Codiff is a desktop code review tool (Electron + React) that visualizes Git diffs, supports AI-generated narrative walkthroughs, and integrates with GitHub/GitLab pull requests. It also provides a web sharing service for walkthroughs and plans, allowing users to share review snapshots publicly. The architecture is a monorepo with three packages: `core` (React UI library), `service` (Cloudflare Workers sharing API), and `web` (Cloudflare Workers frontend for shared content). The Electron main process handles Git state reading, AI agent orchestration, configuration, and window management, while the renderer uses React with custom hooks for review state, comments, walkthrough navigation, and diff search. Key entry points include `bin/codiff.js` (CLI), `electron/main.cjs` (Electron main), `core/index.tsx` (renderer), and `web/src/App.tsx` (web app). Data flows: Git diff data is parsed in `electron/git-state/` and sent to the renderer via IPC for display. AI walkthroughs are generated by calling external agent CLIs (Codex, Claude, OpenCode, Pi) from the main process, with output parsed and cached locally. Sharing involves uploading walkthrough/plan manifests to a Cloudflare Workers API backed by D1 and R2. External dependencies include Git, `gh`/`glab` CLIs, multiple AI agent CLIs, and Cloudflare infrastructure. The codebase is well-tested with extensive unit and integration tests, and includes an evaluation framework for walkthrough quality.