
+    raise ValueError("batching config must be a {'schema_version': 1, 'rules': [...]} object, "
+                     "a list of rules, or a mapping keyed by model|resolution")
+
+
+def _validate_rule_keys(data: dict[str, Any], *, source: str) -> None:
+    unknown = sorted(set(data) - _BATCHING_RULE_KEYS)
+    if not unknown:
+        return
+
+    hints = []
+    for key in unknown:
+        matches = get_close_matches(key, _BATCHING_RULE_KEYS, n=1)
+        if matches:
+            hints.append(f"{key!r} (did you mean {matches[0]!r}?)")
+        else:
+            hints.append(repr(key))
+    raise ValueError(f"batching config rule from {source} contains unknown key(s): {', '.join(hints)}")
+
+
+def _optional_str(value: Any) -> str | None:
+    if value is None:
+        return None
+    return str(value)
+
+
+def _optional_float(value: Any) -> float | None:
+    if value is None:
+        return None
+    return float(value)
+
+
+def _optional_bool(value: Any) -> bool | None:
+    if value is None:
+        return None
+    if isinstance(value, bool):
+        return value
+    if isinstance(value, int | float):
+        if value == 1.0:
+            return True
+        if value == 0.0:
+            return False
+    if isinstance(value, str):
+        lowered = value.strip().lower()
+        if lowered in ("1", "true", "yes", "y", "on"):
+            return True
+        if lowered in ("0", "false", "no", "n", "off"):
+            return False
+    raise ValueError(f"cannot parse boolean batching config value: {value!r}")

fastvideo/batching/signature.py

@@ -0,0 +1,178 @@
+# SPDX-License-Identifier: Apache-2.0
+from __future__ import annotations
+
+import dataclasses
+from dataclasses import dataclass
+from enum import Enum
+from typing import Any
+
+from fastvideo.api.sampling_param import SamplingParam
+
+_SIGNATURE_EXCLUDED_FIELDS = frozenset({
+    "prompt",
+    "prompt_path",
+    "output_path",
+    "output_video_name",
+    "seed",
+    "save_video",
+    "return_frames",
+})
+
+_UNSUPPORTED_DYNAMIC_BATCH_FIELDS = frozenset({
+    "image_path",
+    "pil_image",
+    "video_path",
+    "mouse_cond",
+    "keyboard_cond",
+    "grid_sizes",
+    "pose",
+    "camera_states",
+    "camera_trajectory",
+    "action_list",
+    "action_speed_list",
+    "gt_latents",
+    "conditioning_mask",
+    "c2ws_plucker_emb",
+    "refine_from",
+    "stage1_video",
+    "trajectory_type",
+    "movement_distance",
+    "camera_rotation",
+    "ltx2_images",
+    "ltx2_conditioning_latent_stage1",
+    "ltx2_conditioning_latent_stage2",
+    "ltx2_video_conditions",
+    "init_audio",
+    "inpaint_audio",
+    "inpaint_mask",
+    "continuation_state",
+})
+
+_UNSUPPORTED_EXTRA_KEYS = frozenset({
+    "ltx2_audio_latents",
+    "ltx2_audio_clean_latent",
+    "ltx2_audio_denoise_mask",
+    "audio_num_frames",
+    "video_position_offset_sec",
+})
+
+
+@dataclass(frozen=True)
+class BatchCompatibility:
+    can_batch: bool
+    reason: str | None = None
+
+
+def resolution_key(request: Any) -> str:
+    height = _first_scalar(getattr(request, "height", None))
+    width = _first_scalar(getattr(request, "width", None))
+    num_frames = _first_scalar(getattr(request, "num_frames", None))
+    return f"{height}x{width}x{num_frames}"
+
+
+def dynamic_batch_signature(
+    request: SamplingParam,
+    *,
+    extra: dict[str, Any] | None = None,
+) -> tuple[tuple[str, Any], ...]:
+    """Build a hashable compatibility signature for a generation request."""
+    signature_items: list[tuple[str, Any]] = []
+    for field in dataclasses.fields(request):
+        if field.name in _SIGNATURE_EXCLUDED_FIELDS:
+            continue
+        signature_items.append((field.name, _freeze_signature_value(getattr(request, field.name, None))))
+    if extra:
+        signature_items.append(("extra", _freeze_signature_value(extra)))
+    return tuple(signature_items)
+
+
+def can_dynamic_batch(
+    base: SamplingParam,
+    candidate: SamplingParam,
+    *,
+    base_extra: dict[str, Any] | None = None,
+    candidate_extra: dict[str, Any] | None = None,
+) -> BatchCompatibility:
+    """Return whether two FastVideo generation requests can be merged."""
+    base_ready = _request_is_batchable(base, extra=base_extra)
+    if not base_ready.can_batch:
+        return base_ready
+    candidate_ready = _request_is_batchable(candidate, extra=candidate_extra)
+    if not candidate_ready.can_batch:
+        return candidate_ready
+
+    base_sig = dynamic_batch_signature(base, extra=base_extra)
+    candidate_sig = dynamic_batch_signature(candidate, extra=candidate_extra)
+    if base_sig == candidate_sig:
+        return BatchCompatibility(can_batch=True)
+
+    mismatch = _first_mismatch(base_sig, candidate_sig)
+    return BatchCompatibility(can_batch=False, reason=mismatch or "signature_mismatch")
+
+
+def _request_is_batchable(
+    request: SamplingParam,
+    *,
+    extra: dict[str, Any] | None = None,
+) -> BatchCompatibility:
+    if not isinstance(request.prompt, str):
+        return BatchCompatibility(can_batch=False, reason="prompt_type")
+    if request.prompt_path is not None:
+        return BatchCompatibility(can_batch=False, reason="prompt_path")
+    if request.num_videos_per_prompt != 1:
+        return BatchCompatibility(can_batch=False, reason="num_videos_per_prompt")
+    if request.return_continuation_state:
+        return BatchCompatibility(can_batch=False, reason="return_continuation_state")
+
+    for name in _UNSUPPORTED_DYNAMIC_BATCH_FIELDS:
+        value = getattr(request, name, None)
+        if _is_present(value):
+            return BatchCompatibility(can_batch=False, reason=name)
+
+    if extra:
+        unsupported = sorted(set(extra) & _UNSUPPORTED_EXTRA_KEYS)
+        if unsupported:
+            return BatchCompatibility(can_batch=False, reason=f"extra.{unsupported[0]}")
+
+    return BatchCompatibility(can_batch=True)
+
+
+def _freeze_signature_value(value: Any) -> Any:
+    if isinstance(value, str | int | float | bool | type(None)):
+        return value
+    if isinstance(value, Enum):
+        return value.value
+    if isinstance(value, dict):
+        return tuple(
+            (str(key), _freeze_signature_value(item)) for key, item in sorted(value.items(), key=lambda kv: str(kv[0])))
+    if isinstance(value, list | tuple):
+        return tuple(_freeze_signature_value(item) for item in value)
+    return repr(value)
+
+
+def _is_present(value: Any) -> bool:
+    if value is None:
+        return False
+    if value is False:
+        return False
+    return not (isinstance(value, list | tuple | dict | set) and not value)
+
+
+def _first_scalar(value: Any) -> Any:
+    if isinstance(value, list | tuple):
+        return value[0] if value else None
+    return value
+
+
+def _first_mismatch(
+    base_sig: tuple[tuple[str, Any], ...],
+    candidate_sig: tuple[tuple[str, Any], ...],
+) -> str | None:
+    if len(base_sig) != len(candidate_sig):
+        return "sampling_params"
+    for (name, base_value), (candidate_name, candidate_value) in zip(base_sig, candidate_sig, strict=True):
+        if name != candidate_name:
+            return "sampling_params"
+        if base_value != candidate_value:
+            return f"sampling_params.{name}"
+    return None

fastvideo/configs/pipelines/base.py

@@ -276,6 +276,27 @@ class PipelineConfig:
                 f"Length of text postprocess functions ({len(self.postprocess_text_funcs)}) must be equal to length of text preprocessing functions ({len(self.preprocess_text_funcs)})"
             )
 
+    def estimate_request_cost(self, request: Any) -> float:
+        """Estimate relative memory/compute cost for batching admission.
+
+        The default is intentionally simple and model-agnostic: pixel count
+        times frame count. Pipeline subclasses can override this when they have
+        calibrated costs.
+        """
+        height = getattr(request, "height", None)
+        width = getattr(request, "width", None)
+        num_frames = getattr(request, "num_frames", None)
+        if isinstance(height, list):
+            height = height[0] if height else None
+        if isinstance(width, list):
+            width = width[0] if width else None
+        if isinstance(num_frames, list):
+            num_frames = num_frames[0] if num_frames else None
+        height = int(height or 1)
+        width = int(width or 1)
+        num_frames = int(num_frames or 1)
+        return float(max(1, height) * max(1, width) * max(1, num_frames))
+
     def dump_to_json(self, file_path: str):
         output_dict = shallow_asdict(self)
         del_keys = []

fastvideo/entrypoints/openai/api_server.py

@@ -10,6 +10,7 @@ from fastapi.middleware.cors import CORSMiddleware
 
 from fastvideo.api.presets import validate_preset_selection
 from fastvideo.api.schema import GenerationRequest
+from fastvideo.entrypoints.openai.batching import VideoBatchScheduler
 from fastvideo.entrypoints.openai.state import (
     DEFAULT_OUTPUT_DIR,
     clear_state,
@@ -59,11 +60,29 @@ async def lifespan(app: FastAPI) -> AsyncIterator[None]:
     generator = VideoGenerator.from_fastvideo_args(args)
     logger.info("Model loaded successfully.")
 
-    set_state(generator, args, output_dir, default_request=default_request)
+    video_batch_scheduler: VideoBatchScheduler | None = None
+    if args.batching_mode == "dynamic" and args.batching_max_size > 1:
+        video_batch_scheduler = VideoBatchScheduler(generator, args)
+        await video_batch_scheduler.start()
+        logger.info(
+            "Started dynamic video batch scheduler: max_size=%d delay_ms=%.2f",
+            args.batching_max_size,
+            args.batching_delay_ms,
+        )
+
+    set_state(
+        generator,
+        args,
+        output_dir,
+        default_request=default_request,
+        video_batch_scheduler=video_batch_scheduler,
+    )
 
     yield  # server is running
 
     logger.info("Shutting down — releasing model resources ...")
+    if video_batch_scheduler is not None:
+        await video_batch_scheduler.stop()
     generator.shutdown()
     clear_state()
     logger.info("Shutdown complete.")

fastvideo/entrypoints/openai/batching.py

@@ -0,0 +1,183 @@
+# SPDX-License-Identifier: Apache-2.0
+from __future__ import annotations
+
+import asyncio
+import time
+from collections import deque
+from dataclasses import dataclass
+from typing import Any
+
+from fastvideo.api.sampling_param import SamplingParam
+from fastvideo.batching.signature import can_dynamic_batch
+from fastvideo.fastvideo_args import FastVideoArgs
+from fastvideo.logger import init_logger
+
+logger = init_logger(__name__)
+
+
+@dataclass
+class _VideoBatchJob:
+    request_id: str
+    kwargs: dict[str, Any]
+    future: asyncio.Future
+    enqueue_time: float
+
+
+class VideoBatchScheduler:
+    """Async FIFO scheduler for OpenAI-compatible video generation."""
+
+    def __init__(self, generator: Any, fastvideo_args: FastVideoArgs) -> None:
+        self._generator = generator
+        self._fastvideo_args = fastvideo_args
+        self._queue: asyncio.Queue[_VideoBatchJob | None] = asyncio.Queue()
+        self._pending: deque[_VideoBatchJob] = deque()
+        self._task: asyncio.Task | None = None
+        self._stopped = False
+
+    @property
+    def enabled(self) -> bool:
+        return self._fastvideo_args.batching_mode == "dynamic" and self._fastvideo_args.batching_max_size > 1
+
+    async def start(self) -> None:
+        if self._task is not None:
+            return
+        self._task = asyncio.create_task(self._run(), name="fastvideo-video-batch-scheduler")
+
+    async def stop(self) -> None:
+        self._stopped = True
+        await self._queue.put(None)
+        if self._task is not None:
+            await self._task
+            self._task = None
+
+    async def submit(self, request_id: str, kwargs: dict[str, Any]) -> Any:
+        if self._stopped:
+            raise RuntimeError("Video batch scheduler is stopped; cannot submit new requests")
+        loop = asyncio.get_running_loop()
+        future = loop.create_future()
+        await self._queue.put(
+            _VideoBatchJob(
+                request_id=request_id,
+                kwargs=dict(kwargs),
+                future=future,
+                enqueue_time=time.perf_counter(),
+            ))
+        return await future
+
+    async def _run(self) -> None:
+        while not self._stopped:
+            job = await self._get_next_job()
+            if job is None:
+                break
+            batch = await self._collect_batch(job)
+            await self._dispatch(batch)
+
+        while self._pending:
+            pending = self._pending.popleft()
+            if not pending.future.done():
+                pending.future.set_exception(RuntimeError("Video batch scheduler stopped before dispatch"))
+
+    async def _get_next_job(self) -> _VideoBatchJob | None:
+        if self._pending:
+            return self._pending.popleft()
+        return await self._queue.get()
+
+    async def _collect_batch(self, first: _VideoBatchJob) -> list[_VideoBatchJob]:
+        batch = [first]
+        max_size = self._fastvideo_args.batching_max_size
+        delay_s = max(0.0, self._fastvideo_args.batching_delay_ms / 1000.0)
+        deadline = first.enqueue_time + delay_s
+
+        while len(batch) < max_size:
+            if delay_s > 0:
+                timeout = deadline - time.perf_counter()
+                if timeout <= 0:
+                    break
+                try:
+                    candidate = await asyncio.wait_for(self._get_next_job(), timeout=timeout)
+                except TimeoutError:
+                    break
+            else:
+                # delay=0 means "don't wait": greedily drain whatever is
+                # already queued so max_size still coalesces.
+                if self._pending:
+                    candidate = self._pending.popleft()
+                else:
+                    try:
+                        candidate = self._queue.get_nowait()
+                    except asyncio.QueueEmpty:
+                        break
+            if candidate is None:
+                await self._queue.put(None)
+                break
+            if self._jobs_are_compatible(batch[0], candidate):
+                batch.append(candidate)
+                continue
+            self._pending.appendleft(candidate)
+            break
+        return batch
+
+    async def _dispatch(self, batch: list[_VideoBatchJob]) -> None:
+        loop = asyncio.get_running_loop()
+        request_ids = [job.request_id for job in batch]
+        queue_wait_ms = (time.perf_counter() - min(job.enqueue_time for job in batch)) * 1000.0
+        if self._fastvideo_args.enable_batching_metrics:
+            logger.info(
+                "Dispatching video batch: request_ids=%s size=%d queue_wait_ms=%.2f",
+                request_ids,
+                len(batch),
+                queue_wait_ms,
+            )
+
+        try:
+            results = await loop.run_in_executor(
+                None,
+                lambda: self._generator.generate_video_batch([job.kwargs for job in batch]),
+            )
+        except Exception as exc:
+            for job in batch:
+                if not job.future.done():
+                    job.future.set_exception(exc)
+            return
+
+        if len(results) != len(batch):
+            error = RuntimeError(f"Video batch returned {len(results)} results for {len(batch)} requests")
+            for job in batch:
+                if not job.future.done():
+                    job.future.set_exception(error)
+            return
+
+        for job, result in zip(batch, results, strict=True):
+            if not job.future.done():
+                job.future.set_result(result)
+
+    def _jobs_are_compatible(self, base: _VideoBatchJob, candidate: _VideoBatchJob) -> bool:
+        try:
+            base_sampling, base_extra = self._sampling_param_from_kwargs(base.kwargs)
+            candidate_sampling, candidate_extra = self._sampling_param_from_kwargs(candidate.kwargs)
+        except Exception:
+            return False
+        return can_dynamic_batch(
+            base_sampling,
+            candidate_sampling,
+            base_extra=base_extra,
+            candidate_extra=candidate_extra,
+        ).can_batch
+
+    def _sampling_param_from_kwargs(self, kwargs: dict[str, Any]) -> tuple[SamplingParam, dict[str, Any]]:
+        sampling_param = SamplingParam.from_pretrained(self._fastvideo_args.model_path)
+        updates = dict(kwargs)
+        prompt = updates.pop("prompt", None)
+        extra: dict[str, Any] = {}
+        for key in (
+                "ltx2_audio_latents",
+                "ltx2_audio_clean_latent",
+                "ltx2_audio_denoise_mask",
+                "audio_num_frames",
+                "video_position_offset_sec",
+        ):
+            if key in updates:
+                extra[key] = updates.pop(key)
+        sampling_param.update(updates)
+        sampling_param.prompt = prompt
+        return sampling_param, extra

fastvideo/entrypoints/openai/state.py

@@ -11,6 +11,7 @@ from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
     from fastvideo.api.schema import GenerationRequest
+    from fastvideo.entrypoints.openai.batching import VideoBatchScheduler
     from fastvideo.entrypoints.video_generator import VideoGenerator
     from fastvideo.fastvideo_args import FastVideoArgs
 
@@ -20,6 +21,7 @@ _generator: VideoGenerator | None = None
 _fastvideo_args: FastVideoArgs | None = None
 _output_dir: str = DEFAULT_OUTPUT_DIR
 _default_request: GenerationRequest | None = None
+_video_batch_scheduler: VideoBatchScheduler | None = None
 
 
 def get_generator() -> VideoGenerator:
@@ -44,23 +46,31 @@ def get_default_request() -> GenerationRequest | None:
     return _default_request
 
 
+def get_video_batch_scheduler() -> VideoBatchScheduler | None:
+    """Return the video batch scheduler when dynamic batching is enabled."""
+    return _video_batch_scheduler
+
+
 def set_state(
     generator: VideoGenerator,
     fastvideo_args: FastVideoArgs,
     output_dir: str,
     default_request: GenerationRequest | None = None,
+    video_batch_scheduler: VideoBatchScheduler | None = None,
 ) -> None:
     """Set all server state at once (called from lifespan)."""
-    global _generator, _fastvideo_args, _output_dir, _default_request
+    global _generator, _fastvideo_args, _output_dir, _default_request, _video_batch_scheduler
     _generator = generator
     _fastvideo_args = fastvideo_args
     _output_dir = output_dir
     _default_request = default_request
+    _video_batch_scheduler = video_batch_scheduler
 
 
 def clear_state() -> None:
     """Clear server state on shutdown."""
-    global _generator, _fastvideo_args, _default_request
+    global _generator, _fastvideo_args, _default_request, _video_batch_scheduler
     _generator = None
     _fastvideo_args = None
     _default_request = None
+    _video_batch_scheduler = None

fastvideo/entrypoints/openai/video_api.py

@@ -26,6 +26,7 @@ from fastvideo.entrypoints.openai.state import (
     get_generator,
     get_output_dir,
     get_server_args,
+    get_video_batch_scheduler,
 )
 from fastvideo.entrypoints.openai.protocol import (
     VideoGenerationsRequest,
@@ -151,15 +152,19 @@ async def _run_generation(request_id: str, kwargs: dict[str, Any]) -> None:
     is synchronous) and update the store on completion or failure.
     """
     generator = get_generator()
+    scheduler = get_video_batch_scheduler()
     loop = asyncio.get_running_loop()
 
     try:
         start = time.perf_counter()
 
-        result = await loop.run_in_executor(
-            None,
-            lambda: generator.generate_video(**kwargs),
-        )
+        if scheduler is not None and scheduler.enabled:
+            result = await scheduler.submit(request_id, kwargs)
+        else:
+            result = await loop.run_in_executor(
+                None,
+                lambda: generator.generate_video(**kwargs),
+            )
 
         elapsed = time.perf_counter() - start
         update: dict[str, Any] = {

fastvideo/entrypoints/video_generator.py

@@ -18,6 +18,7 @@ import warnings
 from collections.abc import Mapping
 from contextlib import suppress
 from copy import deepcopy
+from dataclasses import dataclass
 from typing import Any
 
 import imageio
@@ -26,6 +27,8 @@ import torch
 import torchvision
 from einops import rearrange
 
+from fastvideo.batching.admission import BatchAdmissionController
+from fastvideo.batching.signature import can_dynamic_batch
 from fastvideo.api.compat import (
     expand_request_prompt_batch,
     generator_config_to_fastvideo_args,
@@ -94,6 +97,11 @@ _FROM_PRETRAINED_CONVENIENCE_KWARGS = frozenset({
     "pin_cpu_memory",
     "enable_torch_compile",
     "torch_compile_kwargs",
+    "batching_mode",
+    "batching_max_size",
+    "batching_delay_ms",
+    "batching_config",
+    "enable_batching_metrics",
     "output_type",
     "nvfp4_fa4",
 })
@@ -112,6 +120,17 @@ def _infer_latent_batch_size(batch: ForwardBatch) -> int:
     return latent_batch_size
 
 
+@dataclass
+class _GenerationWorkItem:
+    prompt: str
+    sampling_param: SamplingParam
+    fastvideo_args: FastVideoArgs
+    batch: ForwardBatch
+    output_path: str
+    target_height: int
+    target_width: int
+
+
 class VideoGenerator:
     """
     A unified class for generating videos using diffusion models.
@@ -439,6 +458,70 @@ class VideoGenerator:
             if log_queue:
                 self.executor.clear_log_queue()
 
+    def generate_video_batch(self, request_kwargs: list[dict[str, Any]]) -> list[dict[str, Any]]:
+        """Generate multiple legacy video requests, batching compatible items."""
+        work_items: list[_GenerationWorkItem] = []
+        reserved_output_paths: set[str] = set()
+        fastvideo_args_by_pipeline_override: dict[tuple[tuple[str, str], ...], FastVideoArgs] = {
+            (): self.fastvideo_args
+        }
+        for raw_kwargs in request_kwargs:
+            kwargs = dict(raw_kwargs)
+            prompt = kwargs.pop("prompt", None)
+            if prompt is None:
+                raise ValueError("Each batched generation request must include prompt")
+            if not isinstance(prompt, str):
+                raise TypeError(f"`prompt` must be a string, but got {type(prompt)}")
+
+            sampling_param = kwargs.pop("sampling_param", None)
+            if sampling_param is None:
+                sampling_param = SamplingParam.from_pretrained(self.fastvideo_args.model_path)
+            else:
+                sampling_param = deepcopy(sampling_param)
+
+            extra_overrides: dict[str, Any] = {}
+            for _ek in _BATCH_EXTRA_PASSTHROUGH_KEYS:
+                if _ek in kwargs:
+                    extra_overrides[_ek] = kwargs.pop(_ek)
+
+            request = legacy_generate_call_to_request(
+                prompt,
+                sampling_param,
+                legacy_kwargs=kwargs,
+            )
+            if not isinstance(request.prompt, str):
+                raise TypeError(f"`prompt` must be a string, but got {type(request.prompt)}")
+
+            fastvideo_args = self.fastvideo_args
+            pipeline_overrides = request_to_pipeline_overrides(request)
+            if pipeline_overrides:
+                override_key = tuple((key, repr(value)) for key, value in sorted(pipeline_overrides.items()))
+                fastvideo_args = fastvideo_args_by_pipeline_override.get(override_key)
+                if fastvideo_args is None:
+                    fastvideo_args = deepcopy(self.fastvideo_args)
+                    for key, value in pipeline_overrides.items():
+                        if not hasattr(fastvideo_args.pipeline_config, key):
+                            raise ValueError(f"Request field {key!r} is not supported by pipeline config overrides")
+                        setattr(fastvideo_args.pipeline_config, key, deepcopy(value))
+                    fastvideo_args_by_pipeline_override[override_key] = fastvideo_args
+
+            resolved_sampling_param = request_to_sampling_param(
+                request,
+                model_path=self.fastvideo_args.model_path,
+            )
+            output_path = self._prepare_output_path(resolved_sampling_param.output_path, request.prompt,
+                                                    reserved_output_paths)
+            work_items.append(
+                self._prepare_generation_work_item(
+                    prompt=request.prompt,
+                    sampling_param=resolved_sampling_param,
+                    fastvideo_args=fastvideo_args,
+                    output_path=output_path,
+                    _extra_overrides=extra_overrides,
+                ))
+
+        return self._generate_prepared_work_items(work_items)
+
     def _generate_request_impl(
         self,
         request: GenerationRequest,
@@ -535,6 +618,29 @@ class VideoGenerator:
 
             logger.info("Found %d prompts in %s", len(prompts), prompt_txt_path)
 
+            if self._dynamic_batching_enabled(fastvideo_args):
+                work_items: list[_GenerationWorkItem] = []
+                reserved_output_paths: set[str] = set()
+                for batch_prompt in prompts:
+                    item_kwargs = dict(kwargs)
+                    item_kwargs["output_path"] = self._prepare_output_path(sampling_param.output_path, batch_prompt,
+                                                                           reserved_output_paths)
+                    work_items.append(
+                        self._prepare_generation_work_item(
+                            prompt=batch_prompt,
+                            sampling_param=sampling_param,
+                            fastvideo_args=fastvideo_args,
+                            **item_kwargs,
+                        ))
+
+                results = self._generate_prepared_work_items(work_items, tolerate_failures=True)
+                for i, (result, batch_prompt) in enumerate(zip(results, prompts, strict=True)):
+                    result["prompt_index"] = i
+                    result["prompt"] = batch_prompt
+                logger.info("Completed batch processing. Generated %d videos successfully.",
+                            sum(1 for result in results if "error" not in result))
+                return results
+
             results = []
             for i, batch_prompt in enumerate(prompts):
                 logger.info("Processing prompt %d/%d: %s...", i + 1, len(prompts), batch_prompt[:100])
@@ -588,6 +694,7 @@ class VideoGenerator:
         self,
         output_path: str,
         prompt: str,
+        reserved_paths: set[str] | None = None,
     ) -> str:
         """Build a unique, sanitized output file path.
 
@@ -602,6 +709,9 @@ class VideoGenerator:
         - Invalid filename characters are removed; if the name changes, a
           warning is logged.
         - If the target path already exists, a numeric suffix is appended.
+        - ``reserved_paths`` lets batch callers resolve every path before any
+          file is written: paths in the set are treated as taken, and the
+          chosen path is added to the set.
         """
         target_ext = ".png" if self._is_image_workload() else ".mp4"
 
@@ -646,15 +756,416 @@ class VideoGenerator:
         if output_dir:
             os.makedirs(output_dir, exist_ok=True)
 
+        def _is_taken(path: str) -> bool:
+            return os.path.exists(path) or (reserved_paths is not None and path in reserved_paths)
+
         new_output_path = os.path.join(output_dir, out_name)
         counter = 1
-        while os.path.exists(new_output_path):
+        while _is_taken(new_output_path):
             name_part, ext_part = os.path.splitext(out_name)
             new_name = f"{name_part}_{counter}{ext_part}"
             new_output_path = os.path.join(output_dir, new_name)
             counter += 1
+        if reserved_paths is not None:
+            reserved_paths.add(new_output_path)
         return new_output_path
 
+    def _dynamic_batching_enabled(self, fastvideo_args: FastVideoArgs) -> bool:
+        batching_mode = getattr(fastvideo_args, "batching_mode", "disabled")
+        batching_max_size = getattr(fastvideo_args, "batching_max_size", 1)
+        return batching_mode == "dynamic" and batching_max_size > 1
+
+    def _prepare_generation_work_item(
+        self,
+        prompt: str | list[str],
+        sampling_param: SamplingParam,
+        fastvideo_args: FastVideoArgs,
+        **kwargs,
+    ) -> _GenerationWorkItem:
+        if isinstance(prompt, str):
+            prompt_for_output = prompt.strip()
+            prompt_value: str | list[str] = prompt_for_output
+        elif isinstance(prompt, list) and all(isinstance(item, str) for item in prompt):
+            prompt_value = [item.strip() for item in prompt]
+            prompt_for_output = prompt_value[0] if prompt_value else ""
+        else:
+            raise TypeError(f"`prompt` must be a string or list of strings, but got {type(prompt)}")
+
+        sampling_param = deepcopy(sampling_param)
+        output_path = kwargs["output_path"]
+        sampling_param.prompt = prompt_value
+        if sampling_param.negative_prompt is not None:
+            sampling_param.negative_prompt = sampling_param.negative_prompt.strip()
+
+        if sampling_param.height <= 0 or sampling_param.width <= 0 or sampling_param.num_frames <= 0:
+            raise ValueError(f"Height, width, and num_frames must be positive integers, got "
+                             f"height={sampling_param.height}, width={sampling_param.width}, "
+                             f"num_frames={sampling_param.num_frames}")
+
+        target_height = align_to(sampling_param.height, 16)
+        target_width = align_to(sampling_param.width, 16)
+        latents_size = [(sampling_param.num_frames - 1) // 4 + 1, sampling_param.height // 8, sampling_param.width // 8]
+        n_tokens = latents_size[0] * latents_size[1] * latents_size[2]
+
+        debug_str = f"""
+                      height: {target_height}
+                       width: {target_width}
+                video_length: {sampling_param.num_frames}
+                      prompt: {sampling_param.prompt}
+                      image_path: {sampling_param.image_path}
+                  neg_prompt: {sampling_param.negative_prompt}
+                        seed: {sampling_param.seed}
+                 infer_steps: {sampling_param.num_inference_steps}
+       num_videos_per_prompt: {sampling_param.num_videos_per_prompt}
+              guidance_scale: {sampling_param.guidance_scale}
+                    n_tokens: {n_tokens}
+                  flow_shift: {fastvideo_args.pipeline_config.flow_shift}
+     embedded_guidance_scale: {fastvideo_args.pipeline_config.embedded_cfg_scale}
+                  save_video: {sampling_param.save_video}
+                  output_path: {output_path}
+        """ # type: ignore[attr-defined]
+        logger.info(debug_str)
+
+        batch = ForwardBatch(
+            **shallow_asdict(sampling_param),
+            eta=0.0,
+            n_tokens=n_tokens,
+            VSA_sparsity=fastvideo_args.VSA_sparsity,
+        )
+
+        extra_overrides = kwargs.get("_extra_overrides", {})
+        for _ek, _ev in extra_overrides.items():
+            batch.extra[_ek] = _ev
+
+        return _GenerationWorkItem(
+            prompt=prompt_for_output,
+            sampling_param=sampling_param,
+            fastvideo_args=fastvideo_args,
+            batch=batch,
+            output_path=output_path,
+            target_height=target_height,
+            target_width=target_width,
+        )
+
+    def _run_forward_batch(
+        self,
+        batch: ForwardBatch,
+        fastvideo_args: FastVideoArgs,
+    ) -> tuple[ForwardBatch, float, float]:
+        start_time = time.perf_counter()
+        result_container = {"output_batch": ForwardBatch(data_type=batch.data_type)}
+        thread_error: dict[str, BaseException | None] = {"error": None}
+        thread_error_traceback: dict[str, str] = {"traceback": ""}
+
+        def execute_forward_thread():
+            import traceback
+            try:
+                result_container["output_batch"] = self.executor.execute_forward(batch, fastvideo_args)
+            except BaseException as error:  # noqa: BLE001
+                thread_error["error"] = error
+                thread_error_traceback["traceback"] = traceback.format_exc()
+
+        thread = threading.Thread(target=execute_forward_thread)
+        thread.start()
+        thread.join()
+
+        if thread_error["error"] is not None:
+            raise RuntimeError("Forward execution thread failed.\n"
+                               f"{thread_error_traceback['traceback']}") from thread_error["error"]
+
+        output_batch = result_container["output_batch"]
+        if output_batch.output is None:
+            raise RuntimeError("Forward execution returned no output tensor. "
+                               "This usually means the executor/pipeline failed earlier.")
+
+        gen_time = time.perf_counter() - start_time
+        logger.info("Generated successfully in %.2f seconds", gen_time)
+        return output_batch, gen_time, start_time
+
+    def _samples_from_output(
+        self,
+        work_item: _GenerationWorkItem,
+        output_batch: ForwardBatch,
+    ) -> torch.Tensor:
+        output = output_batch.output
+        if output is None:
+            raise RuntimeError("Forward execution returned no output tensor.")
+        fastvideo_args = work_item.fastvideo_args
+        sampling_param = work_item.sampling_param
+        latent_batch_size = _infer_latent_batch_size(work_item.batch)
+        skip_pixel_prealloc = fastvideo_args.output_type == "latent"
+        expected_shape = (
+            latent_batch_size,
+            3,
+            sampling_param.num_frames,
+            sampling_param.height,
+            sampling_param.width,
+        )
+        if skip_pixel_prealloc:
+            return output.cpu()
+        samples = torch.empty(expected_shape, device="cpu", pin_memory=fastvideo_args.pin_cpu_memory)
+        if output.shape == samples.shape:
+            samples.copy_(output)
+            return samples
+        logger.warning("Output shape %s does not match expected shape %s; use slow path", output.shape, samples.shape)
+        return output.cpu()
+
+    def _postprocess_generation_output(
+        self,
+        work_item: _GenerationWorkItem,
+        output_batch: ForwardBatch,
+        gen_time: float,
+        start_time: float,
+    ) -> dict[str, Any]:
+        batch = work_item.batch
+        fastvideo_args = work_item.fastvideo_args
+        output_path = work_item.output_path
+        samples = self._samples_from_output(work_item, output_batch)
+        logging_info = output_batch.logging_info
+
+        is_latent_output = fastvideo_args.output_type == "latent"
+        audio_only = bool(output_batch.extra.get("audio_only"))
+
+        postprocess_start = time.perf_counter()
+        frames: list[np.ndarray] | None
+        if is_latent_output or audio_only:
+            frames = None if is_latent_output else []
+        else:
+            videos = rearrange(samples, "b c t h w -> t b c h w")
+            frames = []
+            for x in videos:
+                x = torchvision.utils.make_grid(x, nrow=6)
+                x = x.permute(1, 2, 0).squeeze(-1)
+                x = (x * 255).to(torch.uint8)
+                frames.append(x.contiguous().cpu().numpy())
+        postprocess_time = time.perf_counter() - postprocess_start
+        logger.info("PostDecodeFrameProcessStage completed in %.3f s", postprocess_time)
+        if logging_info is not None:
+            logging_info.add_stage_execution_time("PostDecodeFrameProcessStage", postprocess_time)
+
+        save_to_disk = batch.save_video and not is_latent_output
+        save_video_time = 0.0
+        audio_mux_time = 0.0
+        if save_to_disk:
+            if audio_only:
+                output_path = self._rewrite_extension(output_path, ".wav")
+                save_start = time.perf_counter()
+                self._write_pcm_wav(
+                    output_path,
+                    output_batch.extra["audio"],
+                    int(output_batch.extra["audio_sample_rate"]),
+                )
+                save_video_time = time.perf_counter() - save_start
+                logger.info("Saved audio to %s", output_path)
+            elif self._is_image_workload():
+                assert frames is not None
+                save_start = time.perf_counter()
+                imageio.imwrite(output_path, frames[0])
+                save_video_time = time.perf_counter() - save_start
+                logger.info("Saved image to %s", output_path)
+            else:
+                assert frames is not None
+                audio = output_batch.extra.get("audio")
+                audio_sample_rate = output_batch.extra.get("audio_sample_rate")
+                if audio is not None and audio_sample_rate is not None:
+                    save_start = time.perf_counter()
+                    save_ok = self._save_video_with_audio_ffmpeg_pipe(
+                        output_path=output_path,
+                        frames=frames,
+                        fps=batch.fps,
+                        audio=audio,
+                        sample_rate=int(audio_sample_rate),
+                    )
+                    if not save_ok:
+                        logger.warning("ffmpeg pipe save failed; trying PyAV single-pass save.")
+                        save_ok = self._save_video_with_audio_single_pass(
+                            output_path=output_path,
+                            frames=frames,
+                            fps=batch.fps,
+                            audio=audio,
+                            sample_rate=int(audio_sample_rate),
+                        )
+                    save_video_time = time.perf_counter() - save_start
+                    if save_ok:
+                        audio_mux_time = 0.0
+                    else:
+                        logger.warning("Single-pass save failed; falling back to two-step save/mux.")
+                        save_start = time.perf_counter()
+                        imageio.mimsave(output_path, frames, fps=batch.fps, format="mp4")
+                        save_video_time = time.perf_counter() - save_start
+                        mux_start = time.perf_counter()
+                        mux_ok = self._mux_audio(output_path, audio, int(audio_sample_rate))
+                        audio_mux_time = time.perf_counter() - mux_start
+                        if not mux_ok:
+                            logger.warning("Audio mux failed; saved video without audio.")
+                else:
+                    save_start = time.perf_counter()
+                    imageio.mimsave(output_path, frames, fps=batch.fps, format="mp4")
+                    save_video_time = time.perf_counter() - save_start
+                    audio_mux_time = 0.0
+                logger.info("Saved video to %s", output_path)
+
+            logger.info("VideoSaveStage completed in %.3f s", save_video_time)
+            if logging_info is not None:
+                logging_info.add_stage_execution_time("VideoSaveStage", save_video_time)
+            logger.info("AudioMuxStage completed in %.3f s", audio_mux_time)
+            if logging_info is not None:
+                logging_info.add_stage_execution_time("AudioMuxStage", audio_mux_time)
+
+        e2e_time = time.perf_counter() - start_time
+        logger.info("End-to-end latency: %.2f seconds", e2e_time)
+
+        return {
+            "prompts": work_item.prompt,
+            "samples": samples if batch.return_frames else None,
+            "frames": frames if batch.return_frames else None,
+            "audio": output_batch.extra.get("audio"),
+            "audio_sample_rate": output_batch.extra.get("audio_sample_rate"),
+            "ltx2_audio_latents": output_batch.extra.get("ltx2_audio_latents"),
+            "size": (work_item.target_height, work_item.target_width, batch.num_frames),
+            "generation_time": gen_time,
+            "e2e_latency": e2e_time,
+            "logging_info": logging_info,
+            "trajectory": output_batch.trajectory_latents,
+            "trajectory_timesteps": output_batch.trajectory_timesteps,
+            "trajectory_decoded": output_batch.trajectory_decoded,
+            "video_path": output_path if save_to_disk else None,
+            "peak_memory_mb": output_batch.extra.get("peak_memory_mb"),
+        }
+
+    def _split_output_batch(
+        self,
+        output_batch: ForwardBatch,
+        *,
+        index: int,
+        batch_size: int,
+    ) -> ForwardBatch:
+        extra = {}
+        for key, value in (output_batch.extra or {}).items():
+            if torch.is_tensor(value) and value.ndim > 0 and value.shape[0] == batch_size:
+                extra[key] = value[index:index + 1]
+            elif isinstance(value, list) and len(value) == batch_size:
+                extra[key] = value[index]
+            else:
+                extra[key] = value
+
+        result = ForwardBatch(
+            data_type=output_batch.data_type,
+            output=(output_batch.output[index:index + 1] if output_batch.output is not None else None),
+            logging_info=output_batch.logging_info,
+            extra=extra,
+        )
+        if output_batch.trajectory_latents is not None:
+            result.trajectory_latents = output_batch.trajectory_latents[index:index + 1]
+        result.trajectory_timesteps = output_batch.trajectory_timesteps
+        if output_batch.trajectory_decoded is not None:
+            result.trajectory_decoded = [
+                decoded[index:index + 1] if torch.is_tensor(decoded) and decoded.shape[0] == batch_size else decoded
+                for decoded in output_batch.trajectory_decoded
+            ]
+        return result
+
+    def _merge_work_items(self, work_items: list[_GenerationWorkItem]) -> _GenerationWorkItem:
+        first = work_items[0]
+        sampling_param = deepcopy(first.sampling_param)
+        prompts = [item.prompt for item in work_items]
+        sampling_param.prompt = prompts
+        sampling_param.seed = work_items[0].sampling_param.seed
+
+        merged = self._prepare_generation_work_item(
+            prompts,
+            sampling_param,
+            first.fastvideo_args,
+            output_path=first.output_path,
+            _extra_overrides=first.batch.extra,
+        )
+        merged.batch.seeds = [int(item.sampling_param.seed) for item in work_items]
+        merged.batch.extra["dynamic_batch_size"] = len(work_items)
+        merged.batch.extra["dynamic_batch_output_paths"] = [item.output_path for item in work_items]
+        return merged
+
+    def _can_merge_work_items(
+        self,
+        base: _GenerationWorkItem,
+        candidate: _GenerationWorkItem,
+        admission: BatchAdmissionController,
+        current_group: list[_GenerationWorkItem],
+    ) -> bool:
+        if candidate.fastvideo_args is not base.fastvideo_args:
+            return False
+        compatibility = can_dynamic_batch(
+            base.sampling_param,
+            candidate.sampling_param,
+            base_extra=base.batch.extra,
+            candidate_extra=candidate.batch.extra,
+        )
+        if not compatibility.can_batch:
+            return False
+        current_requests = [item.sampling_param for item in current_group]
+        return admission.reject_reason_for_candidate(current_requests, candidate.sampling_param) is None
+
+    def _run_work_item_group(self, group: list[_GenerationWorkItem]) -> list[dict[str, Any]]:
+        if len(group) == 1:
+            return [self._execute_single_work_item(group[0])]
+        merged = self._merge_work_items(group)
+        output_batch, gen_time, start_time = self._run_forward_batch(merged.batch, merged.fastvideo_args)
+        return [
+            self._postprocess_generation_output(
+                item,
+                self._split_output_batch(output_batch, index=item_index, batch_size=len(group)),
+                gen_time,
+                start_time,
+            ) for item_index, item in enumerate(group)
+        ]
+
+    def _generate_prepared_work_items(
+        self,
+        work_items: list[_GenerationWorkItem],
+        tolerate_failures: bool = False,
+    ) -> list[dict[str, Any]]:
+        """Execute prepared work items, batching compatible neighbors.
+
+        With ``tolerate_failures`` (prompt-file semantics), a failed group
+        yields one ``{"error": ..., "prompt": ...}`` entry per work item so
+        completed results survive and stay aligned with the inputs; otherwise
+        the exception propagates.
+        """
+        if not work_items:
+            return []
+
+        def run_group(group: list[_GenerationWorkItem]) -> list[dict[str, Any]]:
+            if not tolerate_failures:
+                return self._run_work_item_group(group)
+            try:
+                return self._run_work_item_group(group)
+            except Exception as e:
+                logger.error("Failed to generate videos for batched prompts %s: %s",
+                             [item.prompt[:100] for item in group], e)
+                return [{"error": str(e), "prompt": item.prompt} for item in group]
+
+        fastvideo_args = work_items[0].fastvideo_args
+        if not self._dynamic_batching_enabled(fastvideo_args):
+            return [result for item in work_items for result in run_group([item])]
+
+        admission = BatchAdmissionController(fastvideo_args)
+        results: list[dict[str, Any]] = []
+        index = 0
+        while index < len(work_items):
+            group = [work_items[index]]
+            index += 1
+            while index < len(work_items) and len(group) < fastvideo_args.batching_max_size:
+                candidate = work_items[index]
+                if not self._can_merge_work_items(group[0], candidate, admission, group):
+                    break
+                group.append(candidate)
+                index += 1
+            results.extend(run_group(group))
+        return results
+
+    def _execute_single_work_item(self, work_item: _GenerationWorkItem) -> dict[str, Any]:
+        output_batch, gen_time, start_time = self._run_forward_batch(work_item.batch, work_item.fastvideo_args)
+        return self._postprocess_generation_output(work_item, output_batch, gen_time, start_time)
+
     def _generate_single_video(
         self,
         prompt: str,

fastvideo/envs.py

@@ -20,6 +20,7 @@ if TYPE_CHECKING:
     FASTVIDEO_LOGGING_CONFIG_PATH: str | None = None
     FASTVIDEO_TRACE_FUNCTION: int = 0
     FASTVIDEO_ATTENTION_BACKEND: str | None = None
+    FASTVIDEO_FA4: bool = False
     FASTVIDEO_WORKER_MULTIPROC_METHOD: str = "spawn"
     FASTVIDEO_TARGET_DEVICE: str = "cuda"
     MAX_JOBS: str | None = None
@@ -207,9 +208,18 @@ environment_variables: dict[str, Callable[[], Any]] = {
     # - "VIDEO_SPARSE_ATTN": use Video Sparse Attention
     # - "SAGE_ATTN": use Sage Attention
     # - "SAGE_ATTN_THREE": use Sage Attention 3
+    # FLASH_ATTN uses FlashAttention-3/2; to run FlashAttention-4 set
+    # FASTVIDEO_FA4=1 as well (see below).
     "FASTVIDEO_ATTENTION_BACKEND":
     lambda: os.getenv("FASTVIDEO_ATTENTION_BACKEND", None),
 
+    # If set (=1), the FLASH_ATTN backend uses FlashAttention-4
+    # (flash_attn.cute). FA4 is opt-in and never auto-selected just because it
+    # is installed. Below sm90, grad-enabled and GQA calls are routed to FA2
+    # (FA4's backward asserts sm90+ and its pack_gqa fails to JIT there).
+    "FASTVIDEO_FA4":
+    lambda: os.getenv("FASTVIDEO_FA4", "0") != "0",
+
     # Use dedicated multiprocess context for workers.
     "FASTVIDEO_WORKER_MULTIPROC_METHOD":
     lambda: os.getenv("FASTVIDEO_WORKER_MULTIPROC_METHOD", "spawn"),

fastvideo/fastvideo_args.py

@@ -169,6 +169,14 @@ class FastVideoArgs:
     # Prompt text file for batch processing
     prompt_txt: str | None = None
 
+    # Dynamic multimodal generation batching. Defaults preserve the historical
+    # one-request-at-a-time execution path.
+    batching_mode: str = "disabled"
+    batching_max_size: int = 1
+    batching_delay_ms: float = 0.0
+    batching_config: str | None = None
+    enable_batching_metrics: bool = False
+
     # LTX-2 VAE tiling overrides
     ltx2_vae_tiling: bool | None = None
     ltx2_vae_spatial_tile_size_in_pixels: int | None = None
@@ -446,6 +454,37 @@ class FastVideoArgs:
             default=FastVideoArgs.prompt_txt,
             help="Path to a text file containing prompts (one per line) for batch processing",
         )
+        parser.add_argument(
+            "--batching-mode",
+            type=str,
+            choices=["disabled", "dynamic"],
+            default=FastVideoArgs.batching_mode,
+            help="Request batching mode for inference serving.",
+        )
+        parser.add_argument(
+            "--batching-max-size",
+            type=int,
+            default=FastVideoArgs.batching_max_size,
+            help="Maximum number of compatible generation requests to execute as one batch.",
+        )
+        parser.add_argument(
+            "--batching-delay-ms",
+            type=float,
+            default=FastVideoArgs.batching_delay_ms,
+            help="Maximum queue delay in milliseconds before dispatching a dynamic batch.",
+        )
+        parser.add_argument(
+            "--batching-config",
+            type=str,
+            default=FastVideoArgs.batching_config,
+            help="Optional JSON batching admission rule file.",
+        )
+        parser.add_argument(
+            "--enable-batching-metrics",
+            action=StoreBoolean,
+            default=FastVideoArgs.enable_batching_metrics,
+            help="Log dynamic batching utilization and rejection metrics.",
+        )
 
         # LTX-2 VAE tiling overrides
         parser.add_argument(
@@ -753,6 +792,13 @@ class FastVideoArgs:
                           WorkloadType), f"Workload type must be a WorkloadType enum, got {type(self.workload_type)}"
         assert self.workload_type in WorkloadType.choices(), f"Invalid workload type: {self.workload_type}"
 
+        if self.batching_mode not in {"disabled", "dynamic"}:
+            raise ValueError(f"batching_mode must be 'disabled' or 'dynamic', got {self.batching_mode!r}")
+        if self.batching_max_size < 1:
+            raise ValueError("batching_max_size must be >= 1")
+        if self.batching_delay_ms < 0:
+            raise ValueError("batching_delay_ms must be >= 0")
+
         if self.mode in [ExecutionMode.DISTILLATION, ExecutionMode.FINETUNING] and self.inference_mode:
             logger.warning("Mode is 'training' but inference_mode is True. Setting inference_mode to False.")
             self.inference_mode = False

fastvideo/models/dits/causal_wanvideo.py

@@ -323,9 +323,9 @@ class CausalWanTransformerBlock(nn.Module):
         value, _ = self.to_v(norm_hidden_states)
 
         if self.norm_q is not None:
-            query = self.norm_q.forward_native(query)
+            query = self.norm_q(query)
         if self.norm_k is not None:
-            key = self.norm_k.forward_native(key)
+            key = self.norm_k(key)
 
         query = query.squeeze(1).unflatten(2, (self.num_attention_heads, -1))
         key = key.squeeze(1).unflatten(2, (self.num_attention_heads, -1))

fastvideo/models/dits/matrixgame2/causal_model.py

@@ -537,9 +537,9 @@ class CausalMatrixGame2TransformerBlock(nn.Module):
         value, _ = self.to_v(norm_hidden_states)
 
         if self.norm_q is not None:
-            query = self.norm_q.forward_native(query)
+            query = self.norm_q(query)
         if self.norm_k is not None:
-            key = self.norm_k.forward_native(key)
+            key = self.norm_k(key)
 
         query = query.squeeze(1).unflatten(2, (self.num_attention_heads, -1))
         key = key.squeeze(1).unflatten(2, (self.num_attention_heads, -1))

fastvideo/performance/__init__.py

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: Apache-2.0
+"""Performance benchmark and dashboard utilities."""

fastvideo/performance/hf_store.py

@@ -57,9 +57,7 @@ def is_baseline_eligible_record(record: dict[str, Any]) -> bool:
     """
     if record.get("baseline_eligible") is True:
         return True
-    if "baseline_eligible" not in record and "run_source" not in record:
-        return True
-    return False
+    return "baseline_eligible" not in record and "run_source" not in record
 
 
 def resolve_hf_token() -> str | None:

fastvideo/performance/metric_policy.py

@@ -0,0 +1,130 @@
+# SPDX-License-Identifier: Apache-2.0
+"""Metric policy for rolling performance baseline comparisons."""
+
+from __future__ import annotations
+
+from collections.abc import Mapping
+from dataclasses import dataclass
+from typing import Any
+
+
+@dataclass(frozen=True)
+class MetricPolicy:
+    key: str
+    label: str
+    precision: int
+    lower_is_better: bool
+    threshold_percent: float
+    threshold_absolute: float
+    gated: bool = True
+
+
+@dataclass(frozen=True)
+class MetricDelta:
+    absolute: float
+    percent: float
+    threshold_exceeded: bool
+    regressed: bool
+
+
+DEFAULT_METRIC_POLICIES: tuple[MetricPolicy, ...] = (
+    MetricPolicy("latency", "Latency", 3, True, 0.08, 0.5),
+    MetricPolicy("throughput", "Throughput", 3, False, 0.08, 0.05),
+    MetricPolicy("memory", "Memory", 1, True, 0.05, 256.0),
+    MetricPolicy("text_encoder_time_s", "Text Enc", 3, True, 0.05, 0.25),
+    MetricPolicy("dit_time_s", "DiT", 3, True, 0.05, 0.25),
+    MetricPolicy("vae_decode_time_s", "VAE Decode", 3, True, 0.05, 0.25),
+)
+
+def _optional_float(value: Any) -> float | None:
+    if value is None or isinstance(value, bool):
+        return None
+    try:
+        return float(value)
+    except (TypeError, ValueError):
+        return None
+
+
+def _optional_bool(value: Any) -> bool | None:
+    if isinstance(value, bool):
+        return value
+    if isinstance(value, str):
+        normalized = value.strip().lower()
+        if normalized in {"1", "true", "yes", "on"}:
+            return True
+        if normalized in {"0", "false", "no", "off"}:
+            return False
+    return None
+
+
+def resolve_metric_policies(
+    threshold_overrides: Mapping[str, Any] | None,
+) -> tuple[MetricPolicy, ...]:
+    """Return default metric policies with optional per-metric overrides."""
+
+    if not isinstance(threshold_overrides, Mapping):
+        threshold_overrides = {}
+    policies: list[MetricPolicy] = []
+    for base_policy in DEFAULT_METRIC_POLICIES:
+        raw_override = threshold_overrides.get(base_policy.key, {})
+        if not isinstance(raw_override, Mapping):
+            raw_override = {}
+
+        threshold_percent = _optional_float(raw_override.get("threshold_percent"))
+        threshold_absolute = _optional_float(raw_override.get("threshold_absolute"))
+        gated = _optional_bool(raw_override.get("gated"))
+
+        policies.append(
+            MetricPolicy(
+                key=base_policy.key,
+                label=base_policy.label,
+                precision=base_policy.precision,
+                lower_is_better=base_policy.lower_is_better,
+                threshold_percent=(
+                    base_policy.threshold_percent
+                    if threshold_percent is None
+                    else threshold_percent
+                ),
+                threshold_absolute=(
+                    base_policy.threshold_absolute
+                    if threshold_absolute is None
+                    else threshold_absolute
+                ),
+                gated=base_policy.gated if gated is None else gated,
+            )
+        )
+    return tuple(policies)
+
+
+def serialize_metric_thresholds(
+    policies: tuple[MetricPolicy, ...],
+) -> dict[str, dict[str, float | bool]]:
+    return {
+        policy.key: {
+            "threshold_percent": policy.threshold_percent,
+            "threshold_absolute": policy.threshold_absolute,
+            "gated": policy.gated,
+        }
+        for policy in policies
+    }
+
+
+def regression_delta(
+    policy: MetricPolicy,
+    current: float,
+    baseline: float,
+) -> MetricDelta | None:
+    if baseline <= 0:
+        return None
+    absolute_delta = current - baseline if policy.lower_is_better else baseline - current
+    percent_delta = absolute_delta / baseline
+    threshold_exceeded = (
+        percent_delta > policy.threshold_percent
+        and absolute_delta > policy.threshold_absolute
+    )
+    return MetricDelta(
+        absolute=absolute_delta,
+        percent=percent_delta,
+        threshold_exceeded=threshold_exceeded,
+        regressed=policy.gated and threshold_exceeded,
+    )

fastvideo/performance_dashboard/api.py

@@ -13,7 +13,7 @@ from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import FileResponse
 from fastapi.staticfiles import StaticFiles
 
-from fastvideo.tests.performance import hf_store
+from fastvideo.performance import hf_store
 
 from .service import build_latest_summary, build_trends, filter_records
 
@@ -150,7 +150,6 @@ def create_app(store: PerformanceDataStore | None = None) -> FastAPI:
         filtered = filter_records(loaded, model_id=model_id, gpu_type=gpu_type)
         rows = build_latest_summary(
             filtered,
-            max_regression=float(os.environ.get("PERF_MAX_REGRESSION", "0.05")),
             run_source=run_source,
         )
         return {

fastvideo/performance_dashboard/metrics.py

@@ -1,26 +1,8 @@
 # SPDX-License-Identifier: Apache-2.0
 """Metric definitions shared by the performance dashboard backend."""
 
-from __future__ import annotations
+from fastvideo.performance.metric_policy import DEFAULT_METRIC_POLICIES
 
-from dataclasses import dataclass
-
-
-@dataclass(frozen=True)
-class MetricDefinition:
-    key: str
-    label: str
-    precision: int
-    lower_is_better: bool
-
-
-METRICS: tuple[MetricDefinition, ...] = (
-    MetricDefinition("latency", "Latency", 3, True),
-    MetricDefinition("throughput", "Throughput", 3, False),
-    MetricDefinition("memory", "Memory", 1, True),
-    MetricDefinition("text_encoder_time_s", "Text Encoder", 3, True),
-    MetricDefinition("dit_time_s", "DiT", 3, True),
-    MetricDefinition("vae_decode_time_s", "VAE Decode", 3, True),
-)
+METRICS = DEFAULT_METRIC_POLICIES
 
 METRIC_BY_KEY = {metric.key: metric for metric in METRICS}

fastvideo/performance_dashboard/service.py

@@ -13,9 +13,8 @@ from collections import defaultdict
 from datetime import datetime, timezone
 from typing import Any
 
-from fastvideo.tests.performance.hf_store import is_baseline_eligible_record, safe_float
-
-from .metrics import METRICS
+from fastvideo.performance.hf_store import is_baseline_eligible_record, safe_float
+from fastvideo.performance.metric_policy import regression_delta, resolve_metric_policies
 
 Record = dict[str, Any]
 
@@ -95,19 +94,9 @@ def baseline_value(records: list[Record], metric_key: str) -> float | None:
     return float(statistics.median(values))
 
 
-def regression_percent(metric_key: str, current: float | None, baseline: float | None) -> float | None:
-    if current is None or baseline is None or baseline <= 0:
-        return None
-    metric = next(metric for metric in METRICS if metric.key == metric_key)
-    if metric.lower_is_better:
-        return (current - baseline) / baseline * 100.0
-    return (baseline - current) / baseline * 100.0
-
-
 def build_latest_summary(records: list[Record],
                          *,
                          baseline_window: int = 5,
-                         max_regression: float = 0.05,
                          run_source: str | None = None) -> list[Record]:
     rows: list[Record] = []
     for (model_id, gpu_type), group in group_by_model_gpu(records).items():
@@ -123,52 +112,58 @@ def build_latest_summary(records: list[Record],
             if record is not latest and record.get("success", True) and is_baseline_eligible_record(record)
         ]
         baseline_records = baseline_pool[-baseline_window:]
+        metric_policies = resolve_metric_policies(latest.get("regression_thresholds"))
 
         metrics: dict[str, Record] = {}
         regressions: list[float] = []
-        for metric in METRICS:
-            current = safe_float(latest.get(metric.key))
-            baseline = baseline_value(baseline_records, metric.key)
-            regression = regression_percent(metric.key, current, baseline)
-            metrics[metric.key] = {
+        failing_metrics: list[str] = []
+        threshold_exceeded_metrics: list[str] = []
+        for policy in metric_policies:
+            current = safe_float(latest.get(policy.key))
+            baseline = baseline_value(baseline_records, policy.key)
+            delta = None
+            if current is not None and baseline is not None:
+                delta = regression_delta(policy, current, baseline)
+            regression = None if delta is None else delta.percent * 100.0
+            metrics[policy.key] = {
                 "current": current,
                 "baseline": baseline,
                 "regression_pct": regression,
-                "label": metric.label,
-                "lower_is_better": metric.lower_is_better,
-                "precision": metric.precision,
+                "absolute_delta": None if delta is None else delta.absolute,
+                "threshold_percent": policy.threshold_percent * 100.0,
+                "threshold_absolute": policy.threshold_absolute,
+                "gated": policy.gated,
+                "threshold_exceeded": False if delta is None else delta.threshold_exceeded,
+                "regressed": False if delta is None else delta.regressed,
+                "label": policy.label,
+                "lower_is_better": policy.lower_is_better,
+                "precision": policy.precision,
             }
             if regression is not None:
                 regressions.append(regression)
+            if delta is not None and delta.threshold_exceeded:
+                threshold_exceeded_metrics.append(policy.key)
+            if delta is not None and delta.regressed:
+                failing_metrics.append(policy.key)
 
         worst_regression = max(regressions) if regressions else None
         success = bool(latest.get("success", True))
         status = "pass" if success else "fail"
 
         rows.append({
-            "model_id":
-            model_id,
-            "gpu_type":
-            gpu_type,
-            "timestamp":
-            latest.get("timestamp"),
-            "commit_sha":
-            latest.get("commit_sha"),
+            "model_id": model_id,
+            "gpu_type": gpu_type,
+            "timestamp": latest.get("timestamp"),
+            "commit_sha": latest.get("commit_sha"),
             **record_metadata(latest),
-            "success":
-            success,
-            "baseline_n":
-            len(baseline_records),
-            "worst_regression_pct":
-            worst_regression,
-            "regression_threshold_pct":
-            max_regression * 100.0,
-            "computed_regression_status":
-            "fail" if worst_regression is not None and worst_regression > max_regression * 100.0 else "pass",
-            "status":
-            status,
-            "metrics":
-            metrics,
+            "success": success,
+            "baseline_n": len(baseline_records),
+            "worst_regression_pct": worst_regression,
+            "threshold_exceeded_metrics": threshold_exceeded_metrics,
+            "failing_metrics": failing_metrics,
+            "computed_regression_status": "fail" if failing_metrics else "pass",
+            "status": status,
+            "metrics": metrics,
         })
 
     return sorted(rows, key=lambda row: (row["status"] != "fail", row["model_id"], row["gpu_type"]))
@@ -179,14 +174,15 @@ def build_trends(records: list[Record]) -> list[Record]:
     for (model_id, gpu_type), group in group_by_model_gpu(records).items():
         points = []
         for record in group:
+            metric_policies = resolve_metric_policies(record.get("regression_thresholds"))
             point = {
                 "timestamp": record.get("timestamp"),
                 "commit_sha": record.get("commit_sha"),
                 **record_metadata(record),
                 "success": bool(record.get("success", True)),
                 "metrics": {
-                    metric.key: safe_float(record.get(metric.key))
-                    for metric in METRICS
+                    policy.key: safe_float(record.get(policy.key))
+                    for policy in metric_policies
                 },
             }
             points.append(point)

fastvideo/pipelines/stages/denoising.py

@@ -234,7 +234,6 @@ class DenoisingStage(PipelineStage):
 
         boundary_timestep = boundary_ratio * self.scheduler.num_train_timesteps if boundary_ratio is not None else None
         latent_model_input = latents.to(target_dtype)
-        assert latent_model_input.shape[0] == 1, "only support batch size 1"
 
         if fastvideo_args.pipeline_config.ti2v_task and batch.pil_image is not None:
             # TI2V directly replaces the first frame of the latent with

fastvideo/pipelines/stages/input_validation.py

@@ -35,7 +35,11 @@ class InputValidationStage(PipelineStage):
         num_videos_per_prompt = batch.num_videos_per_prompt
 
         assert seed is not None
-        seeds = [seed + i for i in range(num_videos_per_prompt)]
+        if batch.seeds is not None:
+            seeds = batch.seeds
+        else:
+            prompt_count = len(batch.prompt) if isinstance(batch.prompt, list) else 1
+            seeds = [seed + i for i in range(prompt_count * num_videos_per_prompt)]
         batch.seeds = seeds
 
         # Peiyuan: using GPU seed will cause A100 and H100 to generate different results...

fastvideo/pipelines/stages/text_encoding.py

@@ -65,12 +65,20 @@ class TextEncodingStage(PipelineStage):
         assert batch.prompt is not None
         prompt_text: str | list[str] = batch.prompt
         all_indices: list[int] = list(range(len(self.text_encoders)))
-        prompt_embeds_list, prompt_masks_list = self.encode_text(
-            prompt_text,
-            fastvideo_args,
-            encoder_index=all_indices,
-            return_attention_mask=True,
-        )
+        if isinstance(prompt_text, list):
+            prompt_embeds_list, prompt_masks_list = self._encode_prompt_list_individually(
+                prompt_text,
+                fastvideo_args,
+                encoder_index=all_indices,
+                return_attention_mask=True,
+            )
+        else:
+            prompt_embeds_list, prompt_masks_list = self.encode_text(
+                prompt_text,
+                fastvideo_args,
+                encoder_index=all_indices,
+                return_attention_mask=True,
+            )
         if self._last_audio_embeds is not None:
             batch.extra["ltx2_audio_prompt_embeds"] = self._last_audio_embeds
 
@@ -82,13 +90,24 @@ class TextEncodingStage(PipelineStage):
 
         # Encode negative prompt if CFG is enabled
         if batch.do_classifier_free_guidance:
-            assert isinstance(batch.negative_prompt, str)
-            neg_embeds_list, neg_masks_list = self.encode_text(
-                batch.negative_prompt,
-                fastvideo_args,
-                encoder_index=all_indices,
-                return_attention_mask=True,
-            )
+            assert isinstance(batch.negative_prompt, str | list)
+            negative_prompt: str | list[str] = batch.negative_prompt
+            if isinstance(batch.prompt, list) and isinstance(negative_prompt, str):
+                negative_prompt = [negative_prompt] * len(batch.prompt)
+            if isinstance(negative_prompt, list):
+                neg_embeds_list, neg_masks_list = self._encode_prompt_list_individually(
+                    negative_prompt,
+                    fastvideo_args,
+                    encoder_index=all_indices,
+                    return_attention_mask=True,
+                )
+            else:
+                neg_embeds_list, neg_masks_list = self.encode_text(
+                    negative_prompt,
+                    fastvideo_args,
+                    encoder_index=all_indices,
+                    return_attention_mask=True,
+                )
             if self._last_audio_embeds is not None:
                 batch.extra["ltx2_audio_negative_embeds"] = self._last_audio_embeds
 
@@ -101,6 +120,81 @@ class TextEncodingStage(PipelineStage):
 
         return batch
 
+    def _encode_prompt_list_individually(
+        self,
+        texts: list[str],
+        fastvideo_args: FastVideoArgs,
+        *,
+        encoder_index: list[int],
+        return_attention_mask: bool,
+    ) -> tuple[list[torch.Tensor], list[torch.Tensor]]:
+        per_prompt_embeds: list[list[torch.Tensor]] = []
+        per_prompt_masks: list[list[torch.Tensor]] = []
+        per_prompt_audio_embeds: list[list[torch.Tensor] | None] = []
+
+        for text in texts:
+            embeds, masks = self.encode_text(
+                text,
+                fastvideo_args,
+                encoder_index=encoder_index,
+                return_attention_mask=return_attention_mask,
+            )
+            per_prompt_embeds.append(embeds)
+            per_prompt_masks.append(masks)
+            per_prompt_audio_embeds.append(self._last_audio_embeds)
+
+        merged_embeds = [
+            self._cat_tensors([prompt_embeds[encoder_pos] for prompt_embeds in per_prompt_embeds])
+            for encoder_pos in range(len(per_prompt_embeds[0]))
+        ]
+        merged_masks = [
+            self._cat_attention_masks([prompt_masks[encoder_pos] for prompt_masks in per_prompt_masks])
+            for encoder_pos in range(len(per_prompt_masks[0]))
+        ]
+        if per_prompt_audio_embeds and all(audio_embeds is not None for audio_embeds in per_prompt_audio_embeds):
+            audio_embed_lists = [audio_embeds for audio_embeds in per_prompt_audio_embeds if audio_embeds is not None]
+            self._last_audio_embeds = [
+                self._cat_tensors([audio_embeds[encoder_pos] for audio_embeds in audio_embed_lists])
+                for encoder_pos in range(len(audio_embed_lists[0]))
+            ]
+        else:
+            self._last_audio_embeds = None
+        return merged_embeds, merged_masks
+
+    @staticmethod
+    def _cat_tensors(tensors: list[torch.Tensor]) -> torch.Tensor:
+        base_shape = tensors[0].shape[1:]
+        if all(tensor.shape[1:] == base_shape for tensor in tensors):
+            return torch.cat(tensors, dim=0)
+        if all(tensor.ndim == 3 for tensor in tensors):
+            base_trailing_shape = tensors[0].shape[2:]
+            if all(tensor.shape[2:] == base_trailing_shape for tensor in tensors):
+                max_length = max(tensor.shape[1] for tensor in tensors)
+                padded_tensors = []
+                for tensor in tensors:
+                    pad_width = max_length - tensor.shape[1]
+                    if pad_width > 0:
+                        tensor = torch.nn.functional.pad(tensor, (0, 0, 0, pad_width), value=0.0)
+                    padded_tensors.append(tensor)
+                return torch.cat(padded_tensors, dim=0)
+        raise ValueError(f"Cannot concatenate tensors with shapes: {[list(tensor.shape) for tensor in tensors]}")
+
+    @staticmethod
+    def _cat_attention_masks(masks: list[torch.Tensor]) -> torch.Tensor:
+        base_shape = masks[0].shape[1:]
+        if all(mask.shape[1:] == base_shape for mask in masks):
+            return torch.cat(masks, dim=0)
+        if all(mask.ndim == 2 for mask in masks):
+            max_length = max(mask.shape[1] for mask in masks)
+            padded_masks = []
+            for mask in masks:
+                pad_width = max_length - mask.shape[1]
+                if pad_width > 0:
+                    mask = torch.nn.functional.pad(mask, (0, pad_width), value=0)
+                padded_masks.append(mask)
+            return torch.cat(padded_masks, dim=0)
+        raise ValueError(f"Cannot concatenate attention masks with shapes: {[list(mask.shape) for mask in masks]}")
+
     def verify_input(self, batch: ForwardBatch, fastvideo_args: FastVideoArgs) -> VerificationResult:
         """Verify text encoding stage inputs."""
         result = VerificationResult()
@@ -235,6 +329,9 @@ class TextEncodingStage(PipelineStage):
                     attn_masks_list.append(attention_mask)
                     return self.return_embeds(embeds_list, attn_masks_list, return_type, return_attention_mask, indices)
 
+            if len(processed_texts) > 1 and "padding" not in tok_kwargs:
+                tok_kwargs["padding"] = True
+
             # If tokenizer is a multimodal processor (e.g. Qwen2_5_VLProcessor),
             # use its inner tokenizer for text-only encoding.
             tok = getattr(tokenizer, "tokenizer", tokenizer)

fastvideo/tests/api/test_compat_translation.py

@@ -9,7 +9,7 @@ from fastvideo.api.compat import (
     generator_config_to_fastvideo_args,
     legacy_from_pretrained_to_config,
 )
-from fastvideo.api.schema import CompileConfig, GeneratorConfig
+from fastvideo.api.schema import BatchingConfig, CompileConfig, GeneratorConfig
 
 
 class TestLegacyTorchCompileKwargsTranslation:
@@ -200,6 +200,48 @@ class TestLegacyTextEncoderCompileTranslation:
         assert "enable_torch_compile_text_encoder" not in args.kwargs
 
 
+class TestBatchingTranslation:
+
+    def test_flat_kwargs_promote_to_engine_batching(self) -> None:
+        config = legacy_from_pretrained_to_config(
+            "/models/wan",
+            {
+                "batching_mode": "dynamic",
+                "batching_max_size": 4,
+                "batching_delay_ms": 25.0,
+                "batching_config": "/tmp/batching.json",
+                "enable_batching_metrics": True,
+            },
+        )
+
+        assert config.engine.batching.mode == "dynamic"
+        assert config.engine.batching.max_size == 4
+        assert config.engine.batching.delay_ms == 25.0
+        assert config.engine.batching.config_path == "/tmp/batching.json"
+        assert config.engine.batching.enable_metrics is True
+
+    def test_typed_batching_emits_fastvideo_args_kwargs(self, monkeypatch) -> None:
+        _stub_fastvideo_args_from_kwargs(monkeypatch)
+        config = GeneratorConfig(
+            model_path="/models/wan",
+            engine=_engine_with_batching(BatchingConfig(
+                mode="dynamic",
+                max_size=3,
+                delay_ms=10.0,
+                config_path="/tmp/batching.json",
+                enable_metrics=True,
+            )),
+        )
+
+        args = generator_config_to_fastvideo_args(config)
+
+        assert args.kwargs["batching_mode"] == "dynamic"
+        assert args.kwargs["batching_max_size"] == 3
+        assert args.kwargs["batching_delay_ms"] == 10.0
+        assert args.kwargs["batching_config"] == "/tmp/batching.json"
+        assert args.kwargs["enable_batching_metrics"] is True
+
+
 # -------------------------------------------------------------------
 # Helpers
 # -------------------------------------------------------------------
@@ -213,6 +255,13 @@ def _engine_with_compile(compile_config):
     return engine
 
 
+def _engine_with_batching(batching_config):
+    from fastvideo.api.schema import EngineConfig
+    engine = EngineConfig()
+    engine.batching = batching_config
+    return engine
+
+
 def _stub_fastvideo_args_from_kwargs(monkeypatch):
     """Swap ``FastVideoArgs.from_kwargs`` for a capture-only stub so
     translation tests don't need to construct a valid FastVideoArgs."""

fastvideo/tests/api/test_parser.py

@@ -130,6 +130,13 @@ def test_load_run_config_supports_yaml_roundtrip(tmp_path) -> None:
                 "use_fsdp_inference": False,
                 "disable_autocast": False,
                 "quantization": None,
+                "batching": {
+                    "mode": "disabled",
+                    "max_size": 1,
+                    "delay_ms": 0.0,
+                    "config_path": None,
+                    "enable_metrics": False,
+                },
             },
             "pipeline": {
                 "workload_type": None,

fastvideo/tests/attention/test_flash_attn_no_pad_resolver.py

@@ -3,15 +3,16 @@
 
 Landed in PR #1225 slice 5 (Attn-QAT 5/12). The resolver centralises the
 varlen-flash-attn import-fallback logic that several backends
-(``bsa_attn.py``, ``video_sparse_attn.py``) used to duplicate. The fallback
+(``bsa_attn.py``, ``video_sparse_attn.py``) used to duplicate. The resolution
 order is:
 
-    1. ``fastvideo.attention.utils.flash_attn_cute``
+    1. ``fastvideo.attention.utils.flash_attn_cute`` -- only when
+       ``FASTVIDEO_FA4=1`` (explicit opt-in), and then it must import or the
+       resolver raises RuntimeError instead of falling through
     2. ``flash_attn_interface``
     3. ``flash_attn``
 
-These tests verify that the resolver picks the highest-priority impl
-available and falls through cleanly on ``ImportError``. CPU-only, no
+These tests verify the opt-in gate and the FA3/FA2 fallthrough. CPU-only, no
 flash-attn install required.
 """
 
@@ -35,8 +36,36 @@ def _reload_resolver_module():
     return importlib.import_module("fastvideo.attention.utils.flash_attn_no_pad")
 
 
-def test_resolver_falls_back_when_cute_unavailable(monkeypatch) -> None:
-    """When ``flash_attn_cute`` is unimportable, resolver tries the next impl."""
+def test_resolver_skips_cute_without_opt_in(monkeypatch) -> None:
+    """Without ``FASTVIDEO_FA4=1`` the resolver must not even attempt the cute
+    import."""
+    monkeypatch.delenv("FASTVIDEO_FA4", raising=False)
+    attempted: list[str] = []
+    real_import = builtins.__import__
+
+    def spying_import(name, globals=None, locals=None, fromlist=(), level=0):
+        attempted.append(name)
+        return real_import(name, globals, locals, fromlist, level)
+
+    monkeypatch.setattr(builtins, "__import__", spying_import)
+
+    mod = _reload_resolver_module()
+    resolved = mod._resolve_flash_attn_varlen_func()
+    assert resolved is not None
+    assert resolved.__name__ == "flash_attn_varlen_func"
+    assert "fastvideo.attention.utils.flash_attn_cute" not in attempted
+
+
+def test_resolver_raises_when_opted_in_but_cute_unavailable(monkeypatch) -> None:
+    """With ``FASTVIDEO_FA4=1`` an unimportable cute build fails loudly instead
+    of silently falling through to FA3/FA2.
+
+    The resolver runs at module import time, so the reload itself must raise.
+    It raises RuntimeError (not ImportError) so importers that treat
+    ImportError as "flash-attn not installed" (``bsa_attn.py``) cannot swallow
+    the opted-in failure.
+    """
+    monkeypatch.setenv("FASTVIDEO_FA4", "1")
     real_import = builtins.__import__
 
     def patched_import(name, globals=None, locals=None, fromlist=(), level=0):
@@ -46,21 +75,17 @@ def test_resolver_falls_back_when_cute_unavailable(monkeypatch) -> None:
 
     monkeypatch.setattr(builtins, "__import__", patched_import)
 
-    mod = _reload_resolver_module()
-    resolved = mod._resolve_flash_attn_varlen_func()
-    assert resolved is not None
-    assert resolved.__name__ == "flash_attn_varlen_func"
+    with pytest.raises(RuntimeError, match="cute disabled for test"):
+        _reload_resolver_module()
 
 
-def test_resolver_returns_flash_attn_when_cute_and_interface_unavailable(monkeypatch) -> None:
+def test_resolver_returns_flash_attn_when_interface_unavailable(monkeypatch) -> None:
     """The terminal fallback is the plain ``flash_attn`` import."""
+    monkeypatch.delenv("FASTVIDEO_FA4", raising=False)
     real_import = builtins.__import__
 
     def patched_import(name, globals=None, locals=None, fromlist=(), level=0):
-        if name in {
-                "fastvideo.attention.utils.flash_attn_cute",
-                "flash_attn_interface",
-        }:
+        if name == "flash_attn_interface":
             raise ImportError(f"{name} disabled for test")
         return real_import(name, globals, locals, fromlist, level)
 

fastvideo/tests/batching/run_dynamic_batching_parity.py

@@ -0,0 +1,198 @@
+# SPDX-License-Identifier: Apache-2.0
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import time
+from pathlib import Path
+from typing import Any
+
+import torch
+
+from fastvideo import VideoGenerator
+
+DEFAULT_PROMPTS = (
+    "A small robot sketches a city skyline at sunrise, cinematic lighting.",
+    "A glass teapot steams on a wooden table while rain falls outside.",
+)
+
+
+def _build_init_kwargs(args: argparse.Namespace, *, dynamic: bool) -> dict[str, Any]:
+    return {
+        "num_gpus": args.num_gpus,
+        "sp_size": args.sp_size,
+        "tp_size": args.tp_size,
+        "use_fsdp_inference": args.use_fsdp_inference,
+        "dit_cpu_offload": False,
+        "dit_layerwise_offload": False,
+        "flow_shift": args.flow_shift,
+        "text_encoder_precisions": ("fp32",),
+        "output_type": "latent",
+        "batching_mode": "dynamic" if dynamic else "disabled",
+        "batching_max_size": args.batch_size if dynamic else 1,
+        "batching_delay_ms": 0.0,
+    }
+
+
+def _request_kwargs(args: argparse.Namespace, prompt_index: int) -> dict[str, Any]:
+    return {
+        "prompt": args.prompts[prompt_index],
+        "height": args.height,
+        "width": args.width,
+        "num_frames": args.num_frames,
+        "num_inference_steps": args.num_inference_steps,
+        "guidance_scale": args.guidance_scale,
+        "embedded_cfg_scale": args.embedded_cfg_scale,
+        "seed": args.seed + prompt_index,
+        "fps": 24,
+        "save_video": False,
+        "return_frames": True,
+        "output_path": str(Path(args.output_dir) / f"request_{prompt_index}.mp4"),
+    }
+
+
+def _sync() -> None:
+    if torch.cuda.is_available():
+        torch.cuda.synchronize()
+
+
+def _run_sequential(generator: VideoGenerator, args: argparse.Namespace) -> tuple[list[dict[str, Any]], float]:
+    _sync()
+    start = time.perf_counter()
+    results = []
+    for index in range(args.batch_size):
+        kwargs = _request_kwargs(args, index)
+        prompt = kwargs.pop("prompt")
+        results.append(generator.generate_video(prompt=prompt, **kwargs))
+    _sync()
+    return results, time.perf_counter() - start
+
+
+def _run_dynamic(generator: VideoGenerator, args: argparse.Namespace) -> tuple[list[dict[str, Any]], float]:
+    if not hasattr(generator, "generate_video_batch"):
+        raise RuntimeError("VideoGenerator.generate_video_batch is unavailable in this checkout")
+    requests = [_request_kwargs(args, index) for index in range(args.batch_size)]
+    _sync()
+    start = time.perf_counter()
+    results = generator.generate_video_batch(requests)
+    _sync()
+    return results, time.perf_counter() - start
+
+
+def _tensor_metrics(sequential: list[dict[str, Any]], dynamic: list[dict[str, Any]]) -> dict[str, Any]:
+    per_request = []
+    for index, (seq_result, dyn_result) in enumerate(zip(sequential, dynamic, strict=True)):
+        seq = seq_result["samples"].detach().cpu().to(torch.float32)
+        dyn = dyn_result["samples"].detach().cpu().to(torch.float32)
+        diff = (seq - dyn).abs()
+        per_request.append({
+            "index": index,
+            "shape": list(seq.shape),
+            "max_abs_diff": float(diff.max().item()),
+            "mean_abs_diff": float(diff.mean().item()),
+            "allclose_atol_1e_5": bool(torch.allclose(seq, dyn, atol=1e-5, rtol=1e-5)),
+            "allclose_atol_1e_4": bool(torch.allclose(seq, dyn, atol=1e-4, rtol=1e-4)),
+        })
+    return {
+        "per_request": per_request,
+        "max_abs_diff": max(item["max_abs_diff"] for item in per_request),
+        "mean_abs_diff": sum(item["mean_abs_diff"] for item in per_request) / len(per_request),
+        "allclose_atol_1e_5": all(item["allclose_atol_1e_5"] for item in per_request),
+        "allclose_atol_1e_4": all(item["allclose_atol_1e_4"] for item in per_request),
+    }
+
+
+def run_parity(args: argparse.Namespace) -> dict[str, Any]:
+    generator = VideoGenerator.from_pretrained(args.model_path, **_build_init_kwargs(args, dynamic=True))
+    try:
+        sequential, sequential_s = _run_sequential(generator, args)
+        dynamic, dynamic_s = _run_dynamic(generator, args)
+        metrics = _tensor_metrics(sequential, dynamic)
+    finally:
+        generator.shutdown()
+    return {
+        "mode": "parity",
+        "model_path": args.model_path,
+        "num_gpus": args.num_gpus,
+        "shape": {
+            "height": args.height,
+            "width": args.width,
+            "num_frames": args.num_frames,
+            "num_inference_steps": args.num_inference_steps,
+        },
+        "batch_size": args.batch_size,
+        "sequential_time_s": sequential_s,
+        "dynamic_time_s": dynamic_s,
+        "speedup": sequential_s / dynamic_s if dynamic_s > 0 else None,
+        "tensor_metrics": metrics,
+    }
+
+
+def run_benchmark(args: argparse.Namespace, *, dynamic: bool) -> dict[str, Any]:
+    generator = VideoGenerator.from_pretrained(args.model_path, **_build_init_kwargs(args, dynamic=dynamic))
+    run = _run_dynamic if dynamic else _run_sequential
+    try:
+        for _ in range(args.warmup_runs):
+            run(generator, args)
+        times = []
+        for _ in range(args.measurement_runs):
+            _results, elapsed = run(generator, args)
+            times.append(elapsed)
+    finally:
+        generator.shutdown()
+    avg = sum(times) / len(times)
+    return {
+        "mode": "dynamic" if dynamic else "sequential",
+        "model_path": args.model_path,
+        "num_gpus": args.num_gpus,
+        "batch_size": args.batch_size,
+        "measurement_runs": args.measurement_runs,
+        "times_s": times,
+        "avg_time_s": avg,
+        "requests_per_second": args.batch_size / avg if avg > 0 else None,
+    }
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--mode", choices=("parity", "sequential", "dynamic"), required=True)
+    parser.add_argument("--model-path", default="Wan-AI/Wan2.1-T2V-1.3B-Diffusers")
+    parser.add_argument("--num-gpus", type=int, default=1)
+    parser.add_argument("--sp-size", type=int, default=1)
+    parser.add_argument("--tp-size", type=int, default=1)
+    parser.add_argument("--use-fsdp-inference", action="store_true")
+    parser.add_argument("--height", type=int, default=256)
+    parser.add_argument("--width", type=int, default=256)
+    parser.add_argument("--num-frames", type=int, default=9)
+    parser.add_argument("--num-inference-steps", type=int, default=2)
+    parser.add_argument("--guidance-scale", type=float, default=1.0)
+    parser.add_argument("--embedded-cfg-scale", type=float, default=6.0)
+    parser.add_argument("--flow-shift", type=float, default=7.0)
+    parser.add_argument("--seed", type=int, default=1024)
+    parser.add_argument("--batch-size", type=int, default=2)
+    parser.add_argument("--warmup-runs", type=int, default=1)
+    parser.add_argument("--measurement-runs", type=int, default=3)
+    parser.add_argument("--output-dir", default="/tmp/fastvideo_dynamic_batching")
+    parser.add_argument("--output-json", required=True)
+    parser.add_argument("--prompts", nargs="+", default=list(DEFAULT_PROMPTS))
+    return parser.parse_args()
+
+
+def main() -> None:
+    args = parse_args()
+    if len(args.prompts) < args.batch_size:
+        raise ValueError("--prompts must contain at least --batch-size prompts")
+    os.makedirs(args.output_dir, exist_ok=True)
+    if args.mode == "parity":
+        result = run_parity(args)
+    else:
+        result = run_benchmark(args, dynamic=args.mode == "dynamic")
+    output_path = Path(args.output_json)
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+    output_path.write_text(json.dumps(result, indent=2), encoding="utf-8")
+    print(json.dumps(result, indent=2))
+
+
+if __name__ == "__main__":
+    main()

fastvideo/tests/batching/test_admission.py

@@ -0,0 +1,89 @@
+# SPDX-License-Identifier: Apache-2.0
+from __future__ import annotations
+
+from types import SimpleNamespace
+
+import pytest
+
+from fastvideo.batching.admission import (
+    AdmissionLimit,
+    BatchAdmissionController,
+    BatchingRule,
+    load_batching_config,
+)
+from fastvideo.configs.pipelines.base import PipelineConfig
+
+
+def test_admission_limit_rejects_batch_size_and_cost() -> None:
+    limit = AdmissionLimit(max_batch_size=2, max_cost=10.0)
+
+    assert limit.reject_reason(batch_size=3, batch_cost=1.0) == "config_cap:2"
+    assert limit.reject_reason(batch_size=2, batch_cost=11.0) == "cost_budget:11>10"
+    assert limit.reject_reason(batch_size=2, batch_cost=10.0) is None
+
+
+def test_batching_rule_validates_unknown_keys() -> None:
+    with pytest.raises(ValueError, match="did you mean 'max_batch_size'"):
+        BatchingRule.from_dict(
+            {
+                "model_contains": "wan",
+                "max_batch_siz": 2,
+            },
+            source="unit",
+        )
+
+
+@pytest.mark.parametrize(("value", "expected"), [(1, True), (0, False), (1.0, True), (0.0, False)])
+def test_batching_rule_parses_numeric_bool_values(value, expected) -> None:
+    rule = BatchingRule.from_dict(
+        {
+            "model_contains": "wan",
+            "offload": value,
+            "max_batch_size": 2,
+        },
+        source="unit",
+    )
+
+    assert rule.offload is expected
+
+
+def test_load_batching_config_supports_mapping_form(tmp_path) -> None:
+    path = tmp_path / "batching.json"
+    path.write_text(
+        '{"schema_version": 1, "wan|720x1280x81": {"max_batch_size": 3, "max_cost": 9}}',
+        encoding="utf-8",
+    )
+
+    rules = load_batching_config(str(path))
+
+    assert len(rules) == 1
+    assert rules[0].model == "wan"
+    assert rules[0].resolution == "720x1280x81"
+    assert rules[0].max_batch_size == 3
+    assert rules[0].max_cost == 9.0
+
+
+def test_admission_controller_applies_user_and_config_caps(tmp_path, monkeypatch) -> None:
+    path = tmp_path / "batching.json"
+    path.write_text(
+        '{"rules": [{"model_contains": "wan", "resolution": "720x1280x81", "max_batch_size": 3}]}',
+        encoding="utf-8",
+    )
+    monkeypatch.setattr(BatchAdmissionController, "_get_device_memory_gb", staticmethod(lambda gpu_id: 48.0))
+
+    args = SimpleNamespace(
+        batching_mode="dynamic",
+        batching_max_size=4,
+        batching_config=str(path),
+        model_path="/models/wan",
+        dit_cpu_offload=False,
+        dit_layerwise_offload=False,
+        pipeline_config=PipelineConfig(),
+    )
+    request = SimpleNamespace(height=720, width=1280, num_frames=81)
+
+    controller = BatchAdmissionController(args)
+
+    assert controller.enabled is True
+    assert controller.max_admissible_batch_size(request) == 3
+    assert controller.batch_is_full([request, request, request]) is True

fastvideo/tests/batching/test_signature.py

@@ -0,0 +1,57 @@
+# SPDX-License-Identifier: Apache-2.0
+from __future__ import annotations
+
+from fastvideo.api.sampling_param import SamplingParam
+from fastvideo.batching.signature import (
+    can_dynamic_batch,
+    dynamic_batch_signature,
+    resolution_key,
+)
+
+
+def _request(prompt: str = "a prompt", **overrides) -> SamplingParam:
+    request = SamplingParam(prompt=prompt, height=256, width=384, num_frames=17, num_inference_steps=4)
+    for key, value in overrides.items():
+        setattr(request, key, value)
+    return request
+
+
+def test_dynamic_batch_signature_excludes_request_local_fields() -> None:
+    first = _request(seed=1, output_path="/tmp/a.mp4", save_video=True, return_frames=False)
+    second = _request(seed=2, output_path="/tmp/b.mp4", save_video=False, return_frames=True)
+
+    assert dynamic_batch_signature(first) == dynamic_batch_signature(second)
+
+
+def test_can_dynamic_batch_accepts_matching_text_requests() -> None:
+    first = _request("first", seed=1)
+    second = _request("second", seed=2)
+
+    result = can_dynamic_batch(first, second)
+
+    assert result.can_batch is True
+    assert result.reason is None
+
+
+def test_can_dynamic_batch_rejects_sampling_mismatch() -> None:
+    first = _request(guidance_scale=1.0)
+    second = _request(guidance_scale=3.0)
+
+    result = can_dynamic_batch(first, second)
+
+    assert result.can_batch is False
+    assert result.reason == "sampling_params.guidance_scale"
+
+
+def test_can_dynamic_batch_rejects_image_conditioning() -> None:
+    first = _request()
+    second = _request(image_path="/tmp/image.png")
+
+    result = can_dynamic_batch(first, second)
+
+    assert result.can_batch is False
+    assert result.reason == "image_path"
+
+
+def test_resolution_key_uses_generation_shape() -> None:
+    assert resolution_key(_request(height=720, width=1280, num_frames=81)) == "720x1280x81"

fastvideo/tests/entrypoints/test_openai_api.py

@@ -1,10 +1,15 @@
 """Unit tests for the OpenAI-compatible API server helpers (no GPU needed)."""
 
+import asyncio
 import os
+import time
+from types import SimpleNamespace
 from unittest.mock import patch
 
 import pytest
 
+from fastvideo.configs.pipelines.base import PipelineConfig
+from fastvideo.entrypoints.openai.batching import VideoBatchScheduler, _VideoBatchJob
 from fastvideo.api.parser import parse_config
 from fastvideo.api.schema import GenerationRequest
 from fastvideo.entrypoints.openai.protocol import (
@@ -21,6 +26,172 @@ from fastvideo.entrypoints.openai.utils import (
     parse_size,
 )
 
+
+class _FakeBatchGenerator:
+
+    def __init__(self):
+        self.calls = []
+
+    def generate_video_batch(self, request_kwargs):
+        self.calls.append([dict(item) for item in request_kwargs])
+        return [{"prompts": item["prompt"], "video_path": item["output_path"]} for item in request_kwargs]
+
+
+def _make_batch_job(request_id, kwargs):
+    loop = asyncio.get_running_loop()
+    return _VideoBatchJob(
+        request_id=request_id,
+        kwargs=dict(kwargs),
+        future=loop.create_future(),
+        enqueue_time=time.perf_counter(),
+    )
+
+
+def _batch_scheduler_args(**overrides):
+    defaults = dict(
+        model_path="test-model",
+        batching_mode="dynamic",
+        batching_max_size=2,
+        batching_delay_ms=25.0,
+        enable_batching_metrics=False,
+        pipeline_config=PipelineConfig(),
+    )
+    defaults.update(overrides)
+    return SimpleNamespace(**defaults)
+
+
+def test_video_batch_scheduler_groups_compatible_requests(tmp_path):
+    async def run():
+        generator = _FakeBatchGenerator()
+        scheduler = VideoBatchScheduler(generator, _batch_scheduler_args())
+        await scheduler.start()
+        try:
+            first = {
+                "prompt": "first",
+                "height": 256,
+                "width": 256,
+                "num_frames": 1,
+                "num_inference_steps": 2,
+                "seed": 1,
+                "output_path": str(tmp_path / "first.mp4"),
+                "save_video": False,
+            }
+            second = {
+                "prompt": "second",
+                "height": 256,
+                "width": 256,
+                "num_frames": 1,
+                "num_inference_steps": 2,
+                "seed": 2,
+                "output_path": str(tmp_path / "second.mp4"),
+                "save_video": False,
+            }
+            results = await asyncio.gather(
+                scheduler.submit("req-1", first),
+                scheduler.submit("req-2", second),
+            )
+        finally:
+            await scheduler.stop()
+        return generator.calls, results
+
+    calls, results = asyncio.run(run())
+
+    assert len(calls) == 1
+    assert [item["prompt"] for item in calls[0]] == ["first", "second"]
+    assert [result["prompts"] for result in results] == ["first", "second"]
+
+
+def test_video_batch_scheduler_keeps_incompatible_requests_separate(tmp_path):
+    async def run():
+        generator = _FakeBatchGenerator()
+        scheduler = VideoBatchScheduler(generator, _batch_scheduler_args())
+        await scheduler.start()
+        try:
+            text_only = {
+                "prompt": "first",
+                "height": 256,
+                "width": 256,
+                "num_frames": 1,
+                "num_inference_steps": 2,
+                "seed": 1,
+                "output_path": str(tmp_path / "first.mp4"),
+                "save_video": False,
+            }
+            image_conditioned = {
+                "prompt": "second",
+                "height": 256,
+                "width": 256,
+                "num_frames": 1,
+                "num_inference_steps": 2,
+                "seed": 2,
+                "image_path": str(tmp_path / "input.png"),
+                "output_path": str(tmp_path / "second.mp4"),
+                "save_video": False,
+            }
+            results = await asyncio.gather(
+                scheduler.submit("req-1", text_only),
+                scheduler.submit("req-2", image_conditioned),
+            )
+        finally:
+            await scheduler.stop()
+        return generator.calls, results
+
+    calls, results = asyncio.run(run())
+
+    assert len(calls) == 2
+    assert [[item["prompt"] for item in call] for call in calls] == [["first"], ["second"]]
+    assert [result["prompts"] for result in results] == ["first", "second"]
+
+
+def test_video_batch_scheduler_requeues_incompatible_pending_job_at_front(tmp_path):
+    async def run():
+        generator = _FakeBatchGenerator()
+        scheduler = VideoBatchScheduler(generator, _batch_scheduler_args())
+        first = {
+            "prompt": "first",
+            "height": 256,
+            "width": 256,
+            "num_frames": 1,
+            "num_inference_steps": 2,
+            "seed": 1,
+            "output_path": str(tmp_path / "first.mp4"),
+            "save_video": False,
+        }
+        incompatible = {
+            "prompt": "second",
+            "height": 256,
+            "width": 256,
+            "num_frames": 1,
+            "num_inference_steps": 2,
+            "seed": 2,
+            "image_path": str(tmp_path / "input.png"),
+            "output_path": str(tmp_path / "second.mp4"),
+            "save_video": False,
+        }
+        newer = {
+            "prompt": "third",
+            "height": 256,
+            "width": 256,
+            "num_frames": 1,
+            "num_inference_steps": 2,
+            "seed": 3,
+            "output_path": str(tmp_path / "third.mp4"),
+            "save_video": False,
+        }
+
+        scheduler._pending.extend([
+            _make_batch_job("req-2", incompatible),
+            _make_batch_job("req-3", newer),
+        ])
+        batch = await scheduler._collect_batch(_make_batch_job("req-1", first))
+        return [job.request_id for job in batch], [job.request_id for job in scheduler._pending]
+
+    batch_ids, pending_ids = asyncio.run(run())
+
+    assert batch_ids == ["req-1"]
+    assert pending_ids == ["req-2", "req-3"]
+
+
 # ---------------------------------------------------------------------------
 # parse_size
 # ---------------------------------------------------------------------------

fastvideo/tests/entrypoints/test_video_generator.py

@@ -3,6 +3,7 @@ from types import SimpleNamespace
 import warnings
 
 import pytest
+import torch
 
 from fastvideo.api import (
     GenerationRequest,
@@ -13,8 +14,10 @@ from fastvideo.api import (
     load_run_config,
 )
 from fastvideo.api.sampling_param import SamplingParam
+from fastvideo.configs.pipelines.base import PipelineConfig
 from fastvideo.entrypoints.video_generator import VideoGenerator
 from fastvideo.fastvideo_args import WorkloadType
+from fastvideo.pipelines import ForwardBatch
 
 
 def _new_video_generator() -> VideoGenerator:
@@ -37,6 +40,25 @@ def _new_runtime_video_generator() -> VideoGenerator:
     return generator
 
 
+def _batching_fastvideo_args(**overrides):
+    defaults = dict(
+        model_path="test-model",
+        prompt_txt=None,
+        workload_type=SimpleNamespace(value="t2v"),
+        batching_mode="dynamic",
+        batching_max_size=4,
+        batching_config=None,
+        dit_cpu_offload=False,
+        dit_layerwise_offload=False,
+        output_type="latent",
+        pin_cpu_memory=False,
+        VSA_sparsity=0.0,
+        pipeline_config=PipelineConfig(),
+    )
+    defaults.update(overrides)
+    return SimpleNamespace(**defaults)
+
+
 def _patch_from_fastvideo_args(monkeypatch):
     captured = {}
 
@@ -151,6 +173,117 @@ def test_prepare_output_path_empty_prompt_fallback(tmp_path):
     assert os.path.basename(result) == "output.mp4"
 
 
+def test_generate_prepared_work_items_merges_compatible_latent_requests(monkeypatch, tmp_path):
+    vg = _new_video_generator()
+    vg.fastvideo_args = _batching_fastvideo_args()
+    calls = []
+
+    def fake_device_memory(gpu_id):
+        return 48.0
+
+    def fake_run_forward(batch, fastvideo_args):
+        calls.append(batch)
+        batch_size = len(batch.prompt) if isinstance(batch.prompt, list) else 1
+        output = torch.arange(batch_size * 4, dtype=torch.float32).reshape(batch_size, 4, 1, 1, 1)
+        return ForwardBatch(data_type=batch.data_type, output=output, extra={"peak_memory_mb": 1.0}), 0.5, 10.0
+
+    monkeypatch.setattr(
+        "fastvideo.batching.admission.BatchAdmissionController._get_device_memory_gb",
+        staticmethod(fake_device_memory),
+    )
+    monkeypatch.setattr(vg, "_run_forward_batch", fake_run_forward)
+
+    first = SamplingParam(prompt="one", height=8, width=8, num_frames=1, seed=11, return_frames=True, save_video=False)
+    second = SamplingParam(prompt="two", height=8, width=8, num_frames=1, seed=22, return_frames=True, save_video=False)
+    work_items = [
+        vg._prepare_generation_work_item("one", first, vg.fastvideo_args, output_path=str(tmp_path / "one.mp4")),
+        vg._prepare_generation_work_item("two", second, vg.fastvideo_args, output_path=str(tmp_path / "two.mp4")),
+    ]
+
+    results = vg._generate_prepared_work_items(work_items)
+
+    assert len(calls) == 1
+    assert calls[0].prompt == ["one", "two"]
+    assert calls[0].seeds == [11, 22]
+    assert [result["prompts"] for result in results] == ["one", "two"]
+    assert [result["samples"].shape for result in results] == [(1, 4, 1, 1, 1), (1, 4, 1, 1, 1)]
+
+
+def test_generate_prepared_work_items_falls_back_for_incompatible_requests(monkeypatch, tmp_path):
+    vg = _new_video_generator()
+    vg.fastvideo_args = _batching_fastvideo_args()
+    calls = []
+
+    def fake_run_forward(batch, fastvideo_args):
+        calls.append(batch)
+        output = torch.zeros((1, 4, 1, 1, 1), dtype=torch.float32)
+        return ForwardBatch(data_type=batch.data_type, output=output), 0.5, 10.0
+
+    monkeypatch.setattr(vg, "_run_forward_batch", fake_run_forward)
+
+    first = SamplingParam(prompt="one", height=8, width=8, num_frames=1, guidance_scale=1.0, save_video=False)
+    second = SamplingParam(prompt="two", height=8, width=8, num_frames=1, guidance_scale=3.0, save_video=False)
+    work_items = [
+        vg._prepare_generation_work_item("one", first, vg.fastvideo_args, output_path=str(tmp_path / "one.mp4")),
+        vg._prepare_generation_work_item("two", second, vg.fastvideo_args, output_path=str(tmp_path / "two.mp4")),
+    ]
+
+    results = vg._generate_prepared_work_items(work_items)
+
+    assert len(calls) == 2
+    assert all(isinstance(call.prompt, str) for call in calls)
+    assert [result["prompts"] for result in results] == ["one", "two"]
+
+
+def test_generate_video_batch_routes_compat_kwargs(monkeypatch, tmp_path):
+    vg = _new_video_generator()
+    vg.fastvideo_args = _batching_fastvideo_args()
+    calls = []
+
+    def fake_device_memory(gpu_id):
+        return 48.0
+
+    def fake_run_forward(batch, fastvideo_args):
+        calls.append((batch, fastvideo_args))
+        output = torch.zeros((len(batch.prompt), 4, 1, 1, 1), dtype=torch.float32)
+        return ForwardBatch(data_type=batch.data_type, output=output), 0.5, 10.0
+
+    monkeypatch.setattr(
+        "fastvideo.batching.admission.BatchAdmissionController._get_device_memory_gb",
+        staticmethod(fake_device_memory),
+    )
+    monkeypatch.setattr(vg, "_run_forward_batch", fake_run_forward)
+
+    results = vg.generate_video_batch([
+        {
+            "prompt": "one",
+            "height": 8,
+            "width": 8,
+            "num_frames": 1,
+            "embedded_cfg_scale": 7.5,
+            "save_video": False,
+            "return_frames": True,
+            "output_path": str(tmp_path / "one.mp4"),
+        },
+        {
+            "prompt": "two",
+            "height": 8,
+            "width": 8,
+            "num_frames": 1,
+            "embedded_cfg_scale": 7.5,
+            "save_video": False,
+            "return_frames": True,
+            "output_path": str(tmp_path / "two.mp4"),
+        },
+    ])
+
+    assert len(calls) == 1
+    batch, fastvideo_args = calls[0]
+    assert batch.prompt == ["one", "two"]
+    assert fastvideo_args.pipeline_config.embedded_cfg_scale == 7.5
+    assert [result["prompts"] for result in results] == ["one", "two"]
+
+
 def test_from_config_normalizes_and_translates(monkeypatch):
     captured = _patch_from_fastvideo_args(monkeypatch)
     _patch_fastvideo_args_from_kwargs(monkeypatch)

fastvideo/tests/layers/test_rmsnorm_forward_dispatch.py

@@ -0,0 +1,203 @@
+# SPDX-License-Identifier: Apache-2.0
+
+from __future__ import annotations
+
+import argparse
+import json
+import os
+import subprocess
+from pathlib import Path
+from typing import Any
+
+import pytest
+import torch
+import torch.distributed as dist
+from torch.distributed import init_device_mesh
+from torch.distributed.fsdp import CPUOffloadPolicy, fully_shard
+from torch.distributed.tensor import DTensor
+
+from fastvideo.layers.layernorm import RMSNorm
+
+WORLD_SIZE = 2
+HIDDEN_SIZE = 8
+SEED = 1379
+REPO_ROOT = Path(__file__).resolve().parents[3]
+
+
+def _run_torchrun(script_path: Path, mode: str, output_path: Path) -> None:
+    # --standalone binds the rendezvous port atomically, avoiding the
+    # free-port-probe race a hand-picked --master_port would have.
+    cmd = [
+        "torchrun",
+        "--standalone",
+        "--nproc_per_node",
+        str(WORLD_SIZE),
+        str(script_path),
+        "--rmsnorm-fsdp-worker",
+        "--mode",
+        mode,
+        "--output",
+        str(output_path),
+    ]
+    env = os.environ.copy()
+    env.setdefault("TORCHDYNAMO_DISABLE", "1")
+    try:
+        process = subprocess.run(
+            cmd,
+            capture_output=True,
+            text=True,
+            env=env,
+            timeout=120,
+        )
+    except subprocess.TimeoutExpired as error:
+        raise RuntimeError(
+            f"{mode} worker timed out after 120 seconds\n"
+            f"STDOUT:\n{error.stdout}\n"
+            f"STDERR:\n{error.stderr}"
+        ) from error
+    if process.returncode != 0:
+        raise RuntimeError(
+            f"{mode} worker failed with code {process.returncode}\n"
+            f"STDOUT:\n{process.stdout}\n"
+            f"STDERR:\n{process.stderr}"
+        )
+
+
+def _summarize_tensor(tensor: torch.Tensor | Any) -> dict[str, Any]:
+    return {
+        "type": type(tensor).__name__,
+        "is_dtensor": isinstance(tensor, DTensor),
+        "shape": list(tensor.shape) if hasattr(tensor, "shape") else None,
+        "device": str(tensor.device) if hasattr(tensor, "device") else None,
+        "dtype": str(tensor.dtype) if hasattr(tensor, "dtype") else None,
+    }
+
+
+def _run_worker(mode: str, output_path: Path) -> None:
+    if mode not in {
+        "module_no_offload",
+        "direct_no_offload",
+        "module_cpu_offload",
+        "direct_cpu_offload",
+    }:
+        raise ValueError(f"Unsupported mode: {mode}")
+
+    dist.init_process_group("nccl")
+    rank = dist.get_rank()
+    world_size = dist.get_world_size()
+    local_rank = int(os.environ.get("LOCAL_RANK", "0"))
+    device = torch.device(f"cuda:{local_rank}")
+    torch.cuda.set_device(device)
+    torch.manual_seed(SEED + rank)
+
+    try:
+        mesh = init_device_mesh("cuda", (world_size,))
+        norm = RMSNorm(HIDDEN_SIZE, eps=1e-6, has_weight=True).to(device)
+        with torch.no_grad():
+            norm.weight.fill_(1.0)
+
+        fsdp_kwargs: dict[str, Any] = {"mesh": mesh}
+        if mode.endswith("cpu_offload"):
+            fsdp_kwargs["offload_policy"] = CPUOffloadPolicy(pin_memory=False)
+        # fully_shard is applied to the bare RMSNorm to make the hook bypass
+        # observable. Production sharding (fsdp_load.shard_model) only wraps
+        # whole transformer blocks, whose pre-forward all-gather localizes norm
+        # weights before the qk-norm call sites run, so this pins the dispatch
+        # invariant rather than reproducing a production topology.
+        fully_shard(norm, **fsdp_kwargs)
+
+        x = torch.randn(2, 3, HIDDEN_SIZE, device=device, dtype=torch.bfloat16)
+        call_kind = "direct" if mode.startswith("direct") else "module"
+
+        try:
+            if call_kind == "direct":
+                output = norm.forward_native(x)
+            else:
+                output = norm(x)
+            torch.cuda.synchronize(device)
+            result = {
+                "rank": rank,
+                "ok": True,
+                "mode": mode,
+                "weight": _summarize_tensor(norm.weight),
+                "output": _summarize_tensor(output),
+            }
+        except Exception as exc:
+            result = {
+                "rank": rank,
+                "ok": False,
+                "mode": mode,
+                "error_type": type(exc).__name__,
+                "error": str(exc),
+                "weight": _summarize_tensor(norm.weight),
+            }
+
+        gathered = [None for _ in range(world_size)] if rank == 0 else None
+        dist.gather_object(result, object_gather_list=gathered, dst=0)
+        if rank == 0:
+            output_path.write_text(json.dumps(gathered, indent=2), encoding="utf-8")
+        dist.barrier()
+    finally:
+        dist.destroy_process_group()
+
+
+@pytest.mark.parametrize(
+    ("mode", "expect_ok"),
+    [
+        ("module_no_offload", True),
+        ("direct_no_offload", False),
+        ("module_cpu_offload", True),
+        ("direct_cpu_offload", False),
+    ],
+)
+def test_rmsnorm_forward_native_bypasses_fsdp_hooks(mode: str, expect_ok: bool, tmp_path: Path) -> None:
+    if not torch.cuda.is_available():
+        pytest.skip("This test requires CUDA.")
+    if torch.cuda.device_count() < WORLD_SIZE:
+        pytest.skip(f"This test requires at least {WORLD_SIZE} CUDA devices.")
+
+    output_path = tmp_path / f"{mode}.json"
+    _run_torchrun(Path(__file__).resolve(), mode, output_path)
+    results = json.loads(output_path.read_text(encoding="utf-8"))
+    print(f"\n{mode} results:\n{json.dumps(results, indent=2)}")
+
+    if expect_ok:
+        failures = [result for result in results if not result["ok"]]
+        assert not failures, json.dumps(results, indent=2)
+        return
+
+    successes = [result for result in results if result["ok"]]
+    assert not successes, json.dumps(results, indent=2)
+    error_text = "\n".join(result.get("error", "") for result in results)
+    # Pin the specific bypassed-hook failure: "got mixed torch.Tensor and
+    # DTensor" ("Tensor" alone is a substring of "DTensor", so it adds nothing).
+    assert "mixed" in error_text and "DTensor" in error_text, json.dumps(results, indent=2)
+
+
+def test_no_direct_forward_native_calls_in_models() -> None:
+    """Direct .forward_native(...) calls bypass nn.Module.__call__ and FSDP
+    hooks (issue #1379); model code must use module dispatch instead."""
+    models_dir = REPO_ROOT / "fastvideo" / "models"
+    offenders = [
+        str(path.relative_to(REPO_ROOT))
+        for path in sorted(models_dir.rglob("*.py"))
+        if ".forward_native(" in path.read_text(encoding="utf-8")
+    ]
+    assert not offenders, f"Replace .forward_native(...) with module dispatch in: {offenders}"
+
+
+def _parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--rmsnorm-fsdp-worker", action="store_true")
+    parser.add_argument("--mode", type=str, default=None)
+    parser.add_argument("--output", type=str, default=None)
+    return parser.parse_args()
+
+
+if __name__ == "__main__":
+    args = _parse_args()
+    if not args.rmsnorm_fsdp_worker:
+        raise SystemExit("This module is intended to be run by pytest.")
+    if args.mode is None or args.output is None:
+        raise SystemExit("--mode and --output are required in worker mode.")
+    _run_worker(mode=args.mode, output_path=Path(args.output))

fastvideo/tests/modal/launch_l40s_job.py

@@ -32,7 +32,8 @@ import modal
 
 sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
 try:
-    from modal_image_utils import resolve_image_ref  # noqa: E402
+    from modal_image_utils import (  # noqa: E402
+        resolve_image_ref, resolve_uv_torch_backend)
 except ModuleNotFoundError:
     # Remote Modal containers re-import this module but mount only the
     # entrypoint file; the digest resolution already happened at local
@@ -40,6 +41,9 @@ except ModuleNotFoundError:
     def resolve_image_ref(image_ref: str) -> str:
         return image_ref
 
+    def resolve_uv_torch_backend(image_tag: str) -> str | None:
+        return os.environ.get("UV_TORCH_BACKEND")
+
 app = modal.App("fastvideo-gpu-job")
 
 REPO_DIR = "/FastVideo"
@@ -72,12 +76,7 @@ local_secrets = modal.Secret.from_dict({
 # Mutable tags inherit the registry image's baked backend, including custom
 # FASTVIDEO_MODAL_IMAGE overrides. Explicit CUDA tags also work with older
 # images that predate the baked setting, and a caller override always wins.
-uv_torch_backend_override = os.environ.get("UV_TORCH_BACKEND")
-if not uv_torch_backend_override:
-    if "cuda13" in IMAGE_TAG.lower():
-        uv_torch_backend_override = "cu130"
-    elif "cuda12.6" in IMAGE_TAG.lower():
-        uv_torch_backend_override = "cu126"
+uv_torch_backend_override = resolve_uv_torch_backend(IMAGE_TAG)
 
 image = (
     modal.Image.from_registry(IMAGE_REF, add_python="3.12")
@@ -98,6 +97,9 @@ image = (
         "TOKENIZERS_PARALLELISM": "false",
         **({"UV_TORCH_BACKEND": uv_torch_backend_override} if uv_torch_backend_override else {}),
         "FASTVIDEO_ATTENTION_BACKEND": os.environ.get("FASTVIDEO_ATTENTION_BACKEND", "FLASH_ATTN"),
+        # FA4 is opt-in (FASTVIDEO_FA4); keep CI parity with the seeded
+        # references. Caller override wins.
+        "FASTVIDEO_FA4": os.environ.get("FASTVIDEO_FA4", "1"),
     })
 )
 

fastvideo/tests/modal/modal_image_utils.py

@@ -5,6 +5,7 @@ through the ``fastvideo`` package, so they keep working on thin CI hosts that
 have ``modal`` but not torch.
 """
 import json
+import os
 import urllib.request
 
 _REGISTRY = "ghcr.io"
@@ -55,3 +56,23 @@ def resolve_image_ref(image_ref: str) -> str:
         print(f"WARNING: could not resolve {image_ref} to a digest ({error}); "
               "Modal may reuse a stale cached image for this tag.")
     return image_ref
+
+
+def resolve_uv_torch_backend(image_tag: str) -> str | None:
+    """UV_TORCH_BACKEND for a launcher image tag.
+
+    A caller-set UV_TORCH_BACKEND always wins. Otherwise sniff the CUDA
+    version from an explicit image tag (cuda13 -> cu130, cuda12.6 -> cu126)
+    so uv resolves torch against the image's toolkit. Mutable tags (e.g.
+    py3.12-latest) return None and inherit the registry image's baked
+    backend, which keeps a latest-tag CUDA transition safe.
+    """
+    override = os.environ.get("UV_TORCH_BACKEND")
+    if override:
+        return override
+    tag = image_tag.lower()
+    if "cuda13" in tag:
+        return "cu130"
+    if "cuda12.6" in tag:
+        return "cu126"
+    return None

fastvideo/tests/modal/pr_test.py

@@ -5,7 +5,8 @@ import modal
 
 sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
 try:
-    from modal_image_utils import resolve_image_ref  # noqa: E402
+    from modal_image_utils import (  # noqa: E402
+        resolve_image_ref, resolve_uv_torch_backend)
 except ModuleNotFoundError:
     # Remote Modal containers re-import this module but mount only the
     # entrypoint file; the digest resolution already happened at local
@@ -13,6 +14,9 @@ except ModuleNotFoundError:
     def resolve_image_ref(image_ref: str) -> str:
         return image_ref
 
+    def resolve_uv_torch_backend(image_tag: str) -> str | None:
+        return os.environ.get("UV_TORCH_BACKEND")
+
 app = modal.App()
 
 model_vol = modal.Volume.from_name("hf-model-weights")
@@ -24,12 +28,7 @@ print(f"Using image: {image_ref}")
 # Mutable tags inherit the registry image's baked backend, keeping a latest-tag
 # transition safe. Explicit CUDA tags also work with older images that predate
 # the baked setting, and a caller override always wins.
-uv_torch_backend_override = os.environ.get("UV_TORCH_BACKEND")
-if not uv_torch_backend_override:
-    if "cuda13" in image_tag.lower():
-        uv_torch_backend_override = "cu130"
-    elif "cuda12.6" in image_tag.lower():
-        uv_torch_backend_override = "cu126"
+uv_torch_backend_override = resolve_uv_torch_backend(image_tag)
 
 image = (modal.Image.from_registry(
     image_ref, add_python="3.12"
@@ -61,6 +60,10 @@ image = (modal.Image.from_registry(
     **({
         "UV_TORCH_BACKEND": uv_torch_backend_override
     } if uv_torch_backend_override else {}),
+    # FA4 is opt-in (FASTVIDEO_FA4); CI lanes keep it enabled to match the
+    # SSIM/perf baselines. Caller override wins.
+    "FASTVIDEO_FA4":
+    os.environ.get("FASTVIDEO_FA4", "1"),
     "HF_REPO_ID":
     "FastVideo/performance-tracking",
 }))
@@ -273,7 +276,7 @@ def run_self_forcing_tests():
 @app.function(gpu="L40S:1", image=image, timeout=900)
 def run_unit_test():
     run_test(
-        "pytest ./fastvideo/tests/api/ ./fastvideo/tests/contract/ ./fastvideo/tests/dataset/ ./fastvideo/tests/workflow/ ./fastvideo/tests/entrypoints/ ./fastvideo/tests/train/ --ignore=./fastvideo/tests/entrypoints/test_openai_api_integration.py --ignore=./fastvideo/tests/train/models --ignore=./fastvideo/tests/train/methods -vs"
+        "pytest ./fastvideo/tests/api/ ./fastvideo/tests/batching/ ./fastvideo/tests/contract/ ./fastvideo/tests/dataset/ ./fastvideo/tests/workflow/ ./fastvideo/tests/entrypoints/ ./fastvideo/tests/train/ ./fastvideo/tests/stages/ --ignore=./fastvideo/tests/entrypoints/test_openai_api_integration.py --ignore=./fastvideo/tests/train/models --ignore=./fastvideo/tests/train/methods -vs"
     )
 
 

fastvideo/tests/modal/ssim_test.py

@@ -13,7 +13,8 @@ import modal
 
 sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
 try:
-    from modal_image_utils import resolve_image_ref  # noqa: E402
+    from modal_image_utils import (  # noqa: E402
+        resolve_image_ref, resolve_uv_torch_backend)
 except ModuleNotFoundError:
     # Remote Modal containers re-import this module but mount only the
     # entrypoint file; the digest resolution already happened at local
@@ -21,6 +22,9 @@ except ModuleNotFoundError:
     def resolve_image_ref(image_ref: str) -> str:
         return image_ref
 
+    def resolve_uv_torch_backend(image_tag: str) -> str | None:
+        return os.environ.get("UV_TORCH_BACKEND")
+
 app = modal.App()
 
 model_vol = modal.Volume.from_name("hf-model-weights")
@@ -32,12 +36,7 @@ print(f"Using image: {image_ref}")
 # Mutable tags inherit the registry image's baked backend, keeping a latest-tag
 # transition safe. Explicit CUDA tags also work with older images that predate
 # the baked setting, and a caller override always wins.
-uv_torch_backend_override = os.environ.get("UV_TORCH_BACKEND")
-if not uv_torch_backend_override:
-    if "cuda13" in image_tag.lower():
-        uv_torch_backend_override = "cu130"
-    elif "cuda12.6" in image_tag.lower():
-        uv_torch_backend_override = "cu126"
+uv_torch_backend_override = resolve_uv_torch_backend(image_tag)
 
 image = (
     modal.Image.from_registry(image_ref, add_python="3.12")
@@ -64,6 +63,9 @@ image = (
             "BUILDKITE_PULL_REQUEST": os.environ.get("BUILDKITE_PULL_REQUEST", ""),
             "IMAGE_VERSION": image_version,
             **({"UV_TORCH_BACKEND": uv_torch_backend_override} if uv_torch_backend_override else {}),
+            # FA4 is opt-in (FASTVIDEO_FA4); the SSIM references were seeded
+            # with FA4 inference, so keep it enabled in CI. Caller override wins.
+            "FASTVIDEO_FA4": os.environ.get("FASTVIDEO_FA4", "1"),
         }
     )
 )

fastvideo/tests/performance/compare_baseline.py

@@ -8,8 +8,8 @@ This script:
    baseline-eligible successful records (filtered by gpu_type),
 4) writes normalized records back to the HF dataset repo according to
    PERF_UPLOAD_POLICY,
-5) exits non-zero if any metric regresses by more than PERF_MAX_REGRESSION
-   (default 5%).
+5) exits non-zero if any gated metric exceeds both its percent and absolute
+   regression floors.
 """
 
 import glob
@@ -21,21 +21,36 @@ from datetime import datetime, timezone
 from typing import Any
 
 try:
-    from .hf_store import (
+    from fastvideo.performance.hf_store import (
         load_records_for_model,
         safe_float,
         sanitize,
         sync_from_hf,
         upload_record,
     )
+    from fastvideo.performance.metric_policy import (
+        MetricPolicy,
+        regression_delta,
+        resolve_metric_policies,
+        serialize_metric_thresholds,
+    )
 except ImportError:
-    from hf_store import (
+    repo_root = os.path.abspath(os.path.join(os.path.dirname(__file__), "../../.."))
+    if repo_root not in sys.path:
+        sys.path.insert(0, repo_root)
+    from fastvideo.performance.hf_store import (
         load_records_for_model,
         safe_float,
         sanitize,
         sync_from_hf,
         upload_record,
     )
+    from fastvideo.performance.metric_policy import (
+        MetricPolicy,
+        regression_delta,
+        resolve_metric_policies,
+        serialize_metric_thresholds,
+    )
 
 RESULTS_DIR = os.path.join(
     os.path.dirname(os.path.abspath(__file__)),
@@ -46,25 +61,9 @@ TRACKING_ROOT = os.environ.get(
     "/tmp/perf-tracking",
 )
 PERF_REPORTS_DIR = os.environ.get("PERF_REPORTS_DIR", "/root/data/perf_reports")
-MAX_REGRESSION = float(os.environ.get("PERF_MAX_REGRESSION", "0.05"))
 UPLOAD_POLICY = os.environ.get("PERF_UPLOAD_POLICY", "never").strip().lower()
 VALID_UPLOAD_POLICIES = {"never", "pass", "always"}
 VALID_RUN_SOURCES = {"pr", "local", "scheduled_main", "unknown"}
-METRICS = (
-    ("latency", "Latency", 3),
-    ("throughput", "Throughput", 3),
-    ("memory", "Memory", 1),
-    ("text_encoder_time_s", "Text Enc", 3),
-    ("dit_time_s", "DiT", 3),
-    ("vae_decode_time_s", "VAE Decode", 3),
-)
-LOWER_IS_BETTER_METRICS = {
-    "latency",
-    "memory",
-    "text_encoder_time_s",
-    "dit_time_s",
-    "vae_decode_time_s",
-}
 
 
 def _should_persist_tracking() -> bool:
@@ -168,6 +167,7 @@ def normalize_performance_result(result: dict[str, Any]) -> dict[str, Any]:
     text_encoder_time = safe_float(result.get("text_encoder_time_s"))
     dit_time = safe_float(result.get("dit_time_s"))
     vae_decode_time = safe_float(result.get("vae_decode_time_s"))
+    metric_policies = resolve_metric_policies(result.get("regression_thresholds"))
 
     return {
         "model_id": model_id,
@@ -180,6 +180,7 @@ def normalize_performance_result(result: dict[str, Any]) -> dict[str, Any]:
         "text_encoder_time_s": text_encoder_time,
         "dit_time_s": dit_time,
         "vae_decode_time_s": vae_decode_time,
+        "regression_thresholds": serialize_metric_thresholds(metric_policies),
         "success": True,
         **_record_metadata(_detect_run_source(), result),
     }
@@ -229,55 +230,41 @@ def _baseline_metric(records: list[dict[str, Any]], key: str) -> float | None:
     return statistics.median(values)
 
 
+def _metric_policy_summary(policy: MetricPolicy) -> str:
+    gated = "gated" if policy.gated else "info"
+    return (
+        f"{gated}, >{policy.threshold_percent * 100:.1f}% "
+        f"and >{policy.threshold_absolute:.{policy.precision}f}"
+    )
+
+
 def _check_regressions(
     current: dict[str, Any],
     baseline_records: list[dict[str, Any]],
-    max_regression: float,
+    metric_policies: tuple[MetricPolicy, ...],
 ) -> list[str]:
     failures: list[str] = []
 
-    for metric, _label, _precision in METRICS:
-        if metric not in LOWER_IS_BETTER_METRICS:
+    for policy in metric_policies:
+        baseline = _baseline_metric(baseline_records, policy.key)
+        curr = safe_float(current.get(policy.key))
+        if baseline is None or curr is None:
             continue
-        baseline = _baseline_metric(baseline_records, metric)
-        curr = safe_float(current.get(metric))
-        if baseline is None or curr is None or baseline <= 0:
+        delta = regression_delta(policy, curr, baseline)
+        if delta is None or not delta.regressed:
             continue
-        regression = (curr - baseline) / baseline
-        if regression > max_regression:
-            failures.append(f"{current['model_id']} {metric} regressed by "
-                            f"{regression * 100:.1f}% "
-                            f"(current={curr:.3f}, baseline_median={baseline:.3f})")
-
-    baseline_tp = _baseline_metric(baseline_records, "throughput")
-    curr_tp = safe_float(current.get("throughput"))
-    if baseline_tp is not None and curr_tp is not None and baseline_tp > 0:
-        regression = (baseline_tp - curr_tp) / baseline_tp
-        if regression > max_regression:
-            failures.append(f"{current['model_id']} throughput regressed by "
-                            f"{regression * 100:.1f}% "
-                            f"(current={curr_tp:.3f}, baseline_median={baseline_tp:.3f})")
+        failures.append(
+            f"{current['model_id']} {policy.key} regressed by "
+            f"{delta.percent * 100:.1f}% and "
+            f"{delta.absolute:.{policy.precision}f} "
+            f"(current={curr:.{policy.precision}f}, "
+            f"baseline_median={baseline:.{policy.precision}f}, "
+            f"threshold={_metric_policy_summary(policy)})"
+        )
 
     return failures
 
 
-def _metric_delta_percent(
-    metric: str,
-    current: dict[str, Any],
-    baseline_records: list[dict[str, Any]],
-) -> float | None:
-    curr = safe_float(current.get(metric))
-    baseline = _baseline_metric(baseline_records, metric)
-    if curr is None or baseline is None or baseline <= 0:
-        return None
-
-    if metric in LOWER_IS_BETTER_METRICS:
-        return (curr - baseline) / baseline * 100.0
-    if metric == "throughput":
-        return (baseline - curr) / baseline * 100.0
-    return None
-
-
 def _compact_value(value: float | None, precision: int = 3) -> str:
     if value is None:
         return "n/a"
@@ -287,23 +274,42 @@ def _compact_value(value: float | None, precision: int = 3) -> str:
 def _build_summary_row(
     record: dict[str, Any],
     baseline_records: list[dict[str, Any]],
+    metric_policies: tuple[MetricPolicy, ...],
     has_failed: bool,
 ) -> dict[str, Any]:
     """Format a single benchmark result as a row for the Markdown table."""
 
-    metric_values: dict[str, dict[str, float | None]] = {}
+    metric_values: dict[str, dict[str, Any]] = {}
     regressions: list[float] = []
-    for metric, _label, _precision in METRICS:
-        curr = safe_float(record.get(metric))
-        baseline = _baseline_metric(baseline_records, metric)
-        regression = _metric_delta_percent(metric, record, baseline_records)
-        metric_values[metric] = {
+    failing_metrics: list[str] = []
+    threshold_exceeded_metrics: list[str] = []
+    for policy in metric_policies:
+        curr = safe_float(record.get(policy.key))
+        baseline = _baseline_metric(baseline_records, policy.key)
+        delta = (
+            regression_delta(policy, curr, baseline)
+            if curr is not None and baseline is not None
+            else None
+        )
+        regression = None if delta is None else delta.percent * 100.0
+        absolute_delta = None if delta is None else delta.absolute
+        metric_values[policy.key] = {
             "curr": curr,
             "base": baseline,
             "regression_pct": regression,
+            "absolute_delta": absolute_delta,
+            "threshold_percent": policy.threshold_percent * 100.0,
+            "threshold_absolute": policy.threshold_absolute,
+            "gated": policy.gated,
+            "threshold_exceeded": False if delta is None else delta.threshold_exceeded,
+            "regressed": False if delta is None else delta.regressed,
         }
         if regression is not None:
             regressions.append(regression)
+        if delta is not None and delta.threshold_exceeded:
+            threshold_exceeded_metrics.append(policy.key)
+        if delta is not None and delta.regressed:
+            failing_metrics.append(policy.key)
 
     worst_regression_pct = max(regressions) if regressions else None
 
@@ -313,40 +319,50 @@ def _build_summary_row(
         "baseline_n": len(baseline_records),
         "metrics": metric_values,
         "worst_regression_pct": worst_regression_pct,
+        "threshold_exceeded_metrics": threshold_exceeded_metrics,
+        "failing_metrics": failing_metrics,
         "failed": has_failed,
     }
 
 
 def _build_markdown_summary(
     summary_rows: list[dict[str, Any]],
-    max_regression: float,
+    metric_policies: tuple[MetricPolicy, ...],
 ) -> str:
     lines = [
         "## Performance Baseline Comparison",
         "",
-        f"Threshold: regressions greater than {max_regression * 100:.1f}% fail",
+        "Threshold: gated metrics fail only when both percent and absolute "
+        "regression floors are exceeded.",
         "",
         ("| Model | GPU | Baseline N | Latency (curr/base) | "
          "Throughput (curr/base) | Memory (curr/base) | "
          "Text Enc (curr/base) | DiT (curr/base) | "
-         "VAE Decode (curr/base) | Worst Regression | Status |"),
-        "|---|---|---:|---|---|---|---|---|---|---:|---|",
+         "VAE Decode (curr/base) | Worst Regression | Exceeded Metrics | "
+         "Failing Metrics | Status |"),
+        "|---|---|---:|---|---|---|---|---|---|---:|---|---|---|",
     ]
 
     for row in summary_rows:
         metric_cells = []
-        for metric, _label, precision in METRICS:
-            values = row["metrics"][metric]
-            metric_cells.append(f"{_compact_value(values['curr'], precision)} / "
-                                f"{_compact_value(values['base'], precision)}")
+        for policy in metric_policies:
+            values = row["metrics"][policy.key]
+            metric_cells.append(f"{_compact_value(values['curr'], policy.precision)} / "
+                                f"{_compact_value(values['base'], policy.precision)}")
 
         worst_reg = ("n/a" if row["worst_regression_pct"] is None else f"{row['worst_regression_pct']:.1f}%")
+        exceeded_metrics = (
+            ", ".join(row["threshold_exceeded_metrics"])
+            if row["threshold_exceeded_metrics"]
+            else "none"
+        )
+        failing_metrics = ", ".join(row["failing_metrics"]) if row["failing_metrics"] else "none"
         status = "FAIL" if row["failed"] else "PASS"
 
         lines.append(f"| {row['model_id']} | {row['gpu_type']} | "
                      f"{row['baseline_n']} | "
                      f"{' | '.join(metric_cells)} | "
-                     f"{worst_reg} | {status} |")
+                     f"{worst_reg} | {exceeded_metrics} | {failing_metrics} | {status} |")
 
     return "\n".join(lines) + "\n"
 
@@ -400,6 +416,7 @@ def main() -> int:
 
     for raw in current_results:
         record = _normalize_record(raw)
+        metric_policies = resolve_metric_policies(record.get("regression_thresholds"))
 
         baseline_records = load_records_for_model(
             TRACKING_ROOT,
@@ -416,7 +433,7 @@ def main() -> int:
             failures: list[str] = []
             record["success"] = True
         else:
-            failures = _check_regressions(record, baseline_records, MAX_REGRESSION)
+            failures = _check_regressions(record, baseline_records, metric_policies)
         if static_threshold_failed:
             failures.append(f"{record['model_id']} fixed-threshold phase failed "
                             f"(PERF_PYTEST_RC={os.environ.get('PERF_PYTEST_RC')})")
@@ -434,10 +451,10 @@ def main() -> int:
             print("Tracking upload skipped for "
                   f"{record['model_id']} ({record['run_source']}, success={record['success']})")
 
-        summary_rows.append(_build_summary_row(record, baseline_records, bool(failures)))
+        summary_rows.append(_build_summary_row(record, baseline_records, metric_policies, bool(failures)))
 
     commit_sha = os.environ.get("BUILDKITE_COMMIT", "unknown")[:7]
-    markdown = _build_markdown_summary(summary_rows, MAX_REGRESSION)
+    markdown = _build_markdown_summary(summary_rows, resolve_metric_policies(None))
     _emit_markdown_summary(markdown, commit_sha)
 
     if all_failures:

fastvideo/tests/performance/dashboard.py

@@ -1,12 +1,19 @@
 # SPDX-License-Identifier: Apache-2.0
 import os
+import sys
 from html import escape
 from datetime import datetime
 
 import plotly.express as px
 import pandas as pd
 
-from hf_store import sync_from_hf, load_as_dataframe
+try:
+    from fastvideo.performance.hf_store import load_as_dataframe, sync_from_hf
+except ImportError:
+    repo_root = os.path.abspath(os.path.join(os.path.dirname(__file__), "../../.."))
+    if repo_root not in sys.path:
+        sys.path.insert(0, repo_root)
+    from fastvideo.performance.hf_store import load_as_dataframe, sync_from_hf
 
 TRACKING_ROOT = os.environ.get(
     "PERFORMANCE_TRACKING_ROOT",

fastvideo/tests/performance/test_benchmark_config_validation.py

@@ -0,0 +1,116 @@
+# SPDX-License-Identifier: Apache-2.0
+
+import pytest
+
+from fastvideo.tests.performance.test_inference_performance import (
+    _benchmark_display_id,
+    _config_identity_metadata,
+    _is_v2_config,
+    _validate_benchmark_config,
+)
+
+
+def _v2_config():
+    return {
+        "benchmark_id": "wan-t2v-1.3b-2gpu",
+        "config_schema_version": 2,
+        "workload_id": "wan-t2v-1.3b",
+        "variant_id": "canonical",
+        "benchmark_version": 1,
+    }
+
+
+def test_v1_benchmark_config_without_schema_version_validates():
+    cfg = {
+        "benchmark_id": "legacy-benchmark",
+    }
+
+    _validate_benchmark_config(cfg, "legacy.json")
+
+    assert _is_v2_config(cfg) is False
+    assert _config_identity_metadata(cfg) == {}
+    assert _benchmark_display_id(cfg) == "legacy-benchmark"
+
+
+def test_v2_benchmark_config_identity_validates_and_is_preserved():
+    cfg = _v2_config()
+    cfg["quality_metadata"] = {"some": "data"}
+
+    _validate_benchmark_config(cfg, "wan.json")
+
+    assert _is_v2_config(cfg) is True
+    assert _config_identity_metadata(cfg) == {
+        "config_schema_version": 2,
+        "workload_id": "wan-t2v-1.3b",
+        "variant_id": "canonical",
+        "benchmark_version": 1,
+        "quality_metadata": {"some": "data"},
+    }
+
+
+def test_v2_benchmark_config_missing_identity_fields_fails_clearly():
+    cfg = _v2_config()
+    del cfg["variant_id"]
+    del cfg["benchmark_version"]
+
+    expected = "wan.json: missing required v2 identity fields: variant_id, benchmark_version"
+    with pytest.raises(ValueError, match=expected):
+        _validate_benchmark_config(cfg, "wan.json")
+
+
+@pytest.mark.parametrize(
+    ("field", "value"),
+    [
+        ("workload_id", {}),
+        ("workload_id", ""),
+        ("workload_id", "   "),
+        ("variant_id", []),
+        ("variant_id", ""),
+        ("variant_id", "   "),
+    ],
+)
+def test_v2_benchmark_config_rejects_invalid_string_identity_values(field, value):
+    cfg = _v2_config()
+    cfg[field] = value
+
+    expected = f"wan.json: v2 identity field {field!r} must be a non-empty string"
+    with pytest.raises(ValueError, match=expected):
+        _validate_benchmark_config(cfg, "wan.json")
+
+
+@pytest.mark.parametrize("value", [None, "1", 1.5, True])
+def test_v2_benchmark_config_rejects_invalid_benchmark_version_values(value):
+    cfg = _v2_config()
+    cfg["benchmark_version"] = value
+
+    expected = "wan.json: v2 identity field 'benchmark_version' must be an integer"
+    with pytest.raises(ValueError, match=expected):
+        _validate_benchmark_config(cfg, "wan.json")
+
+
+def test_partial_v2_identity_requires_schema_version():
+    cfg = {
+        "benchmark_id": "wan-t2v-1.3b-2gpu",
+        "workload_id": "wan-t2v-1.3b",
+        "variant_id": "canonical",
+        "benchmark_version": 1,
+    }
+
+    expected = "wan.json: v2 benchmark identity fields require config_schema_version=2"
+    with pytest.raises(ValueError, match=expected):
+        _validate_benchmark_config(cfg, "wan.json")
+
+
+def test_optional_v2_metadata_fields_must_be_objects():
+    cfg = {
+        "benchmark_id": "wan-t2v-1.3b-2gpu",
+        "config_schema_version": 2,
+        "workload_id": "wan-t2v-1.3b",
+        "variant_id": "canonical",
+        "benchmark_version": 1,
+        "quality_metadata": ["not", "an", "object"],
+    }
+
+    expected = "wan.json: optional v2 metadata field 'quality_metadata' must be an object"
+    with pytest.raises(ValueError, match=expected):
+        _validate_benchmark_config(cfg, "wan.json")

fastvideo/tests/performance/test_compare_baseline_policy.py

@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 from fastvideo.tests.performance import compare_baseline
+from fastvideo.performance.metric_policy import resolve_metric_policies
 
 
 def _raw_result():
@@ -72,9 +73,157 @@ def test_normalized_record_includes_source_metadata(monkeypatch):
     assert record["job_id"] == "job-1"
 
 
+def test_normalized_record_includes_effective_regression_thresholds(monkeypatch):
+    monkeypatch.setenv("PERF_RUN_SOURCE", "pr")
+    raw = _raw_result()
+    raw["regression_thresholds"] = {
+        "latency": {
+            "threshold_percent": 0.09,
+            "threshold_absolute": 0.75,
+            "gated": True,
+        },
+        "throughput": {
+            "gated": False,
+        },
+    }
+
+    record = compare_baseline.normalize_performance_result(raw)
+
+    assert record["regression_thresholds"]["latency"] == {
+        "threshold_percent": 0.09,
+        "threshold_absolute": 0.75,
+        "gated": True,
+    }
+    assert record["regression_thresholds"]["throughput"]["gated"] is False
+
+
+def test_invalid_regression_threshold_container_uses_defaults():
+    policies = resolve_metric_policies(["not", "a", "mapping"])
+
+    latency = next(policy for policy in policies if policy.key == "latency")
+    assert latency.threshold_percent == 0.08
+    assert latency.threshold_absolute == 0.5
+    assert latency.gated is True
+
+
+def test_boolean_regression_threshold_values_are_ignored():
+    policies = resolve_metric_policies({
+        "latency": {
+            "threshold_percent": True,
+            "threshold_absolute": False,
+            "gated": "false",
+        }
+    })
+
+    latency = next(policy for policy in policies if policy.key == "latency")
+    assert latency.threshold_percent == 0.08
+    assert latency.threshold_absolute == 0.5
+    assert latency.gated is False
+
+
 def test_baseline_eligibility_only_for_successful_scheduled_main():
     assert compare_baseline._is_baseline_eligible("scheduled_main", True) is True
     assert compare_baseline._is_baseline_eligible("scheduled_main", False) is False
     assert compare_baseline._is_baseline_eligible("pr", True) is False
     assert compare_baseline._is_baseline_eligible("local", True) is False
 
+
+def test_latency_regression_requires_percent_and_absolute_floors():
+    baseline = [{"latency": 10.0}]
+    current = {"model_id": "wan", "latency": 10.6}
+
+    percent_only = resolve_metric_policies({
+        "latency": {
+            "threshold_percent": 0.05,
+            "threshold_absolute": 0.75,
+        }
+    })
+    absolute_only = resolve_metric_policies({
+        "latency": {
+            "threshold_percent": 0.10,
+            "threshold_absolute": 0.5,
+        }
+    })
+    both = resolve_metric_policies({
+        "latency": {
+            "threshold_percent": 0.05,
+            "threshold_absolute": 0.5,
+        }
+    })
+
+    assert compare_baseline._check_regressions(current, baseline, percent_only) == []
+    assert compare_baseline._check_regressions(current, baseline, absolute_only) == []
+
+    failures = compare_baseline._check_regressions(current, baseline, both)
+    assert len(failures) == 1
+    assert "latency regressed by 6.0% and 0.600" in failures[0]
+
+
+def test_throughput_regression_uses_higher_is_better_direction():
+    baseline = [{"throughput": 10.0}]
+    current = {"model_id": "wan", "throughput": 9.0}
+    policies = resolve_metric_policies({
+        "throughput": {
+            "threshold_percent": 0.05,
+            "threshold_absolute": 0.5,
+        }
+    })
+
+    failures = compare_baseline._check_regressions(current, baseline, policies)
+
+    assert len(failures) == 1
+    assert "throughput regressed by 10.0% and 1.000" in failures[0]
+
+
+def test_memory_regression_uses_metric_specific_absolute_floor():
+    baseline = [{"memory": 10000.0}]
+    current = {"model_id": "wan", "memory": 10600.0}
+    policies = resolve_metric_policies({
+        "memory": {
+            "threshold_percent": 0.05,
+            "threshold_absolute": 256.0,
+        }
+    })
+
+    failures = compare_baseline._check_regressions(current, baseline, policies)
+
+    assert len(failures) == 1
+    assert "memory regressed by 6.0% and 600.0" in failures[0]
+
+
+def test_component_metric_can_gate_independently():
+    baseline = [{"dit_time_s": 8.0}]
+    current = {"model_id": "wan", "dit_time_s": 8.6}
+    policies = resolve_metric_policies({
+        "dit_time_s": {
+            "threshold_percent": 0.05,
+            "threshold_absolute": 0.25,
+        }
+    })
+
+    failures = compare_baseline._check_regressions(current, baseline, policies)
+
+    assert len(failures) == 1
+    assert "dit_time_s regressed by 7.5% and 0.600" in failures[0]
+
+
+def test_informational_metric_remains_visible_without_failing():
+    baseline = [{"throughput": 10.0}]
+    current = {"model_id": "wan", "gpu_type": "NVIDIA L40S", "throughput": 8.0}
+    policies = resolve_metric_policies({
+        "throughput": {
+            "threshold_percent": 0.01,
+            "threshold_absolute": 0.01,
+            "gated": False,
+        }
+    })
+
+    row = compare_baseline._build_summary_row(current, baseline, policies, False)
+
+    assert compare_baseline._check_regressions(current, baseline, policies) == []
+    assert row["metrics"]["throughput"]["regression_pct"] == 20.0
+    assert row["metrics"]["throughput"]["gated"] is False
+    assert row["metrics"]["throughput"]["threshold_exceeded"] is True
+    assert row["metrics"]["throughput"]["regressed"] is False
+    assert row["threshold_exceeded_metrics"] == ["throughput"]
+    assert row["failing_metrics"] == []

fastvideo/tests/performance/test_dashboard_api.py

@@ -68,6 +68,8 @@ def test_summary_endpoint_returns_latest_group_status():
     assert body["count"] == 1
     assert body["status_counts"] == {"pass": 1, "fail": 0}
     assert body["rows"][0]["metrics"]["latency"]["baseline"] == 10.0
+    assert body["rows"][0]["metrics"]["latency"]["threshold_exceeded"] is True
+    assert body["rows"][0]["threshold_exceeded_metrics"] == ["latency", "throughput"]
     assert body["rows"][0]["computed_regression_status"] == "fail"
 
 

fastvideo/tests/performance/test_dashboard_service.py

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
+from fastvideo.performance import hf_store
 from fastvideo.performance_dashboard.service import build_latest_summary, build_trends, filter_records
-from fastvideo.tests.performance import hf_store
 
 
 def _record(ts, commit, latency, throughput, success=True, **metadata):
@@ -28,16 +28,23 @@ def test_build_latest_summary_uses_previous_successful_records_for_baseline():
         _record("2026-01-03T00:00:00+00:00", "c" * 40, 11.0, 9.0),
     ]
 
-    rows = build_latest_summary(records, max_regression=0.05)
+    rows = build_latest_summary(records)
 
     assert len(rows) == 1
     row = rows[0]
     assert row["baseline_n"] == 1
     assert row["metrics"]["latency"]["baseline"] == 10.0
     assert row["metrics"]["latency"]["regression_pct"] == 10.0
+    assert row["metrics"]["latency"]["absolute_delta"] == 1.0
+    assert row["metrics"]["latency"]["threshold_percent"] == 8.0
+    assert row["metrics"]["latency"]["threshold_absolute"] == 0.5
+    assert row["metrics"]["latency"]["threshold_exceeded"] is True
+    assert row["metrics"]["latency"]["regressed"] is True
     assert row["metrics"]["throughput"]["regression_pct"] == 10.0
     assert row["status"] == "pass"
     assert row["computed_regression_status"] == "fail"
+    assert row["threshold_exceeded_metrics"] == ["latency", "throughput"]
+    assert row["failing_metrics"] == ["latency", "throughput"]
 
 
 def test_build_latest_summary_status_uses_latest_record_success_field():
@@ -73,7 +80,7 @@ def test_build_latest_summary_run_source_filter_keeps_canonical_baseline():
         ),
     ]
 
-    rows = build_latest_summary(records, max_regression=0.05, run_source="pr")
+    rows = build_latest_summary(records, run_source="pr")
 
     assert len(rows) == 1
     assert rows[0]["run_source"] == "pr"
@@ -83,6 +90,60 @@ def test_build_latest_summary_run_source_filter_keeps_canonical_baseline():
     assert rows[0]["computed_regression_status"] == "fail"
 
 
+def test_build_latest_summary_requires_absolute_floor_for_computed_regression():
+    records = [
+        _record("2026-01-01T00:00:00+00:00", "a" * 40, 10.0, 10.0),
+        _record(
+            "2026-01-02T00:00:00+00:00",
+            "b" * 40,
+            10.6,
+            10.0,
+            regression_thresholds={
+                "latency": {
+                    "threshold_percent": 0.05,
+                    "threshold_absolute": 0.75,
+                    "gated": True,
+                }
+            },
+        ),
+    ]
+
+    rows = build_latest_summary(records)
+
+    assert round(rows[0]["metrics"]["latency"]["regression_pct"], 1) == 6.0
+    assert round(rows[0]["metrics"]["latency"]["absolute_delta"], 3) == 0.6
+    assert rows[0]["metrics"]["latency"]["threshold_exceeded"] is False
+    assert rows[0]["metrics"]["latency"]["regressed"] is False
+    assert rows[0]["computed_regression_status"] == "pass"
+
+
+def test_build_latest_summary_separates_informational_threshold_crossing():
+    records = [
+        _record("2026-01-01T00:00:00+00:00", "a" * 40, 10.0, 10.0),
+        _record(
+            "2026-01-02T00:00:00+00:00",
+            "b" * 40,
+            10.6,
+            10.0,
+            regression_thresholds={
+                "latency": {
+                    "threshold_percent": 0.05,
+                    "threshold_absolute": 0.5,
+                    "gated": False,
+                }
+            },
+        ),
+    ]
+
+    rows = build_latest_summary(records)
+
+    assert rows[0]["metrics"]["latency"]["threshold_exceeded"] is True
+    assert rows[0]["metrics"]["latency"]["regressed"] is False
+    assert rows[0]["threshold_exceeded_metrics"] == ["latency"]
+    assert rows[0]["failing_metrics"] == []
+    assert rows[0]["computed_regression_status"] == "pass"
+
+
 def test_filter_records_and_trends_preserve_metric_points():
     records = [
         _record("2026-01-01T00:00:00+00:00", "a" * 40, 10.0, 10.0),

fastvideo/tests/performance/test_inference_performance.py

@@ -28,6 +28,17 @@ STAGE_METRIC_MAP: dict[str, str] = {
     "DmdDenoisingStage": "dit_time_s",
     "DecodingStage": "vae_decode_time_s",
 }
+V2_CONFIG_SCHEMA_VERSION = 2
+V2_REQUIRED_IDENTITY_FIELDS = (
+    "workload_id",
+    "variant_id",
+    "benchmark_version",
+)
+V2_OPTIONAL_METADATA_FIELDS = (
+    "recipe",
+    "metric_threshold_policy",
+    "quality_metadata",
+)
 
 # -- Config discovery -------------------------------------------------------
 
@@ -42,6 +53,71 @@ _BENCHMARKS_DIR = os.path.join(
 )
 
 
+def _has_v2_fields(cfg):
+    v2_fields = V2_REQUIRED_IDENTITY_FIELDS + V2_OPTIONAL_METADATA_FIELDS
+    return any(field in cfg for field in v2_fields)
+
+
+def _is_v2_config(cfg):
+    return cfg.get("config_schema_version") == V2_CONFIG_SCHEMA_VERSION
+
+
+def _validate_non_empty_string(value, field, path):
+    if not isinstance(value, str) or not value.strip():
+        raise ValueError(f"{path}: v2 identity field {field!r} must be a non-empty string")
+
+
+def _validate_integer(value, field, path):
+    if isinstance(value, bool) or not isinstance(value, int):
+        raise ValueError(f"{path}: v2 identity field {field!r} must be an integer")
+
+
+def _validate_benchmark_config(cfg, path="<memory>"):
+    missing_common = [field for field in ("benchmark_id",) if field not in cfg]
+    if missing_common:
+        raise ValueError(f"{path}: missing required benchmark config fields: {', '.join(missing_common)}")
+
+    schema_version = cfg.get("config_schema_version")
+    if schema_version is None:
+        if _has_v2_fields(cfg):
+            raise ValueError(f"{path}: v2 benchmark identity fields require config_schema_version=2")
+        return
+
+    if schema_version != V2_CONFIG_SCHEMA_VERSION:
+        raise ValueError(f"{path}: unsupported benchmark config_schema_version={schema_version!r}")
+
+    missing_v2 = [field for field in V2_REQUIRED_IDENTITY_FIELDS if field not in cfg]
+    if missing_v2:
+        raise ValueError(f"{path}: missing required v2 identity fields: {', '.join(missing_v2)}")
+
+    _validate_non_empty_string(cfg["workload_id"], "workload_id", path)
+    _validate_non_empty_string(cfg["variant_id"], "variant_id", path)
+    _validate_integer(cfg["benchmark_version"], "benchmark_version", path)
+
+    for field in V2_OPTIONAL_METADATA_FIELDS:
+        if field in cfg and not isinstance(cfg[field], Mapping):
+            raise ValueError(f"{path}: optional v2 metadata field {field!r} must be an object")
+
+
+def _config_identity_metadata(cfg):
+    if not _is_v2_config(cfg):
+        return {}
+    metadata = {
+        "config_schema_version": cfg["config_schema_version"],
+        "workload_id": cfg["workload_id"],
+        "variant_id": cfg["variant_id"],
+        "benchmark_version": cfg["benchmark_version"],
+    }
+    for field in V2_OPTIONAL_METADATA_FIELDS:
+        if field in cfg:
+            metadata[field] = cfg[field]
+    return metadata
+
+
+def _benchmark_display_id(cfg):
+    return cfg["benchmark_id"]
+
+
 def _discover_benchmarks():
     """Glob benchmark JSON configs and return list of (id, config) tuples."""
     pattern = os.path.join(_BENCHMARKS_DIR, "*.json")
@@ -49,6 +125,7 @@ def _discover_benchmarks():
     for path in sorted(glob.glob(pattern)):
         with open(path) as f:
             cfg = json.load(f)
+        _validate_benchmark_config(cfg, path)
         configs.append(cfg)
     return configs
 
@@ -219,6 +296,7 @@ def _run_benchmark(cfg):
 
     results = {
         "benchmark_id": cfg["benchmark_id"],
+        **_config_identity_metadata(cfg),
         "model_short_name": model_info.get("model_short_name", ""),
         "device": device_name,
         "num_gpus": init_kwargs.get("num_gpus", 1),
@@ -231,6 +309,7 @@ def _run_benchmark(cfg):
         "max_peak_memory_mb": round(max_peak_memory, 1),
         "individual_peak_memories_mb": [round(m, 1) for m in peak_memories],
         "thresholds": thresholds,
+        "regression_thresholds": cfg.get("regression_thresholds", {}),
         "commit": os.environ.get("BUILDKITE_COMMIT", ""),
         "pr_number": os.environ.get("BUILDKITE_PULL_REQUEST", ""),
         "timestamp": datetime.now(timezone.utc).isoformat(),
@@ -275,7 +354,7 @@ def _run_benchmark(cfg):
 @pytest.mark.parametrize(
     "cfg",
     _BENCHMARK_CONFIGS,
-    ids=[c["benchmark_id"] for c in _BENCHMARK_CONFIGS],
+    ids=[_benchmark_display_id(c) for c in _BENCHMARK_CONFIGS],
 )
 def test_inference_performance(cfg):
     """Measure generation latency, peak GPU memory, and component-level timings

fastvideo/tests/stages/test_input_validation_batching.py

@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: Apache-2.0
+from types import SimpleNamespace
+
+from fastvideo.pipelines import ForwardBatch
+from fastvideo.pipelines.stages.input_validation import InputValidationStage
+
+
+def test_input_validation_preserves_explicit_dynamic_batch_seeds() -> None:
+    batch = ForwardBatch(
+        data_type="video",
+        prompt=["one", "two"],
+        seed=100,
+        seeds=[17, 23],
+        height=8,
+        width=8,
+        num_frames=1,
+        num_inference_steps=1,
+    )
+
+    InputValidationStage()._generate_seeds(batch, SimpleNamespace())
+
+    assert batch.seeds == [17, 23]
+    assert [generator.initial_seed() for generator in batch.generator] == [17, 23]
+
+
+def test_input_validation_generates_one_seed_per_prompt() -> None:
+    batch = ForwardBatch(
+        data_type="video",
+        prompt=["one", "two"],
+        seed=100,
+        height=8,
+        width=8,
+        num_frames=1,
+        num_inference_steps=1,
+    )
+
+    InputValidationStage()._generate_seeds(batch, SimpleNamespace())
+
+    assert batch.seeds == [100, 101]
+    assert [generator.initial_seed() for generator in batch.generator] == [100, 101]

fastvideo/tests/stages/test_text_encoding.py

@@ -13,7 +13,13 @@ class TensorDict(dict):
         return TensorDict({k: v.to(device) for k, v in self.items()})
 
 class FakeTokenizer:
+    def __init__(self):
+        self.calls = []
+        self.texts = []
+
     def __call__(self, texts, **kwargs):
+        self.calls.append(kwargs)
+        self.texts.append(list(texts))
         B = len(texts)
         seq_len = int(kwargs.get("max_length", 4))
         return TensorDict({
@@ -21,6 +27,26 @@ class FakeTokenizer:
             "attention_mask": torch.ones(B, seq_len, dtype=torch.long),
         })
 
+
+class FakeChatTokenizer:
+    def __init__(self):
+        self.last_messages = None
+        self.last_kwargs = None
+
+    def apply_chat_template(self, messages, **kwargs):
+        self.last_messages = messages
+        self.last_kwargs = kwargs
+        assert isinstance(messages[0], list)
+        assert messages[0][0]["role"] == "system"
+        assert messages[0][1]["role"] == "user"
+        B = len(messages)
+        seq_len = int(kwargs.get("max_length", 4))
+        return TensorDict({
+            "input_ids": torch.arange(B * seq_len).view(B, seq_len),
+            "attention_mask": torch.ones(B, seq_len, dtype=torch.long),
+        })
+
+
 class FakeTextEncoder(torch.nn.Module):
     def __init__(self, hidden_size=8):
         super().__init__()
@@ -38,6 +64,14 @@ class FakeTextEncoder(torch.nn.Module):
 def id_preprocess(x: str) -> str:
     return x
 
+
+def chat_list_preprocess(x: str):
+    return [
+        {"role": "system", "content": "Describe the video."},
+        {"role": "user", "content": x if x else " "},
+    ]
+
+
 def take_mean_postprocess(outputs: BaseEncoderOutput) -> torch.Tensor:
     # [B, T, H] -> [B, H]
     return outputs.last_hidden_state.mean(dim=1)
@@ -131,6 +165,66 @@ def test_forward_integration_cfg_off_and_on():
     assert len(out2.prompt_attention_mask) == 2
     assert len(out2.negative_attention_mask) == 2
 
+def test_encode_text_adds_padding_for_prompt_lists():
+    fastvideo_args, hidden = make_args(num_encoders=1, text_len=4, hidden_size=8)
+    stage = make_stage(num_encoders=1, hidden_size=hidden)
+
+    stage.encode_text(["short", "a longer prompt"], fastvideo_args, encoder_index=[0])
+
+    assert stage.tokenizers[0].calls[-1]["padding"] is True
+
+
+def test_forward_prompt_list_preserves_single_prompt_text_encoding_path():
+    fastvideo_args, hidden = make_args(num_encoders=1, text_len=4, hidden_size=8)
+    stage = make_stage(num_encoders=1, hidden_size=hidden)
+    batch = ForwardBatch(
+        data_type="video",
+        prompt=["short", "a longer prompt"],
+        negative_prompt="",
+        do_classifier_free_guidance=False,
+        prompt_embeds=[],
+        negative_prompt_embeds=None,
+        prompt_attention_mask=[],
+        negative_attention_mask=None,
+    )
+
+    out = stage.forward(batch, fastvideo_args)
+
+    assert stage.tokenizers[0].texts == [["short"], ["a longer prompt"]]
+    assert out.prompt_embeds[0].shape == (2, hidden)
+    assert out.prompt_attention_mask[0].shape == (2, 4)
+
+
+def test_encode_prompt_list_individually_pads_variable_length_embeds_and_audio():
+    fastvideo_args, _hidden = make_args(num_encoders=1, text_len=4, hidden_size=8)
+    stage = TextEncodingStage(text_encoders=[], tokenizers=[])
+    lengths = {"short": 2, "a longer prompt": 4}
+
+    def fake_encode_text(text, *_args, **_kwargs):
+        length = lengths[text]
+        embeds = [torch.full((1, length, 3), fill_value=float(length))]
+        masks = [torch.ones((1, length), dtype=torch.long)]
+        stage._last_audio_embeds = [torch.full((1, length, 5), fill_value=float(length))]
+        return embeds, masks
+
+    stage.encode_text = fake_encode_text
+
+    embeds, masks = stage._encode_prompt_list_individually(
+        ["short", "a longer prompt"],
+        fastvideo_args,
+        encoder_index=[0],
+        return_attention_mask=True,
+    )
+
+    assert embeds[0].shape == (2, 4, 3)
+    assert masks[0].shape == (2, 4)
+    assert stage._last_audio_embeds is not None
+    assert stage._last_audio_embeds[0].shape == (2, 4, 5)
+    assert torch.equal(embeds[0][0, :2], torch.full((2, 3), 2.0))
+    assert torch.equal(embeds[0][0, 2:], torch.zeros((2, 3)))
+    assert torch.equal(stage._last_audio_embeds[0][0, :2], torch.full((2, 5), 2.0))
+    assert torch.equal(stage._last_audio_embeds[0][0, 2:], torch.zeros((2, 5)))
+
 
 def test_encode_text_hidden_state_flag_follows_encoder_config():
     fastvideo_args, hidden = make_args(num_encoders=1, text_len=4, hidden_size=8)
@@ -156,3 +250,32 @@ def test_encode_text_does_not_force_hidden_states_for_ltx2_prefix():
     stage.encode_text("a", fastvideo_args, encoder_index=[0])
 
     assert stage.text_encoders[0].last_output_hidden_states is False
+
+
+def test_chat_list_preprocess_output_is_not_stripped():
+    fastvideo_args, hidden = make_args(num_encoders=1, text_len=5, hidden_size=8)
+    encoder_config = fastvideo_args.pipeline_config.text_encoder_configs[0]
+    encoder_config.is_chat_model = True
+    encoder_config.treat_empty_as_dot = True
+    fastvideo_args.pipeline_config.preprocess_text_funcs = (chat_list_preprocess, )
+
+    tokenizer = FakeChatTokenizer()
+    stage = TextEncodingStage(
+        text_encoders=[FakeTextEncoder(hidden_size=hidden)],
+        tokenizers=[tokenizer],
+    )
+
+    embeds, masks = stage.encode_text(
+        "a robotic arm welding a metal structure",
+        fastvideo_args,
+        encoder_index=[0],
+        return_attention_mask=True,
+    )
+
+    assert embeds[0].shape == (1, hidden)
+    assert masks[0].shape == (1, 5)
+    assert tokenizer.last_messages == [[
+        {"role": "system", "content": "Describe the video."},
+        {"role": "user", "content": "a robotic arm welding a metal structure"},
+    ]]
+    assert tokenizer.last_kwargs["return_tensors"] == "pt"

fastvideo/tests/train/methods/test_wan_causal_dfsft.py

@@ -127,4 +127,12 @@ def test_wan_causal_dfsft_single_train_step(
 
     # 5a-ii: device-keyed grad-norm regression on top of the same harness.
     # Skips when the current GPU has no seeded reference.
-    check_grad_norm_regression("test_wan_causal_dfsft", model.transformer)
+    # rtol above the harness default: the causal model compiles flex_attention
+    # with max-autotune (required for Wan 1.3B's head config), and the
+    # timing-based kernel selection is bimodal across L40S containers —
+    # observed 3.2562 vs 3.5860 (10.13% apart) with identical code, straddling
+    # the default 10%. 12% covers both winners; real wiring breakage (dead
+    # grads, scale bugs) still lands far outside it.
+    check_grad_norm_regression("test_wan_causal_dfsft",
+                               model.transformer,
+                               rtol=0.12)