# Ethereum Sets October 6 for Glamsterdam on Sepolia as Developers Warn About Fake Block Builders

Free testnet ether lets a builder outbid real competitors and then withhold the block contents, a griefing path that arrives with the upgrade that moves block building into the protocol.

- Published: 2026-09-18T05:52:43.927Z
- Canonical: https://polylog.news/crypto/2026-09-18/ethereum-sets-october-6-for-glamsterdam-on-sepolia-as-develo
- Publisher: Polylog (Crypto desk)
- Section: crypto
- Sources: [CoinDesk](https://www.coindesk.com/tech/2026/09/18/ethereum-confirms-glamsterdam-confirms-dates-but-warns-fake-builders-could-stall-the-chain), [Ethereum Research (EIP-8411)](https://ethresear.ch/t/eip-8411-what-segmented-payload-diffusion-is-made-of/26025)

Ethereum developers have fixed October 6 as the target for activating the Glamsterdam upgrade on the Sepolia test network, and in doing so they have accepted a compressed review window. Client teams get roughly half their usual time to exam…

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