Claude Code hook system for pre/post tool execution. Triggers on: hooks, PreToolUse, PostToolUse, hook script, tool validation, audit logging.
/plugin marketplace add 0xDarkMatter/claude-mods/plugin install 0xdarkmatter-claude-mods@0xDarkMatter/claude-modsThis skill is limited to using the following tools:
references/configuration.mdreferences/hook-events.mdreferences/security-patterns.mdExecute custom scripts before/after Claude Code tool invocations.
| Event | When | Has Matcher |
|---|---|---|
PreToolUse | Before tool execution | Yes |
PostToolUse | After tool completes | Yes |
PermissionRequest | Permission dialog shown | Yes |
Notification | Notifications sent | Yes |
UserPromptSubmit | User submits prompt | No |
Stop | Agent finishes | No |
SubagentStop | Subagent finishes | No |
PreCompact | Before context compaction | No |
SessionStart | Session begins/resumes | No |
SessionEnd | Session ends | No |
Add to ~/.claude/settings.json or .claude/settings.local.json:
{
"hooks": {
"PreToolUse": [{
"matcher": "Bash",
"hooks": [{
"type": "command",
"command": "$CLAUDE_PROJECT_DIR/hooks/validate.sh",
"timeout": 5000
}]
}]
}
}
| Pattern | Matches |
|---|---|
"Write" | Only Write tool |
"*" or "" | All tools |
"mcp__*" | All MCP tools |
"Bash" | Bash commands |
#!/bin/bash
# Receives JSON via stdin: { "tool_name": "...", "tool_input": {...} }
INPUT=$(cat)
TOOL=$(echo "$INPUT" | jq -r '.tool_name')
# Exit codes:
# 0 = Success (continue)
# 2 = Block with error (stderr shown to Claude)
# Other = Non-blocking error
| Use Case | Event | Example |
|---|---|---|
| Validate inputs | PreToolUse | Block dangerous commands |
| Audit logging | PostToolUse | Log all tool usage |
| Custom approval | PermissionRequest | Slack notification |
| Session init | SessionStart | Load project context |
"$VAR" not $VAR.. traversal)$CLAUDE_PROJECT_DIR for paths# Debug hook loading
claude --debug
# List registered hooks
/hooks
# Test script manually
echo '{"tool_name":"Bash"}' | ./hooks/validate.sh
./references/hook-events.md - All events with input/output schemas./references/configuration.md - Advanced config patterns./references/security-patterns.md - Production securitySee Also: claude-code-debug for troubleshooting, claude-code-headless for CLI automation
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