Dev, main, and prod all point at the same Redis and the same Postgres on Ballpark Genius. That’s not a design decision I’m proud of, it’s a decision made by “there’s only one of me and eleven of these projects.” It works fine right up until an agent decides redis-cli FLUSHALL is a reasonable way to test a cache bug in a worktree that isn’t prod.

So I wrote a PreToolUse hook. It sits in front of every Bash call and denies anything that looks destructive against those two: redis-cli DEL/FLUSHALL/SET/HSET/EXPIRE/RENAME, and psql DROP/DELETE/TRUNCATE/UPDATE/anything with ALTER ... DROP|RENAME. Read-only and additive operations pass right through. It’s not a “no touching the database” hook, it’s a “no overwriting production by accident” hook.

It pairs with a hook that already blocked killing or restarting the dev servers, and with a step in this project’s architecture-check skill that makes me, or an agent reading the skill, state a blast-radius verdict before writing code that touches shared infra. Three separate nets for the same failure mode, because I’ve watched it happen at least once each way.

The honest reason I built this w/ a hook instead of a note in CLAUDE.md: instructions are advisory, hooks are not. I’d rather over-trust a shell script than a language model’s reading comprehension when the blast radius is “the database everyone’s using.”