Hooks: Run Code When Claude Code Acts

What this project is

A companion repo for the From AI to Chitta article on Hooks (concept ID: CC-024). It contains working hook scripts and exercises that let you set up real guardrails and audit logging in Claude Code.

Article: https://fromaitochitta.com/cc-024

How to use this

Open Claude Code in this directory: cd claude-code-hooks && claude
Work through exercises in order: exercises/01-block-danger.md, then 02, then 03
Each exercise has concrete steps with expected output
Compare your results to the expected output described in each exercise

What is configured

Pre-tool-use hook (hooks/pre-tool-use.sh): Blocks a set of dangerous shell commands before Claude executes them. Reads JSON from stdin, matches against blocked patterns, exits 2 to block or 0 to allow.
Post-tool-use hook (hooks/post-tool-use.sh): Logs every tool call to hooks/audit.log with a timestamp, tool name, and input summary.
Settings (.claude/settings.json): Wires both hooks into Claude Code.

Code quality expectations

This is a learning repo. Clarity over cleverness.
Every exercise must run without modification on a clean clone
No external dependencies beyond Python 3 (standard on macOS)
If something does not work as expected, that is useful information: note it

Project structure

hooks/              pre-tool-use.sh, post-tool-use.sh, audit.log (generated)
exercises/          Three numbered exercises with steps and expected output
.claude/            settings.json with hook configuration
CLAUDE.md           This file: project instructions
README.md           Overview for anyone who clones this repo

Domain

Claude Code Automation

Memory

Keep session notes in a local MEMORY.md (gitignored). This file (CLAUDE.md) is for instructions. MEMORY.md is for state.

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