sync

the structural sync protocol is a cross-cutting spec spanning radio, cybergraph, bbg, cyb/sync, and foculus.

see cybergraph/specs/structural-sync for the full protocol.

bbg's role in sync

bbg is a pure state library. it has no network code and no sync protocol.

what bbg provides to the sync protocol:

layer 3 (completeness): Lens polynomial commitments. each neuron commits its signal chain; bbg commits the finalized signals dimension of BBG_poly. withholding is algebraically detectable.

query wire: prove(key, dimension) → QueryProof. cybergraph serves these proofs over the query wire protocol. bbg builds them.

BBG_root: the checkpoint used by the local sync protocol and the light client. BBG_root = H(Lens.commit(BBG_poly) ‖ Lens.commit(A) ‖ Lens.commit(N)).

signal finalization: after cybergraph validates a signal (layers 1–2) it calls bbg.apply(tx). bbg applies the state transition and recomputes BBG_root.

what bbg does NOT own: signal structure, hash chains, equivocation detection, VDF, CRDT merge, transport. those live in cybergraph and cyb/sync.