Ethereum's Glamsterdam upgrade will go live on the Sepolia test network on October 6; no mainnet date yet

What happened

On September 17, 2026, the Ethereum Foundation Blog published an announcement under the Protocol byline. It says the Glamsterdam network upgrade follows the Fusaka upgrade and advances Ethereum's L1 scaling roadmap. L1, or layer 1, is Ethereum's base network itself. Glamsterdam is scheduled to activate on Sepolia at epoch 353,024, slot 11,296,768, which is 13:53:36 UTC on October 6, 2026. Epochs and slots are the units of time Ethereum uses to schedule blocks. Sepolia is a test network: it runs the same software as Ethereum's live network, known as mainnet, so changes can be tried out before they reach real users. The Foundation said activation times for Hoodi, another network, and for mainnet have not been decided and will be announced once client teams decide. This announcement does not schedule a mainnet upgrade.

According to the announcement, Glamsterdam combines the Amsterdam upgrade to the execution layer, the part of Ethereum that runs transactions, with the Gloas upgrade to the consensus layer, the part that agrees on which blocks are valid. EIP-7773 tracks the upgrade as a whole and lists 18 EIPs scheduled for inclusion. An EIP, or Ethereum Improvement Proposal, is the formal written specification of a single change.

Read the full description

Sources are collected, independently checked, then reviewed by Jev.

Two core changes: ePBS and block-level access lists

Enshrined proposer-builder separation (EIP-7732)

Two roles are involved in making each block. A proposer puts a block forward for the network. A builder assembles the block's contents, which the protocol calls the execution payload. According to the Ethereum Foundation, EIP-7732 writes this division of labor directly into the consensus protocol. The proposer first includes the builder's commitment to an execution payload, and the builder reveals the payload afterward. The protocol itself handles payment to the proposer, which reduces reliance on trusted middleware, the outside software that has brokered this exchange. The Foundation also said the change separates consensus validation from execution validation. This gives validators, the participants who check and vote on blocks, more time to validate the execution payload. A new "payload timeliness committee" attests to whether the builder revealed the payload on time and whether the corresponding blob data is available.

Block-level access lists (EIP-7928)

According to the announcement, EIP-7928 introduces mandatory block-level access lists. These record the accounts and storage locations accessed within a block, along with post-transaction state changes. The Foundation said this lets clients, the software that runs an Ethereum node, read state in parallel, validate transactions in parallel and compute the state root more efficiently. Put simply, nodes can handle more work at once instead of queuing items one by one.

Who needs to do what

In the announcement's FAQ, the Ethereum Foundation said mainnet users and ETH holders do not need to take any action because of this announcement. Mainnet activation will be covered in a separate announcement. Node operators on Hoodi or mainnet likewise need not act on this Sepolia announcement. Sepolia is a test network, and this activation is a testing step before the upgrade goes to mainnet.

For developers, the impact is more direct. The Foundation recommends testing contracts and gas estimation against the new rules. It notes that contracts relying on fixed gas stipends, hardcoded gas limits or assumptions about remaining gas may need changes. The Foundation also said the Ethereum Bug Bounty Program, which rewards people who report security flaws, is now active for the Glamsterdam specifications and EIPs. Client implementations become eligible once their releases are added to the client release tables in the announcement.

• Sepolia node operators: according to the announcement, must update both execution-layer and consensus-layer clients before 13:53:36 UTC on October 6, 2026.
• Sepolia stakers: according to the announcement, must update both the beacon node and the validator client, and review the new ePBS duties.
• Application developers: according to the announcement, should test whether contracts and gas estimation are affected by the new pricing.
• General users and ETH holders: according to the announcement, no action is needed at this time.

Sepolia client releases

The announcement also notes that Prysm 7.2.0 supports the Sepolia fork but defaults to a 60M gas limit after activation. Validators who want to propose blocks with a 200M gas limit must set it explicitly via version 2 proposer settings or the keymanager API. The Foundation further recommends using only releases whose release notes explicitly confirm support for this Sepolia activation.

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