Ethereum Glamsterdam Moves to Sepolia on October 6, Hoodi Test Tentatively October 27

Ethereum developers have scheduled the public Sepolia test of the Glamsterdam upgrade for October 6, 2026, with the software release deadline set for September 29. The test window has been compressed to seven days for security reviews, half the standard 14-day period. A follow-up test on the Hoodi network is tentatively planned for October 27, depending on how Sepolia performs.

No mainnet activation date has been set. Developers will need to observe the testnet results before making any decision about deploying to Ethereum’s main network.

Glamsterdam is described as formalizing the handoff between validators and specialized block builders directly in the protocol. A recent private rehearsal reportedly raised the test network’s block gas limit toward 200 million without compromising finality, which points to the scaling ambitions behind the upgrade.

Developers have also flagged a security concern specific to testnets. Because test ether is free, attackers could create disposable builder identities, win auctions with inflated bids and then withhold the promised transaction payloads, disrupting infrastructure testing. This poses no threat to mainnet funds, but it could complicate the test process.

For ETH holders, the key point is that Glamsterdam remains a testing-phase story. The Sepolia and Hoodi outcomes over the next several weeks will determine how quickly a mainnet date can be proposed.