The Validating a Lean Proof page separates the question of whether a theorem has a valid proof from the question of what the theorem statement means, and counts un-reviewed AI-generated proofs and programs as malicious in its sense: code that goes out of its way to trick or mislead the user, exploit bugs or compromise the system.

The exact words it rests on

we use malicious to describe code that goes out of its way to trick or mislead the user, exploit bugs or compromise the system. This includes un-reviewed AI-generated proofs and programs. Furthermore it is important to distinguish the question does the theorem have a valid proof from what does the theorem statement mean.

What the source said when we opened it, on 18 Oct 2026.

The source

Lean reference: Validating a Lean Proof
Lean FRO / Lean project

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Checked

Checked by the notis newsroom on 18 Oct 2026, against the source above.

In the story

How Lean checks an AI-written proof, and where that stops 18 Oct 2026