If you searched "Fusaka mainnet date" this week, your results are six months out of date — the upgrade you're looking for already shipped, and the fork actually dominating Ethereum's roadmap right now has a different name.
What Is Glamsterdam — and Why Are Traders Still Searching for Fusaka?
Glamsterdam is Ethereum's next major hard fork and the upgrade that genuinely entered its final development stage in mid-June 2026 — not Fusaka, which is already complete. Fusaka activated on Ethereum mainnet on December 3, 2025, at epoch 411392 (block 23,935,694) . So any "Fusaka launch countdown" still circulating is stale; the live story is its successor.
Quick Answer: Fusaka is done — it went live December 3, 2025 at block 23,935,694. The active Ethereum fork now is Glamsterdam, which entered its final devnet phase around June 16, 2026 and is described by Ethereum Foundation engineers as the largest fork since the Merge.
The confusion is understandable: the two forks share roadmap DNA, and Glamsterdam picks up where Fusaka's blob-scaling work left off. But the focus of AllCoreDevs has clearly moved on. As of June 2026, developers are running multi-client devnets — glamsterdam-devnet-5 and devnet-6 — with the full slate of planned EIPs, after the Soldøgn interop devnet concluded around May 2, 2026 .
The scale of the upgrade is what has caught attention. Ethereum Foundation devops engineer Parithosh Jayanthi framed the current milestone plainly:
"[This is] the last phase before we work on hardening and then shipping the testnets," he said, calling Glamsterdam "probably the largest fork we've had since the Merge" (source: CoinDesk, 2026-06).
For traders pricing in a catalyst, the timing detail matters most. Glamsterdam's schedule has already slipped from an original June 2026 goal toward a second-half target now centered on Q3 2026, and no firm mainnet date is locked as of mid-June . Devnet completion is followed by a testnet hardening phase, so "final development stage" signals progress — not an imminent activation block. The sections below separate what Fusaka actually delivered from what Glamsterdam still has to prove.
Fusaka's Post-Launch Reality: Blobs Are Under-Used Six Months In
Six months after activation, Fusaka's blob capacity is being used well below its new ceiling — demand, not protocol capacity, is now the binding constraint. A MigaLabs review of more than 750,000 slots since launch found median blobs per block actually fell from roughly 6 before the first parameter increase to about 4 afterward . The headroom is there; layer-2 networks simply have not filled it yet.
That headroom came from Blob Parameter Only (BPO) forks, the lightweight coordinated forks Fusaka introduced to tune blob targets without a full hard fork. BPO1 (December 9, 2025) lifted the target to 10 and the max to 15, and BPO2 (January 7, 2026) pushed the target to 14 and the max to 21 . PeerDAS makes that scaling possible by letting each node custody only about one-eighth of blob data while any 50% of the network can reconstruct the whole — the mechanism meant to underpin up to 8x blob throughput .
Reliability is the trade-off traders should watch. The baseline block miss rate sits near 0.5%, but it climbs once blocks carry 16 or more blobs, reaching roughly 1.79% — about 3.5x baseline — at the 21-blob ceiling .
| Stage | Date | Blob target / max | Observed block miss rate |
|---|---|---|---|
| Post-Dencun baseline | Pre-Fusaka | 6 / 9 | ~0.5% |
| BPO1 | Dec 9, 2025 | 10 / 15 | ~0.5% |
| BPO2 | Jan 7, 2026 | 14 / 21 | 0.77%–1.79% (16+ blobs) |
Because of that miss-rate curve, developers are holding BPO3 and BPO4 pending a telemetry review of the first two increments rather than pushing parameters higher on schedule . The long-run ambition of 128 blobs per block remains theoretical — a destination, not a roadmap with locked dates. The practical takeaway for ETH holders: Fusaka shipped the supply side of cheaper L2 data, and the next leg depends on rollups generating demand to use it.
Glamsterdam's Two Headline EIPs: ePBS and Block-Level Access Lists
Glamsterdam is anchored by two proposals that reshape how Ethereum blocks are built and executed: EIP-7732 (Enshrined Proposer-Builder Separation, or ePBS) and EIP-7928 (Block-level Access Lists, or BALs). ePBS moves the separation of block proposing and block building onto the protocol itself, so validators no longer depend on third-party MEV relays to source blocks — shrinking the manipulation surface that currently sits off-chain . BALs let a block declare in advance which accounts and state slots it will touch, allowing clients to execute non-overlapping transactions in parallel and lift effective L1 throughput without raising the gas limit .
The bundle does not stop at those two. Glamsterdam carries a broad gas repricing that makes compute opcodes cheaper while raising the cost of state-access opcodes — a deliberate shift of the cost burden away from small contract calls and toward heavy storage reads . Work to reduce L1 slot time is also in scope, which would tighten the interval between blocks and complement the parallel-execution gains from BALs .
| Component | EIP / scope | What it changes |
|---|---|---|
| Enshrined PBS | EIP-7732 | Moves proposer-builder separation on-chain, removing reliance on external MEV relays |
| Block-level Access Lists | EIP-7928 | Blocks pre-declare touched accounts/state, enabling safe parallel execution |
| Gas repricing | Bundle-wide | Cheaper compute opcodes, costlier state-access opcodes |
| Slot time | Bundle-wide | Effort to shorten L1 block interval |
Taken together, the combined EIP slate is what makes this the heaviest upgrade in years. EF devops engineer Parithosh Jayanthi described the current multi-client devnet phase — running the full slate of planned EIPs — as "the last phase before we work on hardening and then shipping the testnets," and called Glamsterdam "probably the largest fork we've had since the Merge" (source: CoinDesk, 2026-06). For ETH holders, the distinction matters: Fusaka scaled data availability, but Glamsterdam targets execution efficiency and the validator economy directly.
Base Case: Q3 2026 Mainnet, L2 Fee Compression Continues
The base case is a Glamsterdam mainnet activation in the second half of 2026, most plausibly Q3, with continued downward pressure on Layer-2 fees in the run-up. A stable multi-client devnet has been running since the Soldøgn interop devnet concluded around May 2, 2026 , and testnet hardening typically follows the final devnet phase within weeks. The Ethereum Foundation's February 18, 2026 Protocol Priorities update points to a second-half-2026 window after the timeline slipped from an original June goal toward Q3 .
The standard Ethereum upgrade trajectory remains intact, which is the spine of this scenario. Both Pectra and Fusaka activated within a few weeks of completing their final devnet phases, so the move from devnet to testnets to mainnet is a well-rehearsed sequence rather than an open-ended research project. PeerDAS, live since Fusaka activated on December 3, 2025, is already expanding blob data availability on mainnet , so Glamsterdam does not depend on unproven data-scaling infrastructure to ship.
Crucially, Glamsterdam's Block-level Access Lists add parallel-execution throughput on top of that data layer without requiring another blob parameter change. The base case therefore stacks two independent efficiency gains — cheaper data availability from Fusaka's PeerDAS and faster execution from BALs — rather than relying on a single lever.
On price, the base case assumes a pre-mainnet bid for ETH consistent with prior upgrade cycles, where the asset tended to outperform Bitcoin by roughly 8–12% in the 30 days before activation. Treat that as the scenario's working assumption rather than a fixed promise; with no locked mainnet date, the window for any such bid is wide and easily disrupted.
Layer-2 tokens are the clearest second-order beneficiaries. ARB, OP and broader ecosystem assets gain from continued data-availability cost compression as blob capacity stays cheap relative to demand. Glamsterdam's Enshrined Proposer-Builder Separation (ePBS) adds a further channel by reducing the MEV extraction that currently taxes L2 sequencers at the relay layer . In the base case, that combination keeps settlement costs trending lower without any dramatic re-rating — steady compression, not a step change.
Bull Case: ePBS Unlocks Institutional Validator Demand
The bull case rests on Enshrined Proposer-Builder Separation closing the trust gap that currently keeps large, compliance-bound validators on the sidelines. Today, validators capture MEV by routing block-building through third-party relays they cannot fully vet; ePBS (EIP-7732) moves that separation on-chain, removing reliance on unvetted relay infrastructure . For institutional staking desks, that is the difference between a documented protocol guarantee and an off-protocol dependency — a meaningful unlock for regulated validator demand.
The second lever is throughput. Block-level Access Lists (EIP-7928) let blocks declare the accounts and state they will touch, enabling faster parallel execution and raising the L1 transactions-per-second ceiling . A higher base-layer ceiling narrows the throughput-narrative edge that has anchored Solana's ETH/SOL positioning case through 2025 and into 2026, a recurring framing in trader discourse rather than a settled fact.
Glamsterdam's gas repricing reshapes which applications benefit. The fork makes compute cheaper while raising the cost of state access , structurally favoring compute-intensive DeFi protocols over state-heavy ones. The bull read is a gradual TVL rotation toward ETH-native applications whose execution profiles are rewarded by the new pricing curve.
The clean-execution scenario ties these threads together: a Q3 2026 mainnet activation, in line with the second-half target after the timeline slipped from its original June goal , re-ignites the ETH upgrade narrative just as PeerDAS-driven L2 fee compression compounds. EF engineer Parithosh Jayanthi has called Glamsterdam "probably the largest fork we've had since the Merge" , and a friction-free ship would plausibly accelerate staking inflows and push L1 adoption metrics higher into Q4. None of this is assured — it is the upside path if execution stays on schedule. See CoinDesk's Glamsterdam coverage for the developer detail.
Bear Case: Scope Creep, Timeline Slip, and the Fee-Burn Paradox
The bear case starts with the calendar. Glamsterdam has already slipped once — from an original June 2026 goal toward a second-half target now centered on Q3 . For a fork its developers themselves call "probably the largest fork we've had since the Merge" , that complexity cuts against the schedule. We put the probability of a further slip into Q4 2026 at roughly 20–30% if multi-client testing of the full EIP slate surfaces consensus-layer bugs during hardening.
That risk concentrates in EIP-7732. Enshrined Proposer-Builder Separation is technically heavy and lands on the consensus layer, where errors propagate across the validator set rather than staying contained in execution. A late rollback or de-scope of ePBS would simultaneously dent staking-yield expectations and the institutional-demand narrative that underpins the bull case — two pillars softening at once.
The subtler problem is the fee-burn paradox. More blobs mean more L2 throughput, which means more activity settling cheaply off-chain and less fee pressure burning ETH on L1. Fusaka's blob expansion has already eased deflation: a MigaLabs review of 750,000+ slots found median blobs per block fell from about 6 before BPO1 to roughly 4 after , confirming demand — not capacity — is the binding constraint. Glamsterdam deepens that trend by making rollup execution cheaper still, so scaling success can paradoxically weaken ETH's monetary tailwind even as fundamentals improve.
The full bear scenario stacks these: a Q4 slip arrives alongside a macro risk-off turn, and ETH underperforms BTC and SOL on a relative basis through year-end despite genuine protocol progress. In that path the upgrade still ships and the technology still works — the market simply prices the delay and the diluted burn faster than it prices the long-term scaling win.
Portfolio Implication: Sizing ETH Around an Upgrade Catalyst With No Fixed Date
For traders, the practical takeaway is to treat Glamsterdam as a catalyst with a probable window rather than a fixed date, and size exposure accordingly. Ethereum has historically outperformed Bitcoin in the roughly six-to-eight-week run-up to a major hard fork, then given back relative strength in the two-to-four weeks after activation as the event prices in — a sell-the-news pattern that held through both Pectra and Fusaka. With Glamsterdam, the catalyst is real but the entry timing is not yet pin-downable.
The core problem is the calendar. There is no locked mainnet date: the Ethereum Foundation's February 18, 2026 Protocol Priorities update and subsequent reporting point to a second-half-2026 target, and the timeline has already slipped from an original June goal toward Q3 2026 . Because the pre-mainnet positioning window is therefore uncertain, the prudent move is to size ETH upgrade exposure to reflect a meaningful chance — on the order of 20–30% — that activation slips into Q4, which would push and possibly dilute the run-up trade.
Two adjustments follow from that. First, traders who want leveraged exposure to the blob and data-availability theme can use L2 governance tokens such as ARB and OP, which benefit from the cheaper data availability Glamsterdam extends without carrying direct execution-layer or activation-timing risk on the L1 fork itself. Second, the signal to scale up or trim is concrete: watch the glamsterdam-devnet milestone announcements — June 2026 work referenced glamsterdam-devnet-5/6 — and, decisively, public testnet launch confirmation . EF engineers describe the current phase as the last step before hardening and shipping testnets, so a dated testnet is the cleanest evidence the fork is weeks-to-months from mainnet rather than quarters.
The bottom line: own the thesis, not the date. Glamsterdam is genuine scaling progress, but its payoff is a sequence of verifiable milestones, not a single price event. Build ETH and L2 exposure that survives a Q4 slip, let the devnet-to-testnet cadence dictate when you add, and keep position size matched to a catalyst whose timing the market itself has not yet settled.
Frequently asked questions
Is Fusaka the same as Glamsterdam?
No. They are two separate, sequential Ethereum upgrades. Fusaka activated on mainnet on December 3, 2025 at 21:49:11 UTC and is already a completed upgrade . Glamsterdam is Fusaka's successor, and as of mid-June 2026 it sits in final multi-client devnet testing rather than on mainnet . Traders searching "Fusaka final stage" are almost always looking for Glamsterdam.
When is the Glamsterdam mainnet date?
There is no firm mainnet date as of mid-June 2026. The fork's original June target has slipped toward Q3 2026, with developers describing the current phase as "the last phase before we work on hardening and then shipping the testnets" . The clearest signal is the testnet launch: watch the glamsterdam-devnet milestones converge and a public testnet date get announced before assuming a mainnet window.
What is ePBS and why does it matter for ETH traders?
ePBS is Enshrined Proposer-Builder Separation, defined in EIP-7732, one of Glamsterdam's two headline proposals . It moves block-building separation on-chain, reducing MEV manipulation and removing validators' reliance on third-party relays. For traders, that matters because cleaner validator economics and a lower technical barrier to solo and institutional staking feed directly into staking yield and long-term ETH demand.
Will Glamsterdam lower Ethereum gas fees?
Not directly on Ethereum's base layer. Like Fusaka, the primary beneficiaries are Layer-2 rollups: Block-level Access Lists (EIP-7928) improve parallel throughput, and continued blob expansion keeps L2 data-availability costs low . L1 gas depends on demand, and post-Fusaka telemetry shows the network running below capacity — median blobs per block fell to roughly 4 against a 14-blob target .
Do ETH holders need to do anything for the Glamsterdam upgrade?
No. ETH holders take no action — there is no token to convert, swap, or "upgrade." Glamsterdam, like every Ethereum hard fork including Fusaka, is a node-level protocol change handled by validators and node operators, not by individual wallets . Any message instructing you to "upgrade your ETH" or migrate tokens to a new contract is a scam, not a protocol requirement.
