[kokyouu]

Motivation

A custom --generation-config directory may contain LMDeploy-compatible keys such as stop_words. The loader retains those keys, while the serving endpoints also supply mapped/computed kwargs (for example, stop_words=request.stop). The builder currently removes overlaps only from the request before merging server defaults. The default therefore reaches the constructor alongside the explicit kwarg and raises TypeError: GenerationConfig() got multiple values for keyword argument 'stop_words'.

This is reproducible offline with a temporary generation_config.json containing {"do_sample": true, "temperature": 0.6, "stop_words": ["default-stop"]}, loaded through resolve_default_gen_config and passed to build_serving_generation_config. Both an omitted stop and an explicit request stop fail on main. random_seed and computed logprobs have the same collision when present in the defaults.

Modification

• Remove explicit kwarg overlaps from the merged config, so they cannot be reintroduced by the server defaults.
• Preserve explicit kwarg precedence, including None, without mutating the defaults or changing the special handling of generation length and sampling mode.
• Add four direct regressions for mapped/computed values, plus two regressions that load a real local config file and use the serving builder.

Validation

• On base aba987ad2266d2fd2204e9d22d1ce43a5984dc91, the six added cases fail with duplicate-keyword TypeError.
• After the fix: 386 passed across the generation-config suite, parser suite, chat runner, Responses request conversion, completions/chat-completions, generate-logprobs and Anthropic tests.
• All applicable repository pre-commit hooks pass for the two changed files; git diff --check passes.

Local validation uses Python 3.12.3 on Windows with PyTorch 2.7.1 and Transformers 4.57.1. No model downloads, GPU inference, full-repository suite or dependency-version matrix was run. The existing deprecation/Pydantic/optional-JIT warnings remain.

Checklist

• Run the repository's pre-commit hooks on the changed files.
• Add regression tests and run adjacent unit suites.
• Update the helper docstring to describe explicit kwarg precedence.
• No dependency changes or intentional compatibility break.

Developed with AI assistance; the patch, baseline failures and final test results were checked locally.