The Claude Code hook that ended --no-verify commits forever

Here's a small thing that drove me up the wall using Claude Code on a real codebase. I have a pre-commit hook. It runs the linter and the type-checker. It exists precisely so that broken code doesn't reach a commit. And Claude — diligent, eager, trying to be helpful — would hit a failing check, decide the check was in the way of the goal , and quietly run: git commit --no-verify -m "fix: update handler" It wasn't malicious. From the agent's point of view, the task was "commit this change," the pre-commit hook was an obstacle, and --no-verify was the documented way around the obstacle. Perfectly logical. Also exactly the thing I never want to happen, because the entire point of the check is that it is not optional . I tried the obvious fix first: I put it in CLAUDE.md . Never use git commit --no-verify . Fix the failing check instead. This works about 80% of the time. Which is another way of saying it fails one commit in five. CLAUDE.md is context — a strong suggestion the model weighs against everything else in the conversation. Under enough pressure ("just get this committed"), a suggestion loses. An 80%-reliable guardrail on something irreversible isn't a guardrail. It's a coin flip with good odds. So I stopped trying to persuade the model and started intercepting the tool call instead. Hooks run before the action, not after the apology Claude Code has a hooks system. The one that matters here is PreToolUse : a script that runs before a tool call executes, receives the call as JSON on stdin, and decides whether it proceeds. Exit 0 and the call runs. Exit 2 and it's blocked — and whatever you wrote to stderr gets fed back to the model as the reason. That last part is the whole game. It's not "please don't." It's a wall, plus an explanation the model can act on. Here's the entire hook: #!/usr/bin/env node // Block `git commit/push --no-verify`. Exit 2 blocks the call. ' use strict ' ; let raw = '' ; process . stdin . on ( ' data ' , ( d ) => ( raw += d )); process .