Ethereum core developers have tentatively targeted October 6, 2026, for the Glamsterdam upgrade to activate on the Sepolia testnet, with the proposed transition expected around 13:53 UTC. The date represents Ethereum’s next major public testing milestone but remains dependent on developers achieving sufficient stability across the preceding Glamsterdam devnets.
Ethereum’s official Glamsterdam roadmap now lists the October 6 Sepolia fork as the upgrade’s next milestone while keeping mainnet deployment targeted broadly for Q4 2026. The schedule remains provisional because client teams are still resolving consensus and execution issues discovered during private testing.
Devnet Problems Keep Sepolia Date Conditional
Testing has exposed several issues that developers want resolved before moving confidently onto public testnets. The official ACDC #186 agenda documented non-finality problems around Glamsterdam testing, including a Devnet-8 builder-deposit caching issue affecting multiple consensus clients. Developers have made stable multi-client finalization a prerequisite for proceeding safely toward Sepolia.
Execution-layer work has also continued around EIP-8037, which changes Ethereum’s state-gas accounting. Recent specification work has focused on cross-frame gas behavior and other edge cases identified during testing. The continuing EIP-8037 revisions show that Glamsterdam’s remaining work involves protocol correctness as well as simple client compatibility.
Further devnet iterations are therefore being used to validate fixes before the public fork. Developers have discussed moving through additional environments beyond Devnet-9, including preparations for newer test configurations if instability persists. If upcoming devnets fail to finalize reliably or reveal another major bug, the October 6 Sepolia target can still move.
Glamsterdam Mainnet Timing Remains Open
No firm activation date has been established for Hoodi or Ethereum mainnet. The official roadmap continues to describe Glamsterdam as being in devnet testing, with mainnet expected during Q4 but not yet scheduled. Ethereum is prioritizing successful testnet progression over committing prematurely to a December mainnet deadline.
That approach reflects the scope of Glamsterdam, which combines significant execution and consensus-layer changes rather than a narrow software patch. Moving from private devnets to Sepolia provides developers with a broader production-like environment in which to test client interoperability and protocol behavior before mainnet exposure.
For application developers, wallets, RPC providers and other infrastructure teams, the October target provides a planning point but not a final guarantee. The key signal is that Glamsterdam is approaching public testnet deployment while still treating stability as the gatekeeper for the broader rollout, leaving the final mainnet schedule dependent on what Sepolia and subsequent testing reveal.
