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Ethereum confirms Glamsterdam dates, but warns 'fake' builders could stall the chain
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- DeepHorus
Ethereum developers have locked in Oct. 6 as the public test date for the "Glamsterdam" upgrade, but they warn that attackers using fake identities and free test ether could stall the rehearsal. During Thursday's core developer call, consensus developer Potuz said anyone could spin up thousands of builders, rotate them, offer high bids, and then withhold transaction payloads. The attack would not endanger mainnet funds, but it could freeze traffic on the Sepolia test network and derail infrastructure testing.
Glamsterdam is Ethereum's next major upgrade, designed to fit more activity into each block without overwhelming validators. Together with gas pricing changes, it aims to support a block gas limit of about 200 million, creating room for more payments and trades. The upgrade moves the relationship between validators and specialized block builders into Ethereum's protocol, with builders competing to assemble and reveal transaction blocks.
On a free test network, this process is easy to abuse. A malicious operator can outbid legitimate builders repeatedly and then withhold promised payloads, leaving blocks empty. Existing safeguards typically fall back to locally built blocks only after several payloads go missing, so the attack could stall the network.
Potuz argued that client teams need to identify and reject individual builders so attackers cannot return under new identities. The warning came one day after a large private rehearsal completed the Glamsterdam transition and raised its block gas limit toward 200 million without losing finality. That success gave developers confidence to proceed.
Client teams now have until Sept. 29 to release Sepolia-ready software, leaving seven days before the fork β half the 14 days normally reserved for security reviews. Developers accepted the narrower window because Sepolia is relatively centralized and easier to recover. Production builder software from teams Titan and Ultrasound has also not yet completed a Glamsterdam fork transition.
Sepolia's test is scheduled for Oct. 6, with Hoodi testing tentatively set for Oct. 27. Mainnet activation remains unscheduled. The upgrade's success depends on filtering out malicious builders before Glamsterdam reaches Ethereum itself.
