TLDR
Ethereum developers have moved the Glamsterdam upgrade, billed as the biggest protocol overhaul since the Merge, into its final development phase with closed devnet testing.
- Glamsterdam is now running on private devnets with all planned Ethereum Improvement Proposals included, ahead of code hardening and public testnets.
- The upgrade targets Layer 1 scaling, MEV risk, and fee structure through enshrined proposer builder separation, block level access lists, and major gas repricing.
- There is no confirmed mainnet date yet, but activation is guided for the second half of 2026, with key milestones in upcoming public testnets and client releases.
Deep Dive
1. What Final Development Phase Actually Means
Reports describe Glamsterdam as having entered its final development stage, with core teams running closed developer networks that already include the full set of intended EIPs for the fork. These devnets are where client teams test interoperability and catch bugs before the code is hardened and pushed to public testnets, according to Ethereum Foundation developer Parithosh Jayanthi in a detailed summary.
From here, the typical sequence is: stabilize specs on devnets, deploy to public testnets (Sepolia, Holesky, etc.), then schedule a mainnet activation once clients and infrastructure providers are ready.
The design is largely locked in; the remaining work is about implementation quality and cross client stability rather than changing the upgrades direction.
2. What Glamsterdam Will Change
Glamsterdams flagship feature is enshrined proposer builder separation (ePBS, EIP 7732), which moves the separation of block proposers and builders into the protocol itself to reduce reliance on off chain relays and mitigate maximal extractable value (MEV) centralization.
A second pillar is Block level Access Lists (EIP 7928), which let each block pre declare which accounts and contract storage it will touch, enabling nodes to preload data and process more work in parallel, improving Layer 1 throughput and predictability as outlined in upgrade coverage.
Glamsterdam also introduces broad gas repricing: computation becomes cheaper, while state access and storage become more expensive, aligning fees more closely with real resource usage and making designs that hoard state relatively costlier.
For users this is primarily about potential fee structure changes and more robust decentralization, while developers may need to refactor contracts that are storage heavy or latency sensitive.
3. Timeline, Risks, and What to Watch
Current reporting points to a mainnet target in the second half of 2026, but developers stress there is no fixed timeline yet, since issues found on devnets or testnets can delay activation. The Ethereum roadmap expects Glamsterdam to be the first of two major 2026 upgrades, followed by Hegota later in the year in a roughly semiannual cadence.
Key checkpoints to watch are: 1) announcements that Glamsterdam has been enabled on public testnets, 2) client releases that mark the fork as ready, and 3) a finalized mainnet block height or epoch. Validators and node operators will eventually need to upgrade clients, but regular ETH holders should not need to move funds or change wallets.
The upgrade is progressing but not imminent on mainnet; traders, app teams, and infra providers should treat testnet milestones and gas repricing details as the main signals for when and how to adapt.
Conclusion
Glamsterdam moving into its final development phase confirms that Ethereums next large protocol overhaul is structurally defined and now focused on implementation, testing, and coordination. By combining ePBS, block level access lists, and gas repricing, it aims to make the base layer more scalable and resilient while reshaping incentives around MEV and state usage. The decisive information for users and builders will come as public testnets go live and client teams publish final configs, which will clarify the exact timing and practical impact on fees and infrastructure.
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