fix: async tasks receive empty context due to last_sync_output truncation

[rafaelipuente]

Description

Fixes #6417.

Tasks configured with async_execution=True do not receive the correct context from prior tasks. In both _execute_tasks and _aexecute_tasks, the context for async tasks was built from [last_sync_output] if last_sync_output else [], but last_sync_output is only populated when resuming from a skipped/conditional task in prepare_task_execution and is otherwise None during a normal run. As a result, async tasks received an empty context and could not access the outputs of previous tasks.

Fix

Pass the full task_outputs list to _get_context() for async tasks in both executors, mirroring the behavior of synchronous tasks.

This complements #6415 (same code fix) by adding regression test coverage for both execution paths.

Testing

• Added two regression tests in lib/crewai/tests/crew/test_async_crew.py:
  • native async path (_aexecute_tasks): asserts the async task's context contains the prior sync task's output
  • thread-based path (_execute_tasks): captures the context passed to execute_async and asserts it contains the prior sync task's output
• Both tests fail on main (async task context is empty) and pass with the fix.
• Full lib/crewai/tests/crew/test_async_crew.py suite passes (13 tests); ruff lint/format clean on changed files.

(Note: authored with the assistance of an AI coding agent. Please apply the llm-generated label.)

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⚙️ Run configuration

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Run ID: 73ce88a8-3225-42d7-a1b4-0d0bd1d2de39

📥 Commits

Reviewing files that changed from the base of the PR and between 2b90117 and 8485b5f.

📒 Files selected for processing (2)

• lib/crewai/src/crewai/crew.py
• lib/crewai/tests/crew/test_async_crew.py

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📝 Walkthrough

Walkthrough

Modified Crew._aexecute_tasks and Crew._execute_tasks so async tasks receive context built from the full accumulated task_outputs instead of only last_sync_output, which was often None. Added two regression tests confirming async tasks now receive prior sync task outputs in their context.

Changes

Async task context fix

Layer / File(s)	Summary
Async and sync executor context construction lib/crewai/src/crewai/crew.py	Both _aexecute_tasks and _execute_tasks now derive async task context from accumulated task_outputs instead of the last_sync_output-based list.
Regression tests for context propagation lib/crewai/tests/crew/test_async_crew.py	Added tests verifying async tasks receive "Sync result" in their context for both the async (_aexecute_tasks) and threaded (_execute_tasks) execution paths.

Sequence Diagram(s)

sequenceDiagram
  participant Crew
  participant SyncTask
  participant AsyncTask

  Crew->>SyncTask: execute_sync()
  SyncTask-->>Crew: append output to task_outputs
  Crew->>AsyncTask: aexecute_sync(context=task_outputs)
  AsyncTask-->>Crew: result reflects full prior context

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Related Issues: #6417

Suggested labels: bug, llm-generated

Suggested reviewers: joaomdmoura

_🐰

  A hop, a fix, a context found,
  No more truncated outputs bound.
  Async tasks now see it all,
  Sync results answer the call.
  Tests confirm the fix stands tall.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the fix: async tasks now receive full context instead of truncated last_sync_output.
Description check	✅ Passed	The description matches the code changes and regression tests for async task context.
Linked Issues check	✅ Passed	The PR satisfies #6417 by using task_outputs for async task context in both executors and adding regression tests.
Out of Scope Changes check	✅ Passed	The changes stay within the bug fix and test coverage described by the linked issue.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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