TLDR
- Ethereum developers scheduled the Glamsterdam Sepolia test for Oct. 6 ahead of a future mainnet launch.
- Developers warned that fake builder identities could disrupt testing by winning block auctions and withholding transaction payloads.
- The attack would not threaten mainnet funds, but it could freeze Sepolia traffic and delay upgrade testing.
- Ethereum Glamsterdam aims to support a block gas limit near 200 million, allowing more activity per block.
- Client teams must release Sepolia-ready software by Sept. 29, while the next Hoodi test is tentatively set for Oct. 27.
Ethereum developers have set Oct. 6 for the Sepolia test of the Ethereum Glamsterdam upgrade. The test will check whether the network can handle planned changes before developers schedule a mainnet launch. The team also warned that fake builder identities could disrupt the rehearsal. An attacker could use free test ether, place high bids to build blocks, win repeatedly, then refuse to reveal transaction data.
Ethereum Glamsterdam Test Faces Builder Risk
Glamsterdam moves the link between validators and block builders into Ethereum’s protocol. Builders prepare blocks and bid for the right to supply them. Validators accept the winning bid and expect the builder to deliver the transactions.
On Sepolia, that process creates a cheap attack path because test ether has little value. A bad actor could create many builder accounts, submit unrealistic bids, win auctions, and withhold payloads. This could leave blocks without transaction data and slow testing.
Developers Seek Stronger Builder Controls
Ethereum consensus developer Potuz said an attacker could rotate through many builders and keep submitting high bids. Current safeguards usually switch to locally built blocks only after several missing payloads.
Developers want clients to identify and reject individual builders more effectively. That step would make it harder for the same operator to return under a new identity after a client blocks an earlier account.
Sepolia Timeline Leaves Short Review Window
Client teams have until Sept. 29 to publish software ready for the Sepolia fork. That gives teams seven days before the Oct. 6 test, compared with the usual 14-day period for security reviews and bug-bounty work.
Developers accepted the shorter schedule because Sepolia has fewer independent participants and offers an easier recovery path. Titan and Ultrasound have not completed an Ethereum Glamsterdam fork transition with their production builder software.
Upgrade Targets Higher Ethereum Capacity
Ethereum Glamsterdam aims to fit more activity into each Ethereum block while keeping verification manageable. Developers expect the upgrade, alongside gas-pricing changes, to support a block gas limit near 200 million.
A private rehearsal completed the transition and raised the gas limit toward that level without losing finality. In related network work, Ethereum and Base recently split their account abstraction plans, as covered in recent Ethereum development reporting. Developers tentatively plan the Hoodi public test for Oct. 27, while mainnet activation remains unscheduled.
