BFT (Byzantine Fault Tolerant): A consensus property that preserves safety and liveness even when a bounded fraction of validators are faulty or malicious.
Batch settlement: Periodically committing a batch of HPEC's off-chain results to Altius L1 as on-chain state commitments.
Engine API: The standard interface (newPayload / forkchoiceUpdated) over which a chain's execution and consensus layers communicate.
EVM compatibility (Prague): Support for the Ethereum Virtual Machine at the Prague upgrade level, so standard contracts, ABIs, tooling, and JSON-RPC work unchanged.
Nibble partitioning: Routing trie keys to SSMT worker threads by the first 4-bit nibble of the key; 16 nibbles are distributed across up to 16 worker threads.
Settlement bridge: The set of L1 contracts (custody vault, state-commitment bridge, settlement verifier, forced-exit module) that anchor HPEC's off-chain execution on-chain.
Sparse trie: A transient, partially-materialized trie holding only the nodes a block touches, enabling incremental state-root computation that reuses unchanged subtree hashes.
SSMT (Scalable State Merkle Trie): Altius Labs' parallel engine that computes the Ethereum state root off the execution client's critical path.
State root: The single hash committing to the entire account/storage state, recorded in each block header.