Problem
Reviewing a Git diff in a SaaS tool sends code away and mixes remote UI with local history. Review needs to work offline, with hunks, filters, bookmarks, and line-anchored comments.
Constraints
Preferences and reports must live in the repository itself (.diffvision/). The npm CLI starts local backend and UI. Assistant integration cannot be sold as ready while it is still a prototype.
Decision
CLI inspects Git, parses unified diff, and serves a web interface. Fastify backend with snapshot and WebSocket; React/Vite UI. Markdown/JSON export in the repository. diffvision-mcp package over stdio to summarize the repository, read patches, and record comments. The visual AI review assistant is declared mock/prototype; comment writing over MCP works.
Current state
Distributed as an npm CLI, running local-first.
Limitations
It does not replace the GitHub review flow. The visual AI flow must not be read as a finished product.