Why does KIP21 cap the number of lanes allowed in one Kaspa block?

KIP21 caps each Kaspa block at 50 distinct non-coinbase lanes to keep the computational work any single node must do per block predictable and bounded. When a block arrives, every participating lane triggers local SMT (Sparse Merkle Tree) updates — bookkeeping that tracks each lane's current state. Without a cap, a block packed with hundreds of lanes could force nodes to perform an unbounded amount of work before they could move on to the next block. The 50-lane ceiling sets a known worst case, so node operators can size their hardware accordingly. For beginners, this means Kaspa's protocol actively protects the network from blocks that demand too much processing — a practical safeguard built into how blocks are admitted.