Mathematician tests GPT-6 Astra: live Lean proof verification while writing arguments
teortaxesTex · x · 2026-09-04
A mathematician shares his hands-on experience with GPT-6 Astra: you can converse with the model and prove statements live in Lean. Once the logic is set, each lemma flows — Astra is fast enough that formalization happens as you write your argument in Codex, unlike earlier models where verification lagged behind.
Asking the model to use literate programming plus LaTeX yields proofs interleaved with digestible chunks of Lean code, everything explained as written. His verdict: mathematicians can finally focus entirely on ideation and exploration — the "aha" is now followed by a green tick confirming the proof is captured.
The quoted tweet from markchen90 frames Astra as the culmination of years of OpenAI work on pretraining, RL, and post-training: its most capable and aligned model yet, able to build and test software, work across apps, and tackle open scientific problems.
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