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[Bugfix][Spec Decode] Fix multimodal embedding merge in Llama 4 and Mistral Large 3 EAGLE drafters - #57633
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…istral Large 3 EAGLE drafters EagleLlama4ForCausalLM and EagleMistralLarge3ForCausalLM borrowed SupportsMultiModal.embed_input_ids, which calls self._embed_text_input_ids and relies on SupportsMultiModal state the drafters never inherit. Any multimodal target with one of these drafters failed at startup with `AttributeError: 'EagleLlama4ForCausalLM' object has no attribute '_embed_text_input_ids'` as soon as the draft prefill embedded a batch. Embed the draft input ids directly and merge the external multimodal embeddings, matching EagleMistralForCausalLM. Co-authored-by: Claude <noreply@anthropic.com> Signed-off-by: Nishant Revur <kumrfni@amazon.com>
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@njhill @TQCB gentle ping, since this has been open about two weeks without review. This fixes a startup regression introduced by #50417. That PR marked EagleLlama4ForCausalLM and EagleMistralLarge3ForCausalLM as SupportsMultiModalEmbeddings, which made their aliased SupportsMultiModal.embed_input_ids reachable. The alias calls _embed_text_input_ids, which these drafters don't inherit, so any multimodal target paired with them crashes during the profile run. Repro and traceback are in #57630. It still reproduces on main as of today (edaf3e7), and the branch applies cleanly. The fix is ~40 lines with a unit test, and it was verified end to end on 4x L4 with Llama 4 Scout + EAGLE. |
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✅ @nishantrevur, CI is now available for this PR.
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…istral Large 3 EAGLE drafters (vllm-project#57633) Signed-off-by: Nishant Revur <kumrfni@amazon.com> Co-authored-by: Claude <noreply@anthropic.com>
Purpose
Fixes #57630.
Regression from #50417 (first released in v0.28.0): that change marked these drafters as
SupportsMultiModalEmbeddingsso the speculator started routing multimodal batches through theirembed_input_ids, which had been an unreachable alias ofSupportsMultiModal.embed_input_idsuntil then. cc @TQCBEagleLlama4ForCausalLMandEagleMistralLarge3ForCausalLMimplementSupportsMultiModalEmbeddingsby borrowing the method objectSupportsMultiModal.embed_input_ids. That method callsself._embed_text_input_ids(...)and readsself._has_oov_mm_tokens, both of which live onSupportsMultiModal, which the drafters do not inherit. Any multimodal target paired with one of these drafters fails during the first draft prefill (already in the profile run at startup):Reproduced on main (bf13ecc) and present in v0.28.0 and v0.29.0 with
RedHatAI/Llama-4-Scout-17B-16E-Instruct-quantized.w4a16+morgendave/EAGLE-Llama-4-Scout-17B-16E-Instruct, TP=4,--speculative-config '{"method":"eagle","model":...,"num_speculative_tokens":3}', default cudagraph mode. The same aliasing exists inEagleMistralLarge3ForCausalLM; Model Runner V1 takes the sameembed_input_idspath.Change
Replace the borrowed method with an explicit
embed_input_idsin both drafters that embeds the draft input ids viaself.model.embed_input_idsand merges external multimodal embeddings with_merge_multimodal_embeddings, the same shapeEagleMistralForCausalLMalready uses. No behavior change for text-only batches.Test plan
New test
test_mm_capable_drafter_merges_multimodal_embeddings(parametrized over both classes) checks text-only embedding and the merge of multimodal rows; it raisesAttributeErroron main.E2E (4x NVIDIA L4, TP=4, TRITON_ATTN,
RedHatAI/Llama-4-Scout-17B-16E-Instruct-quantized.w4a16+morgendave/EAGLE-Llama-4-Scout-17B-16E-Instruct,num_speculative_tokens=3,max_patches=4, 18 text + 12 image prompts, greedy, 48 new tokens):AttributeError: ... '_embed_text_input_ids')Image prompts now draft with acceptance close to text prompts, i.e. the drafter is receiving the image embeddings.
Disclosure
AI assistance (Claude) was used to investigate and draft this change; every line was reviewed and the tests were run by the submitter.