[Jacqueline122]

Why are these changes needed?

failure_attribution() currently treats text in any model response as an answer. An agent can say "I will look that up.", encounter a tool failure, and finish with no answer, yet receive value="none" and failed=False.

Check the final ModelResponse instead, matching the evaluator's output projection. Interim text no longer hides tool_failure or no_answer; a run with a nonempty final response retains its existing mechanical-failure classification. The helper docstring now describes this behavior.

Validation:

• Added six regression cases covering successful/failed tools and final responses containing None, empty text, or a nonempty answer. These check the failure mode, failed flag, and decisive step.
• Relevant attribution and runtime smoke tests: 14 passed. I personally reran them locally.
• Before the fix, the attribution module with the added regression cases reported 4 failed, 8 passed.
• Re-ran an offline reproduction through the real Agent, tool execution, OTEL capture/reconstruction, and eval runner, using the public TestConfig for model responses.
• Ruff 0.16.10 lint/format and git diff --check passed.
• Additional targeted mypy 2.4.0 checking reports the same five existing generic/type errors before and after the fix, with no new diagnostics. This is not a clean mypy result.
• The full test suite and GitHub CI have not been verified yet.

Related issue number

Fixes #3505

Checks

• I've included any doc changes needed for https://docs.ag2.ai/. See https://docs.ag2.ai/latest/docs/contributor-guide/documentation/ to build and test documentation locally.
  • The helper docstring was updated. No public API change or website documentation update is needed for this correction.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

AI assistance

OpenAI Codex assisted with investigation, reproduction, the implementation in ag2/eval/scorers/attribution.py, regression tests in test/eval/scorers/test_attribution.py, and drafting the issue and PR description.

• I understand the changes in this PR and can explain them in my own words.
• I have verified that the PR description accurately reflects the actual diff.
• If AI assistance was used, I reviewed, tested, and validated the generated code/text before submitting.

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
ag2/eval/scorers/attribution.py	83.14% <100.00%> (+0.19%)	⬆️

... and 14 files with indirect coverage changes

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