Anthropic’s Fable 5.2 designs three hardware prototypes

By Nathan Brooks

Anthropic says Claude Fable 5.2 scored 69% on PCB Gym, versus 25% for Fable 5. Anthropic’s Science team says the model also designed three electronic prototypes that hardware startup Diode Computers built without revision. Both claims appear in a research post published Nov. 9.

Anthropic’s Science team put it plainly: “Claude can both design and prototype electronic hardware from start to finish.” That is a workflow claim, not a certification claim.

What did Claude design?

From a short prompt, Claude wrote device specifications, drew schematics and selected components. It read datasheets when a design depended on a specific part, then placed and routed the circuit boards.

It also wrote firmware, modeled the enclosures in CAD and generated code to check whether the boards would fit. Claude prepared the parts list, checked manufacturability and verified that distributors had components in stock.

The first device is a puck-shaped speakerphone that plugs into a computer over USB-C. It includes microphones, a speaker, Bluetooth and a touch wheel.

The second is a voice-assistant hub with USB and Ethernet. The third is a battery-powered handheld virtual pet. Anthropic says all three work, and the speakerphone has been in use for weeks.

Diode’s engineers built and tested the hardware from Claude’s output. Anthropic says their prompts were mostly short directives such as “clean up the schematic” and “continue.”

Claude was not connected to test equipment or factory machines. The model’s design work and the engineers’ physical work therefore remained separate stages.

How did the boards get built?

The post gives several examples of Claude catching its own problems. When KiCad’s built-in router was too slow for the hub’s long tracks, Claude wrote its own router in about half an hour.

It found that the speakerphone’s mute switch would hit the enclosure wall and added a 25-degree tilt to the assembly instructions. It also reshaped the hub’s case into a wedge to shorten the microphone ports.

Anthropic wrote: “Diode manufactured all three boards directly from Claude’s design files, without any back-and-forth over adjustments.” The statement covers board manufacture. It does not cover product qualification.

What do the benchmarks show?

PCB Gym is an internal benchmark that Diode ran. It asks models to place parts and reroute connections on stripped boards; Fable 5.2 scored 69%, against 25% for Fable 5.

On the public BenchCAD 2.1 benchmark, which tests rebuilding 3D parts and boards from drawings, Anthropic reports a score of 83.5%. That is nearly double Fable 5.1’s result, although the post gives no numerical score for the earlier model.

Earlier models placed supporting parts too far from their chips and rarely revised their work. Diode was left with many boards about 95% complete but unusable, according to the post.

The benchmark gains indicate better placement, routing and mechanical design. They do not establish that the prototypes are ready for volume production.

What still has to be proved?

Anthropic has a commercial relationship with Diode, and the two companies have worked on circuit-board design since 2025.

Anthropic describes the three devices as early prototypes. They have not undergone electrical validation, antenna tuning, thermal testing or certification, and were not designed for mass production.

Next, Anthropic plans to test denser, faster boards, check designs in simulation and learn from measurements on the finished devices. The prototypes work. Qualification remains outstanding.

If those denser designs survive validation, tuning and repeatable manufacturing, Claude may move further into production engineering. The competitive test is whether Anthropic can turn a three-board demonstration into repeatable production; the post discloses no capacity or pricing figures.