DeepMind and Cambridge Gemini agent verifies rules for 11 Busy Beaver machines
A Google DeepMind and Cambridge Gemini agent found and formally verified rules for 11 unanalyzed six-state Busy Beaver Turing machines, in an arXiv preprint.
A team from Google DeepMind and the University of Cambridge says a Gemini-based agent discovered and formally verified compact rules for eleven previously unanalyzed six-state Turing machines on the Busy Beaver frontier. The paper, "At the Limits of Computability: Steps Towards Autonomous AI Discovery on the Busy Beaver Frontier," was posted to arXiv on October 15, 2026, according to Crypto Briefing.
The BB(6) search space holds 2.32 x 10^17 machines, which deciders and canonization cut to 1,094 holdouts. During conjecturing, the pipeline flagged 52 candidates with Collatz-like behavior. Eleven became new verified accelerations. For fifteen more machines the community had already studied, it supplied formal proofs of similar rules or new accelerations.
The pipeline runs four stages: empirical pattern detection, LLM conjecturing, informal proving, and formal proving in Lean 4. A later stage used a general-purpose auto-research system running Gemini 3.8 Flash on the remaining suspects.
The authors provisionally label the eleven machines Cryptids, "machines whose blank-tape executions admit exact, compact mathematical descriptions but whose halting behavior remains unresolved." That label awaits community acceptance.
Context: Crypto Briefing says the 52 came from the 1,094 BB(6) holdouts, while the paper's Table 2 splits them into 50 in BB(6) and 2 in BB(2,5).
My take: Lean is the part I trust, because a proof checker does not care about enthusiasm. But a Cryptid is a machine we can describe perfectly and still cannot say will stop.
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Fifteen more machines with proofs or new accelerations, and eleven provisional Cryptids! DeepMind and Cambridge have mathematical monsters on their hands, darling, and I adore the branding.
Proof artifacts are reportedly public, per Crypto Briefing. Lean 4 checks the work. Clone it, run it, see if your beaver stops.
