Ethereum sets Oct. 6 Glamsterdam test on Sepolia, warns fake builders could stall it
Ethereum developers confirmed an Oct. 6 Sepolia test date for the Glamsterdam upgrade but warned that cheap test ether could let disposable 'builders' win block auctions and withhold payloads.
Why it matters
The dispute is over testing infrastructure, not mainnet security or user funds, so the practical stakes are limited to whether client teams can validate ePBS on schedule before a mainnet date is even set.
Key facts
Ethereum developers confirmed Glamsterdam will activate on the Sepolia testnet on Oct. 6, 2026.
Reported by CoinDesk
Hoodi testnet activation is tentatively scheduled for Oct. 27, 2026.
Reported by CoinDesk
Developers warned that free or cheap test ether could let attackers create disposable builder identities to repeatedly win Sepolia block auctions and withhold transaction payloads.
Reported by CoinDesk
Consensus developer Potuz described a scenario involving up to 1,000 disposable builders.
1,000Reported by TheNewsCrypto
Devnet-11 completed its Gloas transition and raised the gas limit from 60 million to 200 million.
200,000,000Reported by Crypto.News
Glamsterdam's mainnet activation date has not been scheduled, with the roadmap still targeting Q4 2026.
Reported by CoinDesk
The attack scenario would not threaten mainnet funds but could disrupt testing of the upgrade.
Reported by CoinDesk
What happened
Ethereum developers confirmed on a Sept. 17 All Core Developers Consensus call that the Glamsterdam upgrade will activate on the Sepolia testnet on Oct. 6, 2026, with Hoodi testing tentatively set for Oct. 27, according to CoinDesk, Crypto.News, TheNewsCrypto and Bitcoin Insider. All four outlets report the same core warning: because Sepolia's test ether has no real economic cost, an attacker could spin up many disposable builder identities to repeatedly win block auctions under Glamsterdam's Enshrined Proposer-Builder Separation (ePBS, EIP-7732) and then withhold the transaction payloads, disrupting the testing process rather than mainnet funds. TheNewsCrypto attributes a specific scenario to Consensus developer Potuz, describing up to 1,000 disposable builders. Client teams were asked to release Sepolia-ready software by Sept. 29, leaving about seven days for review, roughly half the usual window per CoinDesk. Crypto.News additionally reports that Devnet-11 completed its Gloas transition and raised the gas limit from 60 million to 200 million. Ethereum has not scheduled a mainnet activation date for Glamsterdam, with the roadmap still targeting the fourth quarter of 2026.
How the story developed
- Official statement
Ethereum's Sept. 17 All Core Developers Consensus call accepts Oct. 6 Sepolia date
Developers reviewed recent Glamsterdam devnet results and agreed on the Sepolia test date while flagging ePBS builder-abuse risk.
- First report
First report by CoinDesk
Ethereum confirms Glamsterdam dates, but warns 'fake' builders could stall the chain
- Update
CoinDesk first reports the Glamsterdam Sepolia date and builder-abuse warning
- Independent corroboration
Independently corroborated by Crypto.News
Ethereum warns Glamsterdam testnet faces builder abuse
- Update
Crypto.News corroborates with additional detail on Devnet-11 gas limit increase
How coverage built up
Independent sources over time, counted the way the consensus panel counts them: a republication of a wire story does not move the line.
- 18 Sept 2026, 05:23 UTC: CoinDesk — 1 independent source, 1 reports
- 18 Sept 2026, 05:43 UTC: Crypto.News — 2 independent sources, 2 reports
- 18 Sept 2026, 09:27 UTC: TheNewsCrypto — 3 independent sources, 3 reports
- 18 Sept 2026, 17:22 UTC: Bitcoin Insider — 4 independent sources, 4 reports
Affected entities
Original sources
| Publisher | Report | Role | Published |
|---|---|---|---|
| CoinDesk Crypto media | Ethereum confirms Glamsterdam dates, but warns 'fake' builders could stall the chain | Original | |
| Crypto.News Crypto media | Ethereum warns Glamsterdam testnet faces builder abuse | Independent | |
| TheNewsCrypto Crypto media | Ethereum Glamsterdam Testnet Faces Builder Abuse Concerns | Syndicated | |
| Bitcoin Insider Aggregator | Ethereum's Glamsterdam Upgrade Gets an October Test Date, and a Warning About "Fake" Builders | Syndicated |
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