Gro-Tsen on X: "So, someone came up with an AI-generated formal proof, in Lean, of a solution to the Collatz problem, and it turned out that the “proof” was merely exploiting a bug in the Lean kernel (allowing you to prove anything)." / X<br>Post

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Gro-Tsen<br>@gro_tsen

So, someone came up with an AI-generated formal proof, in Lean, of a solution to the Collatz problem, and it turned out that the “proof” was merely exploiting a bug in the Lean kernel (allowing you to prove anything).<br>span:not(:empty)~span:not(:empty)]:before:content-['·'] [&>span:not(:empty)~span:not(:empty)]:before:px-1 [&>span:not(:empty)~span:not(:empty)]:before:shrink-0">3:10 PM · Jul 29, 2026239.5KViews

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20h

More details and explanations at:

infosec.exchange<br>abadidea (@[email protected])<br>Okay, we have a new contender for Most AI Thing to Ever Happen 1) July 25th: someone messes around with an LLM and posts a proof of the Collatz conjecture that does, in fact, verify in the theorem...

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20h

Keep this in mind when someone claims that requiring formal proofs in Lean is the end-all solution to AI slop and hallucination in mathematical proofs.

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20h

(There are other — more frequent — problems, of course, like the fact that the formally proven theorem might not match the informally understood one. Or, more basically, that the proof might be unreadable for humans, making it useless.)

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18h

* Not that this changes any of the above, but I am informed that the person posting the proof was actually aware that this was a Lean kernel soundness bug, and it was not intended to be taken seriously as a solution to Collatz's problem.

span:not(:empty)~span:not(:empty)]:before:content-['·'] [&>span:not(:empty)~span:not(:empty)]:before:px-1 [&>span:not(:empty)~span:not(:empty)]:before:shrink-0 min-w-0 overflow-hidden">Jason Rute<br>@JasonRute

19h

Replying to @gro_tsenI think they just use collatz as a fun way to demonstrate the lean soundness bug. There is a history of this in the theorem proving community. The author knew it was a soundness bug and it was intentional.

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