[Frontend] Delegate preprocessing to OpenAIServingRender

[sagearc]

Purpose

OpenAIServingRender (#36166) owns the authoritative preprocessing logic for chat and completion requests, but OpenAIServingChat and OpenAIServingCompletion were duplicating it rather than delegating.

Changes:

• Split render_chat_request / render_completion_request into a public entry point (with model check) and a private helper (render_chat / render_completion) with no model/engine checks.
• OpenAIServingChat and OpenAIServingCompletion now accept openai_serving_render and delegate their preprocessing to those helpers after doing their own engine-aware checks.
• OpenAIServingRender is created first in init_generate_state so it can be passed to all serving classes.

Test Plan

Test Result

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[gemini-code-assist]

Code Review

This pull request refactors the preprocessing logic for chat and completion requests by centralizing it into OpenAIServingRender. This is a good architectural improvement that reduces code duplication.

However, I've identified a critical issue. The warmup() method in vllm/entrypoints/openai/chat_completion/serving.py was not updated to reflect this refactoring. It still calls self._preprocess_chat(), which has been moved to OpenAIServingRender. This will cause an AttributeError and prevent the server from starting.

Since this code is not in the diff, I cannot add a specific comment. The fix is to update the call in warmup() to delegate to self.openai_serving_render._preprocess_chat(...). This is a critical fix.

[mergify]

Hi @sagearc, the pre-commit checks have failed. Please run:

uv pip install pre-commit
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy failing?

mypy is run differently in CI. If the failure is related to this check, please use the following command to run it locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10

[mergify]

Hi @sagearc, the pre-commit checks have failed. Please run:

uv pip install pre-commit
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy failing?

mypy is run differently in CI. If the failure is related to this check, please use the following command to run it locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10

[mergify]

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

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

[sagearc]

@DarkLight1337 Updated OpenAIRenderer with the new model registry, let me know what do you think

[mergify]

Hi @sagearc, the pre-commit checks have failed. Please run:

uv pip install pre-commit
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy failing?

mypy is run differently in CI. If the failure is related to this check, please use the following command to run it locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10

[DarkLight1337]

Thanks, let's see if tests pass now

[mergify]

Hi @sagearc, the pre-commit checks have failed. Please run:

uv pip install pre-commit
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy failing?

mypy is run differently in CI. If the failure is related to this check, please use the following command to run it locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10

[mergify]

Hi @sagearc, the pre-commit checks have failed. Please run:

uv pip install pre-commit
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

Tip

Is mypy failing?

mypy is run differently in CI. If the failure is related to this check, please use the following command to run it locally:

# For mypy (substitute "3.10" with the failing version if needed)
pre-commit run --hook-stage manual mypy-3.10