Plannotator is an interactive plan review tool designed specifically for Claude Code's plan mode. It provides a user interface for marking up and refining plans visually, making it easier to collaborate with team members and provide feedback.

The tool offers several key features including markdown plan rendering with syntax highlighting, text selection annotations for deletion, replacement, insertion, and commenting capabilities. It includes redline mode for quick deletion marking, URL-based sharing via compressed hash without server storage, and a Tater identity system for anonymous collaboration. Users can export to diff format and benefit from dark/light theme support.

When Claude Code calls ExitPlanMode, the Plannotator hook intercepts and opens the UI in the browser. Users can then annotate the plan visually and choose to either approve the plan for Claude to proceed with implementation or request changes which sends annotations back to Claude.

The primary benefit is streamlined team collaboration on Claude Code plans, allowing multiple stakeholders to review and provide feedback efficiently. It automatically integrates with Claude Code's plan mode workflow.

Plannotator is targeted at software engineering teams using Claude Code who need collaborative plan review capabilities. It runs locally as a browser-based tool with no network requests, ensuring plans never leave the user's machine.