Architecture

Prerequisites

Every OP Stack rollup is composed of four main components.

op-geth: Takes transactions from users and uses them to generate blocks and execute blocks.
op-batcher: Batches transactions from users and submits them to the L1.
op-node: Reads batch data from L1 and uses it to drive op-geth in non-sequencer mode to perform state transitions.
op-proposer: Posts an output root to L1 at regular intervals, which captures the L2 state so withdrawals can be processed.

You can read more about the components in the OP Stack Specification.

OP Succinct is designed to be an upgrade that replaces the op-proposer component of the OP Stack and its associated on-chain contracts. This change allows the chain to progress only with ZK-proven blocks, while keeping the other components (op-geth, op-batcher, and op-node) unchanged.

Here is a high-level overview of the new components that are introduced in OP Succinct:

Span Program. A program that derives and executes batches of blocks. The program is written in Rust and designed to be executed inside the zkVM.
Aggregation Program. Aggregates proofs of span programs to reduce on-chain verification cost. This program is also written in Rust and designed to be executed inside the zkVM.
OP Succinct L2 Output Oracle. A solidity smart contract that contains an array of L2 state outputs, where each output is a commit to the state of the L2 chain. This contract already exists in Optimism's original system but is modified to verify proofs as the authentication mechanism.
OP Succinct Proposer. Observes the posted batches on L1 and controls the proving of the span and aggregation programs.