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[TRTLLM-10858][feat] Multi-image support for EPD disagg#11264

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2ez4bz:dev-epd-multi-images
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[TRTLLM-10858][feat] Multi-image support for EPD disagg#11264
2ez4bz wants to merge 1 commit intoNVIDIA:mainfrom
2ez4bz:dev-epd-multi-images

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@2ez4bz 2ez4bz commented Feb 4, 2026

Summary by CodeRabbit

  • New Features

    • Added support for multiple multimodal items (e.g., multiple images) in a single request, replacing the previous single-item limitation.
  • Bug Fixes

    • Enhanced validation for multimodal embeddings with per-item error reporting to identify specific mismatches.
  • Tests

    • Updated multimodal embedding tests to verify multi-item scenarios and parametrization improvements.

Description

  • Why?

Prior to this commit, we only supported a single multimodal input for E/P/D disaggregated serving.

  • What?

This commit does a minor refactor of the multimodal embedding handles that cross process boundaries to enable this.
Existing unit tests are updated accordingly to test this.

Test Coverage

Adjusted existing unit tests to use multiple images in a single request.

PR Checklist

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  • Documentation updated as needed

  • Update tava architecture diagram if there is a significant design change in PR.

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@2ez4bz 2ez4bz requested review from a team as code owners February 4, 2026 07:28
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📝 Walkthrough

Walkthrough

The PR refactors multimodal embedding handling to support multiple multimodal items per request instead of a single item. Changes include updating model input processors to validate multiple handles, converting embedding storage from single dict to list-based structures, updating result handling to use disaggregated parameters, and adjusting tests and API surfaces accordingly.

Changes

Cohort / File(s) Summary
Model Input Processors
tensorrt_llm/_torch/models/modeling_llava_next.py, modeling_qwen2vl.py, modeling_qwen3vl.py
Updated get_prompt_token_ids to validate multiple multimodal handles instead of enforcing exactly one. Each handle's hidden size is checked against model expectations with per-handle error reporting. Removed NotImplementedError constraints.
Embedding Request Handling
tensorrt_llm/_torch/pyexecutor/llm_request.py
Refactored mm_embeddings attribute to hold Optional[List[Dict[str, Any]]] instead of single dict. append_mm_embeddings now accepts multimodal_lengths parameter and splits concatenated embeddings into per-item chunks, storing as a list via SharedTensorContainer. Updated mm_embedding_handle property return type accordingly.
Sampler Integration
tensorrt_llm/_torch/pyexecutor/sampler.py
Updated call to append_mm_embeddings to pass multimodal_lengths parameter, enabling per-modality length handling during batching.
Result Handling
tensorrt_llm/executor/result.py
Changed mm_embedding_handle property to return Optional[List[Dict[str, Any]]] and retrieve from disaggregated_params.multimodal_embedding_handles instead of private attribute. Removed _mm_embedding_handle storage, updated _handle_response to use disaggregated parameters structure.
Public API Updates
tensorrt_llm/llmapi/llm.py
Replaced mm_embedding_handle attribute with disaggregated_params of type DisaggregatedParams in RequestOutput class. Updated documentation and representation fields.
Server Integration
tensorrt_llm/serve/openai_server.py
Updated openai_mm_encoder to read embedding handle from promise.disaggregated_params.multimodal_embedding_handles[0] when available, replacing direct mm_embedding_handle access.
Tests and API Reference
tests/unittest/_torch/multimodal/test_mm_encoder_standalone.py, tests/unittest/api_stability/references_committed/request_output.yaml
Updated test parametrization to handle multiple images and list-based embedding handles. Restructured test logic to reconstruct and concatenate embeddings from handle lists. Updated API stability reference to reflect disaggregated_params property change.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~50 minutes

Possibly related PRs

Suggested reviewers

  • chuangz0
  • hchings
  • dongjiyingdjy
  • yechank-nvidia
  • pcastonguay
  • symphonylyh
🚥 Pre-merge checks | ✅ 2 | ❌ 1
❌ Failed checks (1 warning)
Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 41.67% which is insufficient. The required threshold is 80.00%. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (2 passed)
Check name Status Explanation
Title check ✅ Passed The title clearly and specifically describes the main change: adding multi-image support for E/P/D disaggregation, which aligns with the refactoring of multimodal embedding handles across the changeset.
Description check ✅ Passed The description provides a clear problem statement (single multimodal input limitation), explains the solution (refactoring multimodal embedding handles), and lists test coverage (multiple images in single request), but lacks some expected template sections.

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Actionable comments posted: 0

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (3)
tensorrt_llm/serve/openai_server.py (1)

624-635: ⚠️ Potential issue | 🟠 Major

Don’t drop additional multimodal handles in the MM‑encoder response.
Selecting index 0 silently loses embeddings for multi‑image requests and undercounts tokens. Please return all handles (and update the response schema accordingly) or explicitly reject multi‑image inputs. Also sum tokens across handles.

🔧 Possible fix (return all handles and sum tokens)
-            mm_embedding_handle = (
-                promise.disaggregated_params.multimodal_embedding_handles[0]
-                if promise.disaggregated_params
-                and promise.disaggregated_params.multimodal_embedding_handles
-                else None
-            )
-            if not mm_embedding_handle or "tensor_size" not in mm_embedding_handle:
+            mm_embedding_handles = (
+                promise.disaggregated_params.multimodal_embedding_handles
+                if promise.disaggregated_params
+                else None
+            )
+            if not mm_embedding_handles:
                 return self.create_error_response(
                     message="Multimodal embedding handle missing in response",
                     err_type="InternalServerError",
                     status_code=HTTPStatus.INTERNAL_SERVER_ERROR)
-            num_tokens = int(mm_embedding_handle["tensor_size"][0])
+            if any("tensor_size" not in h for h in mm_embedding_handles):
+                return self.create_error_response(
+                    message="Multimodal embedding handle missing tensor_size",
+                    err_type="InternalServerError",
+                    status_code=HTTPStatus.INTERNAL_SERVER_ERROR)
+            mm_embedding_handle = (
+                mm_embedding_handles[0]
+                if len(mm_embedding_handles) == 1
+                else mm_embedding_handles
+            )
+            num_tokens = sum(int(h["tensor_size"][0]) for h in mm_embedding_handles)
tensorrt_llm/_torch/models/modeling_qwen3vl.py (1)

355-388: ⚠️ Potential issue | 🟡 Minor

Update mm_handles docstring for multi-handle support.

The docstring still claims only a single handle is supported, but the loop now validates multiple handles. This is misleading for API users.

📝 Suggested docstring tweak
-            mm_handles: List of multimodal embedding handles. Currently only a single handle is supported.
+            mm_handles: List of multimodal embedding handles, one per multimodal item.
tensorrt_llm/_torch/models/modeling_llava_next.py (1)

170-201: ⚠️ Potential issue | 🟡 Minor

Update mm_handles docstring for multi-handle support.

The docstring still states that only a single handle is supported, but the code now validates all handles. Please update the description to match behavior.

📝 Suggested docstring tweak
-            mm_handles: List of multimodal embedding handles. Currently only a single handle is supported.
+            mm_handles: List of multimodal embedding handles, one per multimodal item.
🧹 Nitpick comments (1)
tensorrt_llm/_torch/models/modeling_qwen2vl.py (1)

1055-1086: Update the docstring to reflect multi‑handle support.
The argument description still states a single handle, but the code now accepts multiple.

✏️ Docstring update
-            mm_handles: List of multimodal embedding handles. Currently only a single handle is supported.
+            mm_handles: List of multimodal embedding handles, one per multimodal item.

@2ez4bz 2ez4bz force-pushed the dev-epd-multi-images branch 2 times, most recently from 5f13d0c to da3acd5 Compare February 4, 2026 18:34
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2ez4bz commented Feb 4, 2026

/bot run --disable-fail-fast

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PR_Github #34834 [ run ] triggered by Bot. Commit: da3acd5

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PR_Github #34834 [ run ] completed with state SUCCESS. Commit: da3acd5
/LLM/main/L0_MergeRequest_PR pipeline #26873 completed with status: 'FAILURE'

⚠️ Action Required:

  • Please check the failed tests and fix your PR
  • If you cannot view the failures, ask the CI triggerer to share details
  • Once fixed, request an NVIDIA team member to trigger CI again

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LGTM

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Thanks for the effort!

# requests.
cache_transceiver_cfg = CacheTransceiverConfig(
backend="DEFAULT") if pd_disagg else None
backend="DEFAULT", max_tokens_in_buffer=10240) if pd_disagg else None
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Do you think it’s in general necessary to set max_tokens_in_buffer for EPD applications? If so, could we improve the error handling when it’s not explicitly set (e.g., provide a clearer error or default behavior)?

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I was actually going to ask you about this as well. If configured incorrectly, it seems to be causing issues in the decode worker - so how is this usually handled in P/D disagg for LLMs? Do we also need to tune this wrt to the maximum input sequence length?

I can certainly look into improving the error message, but do you mind if this is done in a subsequent PR?

* Why?

Prior to this commit, we only supported a single multimodal input for
E/P/D disaggregated serving.

* What?

This commit does a minor refactor of the multimodal embedding handles
that cross process boundaries to enable this.
Existing unit tests are updated accordingly to test this.

Signed-off-by: William Zhang <133824995+2ez4bz@users.noreply.github.com>
@2ez4bz 2ez4bz force-pushed the dev-epd-multi-images branch from da3acd5 to d66918f Compare February 5, 2026 07:27
@2ez4bz 2ez4bz requested a review from a team as a code owner February 5, 2026 07:27
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2ez4bz commented Feb 5, 2026

/bot run --disable-fail-fast

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PR_Github #34938 [ run ] triggered by Bot. Commit: d66918f

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PR_Github #34938 [ run ] completed with state SUCCESS. Commit: d66918f
/LLM/main/L0_MergeRequest_PR pipeline #26954 completed with status: 'FAILURE'

⚠️ Action Required:

  • Please check the failed tests and fix your PR
  • If you cannot view the failures, ask the CI triggerer to share details
  • Once fixed, request an NVIDIA team member to trigger CI again

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