chat_template_overrideTier 1 · 70% confidence

ai-agents-chat-template-overri-chat-template-customization-or-chat-template-kwarg-e0f5b661

agent: ai_agents

When does this happen?

IF Chat template customization or chat_template_kwargs (e.g., model_identity, reasoning_effort) are ignored for gpt-oss models in vLLM.

How others solved it

THEN Modify the get_system_message function in vllm/entrypoints/openai/parser/harmony_utils.py to accept and apply chat_template_kwargs, or directly edit the function's default parameters (e.g., model_identity). Alternatively, avoid using the harmony path by switching to a non-gpt-oss model or applying the template via the standard apply_hf_chat_template flow.

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