fix(hooks): guard against non-string tool output in afterToolResult hooks#1750
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code-yeongyu merged 1 commit intocode-yeongyu:devfrom Feb 13, 2026
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…ooks MCP tools can return non-string results (e.g. structured JSON objects). When this happens, output.output is undefined, causing TypeError crashes in edit-error-recovery and delegate-task-retry hooks that call methods like .toLowerCase() without checking the type first. Add typeof string guard in both hooks, consistent with the existing pattern used in tool-output-truncator.
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All contributors have signed the CLA. Thank you! ✅ |
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No issues found across 2 files
Confidence score: 5/5
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Auto-approved: Simple defensive type guards adding typeof checks for string output. No functional changes, prevents runtime errors. 2 lines, 2 files, clearly safe with no regression risk.
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I have read the CLA Document and I hereby sign the CLA |
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Clean defensive fix — exactly the kind of guard that prevents hard-to-debug crashes. Thank you! 🙏 |
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Summary
Fixes #1749
typeof output.output !== "string"guard inedit-error-recoveryanddelegate-task-retryhooks to preventTypeErrorcrash when MCP tools return non-string resultsProblem
MCP tools (e.g., Linear MCP, Notion MCP) can return structured JSON objects instead of plain strings. When this happens,
output.outputisundefinedin theafterToolResultcallback, causing:Two hooks are affected:
src/hooks/edit-error-recovery/hook.ts— callsoutput.output.toLowerCase()src/hooks/delegate-task-retry/hook.ts— passesoutput.outputtodetectDelegateTaskError()Fix
Added the same guard pattern already used in
tool-output-truncator.ts:This ensures both hooks gracefully skip when the tool output is not a string, consistent with existing conventions in the codebase.
Changes
src/hooks/edit-error-recovery/hook.ts.toLowerCase()src/hooks/delegate-task-retry/hook.tsdetectDelegateTaskError()Summary by cubic
Prevented TypeError crashes in afterToolResult hooks when MCP tools return non-string outputs. Added a string check for output.output in edit-error-recovery and delegate-task-retry, skipping processing if it isn’t a string.
Written for commit bb6a011. Summary will update on new commits.