Ethereum’s Glamsterdam Upgrade Enters Final Testing Phase as ePBS and Access Lists Take Shape

Ethereum’s rollup-centric roadmap doesn’t mean the base layer is done evolving. Core developers have now entered full-scale testing for Glamsterdam, the network upgrade that aims to tackle Layer 1 scaling head-on. According to a report from WuBlockchain, teams are running forks on private developer networks that bundle all planned Ethereum Improvement Proposals, marking the final stretch before the codebase is frozen for public testnet deployment.

The list of changes isn’t incremental. Two features stand out: enshrined proposer-builder separation (ePBS) and block-level access lists. Together, they represent a direct upgrade to how Ethereum processes transactions at the protocol level, something that rollup-focused upgrades like Dencun left largely untouched.

What ePBS and Access Lists Actually Change

Enshrined proposer-builder separation moves block construction dynamics inside the protocol. Today, MEV extraction is outsourced to off-chain builders and relays, creating a landscape where a handful of sophisticated actors dominate block creation. That concentration can erode validator neutrality and pose systemic risks if relays become points of failure or censorship. By enshrining PBS in the consensus layer, Glamsterdam removes the need for trusted third-party infrastructure and forces a cleaner split between proposing validators and block-building entities.

The shift won’t eliminate MEV, but it rearchitects incentives so that validators don’t need to rely on external services that may extract value at their expense. For stakers and solo validators, the change could lower barriers to running a competitive setup—something that matters as staking centralization remains a live concern.

Block-level access lists are less flashy but just as structural. Instead of paying gas for repeated storage reads, wallets and contracts can declare upfront which addresses they will touch. The execution layer skips redundant lookups, cutting costs for complex DeFi transactions or smart contract wallets. For protocols that batch user operations or for users managing non-custodial wallets that require multiple account interactions, that means lower fees without any trust assumptions.

From Private Devnets to Public Testnets

The journey from a private devnet to a live mainnet is long and uneven. Developers will stress-test the fork, hunt for consensus bugs, and iterate before the code can be frozen. Only then do Ethereum’s public testnets get their turn, where client diversity and real-world usage patterns expose edge cases that private testing rarely catches. Multiple client teams—Geth, Nethermind, Besu, and others—must coordinate, and any serious divergence risks pushing the schedule into late 2026 or beyond.

Still, the fact that all planned EIPs are being tested together signals confidence from core developers. Glamsterdam is being treated as a cohesive package, not a piecemeal assembly of tweaks. That matters because bundling complex consensus and execution changes simultaneously reduces the number of disruptive hard forks the network has to absorb.

Why L1 Scaling Still Matters

For all the attention on rollups, Ethereum’s base layer remains the common settlement anchor for L2 networks and the primary chain for a growing volume of tokenized assets. With more than $20 billion in real-world assets on-chain, as detailed in a recent tokenization roundup, settlement finality and L1 throughput are not abstract concerns. Even modest improvements in L1 efficiency directly benefit institutions building on Ethereum.

Developer activity underscores the ongoing commitment. Metrics on blockchain developer contributions continue to place Ethereum at the top of the list, reinforcing that the network’s technical momentum hasn’t stalled. Glamsterdam is the logical next step after the blob space introduced in earlier upgrades; where Dencun scaled data availability, Glamsterdam tightens execution.

At the same time, competitors like Solana are shipping major L1 improvements on a different cadence. Ethereum’s deliberate upgrade rhythm works because its security model is deeper, but the market rewards visible progress. Glamsterdam is the ecosystem’s way of showing that the base layer can absorb meaningful change without losing stability.

What Remains Uncertain

A larger question is whether ePBS will deliver the decentralization benefits its proponents claim. If the market’s existing builder infrastructure adapts faster than validators can adjust, the de facto concentration of block construction might persist even in an enshrined model. Access lists, while useful, depend on wallet developers updating their software to generate accurate declarations—a coordination layer that can lag by months.

Testing on private devnets also doesn’t guarantee a smooth upgrade. Ethereum’s history includes hard-fought delays when bugs surfaced late in the cycle. The timeline for Glamsterdam hitting mainnet remains tentative, and any significant issues discovered during public testnet phases could push the upgrade closer to late 2026. For now, the developer community is moving with clear intent, and the market will watch each testing milestone for signs of slippage or certainty.