debug-hooks

Original：🇺🇸 English

Translated

Systematic hook debugging workflow. Use when hooks aren't firing, producing wrong output, or behaving unexpectedly.

2installs

Sourceparcadei/continuous-claude-v3

Added on2026-02-22

NPX Install

npx skill4agent add parcadei/continuous-claude-v3 debug-hooks

SKILL.md Content

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Debug Hooks

Systematic workflow for debugging Claude Code hooks.

When to Use

"Hook isn't firing"
"Hook produces wrong output"
"SessionEnd not working"
"PostToolUse hook not triggering"
"Why didn't my hook run?"

Workflow

1. Check Outputs First (Observe Before Editing)

bash

# Check project cache
ls -la $CLAUDE_PROJECT_DIR/.claude/cache/

# Check specific outputs
ls -la $CLAUDE_PROJECT_DIR/.claude/cache/learnings/

# Check for debug logs
tail $CLAUDE_PROJECT_DIR/.claude/cache/*.log 2>/dev/null

# Also check global (common mistake: wrong path)
ls -la ~/.claude/cache/ 2>/dev/null

2. Verify Hook Registration

bash

# Project settings
cat $CLAUDE_PROJECT_DIR/.claude/settings.json | grep -A 20 '"SessionEnd"\|"PostToolUse"\|"UserPromptSubmit"'

# Global settings (hooks merge from both)
cat ~/.claude/settings.json | grep -A 20 '"SessionEnd"\|"PostToolUse"\|"UserPromptSubmit"'

3. Check Hook Files Exist

bash

# Shell wrappers
ls -la $CLAUDE_PROJECT_DIR/.claude/hooks/*.sh

# Compiled bundles (if using TypeScript)
ls -la $CLAUDE_PROJECT_DIR/.claude/hooks/dist/*.mjs

4. Test Hook Manually

bash

# SessionEnd hook
echo '{"session_id": "test-123", "reason": "clear", "transcript_path": "/tmp/test"}' | \
  $CLAUDE_PROJECT_DIR/.claude/hooks/session-end-cleanup.sh

# PostToolUse hook (Write tool example)
echo '{"tool_name": "Write", "tool_input": {"file_path": "test.md"}, "session_id": "test-123"}' | \
  $CLAUDE_PROJECT_DIR/.claude/hooks/handoff-index.sh

5. Check for Silent Failures

If using detached spawn with

stdio: 'ignore'

:

typescript

// This pattern hides errors!
spawn(cmd, args, { detached: true, stdio: 'ignore' })

Fix: Add temporary logging:

typescript

const logFile = fs.openSync('.claude/cache/debug.log', 'a');
spawn(cmd, args, {
  detached: true,
  stdio: ['ignore', logFile, logFile]  // capture stdout/stderr
});

6. Rebuild After Edits

If you edited TypeScript source, you MUST rebuild:

bash

cd $CLAUDE_PROJECT_DIR/.claude/hooks
npx esbuild src/session-end-cleanup.ts \
  --bundle --platform=node --format=esm \
  --outfile=dist/session-end-cleanup.mjs

Source edits alone don't take effect - the shell wrapper runs the bundled

.mjs

.

Common Issues

Symptom	Likely Cause	Fix
Hook never runs	Not registered in settings.json	Add to correct event in settings
Hook runs but no output	Detached spawn hiding errors	Add logging, check manually
Wrong session ID	Using "most recent" query	Pass ID explicitly
Works locally, not in CI	Missing dependencies	Check npx/node availability
Runs twice	Registered in both global + project	Remove duplicate

Debug Checklist

Outputs exist? (
```
ls -la .claude/cache/
```
)

Registered? (

grep -A10 '"hooks"' .claude/settings.json

)

Files exist? (
```
ls .claude/hooks/*.sh
```
)
Bundle current? (
```
ls -la .claude/hooks/dist/
```
)
Manual test works? (
```
echo '{}' | ./hook.sh
```
)
No silent failures? (check for
```
stdio: 'ignore'
```
)

Source Sessions

Derived from 10 sessions (83% of all learnings):

a541f08a, 1c21e6c8, 6a9f2d7a, a8bd5cea, 2ca1a178, 657ce0b2, 3998f3a2, 2a829f12, 0b46cfd7, 862f6e2c

debug-hooks

NPX Install

Tags

SKILL.md Content

Debug Hooks

When to Use

Workflow

1. Check Outputs First (Observe Before Editing)

2. Verify Hook Registration

3. Check Hook Files Exist

4. Test Hook Manually

5. Check for Silent Failures

6. Rebuild After Edits

Common Issues

Debug Checklist

Source Sessions