Claude Code Hooks: How to Stop AI Agents From Breaking Your Code

Claude Code hooks enable developers to safeguard their code against AI agents that may inadvertently cause harm. A hook is a command that runs at specific moments within the agent's loop, providing deterministic control over the agent's actions. When an agent is about to perform an action, such as submitting a prompt or calling a tool, the hook executes.

It receives JSON input describing the event and responds with either an exit code or structured JSON on stdout. This response determines whether the action is allowed, denied, or requires further clarification from the model. Claude Code supports 30 events where hooks can be applied, with the most commonly used events being SessionStart, UserPromptSubmit, and PreToolUse.

PreToolUse hooks occur before a tool call is executed, allowing for prevention of harmful actions. PostToolUse hooks happen after a tool call, enabling verification of results and ensuring code integrity. SessionStart hooks provide context to the model at the beginning of a session. The hook configuration lives in .claude/settings.json or ~/.claude/settings.json files.

By implementing hooks, developers add a layer of safety to AI agents that they cannot fully rely on. This deterministic approach offers a more reliable solution than relying solely on prompts, as probabilistic models are prone to unpredictable failures. Claude Code hooks provide a practical and effective method for securing code against AI agents, addressing a critical issue in the rapidly evolving landscape of AI-assisted development.