Core developers set 6 Oct for Glamsterdam on Sepolia after devnet bugs; mainnet date left open

Ethereum Foundation/Ethereum protocol upgrades

At the 3 September consensus-layer call, Ethereum core developers tentatively scheduled the Glamsterdam upgrade on the Sepolia test network for 6 October 2026 at 13:53 UTC. The date depends on a clean run of a new private test network, Devnet-11, after earlier devnets exposed serious bugs. No dates were set for the Hoodi testnet or for mainnet; December was discussed for mainnet but not agreed.

• Devnet-8 hit a consensus bug involving repeated parent hashes; an EF engineer warned a bug of that kind could make the network stop.
• Devnet-9 failed to finalise, with about 1,000 validator nodes affected.
• Client teams also had to fix an implementation error in EIP-8037, which changes how much gas it costs to create new state under a multidimensional gas model.
• Devnet-11 was set to launch on 14 September to check the fixes and that different client software agrees.
• Lido and Optimism asked for confirmed stable client releases and at least one stable day before any fork; a Teku developer argued for more testing before Hoodi.