Definition
A hook is an extension point a program reserves at specific events or lifecycle stages, allowing external code to inject custom logic without modifying the main program.
How it works
The main program calls registered callbacks at key points: external code only needs to register following a convention, and it runs when the event occurs. Git’s pre-commit hook and the lifecycle hooks of front-end frameworks are typical examples.
Usage
Hooks power build automation, plugin systems and audit interception; in AI agent toolchains, hooks are often used to insert validation or human-approval logic before and after tool calls.
Related and confusable terms
An agent is a system that executes tasks autonomously, while a hook is the mechanism for inserting human or custom logic into it; a workflow defines how tasks are orchestrated, and a hook defines the intervention points at specific nodes along that path.