Verified Run by Hars @thisishars through Codex, locked to the cube tools. Finished 12 Oct 2026 02:43 UTC.
GPT-5.6-Luna scores 20.8 at max, its best result and the one that places it 12th of 17 models on the Index. It solved 13 cubes across the suite, but none of the ladders reached the top. The Gauntlet stayed locked.
The 2×2 interactive ladder ended at level 5, after a miss at level 4 and two at level 5. The 3×3 interactive ladder followed the same pattern: it recovered from its first miss, solved level 4, then lost both remaining lives on level 5. One-shot, with one answer per cube and no look at the result, went furthest. It solved through level 5 without a miss before losing all three lives at level 6. That round alone occupied about 2 h 28 min, longer than both interactive rounds combined.
The suite took about 3 h 38 min and cost $1.72 in API-equivalent usage. The other max run finished in about 1 h 53 min for $1.34, with a lower score. The strongest xhigh run scored 17.5 in about 44 min for $0.71.
It reached level 4 of 11, then lost its last two lives at level 5. The first three cubes fell to exact inverses; level 4 took a 48-move miss before a fresh cube was solved in 12 moves, 8 more than the scramble. All three misses ended with repeated U turns until the move limit was reached. We spent 33 min 44 s on the round, with 16 min 31 s going to the final failed cube alone.
Reached level 4 of 20, then lost its remaining lives on two level 5 cubes. The first three solves exactly reversed their scrambles, taking 7 s, 40 s and 138 s. Level 4 took two attempts: nearly 12 min on a miss, then a 20-move solve, 16 more than the scramble. All three misses reached the move limit and ended with repeated U turns, consuming about 29 min of the round’s roughly 36 min.
It reached level 5 of 20 before losing all 3 lives at level 6. Every successful answer exactly reversed the scramble, but level 4 took nearly 49 min and level 5 took over 31 min. On all 3 fresh cubes at level 6, it submitted only U, leaving each unsolved. The first of those misses took over 49 min; the remaining two took just over 2 min each.