Release notes

This is a patch release focused on Optimism / OP Stack support. It adds the OP Karst fork, refreshes the Superchain registry chains, and removes the bundled Base mainnet and sepolia configurations.

Sepolia: Wed, Jun 17, 2026 at 16:00:01 UTC
Mainnet: Wed, Jul 8, 2026 at 16:00:01 UTC

Overview

Full diff: 1.38.0...1.38.1

5 changes since 1.38.0, all OP Stack–related. Highlights:

• OP Karst fork added, with the precompile input-size caps and Engine API capability gating that go with it.
• Superchain registry refresh across all bundled OP chains.
• Base removed from the shipped chain configs and node profiles.

Highlights

Optimism

• Add OP Karst fork (#11917) — Karst timestamp plumbing across the OP forks, Osaka EIPs enabled, propagation of release spec and precompile input-size limits, and ForkInfo support. Includes a refactor that isolates all OP-specific fork flags and transition timestamps inside Nethermind.Optimism (mirroring the Taiko plugin pattern), so Core/Specs/Merge.Plugin/Evm.Precompiles no longer reference any OP fork flag. OP precompile caps now live in dedicated wrapper precompiles registered via OptimismPrecompileProvider, and Engine API V4 is gated behind OP Isthmus activation.
• Update OP Superchain chains (#11855, #11733)

Chain configs

• Update OP Superchain chains, removes Base (#11655) — removes base-mainnet and base-sepolia (including archive configs, profiles, and logo) from the bundled chains, adds support for handling chains deleted from the Superchain registry, and removes arena-z and swell-mainnet.

⚠️ Breaking changes

• Base is no longer bundled. The base-mainnet, base-sepolia, and their _archive configurations have been removed from the shipped chain configs. Operators running Base via Nethermind's built-in configs must supply their own chainspec/config.
• arena-z and swell-mainnet chain configs were also removed as part of the Superchain registry sync.

What's Changed

• Update OP Superchain chains (removes Base) by @emlautarom1 in #11655
• Update OP Superchain chains by @core-repository-dispatch-app in #11733
• Update OP Superchain chains by @core-repository-dispatch-app in #11855
• Add OP Karst fork by @emlautarom1 in #11917
• Update Directory.Build.props for 1.38.1 by @stdevMac in #11973

Full Changelog: 1.38.0...1.38.1

Build signatures

The packages are signed with the following OpenPGP key: AD12 7976 5093 C675 9CD8 A400 24A7 7461 6F1E 617E