Ethereum Confirms October 6 Glamsterdam Testnet Launch On Sepolia
TLDR
Ethereum developers confirmed Glamsterdam will activate on the Sepolia testnet October 6, ahead of a later Hoodi test.
Developers warned that cheap test ether could let fake builders win block auctions and then withhold their payloads.
Client teams have until September 29 to release Sepolia-ready software, leaving only seven days for review.
Devnet-11 finished its Gloas transition and raised the gas limit from 60 million to 200 million without losing finality.
Ethereum has not set a mainnet date for Glamsterdam, with the roadmap still pointing to the fourth quarter of 2026.
Ethereum developers have picked October 6 as the date for the Glamsterdam upgrade to go live on the Sepolia testnet. The decision came out of the September 17 All Core Developers Consensus call.
Developers also raised a warning during that same call. They said cheap test ether could allow bad actors to disrupt the network during the public testing phase.
The concern centers on a new feature called Enshrined Proposer-Builder Separation, or ePBS. This is part of the EIP-7732 proposal included in Glamsterdam.
What Is Enshrined Proposer-Builder Separation?
ePBS separates the job of building transaction blocks from the job of validating them. Builders submit bids for the right to supply a block, and the winning builder is supposed to hand over the transactions inside it.
On the main Ethereum network, this system works because block space costs real money. That cost limits how much bad behavior can happen.
Test ether does not carry that same cost. Consensus developer Potuz explained that an attacker could create many fake builder identities using free test ether.
He said an attacker could bid aggressively, win the auction, and then refuse to hand over the promised block. “I can just spin up a thousand builders,” Potuz said on the call. He added that “any teenager can do this.”
Potuz said this is not a way to steal real ETH. It is a way to disrupt the public test network so that other teams cannot rely on it working properly.
He also said current safety measures may not react fast enough. Some client software only switches to a backup block after several payloads are missed, and attackers could keep returning under new identities.
Devnet-11 And The Path To Sepolia
Before Sepolia, developers ran a rehearsal called Devnet-11. This test network was not designed to include attacks, unlike a separate ongoing test environment called Platåberget.
Devnet-11 began on September 14. It completed its Gloas transition on September 16 and then raised its gas limit from 60 million to 200 million.
The network used 84,000 validators across multiple client teams. It kept its finality intact through the process, according to a CoinDesk report. The 200 million figure is only a test setting, not a confirmed number for the main network.
Client teams normally get 14 days to review software before a public test launch. This time, developers agreed on a September 29 deadline for releases, which leaves seven days before the October 6 launch.
Developer Alex Stokes asked teams to release their software as early as possible. That would give more reviewers time to check the code and give Ethereum’s bug bounty process more time to catch problems.
This compressed schedule follows earlier testing trouble. Devnet-8 had finality issues during its Gloas activation, and Devnet-9 also experienced unplanned non-finality before teams reached Devnet-11.
Sepolia was chosen for the first public run partly because its validator set is controlled by a smaller group of teams. That makes it easier to fix if problems come up.
The Hoodi testnet is expected to follow Sepolia. Hoodi has an open validator set, and its timing depends on how Sepolia performs first.
Ethereum’s public roadmap still lists Glamsterdam for the fourth quarter of 2026. No mainnet activation date or epoch number has been published.
As of now, client teams are working toward the September 29 software deadline, with Sepolia’s test launch set for October 6.
