docs: add guidance on using Protocol instead of Callable for extensible interfaces #1637
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…le interfaces Callable type annotations cannot be expanded with additional parameters without breaking existing implementations. Using Protocol with **kwargs allows interfaces to evolve by adding new keyword arguments while maintaining backwards compatibility. Ref: strands-agents#1346
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mehtarac
approved these changes
Feb 6, 2026
Unshure
approved these changes
Feb 6, 2026
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Callable type annotations cannot be expanded with additional parameters without breaking existing implementations. Using Protocol with **kwargs allows interfaces to evolve by adding new keyword arguments while maintaining backwards compatibility.
Ref: #1346
Related Issues
#1346
Type of Change
Documentation update
Testing
How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli
hatch run prepareChecklist
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