fix(converter): prevent double-encoding in to_json fallback for text-only LLMs (#7429)

[kaan6634]

Summary

Resolves #7429.

When using non-function-calling (text-only) LLMs, Converter.to_json() and ato_json() previously wrapped the LLM string response in json.dumps(), resulting in a double-encoded JSON string ('"{\\"name\\": ...}"'). This caused Task._unpack_model_output() to produce a string instead of a dictionary and fail with a Pydantic TaskOutput.json_dict validation error.

Changes

• Updated Converter.to_json() and ato_json() to coerce text-only LLM output into the target model via _coerce_response_to_pydantic() and serialize using .model_dump_json(indent=2).
• Aligned the text-only path with InternalInstructor.to_json() behavior.
• Added sync and async regression tests in lib/crewai/tests/utilities/test_converter.py.

Testing

Ran unit tests with pytest:

• test_converter_to_json_text_only_llm_single_encoding PASSED
• test_converter_ato_json_text_only_llm_single_encoding PASSED

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📥 Commits

Reviewing files that changed from the base of the PR and between a296a39 and f28ef98.

📒 Files selected for processing (2)

• lib/crewai/src/crewai/utilities/converter.py
• lib/crewai/tests/utilities/test_converter.py

🚧 Files skipped from review as they are similar to previous changes (2)

• lib/crewai/tests/utilities/test_converter.py
• lib/crewai/src/crewai/utilities/converter.py

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📝 Walkthrough

Walkthrough

Changes

The converter now validates non-function-calling LLM responses before JSON serialization. Synchronous and asynchronous paths return single-encoded model JSON. Tests cover string and mapping responses for JSON and Pydantic conversion.

Converter JSON encoding

Layer / File(s)	Summary
Validated JSON output lib/crewai/src/crewai/utilities/converter.py, lib/crewai/tests/utilities/test_converter.py	The converter validates decoded responses with the configured Pydantic model before serialization. Tests verify synchronous and asynchronous JSON output and Pydantic conversion for string and mapping responses.

Priority: ➖ Normal

Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to f28ef

The converter now accepts already-decoded mapping responses without double-encoding them, with sync and async regression coverage. No actionable merge risk remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the primary change: preventing double encoding in Converter.to_json fallback handling for text-only LLMs.
Description check	✅ Passed	The description explains the issue, solution, linked issue, affected APIs, and regression tests. It does not use the template's exact Verification and Additional context sections, but the required inf…
Linked Issues check	✅ Passed	The implementation satisfies the coding requirements in #7429. For non-function-calling LLMs, Converter.to_json() and Converter.ato_json() validate the response with `_coerce_response_to_pydantic(…
Out of Scope Changes check	✅ Passed	The changed production code and tests remain within #7429. The mapping-response support extends the same converter paths that handle text-only responses. The added tests cover the affected sync and as…
Docstring Coverage	✅ Passed	Docstring coverage is 90.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 2 files.

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Actionable comments posted: 1

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Inline comments:
In `@lib/crewai/src/crewai/utilities/converter.py`:
- Line 169: Update _coerce_response_to_pydantic and its asynchronous counterpart
to validate already-decoded non-string responses with
self.model.model_validate(response) before using the JSON-string validation
path, preserving string parsing behavior. Add synchronous and asynchronous
regression tests covering valid mapping responses from non-function-calling
models.

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Configuration used: Organization UI

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📥 Commits

Reviewing files that changed from the base of the PR and between 894898f and a296a39.

📒 Files selected for processing (2)

• lib/crewai/src/crewai/utilities/converter.py
• lib/crewai/tests/utilities/test_converter.py

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