Claude Code hooks explained

What a hook is

A hook is a function that Claude Code calls at a fixed moment in a session. A mod is a set of these functions. The events a mod hooks into decide what it can see and what it can influence, so they are the quickest way to judge a mod.

The five kinds of events

modsforClaude groups hooked events into five categories and shows them on every listing.

Prompt

Runs when you send a message. A mod can add context to the prompt, such as the current branch or the ticket you are working on.

Tool call

Runs around the actions Claude takes, such as reading a file or running a command. Mods use this to log activity, run a formatter after an edit or block commands you never want to run.

Permission

Runs when Claude asks for approval. A mod here can answer routine requests for you. That saves clicks, and it deserves the closest look of all five.

Output and redaction

Runs on what comes back. Typical uses are masking secrets and tokens before they appear on screen or in a transcript.

UI

Draws on screen: status lines, panes, bands and toasts. A mod that only hooks UI events shows information and does not change what Claude does.

Reading a listing

A mod that only uses UI events carries little risk. A mod that hooks prompts, tool calls or permissions sees more and can do more, so read its source with more care. Our guide on installing mods safely lists the checks worth doing first.