hooks-reference

Event-driven hooks in Claude Code automate workflows by intercepting PreToolUse, PostToolUse, and other events. Define a hooks.json file with matcher patterns, hook types, and exit codes to validate inputs, enforce permissions, and control execution flow based on context conditions.

A PreToolUse hook executes before tool invocation, enabling input validation and access control. Configure it in hooks.json with event type, matcher patterns, and a script that reads stdin JSON, performs checks, and returns exit codes to allow or block execution.

Yes. A PreToolUse hook can match file-write operations, validate the target path against sensitive patterns, and return a non-zero exit code to block the operation before it executes, protecting restricted directories from modification.

PostToolUse hooks run after tool completion for auditing, context propagation, and workflow enforcement. They process execution results via stdin JSON and can update decision state or trigger downstream actions based on the tool's output and exit code.

Hooks receive standardized stdin JSON containing event metadata and context. Output JSON can include decision control fields and context updates. The hooks.json structure defines matcher patterns, hook types, exit codes, and script paths to enforce this contract.

No prior experience required. This guidance covers hook concepts from fundamentals through advanced patterns. Start with a simple PreToolUse example to block sensitive operations, then progress to complex workflows combining multiple events, matchers, and context propagation.