The US government, citing national security authorities, has issued an export control directive to suspend all access to Fable 5 and Mythos 5 by any foreign national, whether inside or outside the United States, including foreign national Anthropic employees.
The net effect of this order is that we must abruptly disable Fable 5 and Mythos 5 for all our customers to ensure compliance.
Access to all other Claude models is not affected.
We apologize for this disruption to our customers. We believe this is a misunderstanding and are working to restore access as soon as possible.
Read our full statement: https://t.co/bwn0sximKZ
GPT-5.4 Pro just solved Erdős Problem #1196, a 60-year-old conjecture from Erdős, Sárközy, and Szemerédi on primitive sets.
One shot. ~80 minutes of reasoning.
What makes this different from other AI math results (from what I understand): The world's top expert on this problem, Jared Lichtman (who proved the original Erdős Primitive Set Conjecture during his PhD), worked on #1196 for 7 years alongside Fields Medal-level collaborators; this was not attention-starved.
The AI rejected the standard approach every mathematician had used since Erdős' 1935 paper, a switch from analysis to probability, and instead stayed purely analytic using von Mangoldt weights. Human aesthetic convention had made that path invisible.
Lichtman's analogy: like AI discovering a new chess opening that grandmasters overlooked because of convention.
Terry Tao suspects the trick could simplify the broader theory of prime factorization anatomy, not just solve one conjecture.
Lichtman calls it possibly the first AI "Book proof" for an Erdős problem.
GPT-5.4 pro is the math goat.