Ethereum's Glamsterdam upgrade will activate on the Sepolia testnet at 13:53:36 UTC on Oct. 6, 2026, opening what amounts to a coordination test for a 200 million gas preference on Ethereum blocks.

The activation will not automatically raise Sepolia's block gas limit to 200 million. According to the Ethereum Foundation, Prysm 7.2.0 and Teku 26.9.1 will continue using a 60 million gas preference after activation unless validators explicitly change their settings. Prysm operators must use version 2 proposer settings or the keymanager API, while Teku validators can override the default through their validator configuration.

That distinction turns Sepolia into a referendum on how aggressively validators want to push Ethereum's Layer 1 capacity.

What does Glamsterdam change?

The upgrade merges the Amsterdam execution-layer changes with Gloas on the consensus layer. It introduces enshrined proposer-builder separation (ePBS) alongside block-level access lists that allow clients to parallelize state reads and transaction validation. The Ethereum Foundation has said the combination lays the groundwork for higher Layer 1 throughput — a setup designed to expand capacity without making validation impractical.

The 200 million figure itself comes from EIP-8261, an optional gas-limit schedule that lets consensus clients coordinate recommended preferences at specific epochs. The proposal does not alter Ethereum's consensus-validity rules: blocks remain valid whether their gas limit sits above or below the scheduled value, and validators can explicitly choose their own preference.

Sepolia's realized gas limit will move gradually as validators propose blocks rather than jumping immediately to 200 million when Glamsterdam activates.

What's the precedent?

Ethereum's block gas limit began rising from 30 million toward 36 million in February 2025 — the first adjustment since the network moved to proof-of-stake. The limit climbed to 45 million before Fusaka client releases adopted 60 million as their default.

A higher block gas limit allows more aggregate computation to fit into each block, creating room for more transactions and high-demand applications such as decentralized exchanges and other DeFi protocols. Additional capacity can ease congestion and reduce pressure on transaction fees when demand rises, though it does not change Ethereum's underlying block times.

Fusaka also introduced a 16.7 million gas cap for individual transactions, limiting how much of a single block any one operation can consume even as the overall block budget increases. The cap means higher block limits primarily create room for more aggregate activity rather than allowing individual smart-contract transactions to expand without restraint.

What are the operational requirements?

Node operators must update both execution and consensus clients before the Oct. 6 fork, while stakers must also upgrade their beacon node and validator software. Operators who want to test the upper bound will need to reconfigure their clients ahead of activation rather than waiting for the network to push toward 200 million organically.

What happens next?

Sepolia provides the first scheduled test of Glamsterdam before Ethereum developers decide how to proceed elsewhere. Hoodi and mainnet activation dates remain undecided, leaving validator participation in the 200 million preference among the signals developers can observe before the upgrade advances toward production.