Return 400 for chat template build errors

[shihaobai]

No description provided.

[gemini-code-assist]

Code Review

This pull request refactors the exception handling in build_prompt.py when applying a chat template, catching Exception instead of BaseException and raising a ValueError. The reviewer recommends preserving the exception chain by removing from None when raising the ValueError to ensure that the original traceback (such as Jinja2 rendering errors) is not lost, which is important for server-side debugging.

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[gemini-code-assist]

Suppressing the exception context with from None makes it difficult to debug chat template rendering issues on the server side, as the original traceback (e.g., from Jinja2) is lost. Consider preserving the exception chain by raising the ValueError without from None so that the underlying cause is visible in server logs.

Suggested change

	except Exception as e:
	raise ValueError(f"Failed to build prompt: {e}") from None
	except Exception as e:
	raise ValueError(f"Failed to build prompt: {e}")