Ethereum developers are tentatively planning to activate the Glamsterdam upgrade on the Sepolia testnet on Oct. 6, 2026, at 13:53 UTC. However, the date is not final because developers still need to complete another private test before moving ahead with the public testnet upgrade.
Developers have now turned their attention to Glamsterdam Devnet-11, which is expected to launch on Sept. 14. Earlier plans had focused on Devnet-10, but testing has continued as developers work through several technical problems.
The Glamsterdam upgrade has not yet completed a stable activation on a private development network. This means the Oct. 6 Sepolia date could still change if the next round of testing finds serious problems.
During a Sept. 3 developer meeting, the team selected Sepolia epoch 351232 as the target for the upgrade. This corresponds to 13:53 UTC on Oct. 6. The target gives developers and infrastructure teams time to prepare, but it does not guarantee that the upgrade will happen on that date.
Earlier testing showed several issues. Devnet-9 experienced problems with finality, meaning validators were unable to reach the required agreement to confirm the chain’s state. The network had around 1,000 validators, making it one of the largest Glamsterdam private test networks at that point.
Developers have also found problems involving different Ethereum client implementations. These tests are important because Ethereum relies on multiple independently developed execution and consensus clients. The upgrade must work correctly across different combinations of these systems.
Devnet-11 will give developers another opportunity to test the fixes and make sure the Glamsterdam changes work properly together. Layer-2 networks, staking services and other infrastructure providers also need stable client software before they can safely test their systems.
Some of the problems have been linked to EIP-8037, which changes how Ethereum handles gas costs for creating new state, including accounts, contracts and storage. Developers have had to make changes to their implementations while continuing to test the proposal as part of Glamsterdam.
The upgrade has also faced consensus-layer problems during earlier devnets. One test exposed a situation involving repeated parent hashes that could cause the network to stop progressing. Another test later suffered from non-finality, leading developers to investigate additional edge cases.
Because of these issues, developers are taking a cautious approach. A successful Devnet-11 would improve confidence in moving Glamsterdam to Sepolia, while another major problem could force the team to delay the planned Oct. 6 activation.
No date has been confirmed yet for Glamsterdam on the Hoodi testnet. Developers want more confidence in the upgrade before setting the next public testnet schedule.
A December mainnet launch has been discussed as a possible target, but it is not confirmed. The final timing will depend on the results from private and public testing, client readiness and whether developers can resolve any remaining technical issues.
For now, the next major step is Devnet-11 on Sept. 14. Developers will use the test to check finality, cross-client performance and recent fixes before deciding whether Glamsterdam is ready to move forward to Sepolia on Oct. 6.
