Ethereum’s Glamsterdam upgrade clears rehearsal for October 6 test

Ethereum’s Glamsterdam upgrade just passed its latest private devnet rehearsal, clearing the way for a public testnet deployment on the Sepolia network tentatively scheduled for October 6, 2026, at 13:53 UTC. If all goes according to plan, the upgrade would land on mainnet sometime in Q4 2026, bringing with it one of the most aggressive capacity expansions in the network’s history.

The target: nearly tripling Ethereum’s block gas limit from roughly 60 million to 200 million.

What Glamsterdam actually changes

The upgrade bundles two layers of improvements under one roof. On the consensus side, changes are grouped under the name Gloas. On the execution side, they fall under Amsterdam. Together, they form Glamsterdam, following the naming convention Ethereum has used since merging its upgrade tracks.

The headline feature is enshrined proposer-builder separation, or ePBS, introduced through EIP-7732. Right now, Ethereum’s block production pipeline leans heavily on off-protocol MEV relays, third-party services that sit between validators and block builders to coordinate transaction ordering. These relays introduce centralization risks and trust assumptions. ePBS bakes that separation directly into the protocol itself, reducing dependence on external infrastructure.

The second major technical addition is block-level access lists, or BALs, delivered via EIP-7928. These allow transactions within a block to declare upfront which parts of Ethereum’s state they intend to touch. That declaration enables safer parallel execution of transactions, meaning the network can process more work simultaneously without risking conflicts between operations that modify the same data.

Combined with adjustments to gas pricing models, these changes are projected to reduce transaction fees for many common operations by approximately 78.6%.

The road to Sepolia

The October 6 testnet date is tentative, contingent on continued stability in the private testing environment known as Devnet-11. Previous devnet cycles for Glamsterdam surfaced implementation bugs and finality issues, the kind of problems where the network temporarily loses its ability to confirm blocks as permanent. Those findings prompted the development teams to push back timelines rather than ship known instability to a wider audience.

A longer-lived public test environment called Platåberget was also used for early compatibility checks across Ethereum’s various client implementations. Multiple independent teams build and maintain Ethereum’s software, so every upgrade requires careful coordination to ensure all clients agree on the new rules simultaneously.

This cautious approach mirrors what happened with the Pectra upgrade, which also encountered delays during its devnet phase before eventually reaching mainnet. Fusaka, the upgrade that preceded Glamsterdam in Ethereum’s roadmap, went through a similar gauntlet.

Where Glamsterdam fits in the bigger picture

Glamsterdam sits within the phase of Ethereum’s long-term roadmap known as the Surge, the umbrella term for all scaling-related improvements across both Layer 1 and Layer 2. While much of Ethereum’s recent scaling story has been about L2 rollups handling transaction volume off the main chain, Glamsterdam focuses squarely on making L1 itself more capable.

L2 networks like Arbitrum, Optimism, and Base still settle their transactions back to Ethereum’s base layer. A more capable L1 means those rollups can post data more cheaply and frequently, improving the entire ecosystem’s throughput from the bottom up.

By enshrining proposer-builder separation at the protocol level, Glamsterdam reduces the structural advantage that sophisticated MEV operators currently hold over ordinary users.

If the Sepolia fork on October 6 goes smoothly, attention will shift toward a mainnet activation timeline. Q4 2026 remains the target, though no specific mainnet date has been committed to yet.