OP Labs

Upgrade 20 is here.

The OP Stack fault proof system is getting ready for interoperability. This upgrade lays the groundwork for all OP chains to interact as one.

The key upgrade: U20 replaces each chain's output root with a super root, a timestamp-based commitment built to cover multiple chains at once.

Simple and secure.

Welcome to Optimism, Akosh!

Akosh Farkash is joining as a Senior Software Engineer with over six years of blockchain experience, including at Aztec, Matter Labs, and Protocol Labs. He’s a full stack engineer who’s been programming since 2004.

Excited to have you onboard.

Subblocks go live on OP Sepolia Monday, Aug 17.

Preconfirmations move from 250ms to 200ms.

Four payload fields are set to their zero value:
- state_root
- block_hash
- withdrawals_root
- withdrawals to their zero value

For teams consuming the subblock stream directly:

- Audit integrations for reads of state_root, block_hash, withdrawals_root, and withdrawals.

- Confirm that a zero value in any of them cannot propagate into downstream state, balances, or proofs.

- RPC providers that forward stream payloads to their own consumers should pass this notice on to those consumers.

OP Mainnet follows Aug 31.

Full notice: docs.optimism.io/notices/subblo…

Upgrade 19, the Karst hard fork, is scheduled to activate on Mainnet OP Stack chains Wed, Jul 8, 2026 at 16:00:01 UTC. Please refer to the notice page for full details and required actions.

docs.optimism.io/notices/upgrad…