Ethereum developers have tentatively scheduled the Glamsterdam upgrade for Ethereum's Sepolia testnet on October 6 at 13:53 UTC, even as private devnet testing continues to uncover technical issues.
The date provides a pathway toward a potential December mainnet release, though it remains conditional on the next testing phase producing a stable network.
Testing Obstacles Remain
Protocol specialist Christine D. Kim reported that developers agreed to the October 6 Sepolia date while acknowledging significant caveats. Most notably, Glamsterdam has yet to run successfully on a stable private devnet.
Glamsterdam-Devnet-9, which launched on September 1 with 1,000 validator nodes, exposed several problems. Stefan Starflinger, an Ethereum Foundation developer operations engineer, noted that the network's size revealed unresolved edge cases and issues. The network is currently failing to finalize, meaning too few validators are correctly proposing and attesting to the chain head.
The previous devnet iteration discovered a more critical flaw: a bug that could freeze the entire network if a validator proposed a block sharing its parent's hash.
Maria Silva, an Ethereum Foundation researcher, identified a separate bug tied to EIP-8037, the State Creation Gas Cost Increase, which requires updates across all execution-layer clients.
Contingency Planning Underway
Developers are preparing Devnet-11 for testing following these discoveries, skipping the originally planned Devnet-10. Parithosh Jayanti, the Ethereum Foundation developer operations engineer who chaired the call, indicated that if the new devnet encounters additional failures, the team would reassess whether the October 6 date remains viable.
Developers have also deferred setting a date for Hoodi, Ethereum's second public testnet, with Consensys developer Enrico del Fante arguing that waiting additional weeks before committing would be prudent given the problems uncovered during Devnet-9 testing.
Mainnet Timeline Remains Uncertain
While developers continue to target a mainnet release before the end of 2026, client implementations are not yet considered ready for mainnet deployment. The Sepolia testnet date does not increase certainty around the final mainnet activation.
Glamsterdam is followed by the separate Hegotá upgrade, targeted for 2029, which will focus on quantum-resistant infrastructure.
