Ethereum Schedules Oct. 6 Sepolia Fork for Glamsterdam Upgrade

Ethereum is scheduled to activate the Glamsterdam upgrade on its Sepolia testnet Oct. 6, advancing testing of protocol changes intended to expand Layer 1 capacity and processing efficiency.

The fork is set for 9:53:36 a.m. ET (13:53:36 UTC) at epoch 353,024. It will deploy Glamsterdam on Sepolia, not Ethereum’s mainnet.

Glamsterdam combines the planned Amsterdam execution-layer upgrade with the Gloas consensus-layer upgrade. Its two headline features are enshrined proposer-builder separation, or ePBS, and block-level access lists, or BALs.

ePBS would move proposer-builder coordination into Ethereum’s protocol, reducing reliance on third-party relay infrastructure. BALs would provide an advance map of the accounts and storage locations touched by transactions in a block.

That information is designed to help clients process non-overlapping work in parallel, speed validation and execution, and support executionless synchronization. Ethereum’s block-propagation window could also expand from about two seconds to about nine seconds under the planned changes.

Glamsterdam also includes gas repricing intended to better reflect state-access and state-creation costs. The changes are designed to support a roughly threefold increase in base throughput.

Gas repricing may affect contracts and infrastructure that rely on fixed gas assumptions. The work follows Fusaka and is being tested across devnets and public testnets.

A mainnet rollout is still planned for the fourth quarter of 2026, although Ethereum developers have not set a firm activation date. The scheduled Sepolia milestone is the next defined public-testing step toward a possible mainnet release.