Ethereum's Glamsterdam upgrade scheduled to fork Sepolia testnet on Oct 6

The Ethereum Foundation set October 6, 2026 at 13:53:36 UTC as the activation time for the Glamsterdam upgrade on the Sepolia test network, according to its calendar and a blog post dated September 17. Mainnet timing was still open, with the target set for the fourth quarter of 2026 and no date confirmed. The test fork does not change ETH on the mainnet, and the upgrade includes enshrined proposer-builder separation.

• Sepolia testnet activation scheduled for October 6, 2026 at 13:53:36 UTC
• Mainnet targeted for Q4 2026 with no date confirmed
• Upgrade includes enshrined proposer-builder separation (ePBS)
• Test fork does not affect ETH on the mainnet