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Claude AI outperforms GPT-5.5 by 13 points in FrontierMath tier-4 tests, showcasing advanced reasoning and problem-solving ca

Editorial illustration for Claude Fable 5 beats GPT‑5.5 by 13 points on FrontierMath tier‑4 tests

LLMs & Generative AI

Claude Fable 5 beats GPT‑5.5 by 13 points on...

By AI Daily Post Edited by
• Updated: • 3 min read

Thirteen points is a thrashing. On FrontierMath's hardest tier, the new standard is set not by OpenAI, but by Anthropic's Claude Fable 5.

This isn't a minor edge. It's a decisive lead. Fable 5 scored roughly 88 percent.

GPT-5.5 managed 75. The gap is the story. Just a short time ago, Anthropic's own previous model struggled to hit 10 percent on these same problems.

The climb has been vertiginous. The benchmark, once a distant summit, is now a staging ground. Real-world proofs are following.

An OpenAI model solved a stubborn Erdős problem. So did Claude Mythos. The machines are now doing the kind of math that used to get people named after theorems.

Anthropic's models are getting dramatically better at math in a short span of time. As recently as early 2026, predecessor model Opus 4.5 scored below 10 percent on tier 4. OpenAI's GPT-5.5 reaches about 75 percent on the same tier, well behind Fable 5, although GPT-5.6 is already in the making.

OpenAI is not out of the race. Seventy-five percent on tier four remains a formidable technical feat. GPT-5.6 is already being built.

The competition is a siege. But for now, the narrative belongs to Anthropic. They have demonstrated a velocity that redefines the field's pace.

The lead is significant. It is also likely temporary. In this kind of race, a thirteen-point advantage is both a trophy and a target.

Everyone is chasing the same frontier. The difference is who's currently standing on it.

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Common Questions Answered

What is Claude Fable 5's score on FrontierMath tier-4 tests compared to GPT-5.5?

Claude Fable 5 scored approximately 88 percent on FrontierMath's hardest tier-4 tests, while GPT-5.5 managed 75 percent, giving Anthropic's model a decisive 13-point lead. This significant gap represents a major breakthrough in advanced mathematical problem-solving capabilities among frontier AI models.

Why is the 13-point difference between Claude Fable 5 and GPT-5.5 considered significant?

The 13-point advantage on FrontierMath tier-4 tests is described as a decisive lead that represents more than a minor edge in performance. This gap demonstrates Anthropic's ability to achieve substantially higher accuracy on the hardest mathematical benchmarks, establishing a new standard in the field.

What does the article suggest about the competitive landscape between Anthropic and OpenAI?

While Anthropic currently holds the lead with Claude Fable 5, the article notes that OpenAI's 75 percent score on tier-4 remains a formidable technical achievement and that GPT-5.6 is already being developed. The competition is described as intense, with Anthropic's current advantage likely to be temporary as both companies continue advancing their models.

How does Anthropic's velocity in AI development compare to the rest of the field according to this article?

Anthropic has demonstrated a velocity that redefines the field's pace, as evidenced by their current leadership position with Claude Fable 5. The article suggests that Anthropic's rapid progress has shifted the narrative in the AI competition, though this lead is expected to be challenged as other organizations continue their development efforts.

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