Combination pipelines
The named search experiments that chase score. Each is a pipeline rather than a single algorithm: it builds a board with one engine, then lifts or finishes it with another. Each records its idea, its best board, and the questions it left open.
Run the same beam search across nine different scan orders, so it lands in different regions instead of always converging to the same one. The zigzag order found a brand-new 458 board.
Fix a perfect border, then search the interior with the border's edges treated as hard constraints from the very first cell.
Decide in advance not when a board may break, but where: confine every mismatch to a chosen shape of cells, and search for the best shape.
Throw hundreds of cheap short searches at the board, keep only the deepest starts, and promote the survivors through longer and longer rounds.
Tile the board into small blocks, solve each one to proven optimality, and glue them together, paying for the seams instead of forbidding them. From scratch, with no record to copy, it reaches 448.
Build the whole board from scratch with no pre-set frame, in stages, letting the border emerge last from whatever pieces are left.