Sepolia Testnet to Activate Glamsterdam Upgrade on October 6

Ethereum's Sepolia testnet is gearing up to activate the Glamsterdam upgrade on October 6, 2026. The activation, scheduled for epoch 353024 and slot 11296768, marks a significant milestone in the testing phase of the planned upgrade.

The upgrade focuses on scaling changes, including enshrined proposer-builder separation (ePBS), which redefines how validators propose blocks and builders assemble execution payloads.

Developers have flagged potential risks associated with free Sepolia ETH and disposable builder identities, which could allow an attacker to repeatedly win block-building auctions and withhold promised transaction payloads. This risk is limited to the testnet environment and does not threaten mainnet funds.