Claude Fable Uses Browser and Template Hacks to Test UI Bugs

AI summary

Simon Willison describes Claude Fable 5 as extremely proactive in investigating a UI scrollbar bug in Datasette Agent. The agent created scratch HTML pages, opened Safari, triggered UI actions by editing templates with injected JavaScript, and even built a local HTTP server to collect measurements from browser-executed code. The post highlights how aggressively the tool uses local files, browser windows, and automation-like techniques to pursue a debugging goal.