“Claude Fable 5.2 sets a new record on the Epoch Capabilities Index (ECI) at 174.”

Claude Fable 5.2 sets a new record on the Epoch Capabilities Index (ECI) at 174. The previous high was GPT-6 Astra’s 169. Fable 5.2’s score is above what the pre-Astra trend for reasoning models would have predicted.

This is notable given recent discussion of AI contributions to AI R&D, and we hope to release more work in this area soon.

This is based on testing we did prior to launch using only our own benchmarks. The ECI is continually updated as more benchmark results become available, and may change in the future.