Hooks move agents from advice to automation

Skills tell an agent what to do. Hooks make certain things happen regardless of what the agent decides.

They fire on lifecycle events — before a tool executes, after it finishes, on message submit, on stop, before compaction, on permission requests. Unlike skills, they're deterministic: the hook runs every time, not when the model judges it relevant.

Practical uses: auto-format after edits, block writes to protected paths, desktop notifications when Claude is waiting, re-inject context after compaction. Full schema in the Anthropic hooks guide.

The fastest way to start: Hookify. /hookify Warn me when I use rm -rf commands produces a working hook file immediately. Run it with no arguments and it auto-generates rules from behaviors you've already corrected in the current session.

Skills encode knowledge. Hooks enforce behavior. Both belong in a mature setup.