Ethereum Glamsterdam Upgrade Activates on Sepolia Testnet

The Ethereum network reached a key milestone in its Layer 1 scaling roadmap on October 6, 2026, with the activation of the Glamsterdam upgrade on the Sepolia testnet ¹. The upgrade went live at epoch 353,024, slot 11,296,768, at exactly 13:53:36 UTC ¹. Glamsterdam represents a dual-layer protocol change, combining the Amsterdam execution layer upgrade with the Gloas consensus layer upgrade ¹.

By deploying these changes to Sepolia, core developers are testing a suite of Ethereum Improvement Proposals (EIPs) designed to increase transaction throughput, optimize gas accounting, and reduce reliance on external infrastructure ¹. At the time of writing, the broader market remains stable, with $ETH trading at $2,715, down 0.3% over the past 24 hours.

Enshrined Proposer-Builder Separation and Block-Level Access Lists

The primary architectural change in Glamsterdam is the introduction of Enshrined Proposer-Builder Separation (ePBS) via EIP-7732 ¹. Historically, Ethereum validators have relied on external, trusted middleware to coordinate the exchange of blocks between builders and proposers ¹. EIP-7732 integrates this separation directly into the consensus protocol ¹. Under this new design, a block proposer includes a builder's commitment to an execution payload, and the builder subsequently reveals the actual payload ¹.

The consensus protocol itself manages the payment to the proposer, eliminating the need for third-party relays ¹. Furthermore, ePBS separates consensus validation from execution validation ¹. This structural change provides validators with additional time to validate execution payloads ¹. A newly established payload timeliness committee is tasked with attesting to whether the builder revealed its payload and if the corresponding blob data was available on time ¹.

Alongside ePBS, Glamsterdam introduces EIP-7928, which establishes enforced block-level access lists (BALs) ¹. These lists record the specific accounts and storage locations accessed during a block, alongside post-transaction state changes ¹. By providing this structured data, BALs allow client software to read state from disk in parallel, validate transactions in parallel, and compute state roots with greater efficiency ¹. Together, ePBS and BALs are intended to scale execution capacity while keeping node validation practical for home operators ¹.

Gas Accounting and State Growth Adjustments

To address the long-term sustainability of the network, Glamsterdam implements significant changes to Ethereum's gas pricing model ¹. The upgrade adjusts gas accounting to more accurately reflect the real-world resource costs of execution and state growth ¹. Specifically, EIP-8037 increases and separately meters the cost of creating state, while EIP-8038 updates state-access costs ¹.

These changes require application developers to thoroughly test their smart contracts and gas estimation systems ¹. Contracts that rely on fixed gas stipends, hardcoded gas limits, or assumptions about remaining gas may fail or behave unpredictably under the new rules ¹. Developers are encouraged to consult the Glamsterdam repricing impact guide to search for affected contracts and access testing resources ¹.

Additional gas-related modifications include EIP-2780, which introduces resource-based intrinsic transaction gas, and EIP-7976, which increases the calldata floor cost ¹. EIP-7981 also increases the cost of access lists, while EIP-7778 implements block gas accounting without refunds ¹.

Client Releases and the Gas Limit Discrepancy

Preparing for the Sepolia activation required coordinated software updates across multiple execution and consensus client teams ¹. Compatible consensus layer releases include Lodestar 1.49.0, Teku 26.9.1, and Prysm 7.2.0 ². On the execution side, compatible versions include Besu 26.9.0, Erigon 3.7.1, Nethermind 2.1.0, Reth 2.7.0, and Go-Ethereum (Geth) versions 1.17.6 and 1.17.7 [2, 6]. Geth 1.17.7 was released as a quick follow-up to fix an Ubuntu PPA publishing failure and includes optimizations for encoding and hashing block-level access lists ⁶.

A key point of coordination for validators was the network gas limit ⁴. The upstream Sepolia configuration scheduled an increase in the network gas limit to 200 million (200M) at the fork via EIP-8261 [3, 4]. However, this configuration change was finalized after some client versions were cut ⁴. For instance, Prysm 7.2.0 and Teku 26.9.1 default to a 60M gas limit after activation ². Validators using these versions who wished to propose blocks with the scheduled 200M limit had to configure their clients explicitly ².

To resolve this, Offchain Labs released Prysm v7.2.1 on October 5, 2026 ⁴. This release integrates the Sepolia gas limit schedule directly, allowing validators to default to the 200M gas limit automatically at epoch 353,024 without manual intervention ⁴. Prysm v7.2.1 also enables cell-level PeerDAS data column dissemination (partial data columns) by default, optimizing how nodes gossip data ⁴.

Implications for Mainnet and Future Upgrades

The successful activation of Glamsterdam on Sepolia is a critical step, but it does not establish a timeline for mainnet deployment ¹. The Ethereum Foundation has stated that activation dates for the Hoodi testnet and the Ethereum mainnet have not yet been decided ¹. These timelines will be determined by client development teams after analyzing the stability and performance of the upgrade on Sepolia ¹.

For developers, the upgrade introduces several quality-of-life improvements beyond scaling ¹. These include EIP-7708, which ensures ETH transfers emit a log, EIP-7843, which adds a slot-number opcode, and EIP-7954, which increases the maximum contract size ¹. The upgrade also introduces a deterministic factory contract under EIP-7997 and new stack-manipulation instructions via EIP-8024 ¹.

What to Watch

In the coming weeks, core developers will monitor Sepolia's health, focusing on the performance of the payload timeliness committees and the efficiency of parallel transaction validation using block-level access lists ¹. Node operators should watch for upcoming client releases that will officially schedule the Glamsterdam upgrade on the Hoodi testnet and eventually the Ethereum mainnet ¹.

Additionally, developers should monitor the Ethereum Bug Bounty Program, which is now active for Glamsterdam specifications and eligible client implementations, offering reward multipliers for identified vulnerabilities ¹.