The f16/f16 KV pool costs 15640 MiB at 800768 cells. At full 800K the 3090 idled at 23966/24576 MiB and the 1472x1472 image warmup graph failed cudaMalloc (needed +248 MiB). 700416 cells (175104/slot, 4 slots) leaves ~2.3 GiB free after warmup. Parallel stays 4.