Ethereum Classic's Olympia Upgrade — May 2026 Development Checkpoint

Olympia Upgrade — May 2026 Development Checkpoint

Multi-client stability achieved to May 2026 LTS codebases. All three Olympia execution clients are stable, peered, and advertising Olympia as the next hardfork on the wire.

🟢 Fukuii v0.5.0+ — Multi-EVM architecture implemented. Dual Ethereum Classic (PoW) and Ethereum (PoS) execution from a single client. ETH/68 and ETH/69+ PoW compatibility validated on ETC mainnet. Purpose-built for ETC — the primary client for the Olympia era. fukuii.com

🟠 Core-Geth v1.13.0+ — Stable, peered, carrying Olympia support through transition. Go 1.26+ and 2026 LTS dependencies from previous deprecated codebase. https://github.com/ethereumclassic/core-geth

🔵 Besu v26.5.0+ — Migrated to Besu's May 2026 release. ETH/68 and ETH/69+ PoW compatibility resolved.

What changed since April

• Fukuii now runs as a dual-network execution client — native PoW for ETC and Mordor, Engine API V1-V4 for post-Merge Ethereum via any consensus client (Lighthouse, Prysm, Teku, Lodestar, Nimbus)
• Original ETH/69+ (EIP-7642) chain weight resolution implemented for PoW peer ranking — no upstream equivalent exists. Validated to 0.01% accuracy against ETH/68 wire TD on live ETC mainnet
• Besu's ETH/69+ TD logic for PoW networks identified and resolved — enabling stable multi-client peering across all three clients
• Critical security patches, performance hardening, and dependency modernization across the full client stack
• All three clients now advertising Olympia as next hardfork on the network (ECIP-1111, ECIP-1112, ECIP-1121)
• Olympia Contract layer live Demo v0.2 -> v0.3 deployed on Mordor testnet.

Working Demo v0.3 infrastructure — live on Mordor testnet

🏛 olympiatreasury.org — Immutable treasury contract. Deployed and accumulating. (ECIP-1112)
🗳 olympiadao.org — On-chain governance. Proposals, voting, execution — all on-chain. (ECIP-1113, ECIP-1114, ECIP-1119)

Institutional Coordinating Organizations
⚖ ethereumclassicdao.org — Wyoming DAO LLC. Institutional portal for Ethereum Classic — regulatory framework, leadership, coordinating organizations, and the open, permissionless, regulatory-compliant governance architecture for the only Proof-of-Work smart contract platform.

Post-Olympia roadmap

ETC's core software returns to head-of-branch development following the 2024 maintenance period. In addition to full stack client work, the post-Olympia EL plugin roadmap is in active development via the ETC Cooperative — upstream ETC compatibility layers for Go-Ethereum, Nethermind, Erigon, Besu, and Reth.

What's next

Continued client hardening and critical infrastructure cleanup and modernization. Mordor testnet migration to a post-Olympia environment is in preparation. On track for ETC mainnet activation before 2027.

Full client details: ethereumclassic.com/build/clients

The Olympia upgrade gives Ethereum Classic the tools to sustain what it's always been — the original, immutable, Proof-of-Work Ethereum. Delivering production-grade infrastructure for miners, mining pools, exchanges, infrastructure providers, institutions, and custody platforms.

Ethereum Classic - Immutable infrastructure for global finance.