feat(hooks): add retry mechanism for tool calls #1556
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Add `retry` field to AfterToolCallEvent and BidiAfterToolCallEvent that allows hook callbacks to trigger tool re-execution. When set to True, the tool executor discards the current result and invokes the tool again. This provides the hook infrastructure needed for implementing custom retry strategies for tool failures, timeouts, or transient errors.
Add tests verifying: - AfterToolCallEvent.retry field is writable - Setting retry=True causes tool re-execution - Retry works with error results from @tool decorator - Retry works with exceptions from tool.stream - Max retries can be controlled by hook callback - Integration tests with real Agent using HookProvider
Keep the first PR focused on standard AfterToolCallEvent only. BidiAfterToolCallEvent.retry can be added in a follow-up if needed.
- ToolStreamEvents ARE emitted from discarded attempts - ToolResultEvent is NOT emitted for discarded attempts
dbschmigelski
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zastrowm
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| agent, selected_tool, tool_use, invocation_state, result | ||
| ) | ||
| # Check if retry requested for unknown tool error | ||
| if getattr(after_event, "retry", False): |
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What's the reason to use getattr?
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Description
Adds a retry field to AfterToolCallEvent that allows hook callbacks to trigger tool re-execution. When
set to True, the tool executor discards the current result and invokes the tool again with the same
tool_use_id.
This provides the hook infrastructure needed for implementing custom retry strategies for tool
failures, timeouts, or transient errors.
Changes
Streaming behavior
When retry=True:
Callers consuming streamed events should be prepared to see intermediate events from discarded
attempts.
Related Issues
#1405
Documentation PR
Todo
Type of Change
New feature
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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