The Ethereum Foundation’s Protocol Support Team reported on November 15, 2025 that testing for the Fusaka network upgrade and its two planned Blob Parameter Only forks was complete. All three had gone live on Ethereum’s Holešky, Sepolia and Hoodi testnets with what the team characterized as very few issues. Small client problems remained, but the checkpoint said they were not consensus-critical and would not delay the mainnet upgrade scheduled for December 3, 2025.
That status update mattered because Fusaka was intended to change both Ethereum’s base-layer operation and the way the network supplied data availability to layer-two rollups. The event on November 15 was not the upgrade itself: no Fusaka mainnet rules, additional blob capacity or resulting fee changes had yet taken effect. It was a readiness judgment from the protocol team after the testnet sequence, giving node operators a defined deadline for installing compatible client software.
Three testnets completed the sequence
Ethereum’s Fusaka specification records activations on Holešky on October 1, Sepolia on October 14 and Hoodi on October 28, 2025. By November 15, the protocol checkpoint treated that sequence as complete. The foundation said node operators needed to update before the mainnet activation at 21:49 UTC on December 3. Its more precise mainnet announcement and the Fusaka meta-specification placed activation at epoch 411392 and 21:49:11 UTC.
A successful testnet deployment does not prove that a mainnet fork will be trouble-free. Test networks can differ from mainnet in participation, load, infrastructure concentration and economic consequences. The narrower verified claim was that the scheduled test deployments had occurred and that the protocol team had not identified a consensus-critical issue requiring postponement as of November 15.
Why PeerDAS was central
Fusaka’s headline feature was Peer Data Availability Sampling, specified in EIP-7594. Ethereum rollups publish compressed transaction data in blobs. PeerDAS was designed to let nodes check whether that data was available by sampling portions of erasure-coded data rather than requiring every node to download every complete blob. The intended institutional tradeoff was greater network-wide data capacity without a proportional bandwidth increase for each individual node.
Fusaka also encompassed execution-layer limits, cryptographic-operation repricing, deterministic proposer lookahead, a block-size limit, a new opcode and native support for the secp256r1 signature curve. Those features were included in the upgrade specification on November 15, but inclusion and successful testnet deployment were not evidence of measured mainnet performance. Claims about lower user fees, higher realized throughput or improved application adoption remained prospective.
Capacity increases were still future events
The November 15 checkpoint preserved a staged blob schedule. Fusaka itself was due to activate with the existing target of six blobs per block and maximum of nine. The first Blob Parameter Only fork was scheduled for December 9, 2025, increasing the target to 10 and maximum to 15. A second was scheduled for January 7, 2026, increasing them to 14 and 21.
EIP-7892 defined these parameter-only forks as targeted configuration changes affecting the blob target, maximum and base-fee update fraction without introducing unrelated protocol changes. The staged approach allowed developers to observe network behavior before expanding capacity further. On November 15, however, all three mainnet milestones remained scheduled rather than completed.
The event-day conclusion
The defensible conclusion on November 15 was operational: Ethereum’s protocol team considered Fusaka and its planned parameter forks ready to proceed after deployment on three major testnets, subject to node operators updating compatible software. The checkpoint reduced uncertainty about an immediate delay, but it did not eliminate implementation risk or establish any market effect. No ether price, return, trading-volume, fee-reduction or throughput claim is necessary to explain the significance of the development.
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