SeedVR2: bounded long-video restoration (#8102)

Signed-off-by: 0z5a <Dezhen.lu@student.uni-tuebingen.de>
Signed-off-by: 0z5a <dezhen.lu@uni-tuebingen.de>
Signed-off-by: 0z5a <dezhen.lu@student.uni-tuebingen.de>
Signed-off-by: princepride <wangzhipeng628@gmail.com>
Co-authored-by: 0z5a <dezhen.lu@uni-tuebingen.de>
Co-authored-by: princepride <wangzhipeng628@gmail.com>

docs/.nav.yml

@@ -47,6 +47,7 @@ nav:
     - configuration/*
   - Models:
     - models/supported_models.md
+    - SeedVR2: models/seedvr2.md
   - Features:
     - Overview: features/README.md
     - Runtime and Stage Execution:
@@ -151,6 +152,7 @@ nav:
           - Hybrid Sharded Data Parallel (HSDP): design/feature/hsdp.md
           - Pipeline Parallel: design/feature/pipeline_parallel.md
           - Sequence Parallel: design/feature/sequence_parallel.md
+          - Window Sequence Parallel: design/feature/window_sequence_parallel.md
           - Tensor Parallel: design/feature/tensor_parallel.md
           - VAE Patch Parallelism: design/feature/vae_parallel.md
         - Attention Optimization:

docs/configuration/environment_variables.md

@@ -214,7 +214,7 @@ collection, examples, bug reports, or logs.
 
 ## Model-specific variables
 
-The audit found 58 variables read by a single model or pipeline family. They are
+The inventory includes 66 variables read by a single model or pipeline family. They are
 not listed as public usage options here because doing so would turn implementation
 escape hatches into an accidental compatibility contract.
 
@@ -223,11 +223,11 @@ Every audited model-specific name has a migration disposition in the
 
 | Disposition | Count | Required outcome |
 | --- | ---: | --- |
-| Promote | 35 | Move a stable setting into typed stage or model configuration. |
-| Request scope | 6 | Move request-varying behavior into a declared request-option schema. |
+| Promote | 38 | Move a stable setting into typed stage or model configuration. |
+| Request scope | 5 | Move request-varying behavior into a declared request-option schema. |
 | External | 0 | Retain only when a supported third-party library owns the contract. |
-| Internalize | 11 | Keep a debug or diagnostic switch out of public documentation and configuration. |
-| Deprecate/remove | 6 | Remove a compatibility escape hatch that has no continuing contract. |
+| Internalize | 16 | Keep a debug or diagnostic switch out of public documentation and configuration. |
+| Deprecate/remove | 7 | Remove a compatibility escape hatch that has no continuing contract. |
 
 The disposition is a migration target, not a statement that the existing
 environment switch is stable. Promote or request-scope work should land in

docs/design/feature/window_sequence_parallel.md

@@ -0,0 +1,186 @@
+# Window-Aligned Sequence Parallelism (SeedVR2)
+
+## Motivation
+
+SeedVR2's diffusion transformer (`NaDiT`) has no global attention: every layer
+partitions the video tokens into 3D windows and attends only inside a window.
+The window size is normalised against a fixed 720p reference area, so raising the
+output resolution grows the *number* of windows, never their size.
+
+Ulysses redistributes the sequence and head dimensions around attention.
+For SeedVR2, window-aligned SP offers a different communication tradeoff: one
+hidden-state exchange per layout boundary versus Q/K/V and output exchanges
+for Ulysses. The actual performance crossover requires measurement.
+Window-aligned SP instead assigns **whole windows** to ranks:
+
+* every rank keeps **all** attention heads, so no head-count divisibility is
+  required,
+* attention inside a layer needs **zero** communication,
+* regular and shifted layouts alternate at every layer, so the released
+  32-layer model has 31 inter-layer transitions, plus one text reduction per
+  layer and a final video gather. A transition can be a local permutation
+  when ownership does not change.
+
+## Window layouts
+
+`nadit.py` ports the reference windowing verbatim (Apache-2.0,
+ByteDance SeedVR2). For a post-patch token grid `(T, H, W)`:
+
+```text
+scale   = sqrt(45 * 80 / (H * W))          # 720p reference area
+wh, ww  = ceil(round(H * scale) / nh), ceil(round(W * scale) / nw)
+wt      = ceil(min(T, 30) / nt)            # BYTEDANCE_MAX_TEMPORAL_WINDOW
+```
+
+The regular method tiles with `slice(it * wt, min((it + 1) * wt, T))`; the
+shifted method moves every cut by half a window and **clips at the boundary**
+(`max(..., 0)` / `min(..., size)`) -- it is not a cyclic `torch.roll`. Both
+methods produce an exact partition of the grid; the shifted layout is genuinely
+different, so an `A -> B -> A -> B` layer schedule needs both directions of
+re-sharding.
+
+Windows are enumerated `for iw ... for ih ... for it ...` (w outermost, t
+innermost) and tokens inside a window are row-major in `(t, h, w)`. The
+canonical token id is `(t * H + h) * W + w`, which is exactly what the reference
+obtains by windowing `torch.arange`.
+
+Consequences that matter (all verified against the reference):
+
+* Window token counts are **ragged** (edge windows are clipped), so a shard must
+  be balanced by token count, not by window count.
+* The number of layout transitions follows the actual layer schedule. For the
+  released 3B checkpoint (`num_layers=32`, alternating methods) there are 31
+  inter-layer transitions, not 16; `ensure_layout(current, required)` derives
+  them instead of assuming `layer % 2`.
+
+## Planner
+
+`nadit.py` implements a deterministic LPT assignment:
+
+```text
+windows sorted by (-video_token_count, original_window_id)
+each window is placed on the rank with the smallest (assigned_tokens, rank_id)
+each rank then lists its windows in ascending original order
+```
+
+The cache key covers the post-patch token grid, the full window method and
+parameters (via a SHA-1 geometry fingerprint), the geometry version, the **SP
+world size** and the planner version, so a different degree can never reuse a
+stale assignment. Caches are LRU-bounded.
+
+## Plan A redistribution
+
+At a layout boundary the activations must move from the source assignment to the
+destination assignment. With `Z_src[r]` / `Z_dst[d]` the canonical token ids held
+by each rank and `C[r, d]` the number of rows rank `d` needs from rank `r`:
+
+* `input_split_sizes` of rank `r` is row `r` of `C`, `output_split_sizes` is
+  column `r`,
+* each peer segment is packed in **destination-local order**, so the receiver can
+  reorder with a single `argsort` of the concatenated destination positions,
+* `network_exchange_required` is computed from the global count matrix, so every
+  rank takes the same branch; a rank that happens to exchange nothing never
+  skips the collective alone.
+
+The runtime is a variable-split `torch.distributed.all_to_all_single` over an
+regular SP process group (`get_sp_group().device_group`), plus a local-permutation fast
+path when the whole group stays in place (which is the SP=1 case). The first
+version is deliberately synchronous: no extra streams, no per-layer
+`cuda.synchronize()` or barrier "fixups", and no hidden all-gather.
+
+## Text stream
+
+Text is replicated on every rank and stays identical: each layer's attention
+produces one text output per window, ranks sum their local window outputs,
+one SUM all-reduce runs on the window-SP group, and every rank divides by the
+**global** window count of the current layout.
+
+```text
+T_next = (sum_r sum_{w in Omega_r} T_w) / W_global
+```
+
+This is neither a token-weighted mean nor a mean of rank means; a rank with no
+window contributes a zero tensor (with the *same dtype as its peers* -- a dtype
+mismatch changes the collective and deadlocks NCCL, which is why the empty-rank
+path is covered by a GPU test).
+
+## Existing SP configuration
+
+Configure `ulysses_degree=N` to create the existing N-rank SP group. Pass
+`DiffusionParallelConfig` to `SeedVR2NaDiT.build_runtime(parallel_config=...)`;
+the model validates the configuration and obtains `get_sp_group().device_group`.
+This adds no framework parallel option or group-construction branch.
+
+For SeedVR2 this selects **window-aligned Plan A**, not head-sharded Ulysses.
+Every rank retains all 20 attention heads, so SP=8 does not require the head
+count to divide by eight. The model has no `_sp_plan`, and its attention uses
+`skip_sequence_parallel=True`; generic sequence hooks and Ulysses attention
+exchanges are not installed. Reports name the actual execution path explicitly.
+
+SeedVR2 rejects ring, allgather, `advanced_uaa`, and `ulysses_a2a_permute`.
+Other diffusion models keep their existing Ulysses/Ring/AllGather behavior.
+
+## SeedVR2 integration
+
+`SeedVR2WindowRuntime` owns, per request: the layer schedule, the entry
+distribution, `ensure_layout` transitions, the text reduction and the final
+reconstruction back to canonical token order. The DiT forward keeps only this
+rank's video rows from the patch embedding onwards; the patch projection,
+norms, ADA modulation, residual and MLP are all tokenwise, so they run locally.
+
+The block never calls a parallel attention strategy: the shared `Attention`
+layer is created with `skip_sequence_parallel=True`, and window attention is a
+packed-varlen call over `[video window, replicated text]` segments (with a
+grouped-SDPA fallback for backends without a packed-varlen entry point).
+
+## Reference quirks reproduced on purpose
+
+* `vid_out_ada` is declared with `layers=["out"]`, whose embedding regrouping is
+  arithmetically incompatible with its 1-D parameters. The reference never uses
+  that value: it asks the forward-wide cache for `emb_repeat_0_vid`, a key the
+  first block already wrote, and therefore applies the *block* attention
+  modulation together with the learned `out_scale` / `out_shift`. The port
+  applies that effective modulation directly; changing it would break parity.
+* `mm_layers=10` controls weight sharing only. Text is consumed and produced by
+  all 32 blocks; only the last block freezes its text MLP path.
+* RoPE positions are window-local: a video token at window-local `(dt, dh, dw)`
+  uses axial indices `(text_len + dt, dh, dw)`, and every window restarts at 0.
+* The rotary span is `3 * (rope_dim // 3)` (126 of 128 channels for the 3B), so
+  the last two channels pass through unrotated.
+
+## Checkpoint compatibility
+
+The parameter layout of the port mirrors the reference, with one explicit
+exception: the released checkpoint stores the per-block RoPE table as
+`blocks.<i>.attn.rope.rope.freqs`, while this port registers it as
+`blocks.<i>.attn.rope.freqs`. The validation loader normalizes exactly that
+suffix (and only that suffix); every other key must already match.
+
+> The validation loader explicitly normalizes the reference RoPE buffer suffix
+> from `.rope.rope.freqs` to `.rope.freqs`. Checkpoint validation fails on any
+> remaining missing or unexpected key after normalization.
+
+Normalization is restricted and collision-checked: a key that is already
+normalized is left untouched, and two source keys mapping onto the same target
+key raise instead of silently overwriting a tensor. Loading then fails on any
+remaining missing, unexpected or shape-mismatched key, so a checkpoint that does
+not match the port cannot reach inference. Full 32-layer loading is the
+acceptance path; truncating the block list is a development fixture and requires
+an explicit flag.
+
+The native serving loader applies the same suffix normalization and strict
+checkpoint check.
+
+## Integration limits
+
+The native serving pipeline passes its parallel configuration to the DiT runtime
+and returns restored video through the standard media path. The causal VAE can
+run replicated, tiled, or height-sharded across the window-SP group.
+
+## Limitations
+
+* Plan A re-shards the full activation at every layout boundary. Plan B halo
+  exchange is a follow-up with a separate crossover evaluation.
+* The packed-varlen attention kernel needs a backend that accepts
+  `cu_seqlens`; the grouped-SDPA path is the portable fallback and is what the
+  pinned L20 environment exercises.

docs/models/seedvr2.md

@@ -0,0 +1,280 @@
+# SeedVR2 3B video restoration
+
+The native `SeedVR2Pipeline` restores an input video using the released 3B FP16
+NaDiT and s8/c16/t4 causal VAE. It uses fixed checkpoint conditioning, CFG=1,
+and one Euler step. Text prompts do not change conditioning.
+
+## Code ownership
+
+The model package groups each computation stage in one file: `nadit.py` owns
+window geometry, routing, RoPE and the DiT; `vae.py` owns the causal VAE and its
+temporal/spatial tiling; `pipeline_seedvr2.py` owns input validation, decoding,
+conditioning, the Euler step and colour transfer. `config.py` owns model limits,
+and `long_video.py` owns the optional HTTP job/window lifecycle. Framework code
+only registers the model, its pre/postprocessors, metadata and HTTP routes.
+
+`color_correction_method` is model-specific: online requests use the existing
+`extra_params` JSON object, and offline sampling uses
+`extra_args={"color_correction_method": "wavelet"}`. The default remains `lab`;
+invalid values are rejected by model-side validation before inference. It is
+not a top-level field in the common video API.
+
+## Model directory
+
+Place these files together, retaining their names:
+
+| File | SHA-256 of the validated release |
+| --- | --- |
+| `seedvr2_ema_3b_fp16.safetensors` | `2fd0e03a3dad24e07086750360727ca437de4ecd456f769856e960ae93e2b304` |
+| `ema_vae_fp16.safetensors` | `20678548f420d98d26f11442d3528f8b8c94e57ee046ef93dbb7633da8612ca1` |
+| `pos_emb.pt` | `fa07a14844314772266b66c3b95deb0027696d8fe7065721263db5176f45d799` |
+
+Add `model_index.json` containing:
+
+```json
+{"_class_name": "SeedVR2Pipeline"}
+```
+
+The loader checks every checkpoint tensor, including RoPE buffers, and rejects
+missing, duplicate, unexpected, or incompatible tensors. Install PyAV for video
+decoding. The validated environment uses PyAV 18.1, PyTorch 2.13/CUDA 13, and L20 GPUs.
+
+## Serve and restore a video
+
+```bash
+vllm serve "$MODEL_DIR" --omni \
+  --model-class-name SeedVR2Pipeline --dtype float16 --enforce-eager \
+  --num-gpus 1 --host 127.0.0.1 --port 8098
+
+curl --fail-with-body http://127.0.0.1:8098/v1/videos/sync \
+  -F 'prompt= ' \
+  -F 'input_references=@input.mp4;type=video/mp4' \
+  -F 'size=224x128' -F 'num_inference_steps=1' \
+  -F 'guidance_scale=1' -F 'seed=7723' \
+  --output restored.mp4
+```
+
+For two-rank window sequence parallelism, expose two GPUs and replace `--num-gpus 1` with:
+
+```bash
+--num-gpus 2 --distributed-executor-backend mp \
+  --stage-overrides '{"0":{"ulysses_degree":2}}'
+```
+
+Use degree 4 and four visible GPUs for SP4. Window-SP alone replicates the VAE.
+To shard VAE activations across the same ranks, use:
+
+```bash
+--vae-use-tiling --num-gpus 2 --distributed-executor-backend mp \
+  --stage-overrides '{"0":{"ulysses_degree":2,"vae_patch_parallel_size":2,"vae_parallel_mode":"spatial_shard_height"}}'
+```
+
+The VAE patch degree must match the window-SP degree.
+For a 16-frame 1280×720 input restored at its original size, use four GPUs,
+VAE tiling, and height sharding with both degrees set to four:
+
+```bash
+CUDA_VISIBLE_DEVICES=0,1,2,3 vllm serve "$MODEL_DIR" --omni \
+  --model-class-name SeedVR2Pipeline --dtype float16 --enforce-eager \
+  --vae-use-tiling --num-gpus 4 --distributed-executor-backend mp \
+  --stage-overrides '{"0":{"ulysses_degree":4,"vae_patch_parallel_size":4,"vae_parallel_mode":"spatial_shard_height"}}' \
+  --host 127.0.0.1 --port 8098
+```
+
+Request `size=1280x720` for this landscape input or `size=720x1280` for a
+portrait input of the same dimensions. Keep the requested output size equal to
+the input size when testing restoration without upscaling.
+
+The multipart API requires a prompt field; a single space supplies a blank
+prompt. Nonblank text is rejected. Omit `fps` to retain the source frame rate;
+an explicit rate must match the source. Output dimensions are explicit multiples
+of 16. Input frames are resized with antialiased bicubic interpolation. The final
+frame is repeated internally to reach 4n+1, and the decoded output is cropped back
+to the original frame count. Five frames remain five; six frames are internally
+padded to nine and return six.
+
+## Colour correction
+
+Restoration reproduces detail faithfully but shifts global colour, so the
+resized input is used to transfer colour back onto the restored frames. This is
+on by default; pass `extra_params={"color_correction_method":"wavelet"}` to choose how:
+
+| Value | Behavior |
+| --- | --- |
+| `lab` (default) | Swaps the lowest frequency band, then histogram-matches CIELAB chroma. Most faithful colour. |
+| `wavelet` | Swaps only the lowest frequency band, keeping every higher band from the restoration. |
+| `adain` | Matches per-channel mean and standard deviation. Cheapest, and corrects only a global tint. |
+| `none` | Skips the transfer and returns raw restored colour. |
+
+```bash
+curl --fail-with-body http://127.0.0.1:8098/v1/videos/sync \
+  -F 'prompt= ' -F 'input_references=@input.mp4;type=video/mp4' \
+  -F 'size=224x128' -F 'num_inference_steps=1' -F 'guidance_scale=1' \
+  -F 'seed=7723' -F 'extra_params={"color_correction_method":"wavelet"}' \
+  --output restored.mp4
+```
+
+`lab` and `wavelet` retain the restored high-frequency detail; `adain` measurably
+softens it because it rescales every frequency. The transfer runs in FP32 after
+the VAE decode and costs a fraction of a second per frame. Unrecognized values
+are rejected with 400 before the clip is admitted. Correction cannot recover
+colour lost to 4:2:0 chroma subsampling in the returned MP4, which dominates the
+remaining deviation once the transfer is applied.
+
+## Request admission
+
+The default 3B limit is 848×480 pixels per input or output frame and 2,035,200
+pixels across the requested output clip. With VAE tiling and window SP of at
+least four ranks whose `vae_patch_parallel_size` matches `ulysses_degree`, the
+per-frame limit rises to 2560×1472 and the clip budget to 18,841,600 pixels.
+Raising the degree never lowers the budget. Both budgets count temporal
+padding to 4n+1 frames: the default admits up to five 848×480 frames or 93
+192×112 frames; the sharded profile admits up to 45 848×480 frames or five
+2560×1472 frames. A 16-frame 1280×720 or 720×1280 clip pads to 17 frames and
+uses 15,667,200 of the sharded clip's 18,841,600 pixels. Both orientations passed
+original-size HTTP restoration on four RTX 5090 GPUs with VAE tiling and height
+sharding. An independent 257-frame cap bounds per-frame decoder work for tiny
+inputs. The other longer combinations above are admission bounds, not completed
+GPU validation. The decoder checks
+declared duration, frame count, and input dimensions when available, then
+enforces the limits as frames arrive. Requests outside these budgets return 400
+before building the resized whole-clip tensor.
+
+The per-frame cap is calibrated for the smallest qualified device. The clip cap
+scales with the smallest visible device's memory: it stays at the calibrated
+five 2560×1472 frames on a 32 GB device and grows on larger ones from a
+per-rank memory model measured at SP4 (see `sharded_budget` in
+`vllm_omni/diffusion/models/seedvr2/pipeline_seedvr2.py`), which keeps 15% of the device
+free and leaves room for allocator fragmentation. It stops at 2,118,057,984
+padded pixels (513 frames at 1536×2688), the largest clip validated on four
+B300 ranks; 80 GB devices get about 1.08 billion and 141 GB or larger devices
+reach the cap. Clips at the cap in both memory regimes (561 frames at 2560×1472
+and 2,049 frames at 768×1344) peaked at 54 GiB of activations per rank. Set
+these before starting the server to override the caps; each must be a positive
+integer, and validating an override on the target hardware is the operator's
+responsibility:
+
+| Variable | Default | Bounds |
+| --- | --- | --- |
+| `VLLM_OMNI_SEEDVR2_SHARDED_FRAME_PIXELS` | 3,768,320 | Pixels per frame on the sharded profile |
+| `VLLM_OMNI_SEEDVR2_SHARDED_CLIP_PIXELS` | 18,841,600, scaled up with device memory | Padded pixels per clip on the sharded profile |
+| `VLLM_OMNI_SEEDVR2_MAX_FRAMES` | 257 | Decoder-work frame cap, all profiles |
+
+The sharded profile applies to any `ulysses_degree` of four or more, so eight
+ranks inherit a budget calibrated on four. Raising these caps trades a 400 for a
+CUDA OOM: the admission check passes and the request fails later inside the DiT
+forward or the VAE decode, which can abort every in-flight request on the engine
+rather than only the oversized one. Before serving with raised caps, restore the
+largest clip they admit once and confirm it completes.
+
+A 362-frame 1536×2688 2x upscale was restored on eight ranks with
+`ulysses_degree=8`, VAE tiling and height sharding, using 4,300,000 for the
+per-frame cap, the memory-scaled clip cap and 2,000 for the frame cap. The long-video
+route sizes its windows from these caps, so the clip cap sets how many frames
+each window covers.
+
+## Long-video restoration
+
+`POST /v1/seedvr2/restore-long` accepts one uploaded 24 FPS video, a blank
+prompt, `size`, `num_frames` (up to 7,200), and optional `loop_input=true` and
+`extra_params={"color_correction_method":"wavelet"}`, which it applies to every window.
+An output frame must fit the sharded per-frame pixel cap. It returns a job ID; poll
+`GET /v1/seedvr2/restore-long/{id}` and download the completed MP4 from
+`GET /v1/seedvr2/restore-long/{id}/content`. `DELETE
+/v1/seedvr2/restore-long/{id}` asks a running job to stop; it settles as
+`cancelled` at the next window boundary. A job whose owning process is gone,
+such as after a server restart, reports `failed` on the next poll.
+
+Jobs live on the API server's local disk, so the route requires
+`--api-server-count 1` and runs one job at a time. Storage is bounded by an
+upload cap and by deleting settled jobs once they age out:
+
+| Variable | Default | Bounds |
+| --- | --- | --- |
+| `VLLM_OMNI_SEEDVR2_LONG_OUTPUT_DIR` | system temp dir | Parent of the job directories |
+| `VLLM_OMNI_SEEDVR2_LONG_MAX_UPLOAD_BYTES` | 8 GiB | Largest accepted upload |
+| `VLLM_OMNI_SEEDVR2_LONG_JOB_TTL_SECONDS` | 3,600 | Age at which a settled job is deleted |
+| `VLLM_OMNI_SEEDVR2_LONG_MAX_WINDOW` | 121 | Longest model window, in frames |
+
+Download a completed job before its TTL expires; the sweep runs on each new
+submission and removes the output with the job directory.
+
+The service sends windows through the existing SeedVR2 endpoint, blends four
+frames at each boundary, and writes one continuous MP4 encoder. Each window is
+the longest 4n+1-frame clip that the sharded clip-pixel cap, the frame cap and
+`VLLM_OMNI_SEEDVR2_LONG_MAX_WINDOW` admit at the output size. Every window pays
+a fixed round trip through the serving stack and recomputes its overlap, and a
+window of four latent frames gets no temporal attention in the DiT, so raise
+the clip cap as far as the device allows. Windows carry source pixels, which
+the model resizes on the device, and cross the endpoint losslessly; only the
+final MP4 is compressed. The next window is restored while the previous one is
+blended and encoded. It repeats source frames and audio only when
+`loop_input=true`. The sharded serving profile above (VAE tiling, VAE height
+sharding, Ulysses degree of at least four) is required. This route keeps a
+window within the whole-clip pixel budget; it does not raise the
+`/v1/videos/sync` 257-frame or pixel limits. The long route
+uses fixed one-step, CFG=1 conditioning and requires `imageio[ffmpeg]` for
+audio muxing. The 7,200-frame 768×1344 case is still undergoing full GPU E2E.
+
+## Temporal and spatial VAE tiling
+
+Add `--vae-use-tiling` to bound VAE intermediate activations along time. The
+encoder processes nine frames first, then eight per chunk; the decoder processes
+two latent frames per chunk. Each causal convolution carries its past inputs
+within that encode/decode call, with temporal stride and first-frame upsampling
+alignment preserved. GroupNorm and attention still see the entire spatial frame.
+There is no overlap blend or independent restart at chunk boundaries.
+
+Five-frame clips use one temporal chunk. On a single GPU, convolutions with
+more than 256 input rows additionally process tiles of 128 output rows with
+exact halos. GroupNorm and bottleneck attention retain full-frame statistics.
+This bounds convolution workspace; full-frame activations and the DiT's
+whole-clip activations still consume memory.
+
+With VAE patch parallelism, each rank owns a band of latent rows and the
+corresponding encoder/decoder rows. Neighbor exchanges supply convolution halos;
+all-reduced centered statistics preserve full-frame GroupNorm. Bottleneck
+attention gathers the low-resolution frame before splitting it again. Encoder
+parameters are gathered before latent sampling, and decoded pixels are gathered
+before returning the video. Unequal bands are supported; fewer latent rows than
+ranks fall back to replicated execution. Width sharding and batch slicing are
+unsupported. FP16 reduction and convolution order can change rounding, so
+parallel outputs are numerically close rather than bitwise identical.
+
+## Current integration scope
+
+| Property | Contract |
+| --- | --- |
+| Weights / dtype | Released 3B DiT and VAE, FP16 |
+| Reference semantics | C0 whole clip, colour correction on by default |
+| Video input | One uploaded file, or offline TCHW RGB floats / PIL frames |
+| Timing | Constant frame rate, increasing PTS; normalize the video origin to zero |
+| Audio | First mono/stereo track, aligned by source PTS, cropped to the video interval, re-encoded as AAC |
+| Randomness | Per-request generator; preserve reference latent strides when sampling noise |
+| Sequence parallelism | Native engine SP1/2/4 correctness verified on five-frame L20 cases |
+| VAE placement | Replicated by default; optional height sharding on the window-SP group |
+| Unsupported | VFR, multichannel audio, 7B, other sampling schedules, quantization, cache acceleration, VAE width sharding / batch slicing, CPU offload, CFG/TP/PP parallelism, compiled execution, LoRA |
+
+Unsupported engine modes are rejected before process hooks and worker creation.
+`ulysses_degree` selects the model-owned SP group. This branch assigns whole
+windows to ranks; the specialized head-sharded path is a dependent change.
+Ring and AllGather-KV are unsupported.
+
+The practical P0 reference's five-frame batching, overlap, and CPU swapping are
+separate execution semantics. Temporal tiling and VAE patch
+parallelism reduce activation peaks but do not bound the whole-clip DiT memory.
+Large output frames may still exceed device capacity.
+
+Invalid inputs return 400. A single-GPU model OOM fails that request; a
+subsequent short request succeeds. With VAE patch parallelism, restart the
+service after an OOM: another rank may still be waiting in a collective. Cancelling an in-progress video job removes it through the
+existing DELETE endpoint; in-flight GPU work may drain before memory is reusable.
+A lost SP worker fails the request and makes health return 503. Restart the
+service to restore availability; automatic rank recovery is not provided.
+
+## Reproducible deployment
+
+See the [RTX 5090 recipe](https://github.com/vllm-project/vllm-omni/blob/main/recipes/ByteDance/SeedVR2-RTX-5090.md) for the
+input/output contract, complete serving command, and media checks. The local
+tests in `tests/diffusion/models/seedvr2/test_seedvr2_e2e.py` exercise the full
+3B pipeline, all colour modes, and HTTP restoration with USP 1 and 8.

docs/models/supported_models.md

@@ -54,6 +54,7 @@ th {
 | `LingBotVideoPipeline` | LingBot-Video dense and MoE T2I, T2V, TI2V | `robbyant/lingbot-video-dense-1.3b`, `robbyant/lingbot-video-moe-30b-a3b` | ✅︎ | | | | — |
 | `SanaVideoPipeline` | SANA-Video-2B T2V (native 480p/720p; Diffusers adapter validated at both resolutions) | `Efficient-Large-Model/SANA-Video_2B_480p_diffusers`, `Efficient-Large-Model/SANA-Video_2B_720p_diffusers` | ✅︎ | | | ✅︎ | [Repository](https://github.com/vllm-project/vllm-omni/blob/main/recipes/NVIDIA/SANA-Video-2B.md) |
 | `SanaImageToVideoPipeline` | SANA-Video-2B I2V (native and Diffusers adapter validated at 480p/720p) | `Efficient-Large-Model/SANA-Video_2B_480p_diffusers`, `Efficient-Large-Model/SANA-Video_2B_720p_diffusers` | ✅︎ | | | | [Repository](https://github.com/vllm-project/vllm-omni/blob/main/recipes/NVIDIA/SANA-Video-2B.md) |
+| `SeedVR2Pipeline` | [SeedVR2 3B](seedvr2.md) video restoration | `ByteDance-Seed/SeedVR2-3B` | ✅︎ | | | | [Repository](https://github.com/vllm-project/vllm-omni/blob/main/recipes/ByteDance/SeedVR2-RTX-5090.md) |
 | `MiniMaxH3Pipeline` | MiniMax H3 T2VA, first/last-keyframe FL2VA, and mixed-reference Ref2VA | `MiniMaxAI/MiniMax-H3` | ✅︎ | ✅︎ | | | [Published](https://recipes.vllm.ai/MiniMaxAI/MiniMax-H3) |
 | `Magi2Pipeline` | MAGI-2 native Preview-stage T2VA and I2VA (272p/540p) | `sand-ai/MAGI-2-preview` | ✅︎ | | | | [Repository](https://github.com/vllm-project/vllm-omni/blob/main/recipes/SandAI/MAGI-2-preview-L20X.md) |
 | `DreamZeroPipeline` | DreamZero-DROID | `GEAR-Dreams/DreamZero-DROID` | ✅︎ | ✅︎ | ✅︎ | ✅︎ | — |