# Todo 52.13 Provider Cleanup Exception Priority Plan

**Status:** done

## Goal

Preserve the original provider failure, cancellation, or generator-close signal when cleanup of the wrapped provider iterator also fails.

## Observation

`TimingChatClient.stream_chat()` awaits `iterator.aclose()` in `finally`. If a provider exception or `CancelledError` is already propagating and `aclose()` raises another exception, the cleanup exception replaces the original. This can hide the real provider failure and convert cancellation into a normal runtime error instead of preserving interruption semantics.

## Scope

- Add regressions for provider exception plus close failure and cancellation plus close failure.
- Keep the active provider/cancellation/generator-close exception as the primary propagated exception.
- Propagate `aclose()` failure when no other exception is active.
- Always append the timing attempt without changing provider-await elapsed, usage completeness, or parallel-probe behavior.

## Files

- Modify: `src/agent_lab/application/benchmark.py`
- Modify: `tests/test_benchmark_runner.py`

## Verification

- `uv run pytest tests/test_benchmark_runner.py -q`
- `uv run pytest tests/test_benchmark_runner.py tests/test_benchmark_reporting.py -q`
- `uv run pytest`
- `git diff --check`