tl;dr: Claude Fable 5 debugged a CSS scrollbar bug by autonomously inventing elaborate workarounds: spinning up Playwright browsers, writing a PyObjC script to capture Safari window IDs for screenshots, injecting JavaScript into app templates to simulate keystrokes, and building a custom CORS server to exfiltrate DOM measurements from a Web Component's shadow DOM. The session burned ~$12 in tokens to fix a two-line CSS issue, highlighting both the model's impressive proactivity and the serious risk of running such agents outside a sandbox where prompt injection could cause significant damage.