Ethereum developers have tentatively scheduled the Glamsterdam upgrade for the Sepolia testnet on October 6, 2026, at 13:53 UTC. The upgrade will change both Ethereum’s consensus and execution layers, requiring updated client software. The date remains conditional because Glamsterdam has not yet run successfully on a stable private devnet (developer testing network). Glamsterdam-Devnet-9 launched on September 1 with 1,000 validator nodes, but the network is not finalizing (reaching agreement on the chain head) because too few validators are correctly proposing and attesting to it. Ethereum Foundation developer operations engineer Stefan Starflinger said the large network exposed unresolved edge cases, while Devnet-8 contained a bug that could freeze the network if a validator proposed a block with the same hash as its parent. Ethereum Foundation researcher Maria Silva also identified an EIP-8037 State Creation Gas Cost Increase bug requiring updates from every execution-layer client. Developers therefore plan another devnet, with Devnet-11 now the focus instead of the originally planned Devnet-10. Parithosh Jayanti said the October 6 Sepolia date would be reassessed if the next devnet fails. Developers have not set a Hoodi date, and client implementations are not yet considered ready for mainnet. The broader roadmap still targets Glamsterdam for Ethereum mainnet before the end of 2026, with December 2026 previously penciled in, followed by a separate 2029 effort toward quantum-resistant infrastructure through the Hegotá upgrade. The schedule would maintain a pace of major Ethereum upgrades roughly twice a year, as seen when Fusaka activated on schedule last December.