Summary I've debugged the failing test

test_tool_call_validation_error_handling

and completed all requested tasks: Checklist • ✅ Analyzed the failing test from GitHub Actions • ✅ Investigated commit history to find when the test started failing (commit ec9daf3bc) • ✅ Identified root cause of the test failure • ✅ Opened GitHub issue explaining the problem: #12109 - https://github.com/OpenHands/OpenHands/issues/12109 • ✅ Created draft PR with minimal fix: #12110 - https://github.com/OpenHands/OpenHands/pull/12110 Root Cause The test was flaky due to a feedback loop in the event handling: 1. Test calls

controller._step()

2.

_step()

catches

BadRequestError

and adds

ErrorObservation

to event stream 3. Background thread picks up the event and calls

on_event

4.

on_event

calls

should_step(ErrorObservation)

which returns

True

5.

on_event

calls

_step_with_exception_handling()

6.

_step()

catches

BadRequestError

again (mock always raises the same error) 7. Repeat until iteration limit is reached The test expected 1

ErrorObservation

but got 4-10 depending on timing. Fix The minimal fix changes the mock to only raise the error on the first call, then return

NullAction

on subsequent calls. This breaks the feedback loop and makes the test deterministic. Changes: • Added import for

NullAction

• Modified

mock_step()

to track call count and only raise error once The fix was verified to pass consistently across 5 consecutive runs with pytest-xdist (

-n auto

). _{View full conversation}