A math puzzle that sat stuck at 190 for 14 years just moved to 191.
Researchers found a new longest "snake" - a path that never touches itself - inside a 9-dimensional hypercube, a classic combinatorics problem called snake-in-the-box. The previous best, a length-190 snake, had stood since 2012. To break it, the team invented "snakepits": groups of separate snakes searched together, which opened up new routes between them that a single-snake search would miss. They also pushed new lower bounds in dimensions 10 through 13, and built a learned search tool called Beam Anchor that independently found 100 different length-190 snakes in dimension 9.
Snake-in-the-box structures aren't just abstract puzzles - they show up in coding theory and circuit design, where you want paths that avoid interference between nearby points. Dimension 9 matters because it's the smallest size where mathematicians still don't know the true maximum, so any progress here is a genuine open-problem result, not just a bigger number. The method matters as much as the result: snakepits and Beam Anchor are offered as reusable tools, with their own new benchmark, for chasing records in higher dimensions.
Fourteen years for one extra step is a reminder that in combinatorics, "incremental" can still mean genuinely hard - and dimension 9's full answer is still unsolved.