Ethereum sets Oct. 6 Glamsterdam test and warns fake builders could stall it

Ethereum locks in Oct. 6 for its Glamsterdam test run

Ethereum developers have confirmed Oct. 6 as the date for a public test of the Glamsterdam upgrade on Sepolia, one of the network's test networks. The same announcement came with a warning: people using fake builder identities could disrupt that test.

The Oct. 6 event is a dress rehearsal. Glamsterdam will only go live on Ethereum's main network after developers are satisfied that it works safely, and no mainnet date has been set.

The main points

• Sepolia testing is scheduled for Oct. 6, and Hoodi testing is tentatively set for Oct. 27. Mainnet activation remains unscheduled.
• Developers warned that attackers could use free test ether and disposable builder identities to win block auctions and then fail to deliver the transaction data they promised.
• Such an attack would not put mainnet funds at risk, because it only targets a test network where the test ether has no meaningful cost.
• Client teams have a shortened release window, with roughly half the usual review time before Sepolia.

What Glamsterdam is meant to change

Glamsterdam is Ethereum's next major upgrade. It is designed to fit more activity into each block without overwhelming the computers that verify the network. Together with changes to gas pricing, the upgrade is intended to support a block gas limit of about 200 million, which would create room for more payments and trades before users start bidding fees higher.

The upgrade also moves the relationship between validators and specialized block builders into Ethereum's protocol. Validators are the computers that confirm transactions. Builders assemble blocks of transactions and compete to supply them. When a validator accepts the winning bid, the builder is expected to reveal the transactions behind that bid.

Why fake builders could stall the test network

That system is easy to abuse on a test network, according to the developers. A malicious operator can bid far above every legitimate builder, win repeatedly and then withhold the promised transaction data, leaving blocks without payloads.

During Thursday's core developer call, Ethereum consensus developer Potuz described how simple he believes the attack would be. "I can just spin up a thousand builders, rotate them, offer very high bids, and not produce payloads," Potuz said. "Any teenager can do this."

Developers said existing safeguards typically fall back to locally built blocks only after several payloads go missing. Potuz added that clients also need to identify and reject individual builders, so an attacker cannot come back under a new identity.

What is confirmed and what is still unclear

Confirmed by the developers: the Oct. 6 Sepolia test date, the tentative Oct. 27 Hoodi date, and the warning that fake builders could win auctions and withhold data on a test network. The developers also confirmed that the described attack would not threaten mainnet funds.

Not settled: when Glamsterdam will activate on mainnet, and whether clients will add builder identification and rejection before the Oct. 6 test. The supplied material does not say whether such a change is planned for the Sepolia run, and it does not say that any attack has actually happened.

Why this matters

If traffic on the test network is disrupted, developers may struggle to see how the upgrade handles realistic activity. That testing is the step needed before Glamsterdam reaches Ethereum itself.

What happens next

Client teams are working to a shorter release window ahead of the Oct. 6 Sepolia test. Hoodi testing is tentatively planned for Oct. 27, and mainnet activation has not been scheduled.

Sources

• CoinDesk