As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/p/x-epochairesearch-2119903415363113088/

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

Epoch AI (@EpochAIResearch), X, 2026-11-09.
Source: https://x.com/EpochAIResearch/status/2119903415363113088

## Archived text

> 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.

Archived 2026-11-12 via fxtwitter (unofficial).
Counts: 174,402 views, 1,596 likes, 185 reposts, 68 replies (at fetch time)
Media: https://pbs.twimg.com/media/HWto7BnaEAAcolF.jpg?name=orig

## Cited in

- 2026-11-09: [Anthropic releases Claude Fable 5.2 and Claude Mythos 5.2](https://postcutoff.com/e/2026-11-09-claude-fable-5-2-mythos-5-2/)