Constant MOE_ROW_UNION_MAX_IDS 

pub const MOE_ROW_UNION_MAX_IDS: usize = 64;

🪤 glm5next_moe_row_union is ONE block of rows * top_k threads. A CUDA block is capped at 1024 threads, but this kernel’s own scans are O(T^2)/O(T^3) over that extent and the tier family was sized around 64, so 64 is the contract. Threads past a block never run: exceeding it would SILENTLY drop union entries, so the dispatch refuses instead.