What they did
Hiroki Kondo develops karasu, an architecture diagram tool, and wanted a looping demo at the top of its README. He runs Claude Code inside a VS Code devcontainer. Claude Code drafted the script, started the karasu preview server in the container, drove a browser with Playwright and captured frames through the Chrome DevTools Protocol screencast, which only emits a frame when the screen changes. The cursor and captions were overlays drawn on the page, and ImageMagick stitched the frames into a GIF. For the demo subject it reverse-engineered his private AI journaling service into a karasu model, running 13 subagents, one per domain, on about 1.5 million tokens. The recording scripts were committed to the repo so the GIF can be re-shot when the UI changes.
How it went
His first ask, a 3-minute intro video, got exactly that. Once he said the goal was a README loop, Claude Code proposed 20 to 30 seconds and dropped the command-line scenes. The first 18-second prototype had no captions and did not explain itself; about 14 minutes after asking, he had captioned and uncaptioned versions side by side and kept the captioned one. Claude Code also scrubbed the private repo name from captions, breadcrumbs and service names and flagged a leftover comment before commit. The opening terminal scene is a rebuilt replay of a real 15-minute run.
Worth knowing
He kept the work inside the container on purpose rather than letting the agent use computer use in his own logged-in browser, and asked it to list everything it installed and how to undo it. A Japanese font had to be added or the Japanese captions rendered as boxes. Lead with where the video will live, not its length or format.
Postgresql
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