Ethereum’s Glamsterdam Upgrade Slipped Again. Sepolia Now Targets October 6

Ethereum's Glamsterdam upgrade has already missed one Sepolia target and pushed its mainnet window back by months, and the four unresolved problems still haunting its private test networks suggest October 6 faces the same fate.

Ethereum (CRYPTO:ETH) developers tentatively set October 6 at 13:53 UTC as the activation date for the Glamsterdam upgrade on the Sepolia testnet, an agreement reached at the ACDC #186 developer call on September 3. 

Glamsterdam’s Sepolia activation was first scheduled for August 3, and the upgrade’s overall mainnet target slipped from the first half of 2026 to the fourth quarter back in August. We examine what is holding up the timeline and whether October 6 still holds.

How Many Times Has Glamsterdam’s Timeline Slipped?

Ethereum developers originally targeted Glamsterdam for the first half of 2026. Developers pushed that target back to the fourth quarter of 2026 in mid-August, after Platåberget, Glamsterdam’s first dedicated public test network, went live. Platåberget’s launch confirmed the upgrade needed more testing time than developers had originally planned. 

Sepolia’s own date moved on a separate timeline. Developers first scheduled Glamsterdam’s Sepolia activation for August 3, then pushed it back as the devnet phase ran longer than expected. Nine devnets ran in sequence, numbered 0 through 9, between late March and early September, before developers agreed on the October 6 target at the September 3 ACDC meeting. That timeline puts Sepolia’s activation about two months behind its original schedule.