Claude Code builds and browser-tests a GIF optimizer
Willison asked Claude Code for web to compile Gifsicle to WebAssembly and build a preview interface. The agent used Rodney to exercise the page and fix UI bugs during implementation.
simonwillison.netWhat happened
Willison shows the working optimizer and reports browser testing that caught minor UI bugs.
Reported by Simon WillisonHow the agent did it
- Inspect existing tools and compile Gifsicle for a browser runtime.
- Build upload, compression previews and downloadable results.
- Exercise the interface with Rodney and repair observed bugs; preserve the build patch and attribution.
Where a person stepped in
Willison watched progress and added requirements for reproducible build files and upstream credit.
A person approved each step before the agent continued.
More details
About this account
Claude selected build and UI details and used a browser tool to check and revise its own output.
Annotated firsthand prompt and session links. Source has no publication date; sourcePublished is omitted from this record.
Credit: Simon Willison
Added 14 Oct 2026
Source checked 14 Oct 2026
Tools and topics
Claude Code · Gifsicle · WebAssembly · Emscripten · Rodney
Code · Testing
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.
Prompt to try
Editorial adaptation, not the source author’s exact prompt. Replace bracketed inputs and review tool permissions first.
Build a local browser wrapper for [CLI tool]. Reuse the repository conventions, retain upstream attribution and include a reproducible build script. Test upload, settings, preview and download using browser automation. Report observed results and remaining limitations; stop before publishing.