The dotfiles piece from May 22 named hooks as one component of a personal AI stack and moved on. They deserve more than a passing mention. Hooks are the primitive that turns taste into code — the editor's auto-format-on-save for AI work, run on the agent's actions instead of yours.
Anthropic's hooks documentation lists eight event types. Most published examples wire up one of them, demo a tiny safety check, and stop. The real payoff is in pairing the right hook to the right invariant for your work. Below are the five hooks I run, with the actual invariants they enforce.
Hook 1: PreToolUse — Guard the Destructive Commands
PreToolUse fires before any tool call, with the tool name and arguments. The hook can approve, deny, or rewrite. The high-yield use is denying classes of commands you never want the agent to run unattended — rm -rf, git reset --hard, git push --force to main, gcloud auth revoke, kubectl delete against production, anything with a flag that turns "ask first" into "do it now."
The shape of the hook is a small shell script that reads the tool call from stdin, pattern-matches on dangerous combinations, and exits with a non-zero status to deny. Examples in production:
