Anthropic's Fable 5.2 builds operating systems and hardware designs

Anthropic demonstrated the capabilities of Fable 5.2 by having the model design a prototype operating system from an empty folder. The system coordinated over 1,000 sub-agents for eight days to produce a bootable OS with drivers, file storage, and cloud functionality. The company stated that 90% of its code changes are now written by Claude under human supervision, with Fable 5.2 deployed for high-value projects such as migrating production services from Python to Rust.

Beyond software, the model exhibits new capabilities in hardware design and business operations. In one instance, it designed 'PlaneOne,' a minimalist 4G phone with a 45-key thumb keyboard and a 2.7-inch black-and-white screen, providing a full parts list, circuit design, firmware, and printable enclosure. The model can also work autonomously for 10 to 12 hours to audit an entire business, including website, pricing, and competitor analysis. It introduces a new 'I don't know' behavior that reduces hallucinations in high-stakes fields by marking data as verified, unverified, or suspicious.

Every's team reported that Fable 5.2 allowed them to build a working video editor combining Adobe Premiere, After Effects, and Ableton capabilities without reading the underlying code. Developer Riley Brown used the model to create a 60-second ad with realistic physics and lighting in a single live shot. Sholto Douglas from Anthropic noted it is the first model to pass his bar for 'seriously fun and beautiful games,' while Matt Schumer used it to create a playable Harry Potter-themed battle royale game. The model is recommended for large, open-ended projects where users can step away, rather than for specific, short-term tasks where Opus 5.5 remains preferred.