fix: preserve BreakpointException and PipelineRuntimeError in _run_component_async

[rautaditya2606]

Related Issues

• Fixes _run_component_async wraps BreakpointException and PipelineRuntimeError instead of re-raising them #12173

Proposed Changes

• Added except BreakpointException: raise and except PipelineRuntimeError: raise clauses to _run_component_async in pipeline.py, before the general except Exception handler, mirroring the existing logic in the synchronous _run_component.
• Added regression test test_run_component_async_propagates_breakpoint_exception, which calls _run_component_async directly with a break_point and asserts that BreakpointException is propagated instead of being wrapped.
• Added regression test test_run_component_async_does_not_rewrap_pipeline_runtime_error, using a component that raises PipelineRuntimeError directly and asserting that the same exception instance propagates through run_async.
• Added a release note.

How did you test it?

hatch run test:unit test/core/pipeline/test_async_pipeline.py
hatch run test:unit test/core/pipeline/test_breakpoint.py
hatch run test:types haystack/core/pipeline/pipeline.py

All 21 async pipeline tests and 32 breakpoint tests pass. mypy reports no issues.

Notes for the reviewer

• The change is strictly additive: two new except clauses are inserted before the existing generic exception handler. The normal execution path is unchanged.
• BreakpointException is raised before _execute_component_async is called, so the previous except Exception block always intercepted it and wrapped it in a new PipelineRuntimeError, preventing callers from handling breakpoints correctly.
• Preserving PipelineRuntimeError also maintains parity with the synchronous implementation and avoids unnecessary double-wrapping for nested pipelines (for example, Agent components), preserving the original exception context.

Checklist

• I have read the [contributors guidelines](https://github.com/deepset-ai/haystack/blob/main/CONTRIBUTING.md) and the [code of conduct](https://github.com/deepset-ai/haystack/blob/main/code_of_conduct.txt).
• I have updated the related issue with new insights and changes.
• I have added unit tests and updated the docstrings.
• I've used one of the [conventional commit types](https://www.conventionalcommits.org/en/v1.0.0/) for my PR title.
• I have documented my code.
• I have added a release note file, following the [contributors guidelines](https://github.com/deepset-ai/haystack/blob/main/CONTRIBUTING.md#release-notes).
• I have run the pre-commit hooks and fixed any issues.

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[Copilot]

Pull request overview

• Fixes async pipeline error handling to match sync behavior by re-raising BreakpointException and PipelineRuntimeError from Pipeline._run_component_async instead of wrapping them.

Changes:

• Added explicit except BreakpointException: raise and except PipelineRuntimeError: raise in haystack/core/pipeline/pipeline.py before the generic except Exception.
• Added regression tests covering async propagation behavior for BreakpointException and PipelineRuntimeError.
• Added a release note documenting the fix and its impact on async breakpoints / nested pipeline errors.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
haystack/core/pipeline/pipeline.py	Re-raises BreakpointException/PipelineRuntimeError in _run_component_async to avoid accidental wrapping.
test/core/pipeline/test_async_pipeline.py	Adds async regression tests for breakpoint propagation and avoiding double-wrapping PipelineRuntimeError.
releasenotes/notes/fix-async-breakpoint-exception-980c389b99a94039.yaml	Release note describing the async exception propagation fix.

Comments suppressed due to low confidence (1)

test/core/pipeline/test_async_pipeline.py:580

• test_run_component_async_propagates_breakpoint_exception currently triggers the breakpoint via the break_point argument, which raises BreakpointException before _execute_component_async runs; this means the test does not exercise the new except BreakpointException: branch inside the try and would likely have passed even before this PR.

    break_point = Breakpoint(component_name="comp", visit_count=0)
    component_visits = {"comp": 0}
    comp = pipeline._get_component_with_graph_metadata_and_visits("comp", 0)

    # _run_component_async must raise BreakpointException, not wrap it in PipelineRuntimeError.

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[sjrl]

@davidsbatista I can take the review of this one

[sjrl]

Closing. See motivation here #12173 (comment)

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
haystack/core/pipeline
pipeline.py					573
Project Total

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