Sync Committee

A randomly-selected subset of 512 Ethereum validators that serves ~1 day and continuously signs block headers, giving light clients a small, fixed group to follow instead of the entire validator set. It makes verifying the chain feasible on phones, in browsers, and inside other chains' contracts. The trust assumption — that this rotating, slashable committee is honest — is weaker than full-set finality verification but far stronger than trusting a centralised server.