Ethereum developers have scheduled the network’s next major upgrade, Glamsterdam, to activate on the Sepolia testnet on Oct. 6, the Ethereum Foundation said Monday. The date applies only to Sepolia; developers have not set timelines for the validator-focused Hoodi testnet or for mainnet deployment.

Sepolia node operators must update both their execution-layer and consensus-layer clients ahead of activation, the Foundation said. Operators running either client without the required release risk falling off the network when the fork takes effect.

What does Glamsterdam change?

The upgrade carries three structural changes to how Ethereum produces and prices blocks.

• Enshrined proposer-builder separation. The handoff between specialized block builders and validators moves into Ethereum’s own protocol, reducing reliance on outside middleware. Today that coordination largely depends on external infrastructure; enshrining it shifts the responsibility — and the trust assumptions — to the protocol itself.
• Block-level access lists. Blocks will record the accounts and storage locations used during each block, giving clients advance visibility into which state a transaction intends to touch.
• New gas pricing. Fees will better reflect the cost of creating and accessing data on Ethereum. The Foundation warned that contracts relying on fixed gas stipends or hardcoded gas limits may require changes — an operational item for decentralized application developers and auditors before mainnet activation.

Together the changes target block construction economics and state-access efficiency rather than end-user features, continuing Ethereum’s multi-year rework of its consensus and execution machinery.

What happens after Sepolia?

A Sepolia activation is a testing checkpoint, not a launch. Developers have not set dates for Hoodi or mainnet, and mainnet timing typically follows successful testnet runs plus client-readiness checks across execution and consensus teams.

The roadmap beyond Glamsterdam is already taking shape. Developers are targeting 2027 for Hegotá, the upgrade expected to follow Glamsterdam.

Ethereum co-founder Vitalik Buterin said Sunday that Hegotá could be the network’s last “normal” fork before development shifts toward recursive STARKs, automated formal verification, optimized consensus and quantum-safe cryptography. That framing signals a long-horizon pivot in Ethereum’s engineering priorities — from incremental hard forks toward proving systems and cryptographic hardening.

For infrastructure operators, the immediate obligation is concrete: update execution-layer and consensus-layer clients before the Oct. 6 Sepolia activation. For smart-contract teams, the gas-pricing change is the item to model now, since hardcoded gas assumptions that survive Sepolia may still break on mainnet. Developers should expect mainnet timing announcements only after Sepolia and Hoodi both run clean.