I made Claude Code, Codex, and Antigravity build the same Chrome extension, and only one was a keeper

I tested Claude Code, Codex, and Google Antigravity to see which AI coding tool could create the most functional and user-friendly Chrome extension. The three tools all received the same challenge: building a screenshot capture and beautification tool called SnapNest that works offline. They were all given the same detailed instructions, including a list of required features like multiple capture options, a built-in editor, customizable backgrounds, annotations, different export formats, and keyboard shortcuts. The extensions had to have minimal permissions, no external scripts, and zero network requests.

Codex managed to build most of the requested features using the Luna 6 model. However, its interface had several usability issues. The small fonts and unappealing color scheme made it uncomfortable to work with. The annotation tools were particularly problematic, with tiny numbers that were hard to see on screenshots. Despite functional features, Codex's awkward layout and poor usability left it as the least desirable option.

Google Antigravity, powered by the Gemini 3.8 Flash model, offered a more polished experience. While its annotation feature still felt outdated, the better interface and organization made it easier to navigate. The export function supported multiple formats, and the overall editing process was smoother. However, the annotation workflow and blur effect still needed improvement.

Claude Code, powered by Claude Opus 5.5, delivered the best results of the three. Its editor was well-designed, with easy-to-find controls and a natural navigation flow. The numbered annotation feature was well-implemented with good sizing options, and the preset system allowed saving up to 10 styles for quick reuse. The blur effect also produced cleaner results than the other tools. While the export function could be improved, Claude Code's overall quality and comfort made it the clear winner in this comparison.