Replicator streams a source engine's ordered execution history over TCP. Followers re-execute transaction inputs locally and validate the resulting history and persisted state. This replicates execution, not just result records, and assumes a configured source authority rather than consensus between peers.
The source dispatcher serves retained ledger history. The follower authenticates inputs, schedules transactions in stream order, and feeds upstream blocks into Engine's external pacemaker. Block validation checks ordered transaction history; superblocks and checksum checkpoints also compare persisted state. Source signatures are retained unchanged.
State checks exclude volatile accounts and don't prove collision-free state identity. Checkpoints create neither snapshots nor forced disk synchronization. Invalid signatures and detected divergence are terminal replication errors.
A follower owns its storage and local identity, with the source configured as its effective authority. External pacing makes execution follow upstream boundaries instead of generating independent blocks. The source uses an explicit follower allowlist: an empty list admits nobody, and each identity can hold only one active stream. Authenticated handshakes require synchronized peer clocks.
A dispatcher must hold the canonical authority key, including when serving from a relay. A follower with a different local key is a terminal leaf and doesn't start a dispatcher. Shared-key relays share the source's compromise and key-rotation boundary. Peers must agree on record formats and execution semantics.
Fresh followers must connect after the source has completed its first snapshot. They install the newest available snapshot before streaming: replay from the first segment alone cannot reconstruct migrated or startup-seeded initial accounts.
Reconnect resumes after already applied work while preserving stream order. A synchronized ledger position is sufficient while the source retains the required history. Otherwise the follower stages an available snapshot and requests a host restart. The host must drain services and reopen the same storage; reopening installs the snapshot before consuming its remaining tail. Snapshot progress can exceed locally retained transaction history.
Upstream resets discard mirrored volatile state while preserving internal system accounts and authoritative state.
Normal shutdown drains through the next validated block and synchronizes that position. A checkpoint after that block remains pending until reconnect. This requires the source's block heartbeat, reconnecting first if necessary; failure and snapshot-restart paths don't promise the same graceful boundary.
The client owns ordered ingestion and recovery; the server selects streams or snapshots. Protocol framing also defines the authentication handshake.