# Epoch AI gives probabilistic capability rankings for Astra, Opus 5.5 and Fable 5.1

> Original title: With better uncertainty estimates and a joint distribution over all models’ ECIs, we can now compare models directly.

- Source: Epoch AI
- Published: 2026-11-04T21:31:06.000Z
- Bad Influence: https://badinfluence.news/items/brkppbx84ekws1lv04ayiaj3g
- Original: https://x.com/EpochAIResearch/status/2118093707983692105

## Summary

Epoch AI now produces uncertainty estimates and a joint distribution over all models' ECIs, enabling direct model comparisons. It says Astra has a 72% probability of being more capable than Opus 5.5 and a 99% probability of being more capable than Fable 5.1.

## Post

With better uncertainty estimates and a joint distribution over all models’ ECIs, we can now compare models directly.

For example, we can now say Astra has a 72% probability of being more capable than Opus 5.5, but a 99% probability of being more capable than Fable 5.1.

![Dot-and-whisker chart of the ECI gap between GPT-6 Astra and each of the five next-highest models under the new method, with 90% intervals. The probability that GPT-6 Astra is more capable is 54% against GPT-6.1 Sol, 72% against Claude Opus 5.5, 99% against Claude Fable 5.1 and Claude Sonnet 5.5, and 100% against Gemini 4 Argon.](https://badinfluence.news/api/img-proxy?u=https%3A%2F%2Fpbs.twimg.com%2Fmedia%2FHWT7AMVb0AAIlEA.png&mode=thumb&exp=1794096000&sig=50a4714e09a02105)