/dev/fast · 2026-09-24 · notable
Whiteboard — an open-source app for reviewing what coding agents built
Whiteboard is an MIT-licensed desktop app from YC W26 startup /dev/fast. Coding agents like Claude Code and Codex draw sequence and database diagrams of their changes, and you review them next to an AST-aware diff.
A shared canvas where a coding agent draws diagrams of its changes, so you review the design before the line-by-line diff.
What is it?
Whiteboard is an open-source desktop app, launched on Show HN on 24 September 2026, where people and coding agents plan and review software in one workspace. It plugs into agents you already use, such as Claude Code and Codex, and gives them an SDK to draw on an in-app canvas.
How does it work?
An agent's review appears as sequence diagrams and entity-relationship diagrams, and each element links to the code behind it, with VS Code keybindings and LSP navigation from the bundled Code OSS editor. A Rust diff viewer compares code by its syntax tree: it can show long functions as pseudocode and folds tests and docs by default. A Decision Log lets you check the choices the agent made and follow its traces.
Why does it matter?
Agents now write changes too large to read line by line, so reviewing at the level of architecture is a faster way to catch a wrong design early. The founders say teams at Salesforce and Modal already use the app to review architecture and spec-level changes. The desktop app runs locally against your repositories and is MIT-licensed.
Who is it for?
developers reviewing large agent-written changes
Try it
https://install.dev.fast