feat: Add dynamic task ordering capability to Sequential and Hierarchical processes

[devin-ai-integration]

feat: Add dynamic task ordering capability to Sequential and Hierarchical processes

Summary

Implements dynamic task ordering for CrewAI's Sequential and Hierarchical processes by adding a task_ordering_callback field to the Crew class. This allows users to provide a callback function that dynamically determines the next task to execute based on runtime conditions, completed task outputs, and current execution context.

Key Changes:

• Added task_ordering_callback field to Crew class with proper type annotations and validation
• Modified _execute_tasks method to support dynamic task selection via callback
• Implemented comprehensive error handling and fallback to default ordering
• Added validation to ensure callback has correct signature (3 parameters)
• Maintains full backward compatibility - crews without callbacks work unchanged
• Supports returning task index (int), Task object, or None from callback

Review & Testing Checklist for Human

⚠️ HIGH PRIORITY - 5 critical items to verify:

• Test basic functionality end-to-end - Create crews with and without task_ordering_callback and verify they execute correctly in both Sequential and Hierarchical processes
• Verify backward compatibility - Ensure existing crews without callbacks work exactly as before (no regressions)
• Test callback error handling - Verify that invalid callback returns (bad indices, exceptions, wrong types) gracefully fall back to default ordering with appropriate warnings
• Review the while loop execution logic - The core _execute_tasks method was changed from a for loop to a while loop with complex state tracking - ensure no edge cases or infinite loops
• Test infinite loop prevention - Verify that callbacks returning the same task repeatedly don't cause infinite loops (should be prevented by executed_task_indices tracking)

Notes

• Environment Issue: Could not test implementation locally due to corrupted uv.lock file preventing pytest execution
• Risk Level: HIGH - Core execution logic changes in critical path without full testing
• Session: https://app.devin.ai/sessions/f36f5fc69f4d41a5aa0a11c5c66b4bc3 requested by João ([email protected])
• Issue: Fixes [FEATURE] #3620

---

Note

Adds task_ordering_callback to Crew and updates task execution to dynamically select the next task with validation, fallbacks, and tests.

• Core Execution:
  • Add task_ordering_callback field to Crew to dynamically choose the next task (accepts index, Task, or None).
  • Refactor _execute_tasks to a loop tracking executed indices, invoking callback, handling async/sync, and preventing repeats.
  • Default ordering preserved when no callback or invalid returns (with warnings).
• Validation:
  • Add model_validator to verify callback signature (exactly 3 params) and callability.
• Examples:
  • New examples/dynamic_task_ordering_example.py showing priority- and condition-based ordering.
• Tests:
  • Add tests/test_dynamic_task_ordering.py covering reverse/priority ordering, returning Task vs index, invalid indices/types, exceptions, default behavior, and infinite-loop prevention.

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[devin-ai-integration]

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