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Feature Request: tool.execute.before hook with cancel capability #26521
Description
Background
The current plugin API only provides tool.execute.after. This allows post-execution detection but not pre-execution blocking. As demonstrated by AgentSpec (ICSE 2026), AWS Strands, and CommBank Policy Engine, true guardrails require intervention before tool execution.
Request
Add plugin hook tool.execute.before:
- Signature:
(input: ToolInput) => Promise<{ cancel?: string } | void> - When
cancelstring is returned, abort tool execution and relay the message to the agent
Use Cases
- Repeated failure prevention: block 4th execution after 3 failures of the same command pattern
- Safety policies: block file operations outside allowed directories
- Self-improvement: pre-emptively block commands known to fail based on learned patterns
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github-actions commentedon May 9, 2026
This issue doesn't fully meet our contributing guidelines.
What needs to be fixed:
[FEATURE]:(e.g.[FEATURE]: tool.execute.before hook with cancel capability)Please edit this issue to address the above within 2 hours, or it will be automatically closed.
This issue might be a duplicate of existing issues. Please check:
tool.execute.beforealready exists — this issue references it and covers related hook behaviortool.execute.beforenot blocking tool execution correctlytool.execute.before/afterhook payloads — implies the hook already exists; the cancel return value may already be supported or partially implementedIf you believe this was flagged incorrectly, please let a maintainer know.
github-actions commentedon May 9, 2026
This issue has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.
Feel free to open a new issue that follows our issue templates.