TL;DRFable 5 topped GPT 5.5 on every major benchmark but was pulled by the US government after three days, making GPT 5.5 the top model you can actually use.
Anthropic’s Fable 5 spent three days as the most capable AI model ever released to the public. It topped the Chatbot Arena leaderboard, crushed OpenAI’s GPT 5.5 on coding benchmarks by double-digit margins, and gave paying subscribers access to Mythos-class reasoning for the first time. Then, on June 12, the US government ordered Anthropic to shut it down.
The result is a strange moment in AI. The model that demonstrably outperforms everything else on the market is the one you cannot use. GPT 5.5, which OpenAI launched in late April under the internal codename “Spud,” is now the strongest model available to developers and consumers, not because it improved but because its only real competitor was removed.
The benchmark gap between the two is not close. On SWE-Bench Pro, which measures a model’s ability to resolve real software engineering issues across open-source codebases, Fable 5 scored 80.3% to GPT 5.5’s 58.6%, a 22-point difference. On SWE-Bench Verified, a curated subset of the same benchmark, Fable 5 reached 95.0%.
The coding benchmarks tell a similar story. Fable 5 leads the Code Arena by 98 Elo points, scoring 1,665 to GPT 5.5’s 1,501. On FrontierCode Diamond, a benchmark designed to test the most difficult programming tasks, Fable 5 scored 29.3% while GPT 5.5 managed 5.7%, and on the broader Chatbot Arena leaderboard Fable 5 sits at number one with GPT 5.5 in fourth.
