YC Startup /dev/fast Open-Sources Whiteboard, Enabling AI Agents to Draw Code Diagrams

YC W26 startup /dev/fast has open-sourced Whiteboard, a collaborative canvas that allows AI coding agents like Claude Code and Codex to generate architectural diagrams directly alongside code changes. The tool, announced on Hacker News on September 24, 2026, addresses a fundamental workflow gap: developers often struggle to grasp large code changes without visual context. Whiteboard fills that gap by enabling AI agents to sketch sequence diagrams, entity-relationship diagrams, and flowcharts on a canvas integrated into the development environment.