ETH Glamsterdam upgrade enters final devnet

TLDR

Ethereum's Glamsterdam upgrade is now in its final devnet stage, with all planned changes bundled and tested before public testnets and a 2026 mainnet launch.

1. Developers are running closed devnets with the full Glamsterdam EIP set, described as Ethereum's biggest protocol overhaul since the Merge and targeted for the second half of 2026.
2. Glamsterdam introduces enshrined proposer builder separation, block level access lists, and major gas repricing aimed at a 200 million gas limit and significantly lower average transaction fees.
3. Next milestones are public testnets, client readiness, and validator decisions on raising gas limits, with potential trade offs around hardware requirements and implementation risks.

Deep Dive

1. Final Devnet, What It Means

Ethereum (ETH) core teams are now running developer networks that include the complete set of Ethereum Improvement Proposals (EIPs) slated for Glamsterdam, marking the last development phase before public testnets. Reports describe this as Ethereum's largest protocol change since the 2022 Merge, with mainnet activation currently expected in the second half of 2026, though no exact date is fixed yet.

In Ethereum's upgrade pipeline, this devnet phase is where all changes run together across multiple clients in a closed environment, letting teams harden specs and catch cross feature issues before opening up to broader testnets.

2. Core Changes In Glamsterdam

Glamsterdam combines execution layer and consensus layer changes into one hard fork, with two headline features. Enshrined proposer builder separation (ePBS) moves the builder proposer split into the protocol to reduce reliance on external MEV relays and to improve decentralization and censorship resistance.

Block level access lists (BALs) let blocks pre declare which accounts and contract data they touch, enabling more parallel transaction processing and faster node sync. Together with new gas accounting, this clears a path to raising the L1 gas limit from roughly 60 million toward a 200 million target, which some estimates say could unlock up to 10,000 transactions per second equivalent throughput and cut simple transfer fees by more than half under load as described in an upgrade overview from The Defiant.

The gas repricing flips the cost balance so compute becomes cheaper while state growth gets more expensive, nudging developers toward designs that scale better over time.

3. Timeline, Risks, What To Watch

From here, the main steps are: hardening code on devnets, deploying to public testnets like Holesky or newer nets, then scheduling a mainnet fork once multi client stability is proven. Coverage of the process notes that mainnet is targeted for the second half of 2026 but still explicitly marked as timeline dependent on test outcomes in reports such as the Coindesk summary of Glamsterdam's final development stage.

Validators will also need to agree on raising the gas limit as network conditions allow, which increases capacity but can raise hardware and bandwidth requirements and is a live topic in community discussions. There is also the usual client diversity and implementation risk that accompanies large protocol changes, especially with MEV and gas economics shifting.

Conclusion

Glamsterdam reaching its final devnet stage signals that Ethereum is close to locking in a major redesign of how blocks are built, how transactions execute, and how gas costs are structured. If the upgrade delivers its targeted gas limit increase and fee reductions while keeping validators diverse, it could materially improve L1 capacity and MEV fairness and reinforce Ethereum's role as the settlement layer beneath its rollup ecosystem.