feat(hooks): Hook System Documentation

[Edilmo]

TLDR

Creates comprehensive documentation for hook development, plugin creation, and migration from Claude Code, with practical examples and tutorials.

Dive Deeper

This documentation is essential for hook ecosystem adoption. It should include: 1) Hook development guide with examples for each event type, 2) Plugin development tutorial showing how to create npm-based hook plugins with dependency injection, 3) Migration guide from Claude Code with step-by-step instructions and common patterns, 4) Best practices for hook security and performance, 5) Troubleshooting guide for common hook issues. The documentation also includes an example that serves as both comprehensive documentation and a template for advanced hook users.

Reviewer Test Plan

• Verify documentation covers all hook events and types
• Test example configurations work correctly
• Validate plugin development tutorial produces working plugins
• Test migration guide with real Claude Code configurations
• Ensure documentation is clear and comprehensive for developers
• Validate comprehensive showcase example (see Appendix A) works end-to-end
• Follow the steps of the advance example and validate is working.

Testing Matrix

	🍏	🪟	🐧
npm run	x	❓	❓
npx	x	❓	❓
Docker	❓	❓	❓
Podman	❓	-	-
Seatbelt	x	-	-

Linked issues / bugs

Closes #9140

[gemini-code-assist[bot]]

Summary of Changes

Hello @Edilmo, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the Gemini CLI by integrating a robust and extensible hook system. This allows users to intercept and modify the agent's workflow at critical junctures, enabling advanced customizations like dynamic context injection, security validations, and cross-session memory. The changes are accompanied by thorough documentation and a migration path for users transitioning from Claude Code.

Highlights

• Comprehensive Hook System: Introduced a new hook system allowing customization of agent behavior at various lifecycle points, including SessionStart, SessionEnd, PreCompress, BeforeModel, AfterModel, BeforeToolSelection, and Notification events.
• Extensive Documentation: Added detailed guides on hook development, best practices for security and performance, and a comprehensive example of a 'Smart Development Workflow Assistant' integrating all hook events.
• Claude Code Migration Utility: Provided a migration tool to convert existing Claude Code hooks to the Gemini CLI format, including event and tool name mapping.
• CLI Management for Hooks: Implemented /hooks slash commands (panel, enable, disable) to manage and view configured hooks directly within the Gemini CLI UI.

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[jackwotherspoon]

@jkcinouye should review docs here as well prior to merging 👍

[jkcinouye]

Note: The new docs will also need to be added to sidebar.json.

[Edilmo]

Note: The new docs will also need to be added to sidebar.json.

Done