A year ago Anthropic's models could read a chip datasheet but could not reliably lay out a circuit board. Its new write-up says Claude Fable 5.2 can now take a device from a one-line brief to a working prototype, and the details suggest the gain is in exactly the spatial reasoning that held earlier models back.
The three devices were a USB-C speakerphone with Bluetooth, a home voice-assistant hub and a battery-powered handheld pet. For each, Claude wrote the specification, drew schematics, placed parts, routed the copper tracks, designed a 3D-printable case, wrote firmware and produced a parts list. Diode Computers, which builds boards and has a commercial relationship with Anthropic, assembled them from Claude's files with no rounds of manufacturing changes, and the circuitry needed no fixes. Diode's prompting was mostly short instructions such as "continue".
The numbers come from benchmarks. On Diode's internal PCB Gym, which asks models to place and route boards whose layouts have been removed, Fable 5.2 scored 69% against 25% for Fable 5. On the public BenchCAD 2.1, which tests rebuilding parts and boards from drawings, it scored 83.5%, nearly double Fable 5.1. The anecdotes are telling too: Claude reassigned chip pins so tracks under the speakerphone's touch wheel never crossed, ripped up and rerouted the hub's tangled tracks dozens of times, and wrote its own grid router in about half an hour when KiCad's one-track-at-a-time tool proved too slow. It also worked out that the speakerphone board had to be tilted about 25 degrees to fit its case, and reshaped the hub so its microphone port resonance moved from about 3.4 kHz to 8.9 kHz, out of the main speech band.
For readers of our Claude Fable 5.2 review, this sits alongside the model's coding strength rather than replacing it; much of the work was writing scripts, checkers and firmware. Anthropic notes that OpenAI has described similar hardware work, and the separate PCBRouteAgent preprint shows how hard dense routing still is for agents using KiCad tools.
The caveats matter. The devices have had no electrical validation, antenna tuning, thermal testing or certification, and were not designed for mass production. Engineers had to build and test them because Claude had no access to lab equipment. PCB Gym is Diode's own benchmark, the partner is commercial, and three simple consumer gadgets are a demonstration, not evidence that the model can handle dense, high-speed boards.