Glamsterdam explained: what Ethereum's next upgrade means for DeFi

Ethereum's next hard fork, Glamsterdam, went live on the Sepolia testnet on 6 October 2026 at 13:53 UTC. Mainnet is expected in Q4 2026, with no date fixed yet. For DeFi users and builders, it changes three things: who builds blocks, how fast blocks can be processed, and what transactions cost.

Why another upgrade?

Every block on Ethereum today is usually built by a specialist 'builder', not the validator who proposes it. The two sides meet through MEV-Boost relays, which are trusted middlemen outside the protocol. Relays hold the block, check the payment, and pass it on. That works, but it puts a handful of companies in the middle of most Ethereum blocks.

At the same time, nodes still execute transactions one by one. That caps how much gas a block can safely hold. Glamsterdam tackles both problems.

Change 1: Enshrined Proposer-Builder Separation (ePBS, EIP-7732)

ePBS (EIP-7732) writes the proposer-builder split into Ethereum's own rules. It works in four steps:

• Builders send bids to the proposer.
• The proposer commits to one bid, before seeing the block's contents.
• The builder reveals the full block later in the 12-second slot.
• A new group of validators, the Payload Timeliness Committee, confirms the builder delivered on time. The protocol guarantees the payment.

The result: relays become optional. Builders and proposers can trade without a middleman's blessing. Chainstack notes the window for spreading block data across the network grows from about 2 seconds to about 9 seconds. More time means bigger blocks can travel without nodes falling behind.

What it means for DeFi: MEV does not disappear. Arbitrage and liquidations still happen. But the pipeline that decides transaction order becomes more transparent and less dependent on a few relay operators. That reduces a single point of failure for every DEX trade and liquidation on Ethereum.

Change 2: Block-Level Access Lists (BALs, EIP-7928)

A BAL is a map attached to every block (EIP-7928). It lists each account and storage slot the block's transactions touch, plus the values after execution.

With that map, a node can see which transactions do not overlap and run them in parallel. New nodes can also sync faster by reading the final values instead of replaying every transaction.

What it means for DeFi: Parallel execution is what lets Ethereum raise its gas limit safely. The Ethereum Foundation says clients are ready for limits up to 200 million gas, though some clients (Prysm, Teku) still default to 60 million. Validators must opt in to the higher figure. More gas per block usually means lower fees during busy markets, when DeFi users need block space most.

Change 3: New gas rules

Glamsterdam reprices several operations:

• EIP-8037 raises and separately meters the cost of creating new state.
• EIP-8038 updates the gas cost of reading and writing state.
• EIP-7778 removes gas refunds from block gas accounting.
• EIP-7954 raises the maximum contract size, helpful for large DeFi protocols.

The Ethereum Foundation's warning to developers is direct: contracts that rely on fixed gas stipends, hardcoded gas limits or assumptions about remaining gas may need changes. Older vaults, routers and relayers are the most likely to be affected.

Smaller changes DeFi teams will like

• Native ETH transfer logs (EIP-7708). ETH transfers will emit logs, just like ERC-20 tokens. Today, tracking internal ETH movements needs expensive transaction tracing. After the fork, a simple log query will do.
• Deterministic factory contract (EIP-7997). Makes deploying contracts at the same address across chains easier.
• Slot-number opcode (EIP-7843). Lets contracts read the current slot directly, useful for time-based logic such as auctions.

What should you do?

If you are a user: nothing. Your assets stay where they are. Be wary of anyone asking you to 'upgrade' or 'migrate' your ETH; that is a common scam during forks.

If you build in DeFi: run your test suite on Sepolia now. Look for hardcoded gas values, transfer() and send() calls with fixed stipends, and indexers that trace internal ETH transfers.

The bigger picture

Glamsterdam is a step toward Vitalik Buterin's 'Cryptographic World Computer' vision, published on 27 September 2026. He frames the following fork, Hegotá (2027), as likely Ethereum's last 'normal' fork. Glamsterdam lays the groundwork: fairer block building today and room for much higher throughput tomorrow.

Sources: Ethereum Foundation, Glamsterdam testnet announcement; Chainstack, Glamsterdam: what changes for infrastructure; P2P.org, DeFi Dispatch, September 2026.

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