Ethereum developers have scheduled public testing of the Glamsterdam upgrade on Sepolia for Oct. 6, while warning that attackers could use free testnet tokens and disposable builder identities to win block bids and withhold transaction payloads. The scenario could disrupt block production and Glamsterdam testing but would not directly threaten Ethereum mainnet funds. Glamsterdam’s enshrined proposer-builder separation design moves the link between validators and block builders into Ethereum’s protocol: builders bid for the right to supply blocks, while validators accept winning bids and expect transaction payloads to follow. Developers are evaluating safeguards that can identify and permanently reject abusive builders. Devnet-11 began Sept. 14, completed its Gloas transition on Sept. 16 and raised its gas limit from 60 million to 200 million without losing finality across 84,000 validators. Client teams must publish Sepolia-ready software by Sept. 29, leaving seven days for review. Hoodi testing is provisionally scheduled for Oct. 27, subject to Sepolia’s results. Mainnet activation remains unscheduled, with the roadmap targeting the fourth quarter of 2026.