fix(hooks): guard against non-string tool output in afterToolResult hooks

[ojh102]

Summary

Fixes #1749

• Add typeof output.output !== "string" guard in edit-error-recovery and delegate-task-retry hooks to prevent TypeError crash when MCP tools return non-string results

Problem

MCP tools (e.g., Linear MCP, Notion MCP) can return structured JSON objects instead of plain strings. When this happens, output.output is undefined in the afterToolResult callback, causing:

TypeError: undefined is not an object (evaluating 'output.output.toLowerCase')

Two hooks are affected:

• src/hooks/edit-error-recovery/hook.ts — calls output.output.toLowerCase()
• src/hooks/delegate-task-retry/hook.ts — passes output.output to detectDelegateTaskError()

Fix

Added the same guard pattern already used in tool-output-truncator.ts:

if (typeof output.output !== "string") return

This ensures both hooks gracefully skip when the tool output is not a string, consistent with existing conventions in the codebase.

Changes

File	Change
src/hooks/edit-error-recovery/hook.ts	Add string type guard before .toLowerCase()
src/hooks/delegate-task-retry/hook.ts	Add string type guard before detectDelegateTaskError()

---

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.}

[github-actions]

All contributors have signed the CLA. Thank you! ✅
_{Posted by the CLA Assistant Lite bot.}

[cubic-dev-ai]

No issues found across 2 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{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.}

[ojh102]

I have read the CLA Document and I hereby sign the CLA