# Claude Fable 5 outpaces GPT-5.5 by 13 points on FrontierMath's toughest problems

> Source: <https://the-decoder.com/claude-fable-5-outpaces-gpt-5-5-by-13-points-on-frontiermaths-toughest-problems/>
> Published: 2026-06-13 10:16:26+00:00

Anthropic's Claude Fable 5 hits 88 percent accuracy on the hardest FrontierMath tier, a massive jump from Opus 4.5, which sat below 10 percent in early 2026. OpenAI's GPT-5.5 reaches about 75 percent on the same tier. The pace of improvement in AI math keeps accelerating.

The article [Claude Fable 5 outpaces GPT-5.5 by 13 points on FrontierMath's toughest problems](https://the-decoder.com/claude-fable-5-outpaces-gpt-5-5-by-13-points-on-frontiermaths-toughest-problems/) appeared first on [The Decoder](https://the-decoder.com).