Verified Run by us through Codex, locked to the cube tools. Finished 23 Oct 2026 21:39 UTC.
GPT-5.6-Luna scored 13.0 at xhigh, its lowest result across three runs at this effort and below its high run. Its best result came at max; the model sits 12th on the Index. Here, it gave up on level 4 of the 3×3 one-shot ladder with 1 life left, leaving another attempt unused.
On the 2×2 interactive ladder, it exhausted its lives at level 4. Two misses were deliberate throwaways: it used up the move limit by repeating one move to get a fresh cube, including U 38 times on one attempt. The 3×3 interactive ladder ended with all three lives lost at level 3. In one-shot, where it submitted an answer without seeing the result, misses at levels 1 and 2 preceded its stop at level 4. None of the ladders cleared, so the Gauntlet stayed locked.
We spent 35 min 19 s on this run, at an API-equivalent cost of $0.55. The higher-scoring high run took 18 min 5 s and cost $0.31. The other xhigh runs also scored higher, but took about 44 and 45 min and cost $0.71 and $0.85.
It reached level 3 of 11 at xhigh, then lost all 3 lives at level 4 by hitting the move limit. On 2 of those cubes, it repeated U to use up the remaining moves and get a fresh cube, including 38 repetitions on one attempt. The longest solve was level 3: 6 min 3 s and 17 moves, 14 more than the scramble. The final cube received nothing but 48 U moves in 13 s, exhausting its last life.
It reached level 2 of 20, then lost all 3 lives on level 3 by exhausting the 36-move limit each time. The first miss took 4 min 32 s, more than half the round’s 8 min 28 s. Level 2 had been solved in 2 moves, as short as the scramble, but none of the three fresh cubes at the next level was solved. On the second miss, it finished by repeating R until the moves ran out.
At xhigh, it reached level 3 of 20, then gave up on level 4 with 1 life left. Wrong answers at levels 1 and 2 cost the other lives, including a single D turn for a D2 scramble. All 3 successful answers exactly reversed their scrambles. The unanswered level 4 cube took 10 min 16 s, more than all the earlier attempts combined, before it ended the test without submitting any moves.