What is the SeqStateRoot stored in a Kaspa block header?

The SeqStateRoot is a single cryptographic fingerprint added to Kaspa block headers in KIP21 that captures the current state of all active transaction lanes. It is built by combining three inputs: the root of a sparse Merkle tree (a compact summary of which lanes exist and what state they are in), the block's context data, and the miner's payload data. This combined value is then threaded through the chain of selected parent blocks, producing a final value called SeqCommit that is permanently stored in the block header. Because SeqCommit lives in every block header, any node can independently verify the full history of lane states without trusting a third party.