Ethereum's next hard fork, Glamsterdam, enters its final testing phase with a Sepolia testnet deployment scheduled for October 6, 2026, at 13:53 UTC. The upgrade raises the network's gas limit floor from 60 million to 200 million per block — a 3.3x increase — and targets throughput of approximate...
"I can just spin up a thousand builders, rotate them, offer very high bids, and not produce payloads. Any teenager can do this." — Potuz, Ethereum Consensus Developer
Ethereum's next hard fork, Glamsterdam, enters its final testing phase with a Sepolia testnet deployment scheduled for October 6, 2026, at 13:53 UTC. The upgrade raises the network's gas limit floor from 60 million to 200 million per block — a 3.3x increase — and targets throughput of approximately 10,000 transactions per second, roughly ten times current capacity. Mainnet activation is tentatively slated for Q4 2026, though the Ethereum Foundation describes that window as a target, not a commitment.
Glamsterdam follows the Pectra and Fusaka forks deployed in 2025 and represents the most significant structural change to Ethereum's block production since the Merge. The upgrade introduces Enshrined Proposer-Builder Separation (ePBS) at the protocol level, replaces off-protocol relay trust with on-chain auction mechanics, and enables parallel transaction processing through Block-Level Access Lists. Standard ETH transfers could become up to 71% cheaper under the new gas repricing model. Validator exit capacity increases roughly 4x. Development teams face a September 29 deadline to ship Sepolia-compatible software, leaving a compressed seven-day window before fork activation — half the standard 14-day allocation.
However, the testing phase carries a known vulnerability. Developers have publicly warned that the new block-builder auction system on Sepolia can be cheaply exploited using free testnet ether to create fraudulent builder identities, a risk that could disrupt infrastructure testing and delay the mainnet timeline.
Glamsterdam bundles more than 20 Ethereum Improvement Proposals (EIPs) into a single hard fork. The headline items fall into four categories: scaling Layer 1 throughput, restructuring block production, repricing gas for sustainability, and improving validator operations.
The upgrade follows a naming convention shift — Glamsterdam succeeds Fusaka, which succeeded Pectra — and was originally targeted for June 2026. Delays pushed it to a Q3 target, then to Q4. The current roadmap places the Sepolia fork on October 6, a provisional Hoodi testnet on October 27, and mainnet activation sometime in Q4.
Devnet-11, the final private testing environment, completed a successful Glamsterdam transition on September 16, running 84,000 validators across diverse client implementations. The upgrade's scope is why Ethereum core developers have called it the largest protocol change since the Merge.
The gas limit floor rises from approximately 60 million to 200 million per block. This is the primary throughput lever. At current block times (~12 seconds), the higher gas ceiling enables roughly 10,000 transactions per second versus the approximately 1,000 TPS the network processes today.
Two EIPs manage the sustainability implications of this expansion:
EIP-8037 (State Creation Gas Cost Increase) introduces a fixed cost per state byte and a separate state gas reservoir. The design targets a maximum state growth rate of 120 GiB per year, preventing the larger blocks from inflating the state database beyond what consumer-grade hardware can manage.
EIP-8038 (State-Access Gas Cost Update) reprices state-access opcodes to align with modern hardware I/O performance, improving denial-of-service resilience at scale.
The net effect: blocks get larger, but the economic cost of creating new persistent state scales proportionally, preventing a repeat of the storage bloat problems that have plagued earlier capacity expansions.
EIP-7732 is the most architecturally significant component. It moves the proposer-builder separation (PBS) mechanism — currently handled by third-party relays like Flashbots' MEV-Boost — directly into the Ethereum protocol.
Under the current system, approximately 90% of Ethereum blocks are produced through off-protocol relays that validators must trust to deliver valid blocks. This relay dependency introduces centralization risk and an opaque trust layer between validators and block builders.
ePBS eliminates that relay dependency. The protocol itself runs a block-building auction. Builders compete on-chain, validators propose blocks using the winning builder's payload, and a new Payload Timeliness Committee (PTC) enforces dual-deadline logic to ensure data availability.
The practical consequence: the transaction payload propagation window expands from approximately 2 seconds to 9 seconds. This allows builders to construct larger, more optimized blocks without hitting propagation deadlines — a prerequisite for the 200M gas limit to function safely.
According to multiple developer estimates, ePBS could reduce MEV extraction by up to 70% by making the auction transparent and protocol-enforced, rather than reliant on off-chain agreements.
EIP-7928 introduces Block-Level Access Lists (BALs): a mandatory record included in every block that maps every account and storage slot the block touches, along with post-execution state values.
This is the parallelization unlock. Today, Ethereum validators execute transactions sequentially because they cannot know in advance which state a transaction will read or write. BALs provide that dependency map upfront, allowing:
BALs represent a fundamental shift in how Ethereum handles computation. Sequential execution has been a throughput bottleneck since genesis. With dependency mapping, blocks can be validated and synced in parallel, unlocking the capacity gains the higher gas limit enables.
Several EIPs directly affect validator operations and staking economics:
EIP-8061 (Increase Exit and Consolidation Churn) separates exit, activation, and consolidation queues. At current staking levels, this increases exit capacity approximately 4x and consolidation capacity roughly 2x. The weak subjectivity period — the maximum time a node can be offline and still safely sync — drops from approximately 15.7 days to 7 days.
For institutional stakers managing large positions, the 4x exit capacity improvement directly addresses liquidity predictability. During high-demand exit periods (such as the post-Merge validator queue), the current system creates multi-week withdrawal delays. Glamsterdam compresses that timeline.
EIP-8045 (Exclude Slashed Validators) prevents penalized validators from proposing blocks during their penalty period, maintaining chain stability during mass slashing events.
With ePBS, the validator role simplifies: propose the block, attest to the chain, participate in consensus. Block building happens independently through the protocol-level auction. Validators no longer need to trust external relay infrastructure or run MEV-Boost software.
The transition to ePBS introduces a testnet-specific vulnerability that developers have flagged publicly. Because Sepolia uses freely available test ether, an attacker could:
Ethereum consensus developer Potuz described the attack vector during a core developer call, noting its trivial execution cost. The vulnerability does not affect mainnet, where builder identities require real economic stake, but it could disrupt the testing infrastructure needed to validate Glamsterdam before mainnet deployment.
Development teams have a compressed timeline to address this: Sepolia-compatible software must ship by September 29, leaving seven days for review before the October 6 fork. The standard allocation is 14 days. If Sepolia testing encounters significant disruption, the provisional Hoodi test (October 27) and the Q4 mainnet target could slip.
| Milestone | Date | Status | |---|---|---| | Devnet-11 transition | September 16, 2026 | Complete | | Software shipping deadline | September 29, 2026 | Pending | | Sepolia fork | October 6, 2026 | Scheduled | | Hoodi testnet | October 27, 2026 | Provisional | | Mainnet activation | Q4 2026 | Target |
The timeline has already slipped twice — from June to Q3, then from Q3 to Q4. Each delay reflected scope expansion rather than technical failure; the Devnet-11 run with 84,000 validators was successful. The risk factor now is the compressed testing schedule and the Sepolia builder attack vector.
Glamsterdam affects Layer 2 economics through two channels:
Direct fee reduction. EIP-2780 restructures intrinsic transaction gas, making standard ETH transfers between existing accounts up to 71% cheaper. This benefits both L1 users and L2 rollups that post settlement transactions to mainnet.
Indirect capacity benefits. With 200M gas per block and parallel execution, L1 congestion decreases. Rollups that depend on L1 for proving, bridging, and forced exits face lower costs for these operations. Blob capacity, already expanded under prior upgrades from 3 target / 6 max to 6 target / 9 max blobs per block, benefits from the larger block envelope.
EIP-7954 raises the maximum smart contract size from 24 KiB to 64 KiB, enabling more complex on-chain applications — relevant for rollup verification contracts and protocol governance logic.
EIP-7708 makes all ETH transfers and burns emit event logs, creating permanent on-chain records. This addresses a long-standing gap in Ethereum's event architecture and improves tracking for exchanges, bridges, and accounting infrastructure.
Glamsterdam is being delivered under new Ethereum Foundation protocol leadership. Developers Barnabé Monnot and Tim Beiko — who led the protocol team through the Merge, Pectra, and Fusaka — have moved on. Three new leads are in place: Will Corcoran, Kev Wedderburn, and a developer identified as Fredrik.
The transition occurred during the upgrade's development cycle, adding organizational complexity to a technically ambitious fork.
Glamsterdam is not a routine upgrade. It restructures how Ethereum builds, validates, and prices blocks. The 200M gas limit, parallel execution via BALs, and protocol-level builder auctions collectively represent the most significant changes to Ethereum's execution layer since the chain switched from proof-of-work to proof-of-stake in September 2022.
The data supports the scope: 3.3x gas capacity, 10x throughput target, 71% cheaper transfers, 4x faster validator exits, 70% MEV reduction. Each figure represents a measurable change to the network's economic parameters.
The open question is timing. Two prior delays, a compressed testing schedule, a known testnet vulnerability, and a leadership transition all create execution risk. Q4 2026 remains a target. The Sepolia fork on October 6 and the Hoodi test on October 27 will determine whether that target holds.