Debug Hooks

Debug Hooks

Diagnose and fix Claude Code hook errors. Covers startup hook failures, broken MCP configs, missing dependencies, and invalid hook schemas.

Common Hook Errors

Error: node:internal/modules/cjs/loader

Cause: Hook script references a Node.js file that doesn't exist or has bad require/import.

Fix procedure:

1. Read ~/.claude/settings.json — find SessionStart hooks
2. Locate the referenced script path
3. Check if file exists: ls [script-path]
4. If missing: recreate or remove the hook entry
5. If exists: check for bad require() paths inside

Error: startup hook error

Cause: Hook command fails on session start.

Fix procedure:

1. Run the hook command manually in terminal
2. Read error output
3. Common causes:
   • Missing npm package → npm install [package]
   • Wrong node version → check node --version
   • Bad file path → fix path in settings.json
   • Permission denied → chmod +x [script]

Error: Hook silently does nothing

Cause: Wrong event matcher or hook not registered.

Fix procedure:

1. Read hooks/hooks.json or settings.json hooks section
2. Verify event name is exact: PreToolUse, PostToolUse, SessionStart, Stop, SubagentStop, SessionEnd, UserPromptSubmit, PreCompact, Notification
3. Verify matcher regex matches tool names
4. Test with claude --debug to see hook execution logs

Full Diagnostic Procedure

# Step 1: Find all hook configs
find ~/.claude -name "hooks.json" 2>/dev/null
grep -r "hooks" ~/.claude/settings.json

# Step 2: Test each hook script manually
bash [hook-script-path]

# Step 3: Check node/python availability
which node && node --version
which python3 && python3 --version

# Step 4: Validate JSON syntax
cat ~/.claude/settings.json | python3 -m json.tool

Fix Hook Schema Errors

Valid hook entry structure:

{
  "SessionStart": [{
    "hooks": [{
      "type": "command",
      "command": "bash $CLAUDE_PLUGIN_ROOT/scripts/my-hook.sh",
      "timeout": 30
    }]
  }]
}

Common schema mistakes:

• Missing hooks array wrapper
• type not set to "command"
• Hardcoded absolute path instead of $CLAUDE_PLUGIN_ROOT
• Timeout as string instead of number

Remove Broken Hook

To safely remove a broken hook from settings.json:

1. Read the file
2. Identify the broken hook entry
3. Show user the entry to remove
4. Confirm before editing
5. Remove entry and validate JSON

LTX Schema

Emit structured output as LTX rows when reporting hook validation results.

@v1:hook|status|error|fix

Field	Description
hook	Hook identifier or script path
status	ok, warn, error, missing
error	Short error description or - if none
fix	Suggested fix command/action or - if none

Example:

@v1:hook|status|error|fix
SessionStart:session-start.sh|ok|-|-
SessionStart:broken-hook.sh|error|file not found|recreate or remove hook entry

Additional Resources

• references/hook-errors.md — Full error catalog with root causes and fixes
• scripts/validate-hooks.sh — Script to validate all hook configs