┌──────────────────────────────────────────┐
  │            ANATOMY OF A HOOK              │
  ├──────────────────────────────────────────┤
  │  EVENT     PreToolUse / PostToolUse       │
  │  MATCHER   Bash, Write|Edit, ...          │
  │  INPUT     JSON payload on stdin          │
  │  OUTPUT    exit 0 = allow                 │
  │            exit 2 = BLOCK + message       │
  └──────────────────────────────────────────┘

  A hook is a script wired to a Claude Code
  lifecycle event.

  EVENT     When it fires (PreToolUse fires
            BEFORE the agent runs a tool).
  MATCHER   Which tools trigger it (Bash,
            Write|Edit).
  PAYLOAD   The tool call arrives as JSON
            on stdin.
  VERDICT   exit 0 allows. exit 2 blocks and
            shows the agent your message.

  No AI involved. No judgment. Just code
  that runs every single time.