[JunyiXu-nv]

Dev Engineer Review

• Added render_visual_gen_validation_error in tensorrt_llm/serve/_visual_gen_errors.py as the shared VisualGen 422 renderer. It takes the server's error-response factory as a parameter.
• Replaced six validation call sites in openai_server.py and openai_video_routes.py with calls to the shared function.
• Removed the duplicate renderer code: the server-local renderers in openai_server.py and the _render_pydantic_validation_error mixin method in openai_video_routes.py.
• The PR objectives state that the 422 body and status are preserved. The existing exception-handling clauses remain in place.
• Diff scope: 4 files changed, 240 insertions, 66 deletions. No test-list files changed.
• No material source or API risks identified from the diff.

QA Engineer Review

• Modified tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py (+172/-1 lines).
• Added TestVisualGenValidationErrorRendering. It covers route-level and handler-level validation, JSON and multipart requests, unknown fields, field-specific type errors, both Pydantic and FastAPI validation exceptions, empty-error fallback, exact 422 response bodies, and delegation to the response factory.
• The test file is listed in tests/integration/test_lists/test-db/l0_cpu.yml (line 266).
• No test-list files changed.
• The PR objectives report 200 passing tests in the endpoint file and 64 passing API-stability tests. They report no Pyrefly diagnostics for the new module.
• The PR objectives report a CPU serve-battery failure in test_render_standalone.py. It reproduced at the base commit because trtllm-render was not installed locally.
• GPU behavior was not tested locally. The author left GPU validation to CI.
• CI status: the PR objectives report that CI runs for commits 2ca8b27 and 7a4b7aa completed with SUCCESS. The associated L0 MergeRequest pipelines were reported as UNSTABLE. Multi-GPU tests required the ci: full pre-merge approved label. Current-head CI results were not verified.
• Coverage verdict: sufficient for the CPU-testable renderer and endpoint paths. GPU results are not available.

Per-File QA Perspective

• tensorrt_llm/serve/_visual_gen_errors.py: Verify 422 status, field-location formatting, extra_forbidden messages, empty-error fallback (str(exc)), and response-factory delegation.
• tensorrt_llm/serve/openai_server.py: Verify that route-level request-validation responses and image-edit ValidationError responses remain unchanged.
• tensorrt_llm/serve/openai_video_routes.py: Verify that synchronous and asynchronous video validation responses remain unchanged.
• tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py: Covers the shared renderer and the updated VisualGen validation paths. Listed in tests/integration/test_lists/test-db/l0_cpu.yml.

Description

Today the VisualGen 422 validation-error envelope is rendered by two identical copies of the same loop: OpenAIServer._create_visual_gen_validation_error_response (for FastAPI's RequestValidationError, raised when a route's declared request model rejects the JSON body) and _VideoRoutesMixin._render_pydantic_validation_error (for pydantic's ValidationError, raised when a handler builds its own request model from JSON or multipart). OpenAIServer.openai_image_edit calls the mixin's copy, so the host class depends on a method only its mixin base defines. This PR replaces both methods with one module-level function, render_visual_gen_validation_error, in the new private module tensorrt_llm/serve/_visual_gen_errors.py, and points all six call sites at it. The function takes the server's error-response factory (create_error_response) as an argument, so the error envelope and the context-length code rule stay defined in one place and the new module never imports openai_server.

Part of the trtllm-serve refactor (epic TRTLLM-17056, task TRTLLM-17264): isolating VisualGen serving. This PR removes the host-to-mixin call edge so a later PR can move the VisualGen handlers out of OpenAIServer as a plain move.

When this PR was opened, #20865 ("serve: answer a request that fails validation with a readable error", same validation handler) was OPEN and unmerged, so this PR edits the handler in its current shape, the validation_exception_handler closure in OpenAIServer.__init__. Whichever of the two lands second rebases a one-line conflict in the VisualGen branch of that handler. #20865's current head also rewrites the TestNonVisualGenValidationResponse class in tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py (it deletes the mirror comment this PR renames), so the second-lander also resolves a trivial conflict in that test class.

Other open PRs touching the same files when this PR was opened, none on the lines this PR changes: draft #17541 (observability) rewrites the logger import line of tensorrt_llm/serve/openai_video_routes.py, adjacent to this PR's new import; #12746 inserts a model-name check at the top of openai_image_edit, away from the validation clauses. Whoever lands second resolves a trivial conflict.

Behavior

No behavior change: both entry points return the same status and bytes as before; see the characterization tests, which pin the full 422 body and pass unchanged at the merge base (first commit) and at the head.

The merge, side by side

The two deleted methods were statement-for-statement identical (checked by comparing ast.dump of the bodies): the only difference is formatting and the parts: List[str] vs parts: list[str] annotation. Extracted bodies (dedented) diffed with git diff --no-index:

Deleted server copy vs deleted mixin copy

@@ -1,22 +1,21 @@
-def _create_visual_gen_validation_error_response(
-        self, exc: RequestValidationError) -> Response:
-    """Render a ``RequestValidationError`` as the visual-gen 422 envelope.
+def _render_pydantic_validation_error(self, exc: ValidationError) -> Response:
+    """Render a multipart Pydantic ``ValidationError`` as the LLM envelope.
 
-    The body has the LLM-style ``{message, type, code}`` shape with
-    HTTP 422. The ``message`` field names the offending field(s) for
-    each error in ``exc.errors()`` so clients can fix the request
-    without parsing the full Pydantic payload.
+    The visual-gen-scoped 422 envelope is the same shape JSON requests
+    get from the FastAPI ``RequestValidationError`` handler, so JSON
+    and multipart clients see indistinguishable bodies on bad
+    payloads.
     """
-    parts: List[str] = []
+    parts: list[str] = []
     for err in exc.errors():
-        loc = ".".join(
-            str(seg) for seg in err.get("loc", ()) if seg != "body")
+        loc = ".".join(str(seg) for seg in err.get("loc", ()) if seg != "body")
         etype = err.get("type", "")
         msg = err.get("msg", "")
         if etype == "extra_forbidden":
             parts.append(
                 f"Unknown request field {loc!r}. Pass model-specific "
-                "parameters via 'extra_params' instead.")
+                "parameters via 'extra_params' instead."
+            )
         elif loc:
             parts.append(f"{loc}: {msg}")
         else:

Deleted mixin copy vs the new function

@@ -1,10 +1,14 @@
-def _render_pydantic_validation_error(self, exc: ValidationError) -> Response:
-    """Render a multipart Pydantic ``ValidationError`` as the LLM envelope.
+def render_visual_gen_validation_error(
+    exc: Union[RequestValidationError, ValidationError],
+    create_error_response: Callable[..., Response],
+) -> Response:
+    """Render a VisualGen request validation failure as the 422 error envelope.
 
-    The visual-gen-scoped 422 envelope is the same shape JSON requests
-    get from the FastAPI ``RequestValidationError`` handler, so JSON
-    and multipart clients see indistinguishable bodies on bad
-    payloads.
+    Both entry points produce the same body: FastAPI's RequestValidationError
+    when a route's declared request model rejects the JSON body, and pydantic's
+    ValidationError when a handler builds its own request model (multipart,
+    image edit, video). ``create_error_response`` is the server's error-response
+    factory, so the body and the context-length code rule stay in one place.
     """
     parts: list[str] = []
     for err in exc.errors():
@@ -21,7 +25,7 @@ def _render_pydantic_validation_error(self, exc: ValidationError) -> Response:
         else:
             parts.append(msg)
     message = "; ".join(parts) if parts else str(exc)
-    return self.create_error_response(
+    return create_error_response(
         message=message,
         err_type="BadRequestError",
         status_code=HTTPStatus.UNPROCESSABLE_ENTITY,

The new function's body is AST-identical to the deleted ones after substituting the receiver: self.create_error_response becomes the create_error_response argument. The six call sites:

#	Location	Context	Before	After
1	serve/openai_server.py, validation_exception_handler closure in OpenAIServer.__init__	VISUAL_GEN branch for RequestValidationError	self._create_visual_gen_validation_error_response(exc)	render_visual_gen_validation_error(exc, self.create_error_response)
2	serve/openai_server.py, openai_image_edit, inner except ValidationError	handler-built ImageEditRequest	self._render_pydantic_validation_error(exc)	same as 1
3	serve/openai_server.py, openai_image_edit, outer except ValidationError	same	same	same
4	serve/openai_video_routes.py, openai_video_generation_sync, inner except ValidationError	handler-built VideoGenerationRequest	same	same
5	serve/openai_video_routes.py, openai_video_generation_sync, outer except ValidationError	same	same	same
6	serve/openai_video_routes.py, openai_video_generation_async	same	same	same

Every except ValidationError clause stays where it is; only the return expression changes.

CI bookkeeping

• Multi-GPU table: none (openai_server.py is already listed; the new module is VisualGen serving code, deliberately not added)
• CODEOWNERS: none
• legacy-files.txt: none (the new module is ruff-formatted, not registered as a legacy file)
• Test lists: none needed — the new tests go into tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py, already registered in l0_cpu.yml (line 167) and marked cpu_only
• pyproject.toml: no change — main type-checks with Pyrefly since [None][infra] Introduce Pyrefly to do type check #21325, whose project-includes covers the new module
• CBTS dryrun on this range reports scope: None (full fallback: serve/openai_server.py is unclaimed), as expected before the VisualGen package exists

Test Coverage

New class TestVisualGenValidationErrorRendering in tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py (cpu_only, runs in the CPU-Generic stages):

• test_route_level_unknown_field_body_is_exact — pins the full 422 body for an unknown field on POST /v1/images/generations
• test_route_level_type_error_names_the_field — seed: <pydantic msg>, message computed from the model so pydantic wording is not hard-coded
• test_handler_level_bodies_match_route_level — the same payload on POST /v1/videos/sync, POST /v1/videos and POST /v1/images/edits (JSON) returns byte-identical bodies
• test_multipart_handler_level_body_is_exact — multipart POST /v1/videos/sync returns the same body
• test_renderer_accepts_both_exception_types — same status and bytes for a pydantic ValidationError and a RequestValidationError with FastAPI's leading body loc segment
• test_renderer_falls_back_to_str_without_errors — empty error list falls back to str(exc)
• test_renderer_delegates_to_the_factory — the renderer calls the factory exactly once with err_type="BadRequestError", status 422, and returns its result

The first commit adds the endpoint-level tests only and passes at the merge base; the second commit is the refactor plus the renderer-level tests. Commands run locally (CPU container, no GPU):

All commands below ran on a no-GPU x86 dev box against compiled artifacts source-built at the merge base f6c4125c79 (this PR's exact base), PYTHONPATH pointing at the PR worktree. GPU behavior is unchanged by construction (pure-Python rendering refactor); GPU stages are left to CI.

# characterization tests at the merge base (first commit, old code): 4 passed
pytest -m cpu_only tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py -k TestVisualGenValidationErrorRendering -q
# full file at the merge base + tests commit: 163 passed (159 upstream + 4 new)
# full file at the head: 166 passed (163 + 3 renderer-level tests), no failures, no new skips
pytest -m cpu_only tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py -q
# API stability: 64 passed
pytest tests/unittest/api_stability -q
# serve CPU battery: 3438 passed, 1 failed, 1 skipped, 2 xfailed; the one failure (test_render_standalone.py, launcher CUDA-stub test) fails identically at the base commit with 'trtllm-render is not installed' - a local-environment gap (console script not installed in the PYTHONPATH overlay), not this PR
pytest -m cpu_only tests/unittest/llmapi/apps tests/unittest/disaggregated -q
# Pyrefly strict check of the new module (pyrefly 1.4.0, the requirements-dev.txt pin): "No Pyrefly diagnostics.", exit status 0, 0 remaining diagnostics
# main type-checks with Pyrefly since #21325, which covers the new module without a pyproject.toml change
bash scripts/run_pyrefly.sh --strict tensorrt_llm/serve/_visual_gen_errors.py
# old names gone; new name = 1 definition + 6 call sites + 2 imports
git grep -n "_render_pydantic_validation_error\|_create_visual_gen_validation_error_response" -- tensorrt_llm/ tests/   # no output
git grep -n "render_visual_gen_validation_error" -- tensorrt_llm/
# the new module defines exactly one top-level name
python -c "import ast; t=ast.parse(open('tensorrt_llm/serve/_visual_gen_errors.py').read()); print([n.name for n in t.body if hasattr(n,'name')])"   # ['render_visual_gen_validation_error']
# pre-commit on all changed files: passed twice, no file modified on the second run
pre-commit run --files tensorrt_llm/serve/_visual_gen_errors.py tensorrt_llm/serve/openai_server.py tensorrt_llm/serve/openai_video_routes.py tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py
# CI stage for the test file: CPU-Generic-arm-1, CPU-Generic-x86-1
python scripts/test_to_stage_mapping.py --tests "unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py"

Refreshed 2026-11-11 after rebasing onto main bae7da432c (the patch is unchanged; the earlier pyproject.toml hunk is gone because the [tool.mypy] files list it extended no longer exists on main): pytest tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py -q 200 passed; pytest tests/unittest/api_stability -q 64 passed; pre-commit on the four changed files passed twice with no file modified; bash scripts/run_pyrefly.sh --strict tensorrt_llm/serve/_visual_gen_errors.py reports no diagnostics. Same no-GPU x86 box; the compiled artifacts come from a source build at 5d2bbc0dda, with a test-only shim declaring the C++ ops main added since (none of them is reached by these tests).

Property-based check (local, not committed): the new function and the two deleted implementations (extracted verbatim from the base commit) were driven differentially with Hypothesis over generated real pydantic ValidationErrors, RequestValidationErrors (loc shapes with and without the body segment, error types, empty lists) — identical factory calls and rendered bytes on every generated input; a mutation gate planting 8 plausible bugs in the new function (wrong separator, dropped body stripping, wrong status/type, dropped fallback, branch inversions) was caught 8/8 by the properties.

PR Checklist

Please review the following before submitting your PR:

• PR description clearly explains what and why. If using CodeRabbit's summary, please make sure it makes sense.

• PR Follows TRT-LLM CODING GUIDELINES to the best of your knowledge.

• Test cases are provided for new code paths (see test instructions)

• If PR introduces API changes, an appropriate PR label is added - either api-compatible or api-breaking. For api-breaking, include BREAKING in the PR title.

• Any new dependencies have been scanned for license and vulnerabilities

• CODEOWNERS updated if ownership changes

• Documentation updated as needed

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

• The reviewers assigned automatically/manually are appropriate for the PR.

• Please check this after reviewing the above items as appropriate for this PR.

🤖 Generated with Claude Code

[JunyiXu-nv]

/bot run

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No actionable comments were generated in the recent review.

Walkthrough

Visual-generation validation errors from FastAPI and Pydantic now use a shared renderer. It formats error details and returns an HTTP 422 response through the supplied response factory. Image and video validation paths use the renderer, and tests cover its output and fallback behavior.

Changes

Visual-generation validation errors

Layer / File(s)	Summary
Shared validation error renderer tensorrt_llm/serve/_visual_gen_errors.py	Adds a renderer that formats validation details and passes the message, BadRequestError, and HTTP 422 status to the response factory.
Handler integration and validation coverage tensorrt_llm/serve/openai_server.py, tensorrt_llm/serve/openai_video_routes.py, tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py	Image and video validation paths delegate to the shared renderer. Tests check 422 responses, error formatting, fallback behavior, and response-factory arguments.

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Refactor

Suggested reviewers: qijune

Merge Risk: Minimal · up to 1488c

This refactor centralizes how image and video validation errors are rendered, and the 422 response is intended to stay the same. The tests added with it cover the main cases, and no merge-blocking risk was identified.

Security architecture risk: Minimal · up to 1488c

The shared renderer preserves existing validation messages, response formatting, and surrounding request controls. The change adds no request entrypoints or execution privileges, and no material security risk introduced or worsened by this PR was identified.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The changed attacker-facing behavior is confined to rendering validation failures on existing image and video request paths. The full production diff introduces no new route, downstream service access, credential use, or persistence authority. The additional FastAPI route identified in the test file belongs to a test-only dispatch fixture.

Trust Boundaries and Controls

• observed — Request-derived error locations and messages still flow through the existing server-owned JSON response factory. Request input does not select that factory. The VisualGen role gate, image-edit capability and path restrictions, video path restrictions, and caught validation exception types remain unchanged around the replacement calls.

Pre-merge checks: 4

Check name	Status	Explanation
Title check		The title names the main change: two duplicate VisualGen validation-error renderers are merged into one shared function. It follows the required ticket-and-type format, and the title is 75 characters,…
Description check		The description covers what changed and why. It explains the two duplicate renderers, the new shared function in tensorrt_llm/serve/_visual_gen_errors.py, and the six call sites. It states that beha…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title names the main change: two duplicate VisualGen validation-error renderers are merged into one shared function. It follows the required ticket-and-type format, and the title is 75 characters, which is within a normal length. The title matches the changeset in the raw summary, which adds the shared renderer and removes the server-local and mixin-local copies.

Full details: Description check

Explanation

The description covers what changed and why. It explains the two duplicate renderers, the new shared function in tensorrt_llm/serve/_visual_gen_errors.py, and the six call sites. It states that behavior is unchanged and lists the tests added. The description does not follow the template's section headings exactly, but it covers the required information. The checklist is ticked. It does not state an explicit label for API compatibility, although the PR claims no behavior change, so the API-label item is not addressed explicitly.

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• tests/unittest/_torch/visual_gen/test_trtllm_serve_endpoints.py

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CI Report

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[JunyiXu-nv]

/bot run

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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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PR_Github #83949 [ run ] completed with state SUCCESS. Commit: 7a4b7aa
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CI Report

⚠️ Multi-GPU Label Required:
Multi-GPU tests require the ci: full pre-merge approved label on this PR. Either:

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• If needed, ask a member of NVIDIA/trt-llm-ci-approvers to add the label manually.
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[hanjingtian]

Could you please rebase this branch onto the latest upstream main to include the CI hang fix in #22101 (6edbe383497a)? The current branch still contains the regression that can cause pipelines to hang for an extended period and worsen CI queueing

[JunyiXu-nv]

/bot run --disable-fail-fast

[JunyiXu-nv]

Merged the latest upstream main into this branch in 1488c86, including the CI hang fix from #22101 (6edbe38), and restarted CI. The branch history is preserved; no force-push.

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