fix: support async before/after_kickoff_callbacks in akickoff

[magiccao]

Summary

Fixes #6481

Crew.akickoff() is a native async execution path, but before_kickoff_callbacks and after_kickoff_callbacks were invoked synchronously, silently discarding async callables and blocking the event loop on IO-bound sync callbacks.

This PR brings akickoff into alignment with the existing async callback handling for task_callback and step_callback.

Changes

crews/utils.py

Refactors prepare_kickoff by extracting three private helpers:

• _begin_prepare_kickoff — emission counter reset + resuming flag
• _normalize_inputs — input type validation and dict conversion
• _finish_prepare_kickoff — event emission, file handling, input interpolation, agent setup, planning

Adds aprepare_kickoff (async counterpart): identical to prepare_kickoff except the before_kickoff_callbacks loop uses inspect.isawaitable() + await to support coroutine callbacks.

crew.py

• akickoff: replaces prepare_kickoff(...) with await aprepare_kickoff(...)
• akickoff: adds inspect.isawaitable check in the after_kickoff_callbacks loop

Behavior

callback	before	after
sync callable	unchanged	unchanged
async callable in akickoff	now awaited ✅	now awaited ✅
async callable in kickoff_async	still not awaited ⚠️	still not awaited ⚠️

Note on kickoff_async: this PR only fixes async callback support in akickoff. kickoff_async runs kickoff() in a worker thread via asyncio.to_thread, so sync callbacks won't block the event loop — but async before/after_kickoff_callbacks are still not awaited there. Fixing kickoff_async would require a separate effort.

Test plan

• Existing test_async_crew.py tests pass (sync callbacks unaffected)
• test_akickoff_calls_async_before_callbacks — async before callback is awaited; modified inputs reach task interpolation
• test_akickoff_calls_async_after_callbacks — async after callback is awaited; result remains CrewOutput
• test_akickoff_mixed_sync_async_callbacks — mixed pipeline (sync_before → async_before → async_after → sync_after) executes in correct order and preserves the transform chain

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds async-aware handling of before_kickoff_callbacks and after_kickoff_callbacks in Crew.akickoff(). Introduces aprepare_kickoff alongside refactored shared helpers (_begin_prepare_kickoff, _normalize_inputs, _finish_prepare_kickoff) used by both sync and async kickoff preparation, plus new tests covering async and mixed sync/async callback scenarios.

Changes

Async kickoff callback support

Layer / File(s)	Summary
Shared kickoff preparation helpers and async variant lib/crewai/src/crewai/crews/utils.py	Refactors prepare_kickoff into _begin_prepare_kickoff, _normalize_inputs, and _finish_prepare_kickoff helpers; adds new aprepare_kickoff function that awaits before_kickoff_callbacks results when awaitable before forwarding to shared finish logic.
akickoff() awaits async input prep and callback results lib/crewai/src/crewai/crew.py	Imports inspect and aprepare_kickoff; replaces prepare_kickoff call with awaited aprepare_kickoff in akickoff(); awaits after_kickoff_callbacks results when they are awaitable.
Async callback tests for akickoff lib/crewai/tests/crew/test_async_crew.py	Adds asyncio import and three new tests verifying async before-callbacks inject inputs, async after-callbacks are awaited and preserve CrewOutput, and mixed sync/async callbacks execute in correct order.

Sequence Diagram(s)

sequenceDiagram
  participant Caller
  participant Crew
  participant aprepare_kickoff
  participant BeforeCallback
  participant AfterCallback

  Caller->>Crew: akickoff(inputs)
  Crew->>aprepare_kickoff: await aprepare_kickoff(crew, inputs)
  aprepare_kickoff->>BeforeCallback: invoke callback
  BeforeCallback-->>aprepare_kickoff: value or coroutine
  alt result is awaitable
    aprepare_kickoff->>aprepare_kickoff: await result
  end
  aprepare_kickoff-->>Crew: normalized inputs
  Crew->>Crew: execute tasks, build result
  Crew->>AfterCallback: invoke callback(result)
  AfterCallback-->>Crew: value or coroutine
  alt result is awaitable
    Crew->>Crew: await result
  end
  Crew-->>Caller: CrewOutput

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Suggested reviewers: akaKuruma, vinibrsl

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The PR satisfies #6481 by awaiting async before/after kickoff callbacks in akickoff and keeping kickoff_async unchanged.
Out of Scope Changes check	✅ Passed	The refactor and added tests are directly tied to the async callback fix and do not appear out of scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title clearly summarizes the main change: async before/after kickoff callbacks in akickoff.
Description check	✅ Passed	The description matches the code changes and explains the async callback support and refactor.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[ErenAta16]

Same fix as #6500 and #6494 (also open), and like #6500 this one refactors prepare_kickoff into shared helpers (_begin_prepare_kickoff/_normalize_inputs/_finish_prepare_kickoff) rather than duplicating the whole function body for the new async path, so prepare_kickoff and aprepare_kickoff stay in sync automatically as the shared logic evolves — same quality bar as #6500, just a different helper decomposition. Left the fuller three-way comparison on #6500's thread.

Also flagging the same thing I noted there: the description mentions IO-bound sync callbacks blocking the event loop as motivation, but the actual fix (here and in the other two) only adds the inspect.isawaitable check for async callables — a slow sync callback still runs inline. Worth confirming that is intentionally out of scope for this PR rather than an oversight, since the title/description read as covering both.