Hook

What it does

The hook integration installs a UserPromptSubmit hook that injects a short GitWhy awareness paragraph at the start of every agent turn. This guarantees the agent is aware of GitWhy in every conversation, regardless of context window state.

The hook injects tokens on every prompt turn. Use this method only if other methods (MCP, Skill files, Rules) aren’t sufficient for your workflow.

Setup

Run git why setup and select Hook from the menu, or add the hook configuration below manually.

This adds a hook configuration to .claude/settings.local.json (for Claude Code):

{
  "hooks": {
    "UserPromptSubmit": [
      {
        "matcher": "",
        "hooks": [
          {
            "type": "command",
            "command": "git-why hook-run"
          }
        ]
      }
    ]
  }
}

When triggered, git-why hook-run outputs a short instruction paragraph that the agent receives before your prompt.

What gets injected

[GitWhy] You have access to GitWhy for saving context behind code changes.
Save with: git why save (CLI) or gitwhy_save MCP tool.
Retrieve with: git why get <id> or gitwhy_get MCP tool.
When the user says "save with GitWhy", generate structured markdown and save it.

This is approximately 50-60 tokens per prompt turn.

When to use the hook

Use the hook when:

The agent frequently loses awareness of GitWhy mid-session

You want a hard guarantee that every prompt includes GitWhy context

Other integration methods are not available for your agent

Do not use the hook if:

Skill files or Rules are working reliably (lower token cost, same awareness)

You are concerned about per-turn token usage

Agent	Hook support	Config file
Claude Code	Yes	`.claude/settings.local.json`
Agents with UserPromptSubmit	Yes	Varies
Agents without hook support	No	Use Rules instead

Agent

Hook support

Config file

Claude Code

Yes

.claude/settings.local.json

Agents with UserPromptSubmit

Yes

Varies

Agents without hook support

Use Rules instead

Getting Started

Core Features

Sharing & Collaboration

Interfaces

Integration Guide

CLI Reference

Context Format

Plans & Pricing

What it does

Setup

What gets injected

When to use the hook

Agent compatibility

See also

​What it does

​Setup

​What gets injected

​When to use the hook

​Agent compatibility

​See also

What it does

Setup

What gets injected

When to use the hook

Agent compatibility

See also