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[Model] Voxtral Realtime: add support for CUDAGraphMode.FULL_DECODE_ONLY - #51167

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mistralai:voxtral-cudagraph
Sep 14, 2026
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NickLucche merged 1 commit into
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mistralai:voxtral-cudagraph

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This PR allows running Voxtral Realtime full CG graph for decode-only batches.
Currently decode steps are stuck on piecewise capture and pay the per-step launch overhead.
The blocker is the whisper encoder's block-pooling attention builder: its build did a copy.deepcopy of the common
attention metadata and allocated a fresh slot_mapping every step, so the tensor addresses baked in at capture time were dead by replay.

This makes that builder capture-safe for uniform single-token decode and relaxes the assert accordingly.
Prefill/mixed batches still fall back to piecewise.

With CUDAGraphMode.FULL_DECODE_ONLY (single invocation per step):

image
cudaGraphLaunch Avg Latency Throughput
Eager 0 3.454s 60.5 tok/s
Piecewise CG 12,272 1.150s 181.7 tok/s
Full CG (this PR) 208 1.093s 191.1 tok/s

Single H200, Voxtral-Mini-4B-Realtime-2602, max_num_seqs=4, max_model_len=8192, 209 output tokens, 3 iterations averaged.

Batch Size Piecewise (tok/s) Full CG (tok/s) Speedup
1 170.4 201.1 1.18x
4 529.3 655.0 1.24x
8 1019.9 1225.7 1.20x
16 1940.9 2129.9 1.10x

Single H200, Voxtral-Mini-4B-Realtime-2602, max_model_len=16384, max_num_batched_tokens=16384, 3 iterations averaged.

With low batch size gaining the most by kernel launch time slashing, as expected.

cc @LucasWilkinson

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@mergify mergify Bot added multi-modality Related to multi-modality (#4194) mistral Related to Mistral models nvidia labels Aug 5, 2026
@NickLucche NickLucche added the ready ONLY add when PR is ready to merge/full CI is needed label Aug 5, 2026
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/ci run

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✅ Triggered Buildkite CI #82495 for commit 44ae56578719.

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/ci retry

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✅ Buildkite CI #82495 has failed jobs without stable step keys, so they cannot be retried on a new commit. Use /ci run.

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/ci run

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✅ Triggered Buildkite CI #82835 for commit b46340832053.

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Thanks for moving this forward @NickLucche 🙏

coauthored-by: was not parsed correctly in commit.
Could the merger include Co-authored-by: Jorge Gallego Feliciano jorge.gallego@mistral.ai in the squash message?

Appreciate it!

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/ci run

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✅ Triggered Buildkite CI #85769 for commit 476875403c60.

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/ci run

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/ci run

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✅ Triggered Buildkite CI #85981 for commit 99f4872e6ccf.

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LGTM, thanks!

@github-project-automation github-project-automation Bot moved this to Ready in NVIDIA Sep 10, 2026
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/ci run

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/ci run

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✅ Triggered Buildkite CI #88286 for commit 40dd4bcf45b5.

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/ci run

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✅ Triggered Buildkite CI #88348 for commit a026d74c3860.

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This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @NickLucche.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

@mergify mergify Bot added the needs-rebase label Sep 11, 2026
Signed-off-by: NickLucche <nicolo.lucchesi@mistral.ai>
Co-authored-by: Jorge Gallego Feliciano <jorge.gallego@mistral.ai>
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/ci run

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✅ Triggered Buildkite CI #88857 for commit cd745ed90c10.

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NickLucche enabled auto-merge (squash) September 14, 2026 16:48
@NickLucche
NickLucche merged commit 995e858 into vllm-project:main Sep 14, 2026
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@github-project-automation github-project-automation Bot moved this from Ready to Done in NVIDIA Sep 14, 2026
ItsRoy69 pushed a commit to ItsRoy69/vllm that referenced this pull request Sep 15, 2026
…ONLY` (vllm-project#51167)

Signed-off-by: NickLucche <nicolo.lucchesi@mistral.ai>
Co-authored-by: Jorge Gallego Feliciano <jorge.gallego@mistral.ai>
keneoneth pushed a commit to keneoneth/vllm that referenced this pull request Sep 16, 2026
…ONLY` (vllm-project#51167)

Signed-off-by: NickLucche <nicolo.lucchesi@mistral.ai>
Co-authored-by: Jorge Gallego Feliciano <jorge.gallego@mistral.ai>
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