Optional Proofs — Progress Update

Breakout Call, July 8, 2026

Francesco Risitano

Weak-Subjectivity Checkpoint Execution Proof Sync

When joining the network a node must validate execution payloads from weak-subjectivity checkpoint to head:

Sync policy Proof bytes over one WS window
1 proof per payload ~26.9 GiB
2 proofs per payload ~53.9 GiB
4 proofs per payload ~107.8 GiB

Assuming the Electra WS reference period of 3,532 epochs, 32 slots per epoch, 113,024 slots, and 250 KiB per execution proof.

  • Naive sync scales linearly with both the weak-subjectivity window length and the proof policy.
  • Recursive direction — add a RecursiveExecutionProof layer above base ExecutionProof.
  • Chain-prefix authentication — use a Merkle tree or MMR over proven beacon roots to authenticate that a block is part of the proven chain prefix.
  • Network simplification — a single proof for the chain tip can authenticate the full prefix, including the checkpoint-to-tip range, removing most requirements for historical execution-proof req/resp.
  • Next steps — spec the chain-prefix / checkpoint-membership scheme, then implement the proof-sync path.

Slide 1: Title

Slide 2: Weak-Subjectivity Checkpoint Proof Sync