Show HN: Whiteboard (YC W26) open-sources an IDE where humans and agents architect code together
sidharthkmenon · hn · 2026-09-25
A YC W26 team launched Whiteboard, an open-source desktop app that recreates the "whiteboard session" experience for humans and coding agents working in one workspace.
- Built on CodeOSS: inherits VSCode keybindings and LSP support; clicking a sequence diagram, ER diagram, or a quote from an agent's trace jumps straight to the underlying code — solving the gap between spec/diagrams and code that pure HTML tools couldn't bridge.
- Semantic diff viewer: a Rust, AST-aware diff tool that surfaces only relevant changes — large added functions get summarized as pseudocode, unit tests and big doc changes are collapsed by default, all customizable via a WASM plugin system.
- Decision Log: agents get an SDK to query and link their own traces to the whiteboard, so you can see how requirements were implemented and which decisions the agent made autonomously.
It plugs into tools like Claude Code and Codex; the repo is on GitHub.
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