[chrikrah]

Related Issues

• No issue filed. fix: handle empty or missing tool-call arguments in from_openai_dict_format #11972 fixed the same input in ChatMessage.from_openai_dict_format, and fix: accept dict tool arguments in ChatMessage.from_openai_dict_format #12790 moved that into _parse_openai_tool_call_arguments. This fixes the two non-streaming generator paths.

Proposed Changes:

openai.py:671 and openai_responses.py:695 call json.loads on the arguments of each tool call. OpenAI-compatible servers such as vLLM send "" for a tool with no parameters (vllm-project/vllm#19419); None is covered as a defensive case. The converter then drops the call with the "malformed JSON" warning, or the reply raises TypeError. Both streaming paths already turn "" into {}.

Both sites now use _parse_openai_tool_call_arguments from #12790. Malformed JSON is still skipped. A call cut off at finish_reason: length with empty arguments now becomes {}, as it already does when streaming, and _check_finish_reason still logs the truncation on Chat Completions.

How did you test it?

One parametrized test per generator, for "" and None.

$ PYTHONPATH=. python -m pytest test/components/generators/chat/test_openai.py test/components/generators/chat/test_azure.py \
    test/components/generators/chat/test_openai_responses.py test/components/generators/chat/test_openai_responses_conversion.py \
    test/components/generators/chat/test_azure_responses.py -m 'not integration' -q
main 0499239:                          174 passed, 40 deselected
this branch:                           178 passed, 40 deselected
both production files reverted:        4 failed, 174 passed

$ ruff check && ruff format --check    # ruff 0.16.9, four touched files: clean
$ mypy --python-version 3.12 haystack/components/generators/chat/openai.py haystack/components/generators/chat/openai_responses.py
Success: no issues found in 2 source files   # mypy 2.3.1
# not run: integration tests, no server was called

Notes for the reviewer

The Azure generators inherit both methods.

Checklist

• I have read the contributors guidelines and the code of conduct.
• I have updated the related issue with new insights and changes: there is no issue for this path.
• I have added unit tests and updated the docstrings.
• I have used one of the conventional commit types for my PR title.
• I have documented my code: the two-line change needs no new docstring.
• I have added a release note file.
• I have run pre-commit hooks: ruff and mypy ran directly, as quoted above, and the full pre-commit set did not.

@sjrl, you merged #12790 and kept invalid JSON raising. The string "null" still parses to None and becomes ToolCall.arguments. Should the helper map it to {} too?

[vercel]

@chrikrah is attempting to deploy a commit to the deepset Team on Vercel.

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[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
haystack/components/generators/chat
openai.py
openai_responses.py
Project Total

This report was generated by python-coverage-comment-action

[sjrl]

Thanks!