Ethereum (ETH) developers set Oct. 6 for Glamsterdam’s Sepolia test, targeting around 200 million gas while warning an attacker could rotate 1,000 fake builders before a still-unscheduled mainnet launch.
Key Points:
- Ethereum will test Glamsterdam on Sepolia on Oct. 6.
- Attackers could create many builder identities, submit inflated bids and withhold payloads after winning block auctions on the public testnet.
- Client teams face a Sept. 29 software deadline, leaving seven days before the fork.
Ethereum Test Timeline
Developers confirmed the Sepolia date during the Sept. 17 All Core Developers Consensus call, following progress across Glamsterdam development and testing. The public test is the next major checkpoint.
Ethereum’s roadmap still targets the fourth quarter of 2026 for mainnet, although no final activation date has been announced, while Hoodi testing is tentatively scheduled for Oct. 27.
Glamsterdam includes enshrined proposer-builder separation, or ePBS, which moves the separation between block proposers and builders directly into the protocol. Developers are also testing block capacity around 200 million gas.
Client teams have until Sept. 29 to issue Sepolia-ready software, leaving seven days before the fork instead of the usual two-week window for security reviews, testing and bug fixes.
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Potuz Builder Warning
Ethereum consensus developer Potuz warned that Sepolia’s cheap test ETH changes the economics of block auctions, making it easier for attackers to create disposable builder identities. The concern is disruption, not theft of real ETH.
“I can just spin up a thousand builders, rotate them, offer very high bids, and not produce payloads,” Potuz said during the call.
Those accounts could repeatedly win auctions for the right to provide the next block, then refuse to release the expected payload, reducing Sepolia’s value as a realistic public test. “Any teenager can do this,” Potuz added.
Developers accepted the compressed release window partly because Sepolia has fewer independent participants and is easier to monitor and recover, while Titan and Ultrasound have not yet completed Glamsterdam fork transitions.
Glamsterdam follows Ethereum’s earlier scaling work after Fusaka, with this upgrade focused on changing block construction, transaction processing and database management before testing moves from Sepolia to Hoodi.
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