Glamsterdam explained: Ethereum's plan to remove block-building middlemen

Market impact: Glamsterdam is a gradual catalyst for markets rather than an immediate price event. The gains arrive at the infrastructure level and accumulate as capacity grows. The biggest near-term risk sits on the calendar: the upgrade has already been delayed twice, and another postponement after testnet trouble would likely hurt the "Ethereum catch-up" narrative more than a clean test would help it. Fund flows remain the better measure of demand. Until Ether products show lasting inflows, traders are apt to treat upgrade milestones as background noise rather than a reason to buy ETH.

Glamsterdam replaces Ethereum's handshake deals with block-building middlemen for rules the network itself enforces. It is a genuine structural upgrade, but one whose payoff depends on a timeline that has slipped twice before.

Summary:

• The Ethereum Foundation set Glamsterdam to activate on the Sepolia testnet on October 6 at 13:53 UTC; Hoodi and mainnet dates remain unannounced
• The headline change, ePBS (EIP-7732), puts the proposer-builder handoff into Ethereum's protocol, replacing the trusted relays used for about 88% of blocks today
• Block-level access lists (EIP-7928) allow nodes to process transactions in parallel, creating a route to raise the gas limit from around 60 million toward 200 million
• Ordinary ETH holders need do nothing, but node operators and solo stakers take on new validator duties
• Mainnet has shifted from the first half of 2026 to Q4 2026, and the Sepolia date moved from August 3 after bugs on test networks
• Hoodi testing is provisionally set for October 27

Ethereum's next major upgrade, Glamsterdam, was scheduled to go live on the Sepolia test network at 13:53 UTC on October 6, per the Ethereum Foundation, and it did. That makes it the first public fork rehearsal for a change that reshapes how blocks are produced. Dates for the second testnet, Hoodi, and for mainnet have yet to be fixed. The name will mean little to most readers, so it helps to start with the problem the upgrade sets out to solve.

The middlemen behind most Ethereum blocks

Every Ethereum block has a validator responsible for publishing it, known as the proposer. In practice, most proposers do not select which transactions go into their block. That task has been delegated to specialist firms called builders, which compete to compose the most profitable ordering of transactions and bid for the right to have their block published. Proposers and builders are connected through intermediaries called relays, using software known as MEV-Boost. Around 88% of Ethereum blocks are currently produced this way, according to staking provider Everstake.

The arrangement functions, but it rests on trust. A relay sits between two parties that do not trust each other, and nothing in Ethereum's own rules ensures either side honours its commitment. It is a bit like dealing through a broker on a handshake: usually fine, but the protection comes from the broker's reputation rather than from the exchange itself. That leaves a small number of relay operators with an outsized role in a network built to avoid exactly that kind of dependence.

What ePBS changes

Enshrined proposer-builder separation, or ePBS, forms the centrepiece of Glamsterdam and is laid out in a proposal known as EIP-7732. It moves the handoff between proposer and builder into the protocol itself. Builders gain an on-chain identity and submit signed bids, and a new committee of validators, the Payload Timeliness Committee, verifies that the winning builder delivered its block contents on time. In effect, the network itself now vouches for the contract. Everstake notes the change also extends the window for passing block data around the network from roughly two seconds to about nine, which makes room for larger blocks.

Faster processing and bigger blocks

The second headline change, block-level access lists under EIP-7928, concerns speed. Ethereum nodes currently process transactions one after another because they cannot know in advance which parts of the network's state a block will touch. Under the upgrade, each block carries a map of every account and storage slot it uses, letting nodes read data and verify transactions in parallel. Developers see this as a credible path to raising the network's gas limit — the cap on how much work fits into each block — from about 60 million toward 200 million. Sepolia is being used to test capacity at that elevated level, alongside separate gas repricing changes.

What it means for holders, and what it doesn't

For everyday holders, the Ethereum Foundation says no action is required. Those who need to prepare are node operators and solo stakers, who face a new kind of validator duty. The benefit is structural rather than immediate: less reliance on trusted middlemen, more capacity and, as the gas limit rises over time, potentially lower costs.

That is not the same as a reason to buy ether. A better network may support demand for ETH over the long run, but upgrades do not create buyers on a schedule, and spot Ether ETFs recorded three straight days of outflows at the start of October even with Glamsterdam approaching.

A timeline that has already slipped

The calendar deserves caution. Mainnet was originally pencilled in for the first half of 2026 and has since moved to the fourth quarter. The Sepolia date was pushed back from August 3 after developer test networks ran into finalisation failures and a consensus bug. Consensus developer Potuz has also warned that cheap test ether could let an attacker spin up many disposable builders, win auctions with high bids and then fail to deliver blocks, a stress test the new design has to survive.

What to watch next

The first test is whether Sepolia runs and finalises cleanly over the coming days. After that, the questions are whether Hoodi holds its tentative October 27 slot and when developers commit to a mainnet date on their regular All Core Developers calls. A clean run would strengthen the case for a fourth-quarter launch, while another slip would push the benefits into 2027. Either way, the practical takeaway is to treat Glamsterdam as a meaningful upgrade to how Ethereum works, and to judge any ETH price story on demand evidence such as ETF flows rather than on the upgrade calendar alone.

Glamsterdam

The name of Ethereum's next network upgrade, created by blending two words: Gloas and Amsterdam. Ethereum runs on two linked layers, and each gets its own name for every upgrade. The execution layer, which processes transactions and smart contracts, takes the name of a city that has hosted Devconnect, an Ethereum developer conference, so this half is Amsterdam. The consensus layer, where validators agree on the state of the chain, takes the name of a star, so this half is Gloas. Because both layers upgrade together, the two names merge into one: Gloas + Amsterdam = Glamsterdam. The "glam" is a happy accident of the naming, not a description of the upgrade.

Network upgrade (hard fork)

A coordinated change to Ethereum's rules that every node must adopt by a set date. Glamsterdam is the next one, following Fusaka, and the one after is already named Hegotá.

Testnet and mainnet

Mainnet is the live Ethereum network where real ETH moves. Testnets are copies that use valueless test ether, so developers can rehearse an upgrade safely before it touches real money.

Sepolia and Hoodi

Ethereum's two main public testnets. Sepolia is widely used by app developers, while Hoodi is focused on validator and staking operations. An upgrade normally passes through both before mainnet.

Validator

A participant who stakes ETH to help secure the network, checking blocks and taking turns to publish them. Validators earn rewards for doing this correctly.

Proposer

The validator chosen to publish the block for a given time slot. Under today's system, the proposer usually publishes a block someone else built.

Builder

A specialist firm that assembles transactions into the most profitable possible block, then bids for the proposer to publish it.

MEV (maximal extractable value)

The extra profit available from choosing which transactions go into a block and in what order. Competition for MEV is why specialist builders exist.

MEV-Boost and relays

MEV-Boost is optional software that connects proposers to builders. Relays are the middlemen inside that system, holding builders' blocks and bids until a proposer commits. Around 88% of blocks currently flow through this setup.

EIP (Ethereum Improvement Proposal)

A numbered, public design document describing a proposed change to Ethereum. EIP-7732 (ePBS) and EIP-7928 (block-level access lists) are Glamsterdam's two headline proposals.

ePBS (enshrined proposer-builder separation)

Building the proposer-builder relationship directly into Ethereum's rules, so the protocol enforces the deal rather than a trusted relay.

Payload Timeliness Committee

A new group of validators created under ePBS. It confirms whether the winning builder released its block contents on time, giving the protocol a way to judge whether the builder kept its side of the deal.

Block-level access lists

A map attached to each block listing every account and piece of data the block touches. Knowing this in advance lets nodes process transactions in parallel rather than one at a time.

Gas limit

The cap on how much computing work fits into a single block. A higher gas limit means more transactions per block, which can ease congestion and fees.

Finalisation

The point at which a block is locked in and cannot be reversed without enormous cost. A test network failing to finalise is a red flag that the upgrade is not ready.

All Core Developers calls

Regular public meetings where Ethereum's client teams agree on upgrade contents and dates. Mainnet timing for Glamsterdam will be set on one of these calls.