Ethereum’s Sepolia testnet is scheduled to activate the Glamsterdam upgrade on October 6, 2026, at 13:53:36 UTC, according to a proposal merged through Ethereum’s protocol-management process. The activation is set for epoch 353024 and slot 11296768, giving developers a fixed date for the first major public test of the planned upgrade. Developers have warned that Sepolia’s freely available ETH and easily replaceable builder identities could let an attacker repeatedly disrupt Glamsterdam’s block-building auctions by withholding promised transaction payloads; the testing risk does not threaten funds on Ethereum mainnet.
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Sepolia Glamsterdam activation is set for October 6
The October 6 activation places Sepolia at the front of Glamsterdam’s expected deployment sequence. Ethereum’s official Glamsterdam roadmap page describes the upgrade as still in testing and targets mainnet deployment in the fourth quarter of 2026.
Glamsterdam is focused on scaling changes, including enshrined proposer-builder separation, or ePBS. The approach changes how Ethereum’s block proposal process handles the relationship between validators proposing blocks and builders assembling their execution payloads.
Sepolia is therefore more than a date-setting exercise. It is the environment in which developers can examine how the new design behaves under testnet conditions before any decision is made on moving further through the rollout path.
Free Sepolia ETH could let fake builders repeatedly win auctions
CoinDesk reported that free Sepolia ETH and disposable builder identities could allow an attacker to repeatedly win block-building auctions and then withhold promised transaction payloads.
The participant could return under a new identity after disrupting an auction, and the low-cost testnet ETH would remove the financial friction of repeated bids. The reported scenario concerns interference with testing rather than value extraction, and the risk remains limited to Sepolia: it does not threaten mainnet funds, although persistent withheld payloads could stall or complicate testing of Glamsterdam’s auction and delivery mechanics.
Enshrined proposer-builder separation makes payload delivery the test
Glamsterdam’s ePBS design, outlined in EIP-7732, has builders commit to execution payloads for later reveal rather than deliver them at the initial commitment. Payload-timeliness committees would monitor whether winning builders complete that delivery.
Sepolia will test the arrangement in conditions where free testnet ETH and disposable builder identities could support repeated auction wins followed by withheld payloads. The specific concern raised by developers is a winning builder that fails to reveal its payload, potentially disrupting Glamsterdam testing; the risk remains limited to testing and does not threaten mainnet funds.
Hoodi remains tentative as mainnet timing stays undecided
The September 17 All Core Developers consensus call recorded October 6 for Sepolia and tentatively discussed October 27 for Hoodi. The discussion did not set a mainnet fork date.
Sepolia’s October 6 Glamsterdam activation is the next confirmed milestone. It is scheduled to test the upgrade’s scaling work and the payload-delivery safeguards associated with its enshrined proposer-builder separation design.
The official roadmap targets Glamsterdam mainnet deployment in the fourth quarter of 2026 and says the upgrade remains in testing; that target does not establish a final launch timetable.
Disclaimer: This article is provided for informational purposes only. It is not offered or intended to be used as legal, tax, investment, financial, or other advice.
原文: https://cryptodaily.co.uk/2026/09/ethereum-glamsterdam-sepolia-october-6-builder-auction-risk
