Ethereum’s Fusaka upgrade is now live on mainnet, marking a major structural change in how the network manages data and scaling. The upgrade was activated at epoch 411392 at 21:49:11 UTC, with the official Ethereum account first reporting “upgrade in progress… activating Fusaka at epoch 411392 // 21:49:11 UTC”, then confirming that “Fusaka is live on the Ethereum mainnet!”
In its announcement, the account highlighted three core elements of Fusaka. PeerDAS now “unlocks 8x data throughput for rollups,” significantly increasing the amount of data that rollup-based Layer 2 networks can publish to the network. The upgrade also introduces “UX improvements via R1 curve and pre-confirmations” and is described as “explicit preparation for L1 scaling with a gas limit increase and more.” The project adds that community members and core developers “will continue to monitor issues over the next 24 hours.”
Why Fusaka is “important” for Ethereum
Vitalik Buterin laid out the gist of the upgrade in unusually direct terms. “PeerDAS in Fusaka is important because it is literally partitioning,” he wrote. “Ethereum achieves block consensus without requiring a single node to see more than a tiny fraction of the data. And this is resistant to 51% attacks – this is probabilistic client-side verification, not validator voting.” In other words, the network can now agree on blocks even if no node needs to download all the associated data, instead relying on probabilistic client-side verification.
Buterin linked this to a long-standing line of research, noting that “sharding has been a dream for Ethereum since 2015, and data availability sampling since 2017,” and linking this to early research on data availability and erasure coding. With Fusaka, this architecture is no longer just a roadmap concept but an active mechanism securing Ethereum’s data layer.
At the same time, Buterin made it clear that Fusaka is not completing the sharing roadmap. He pointed out that “there are three reasons why the partition in Fusaka is incomplete.” First, he argued that “we can process O(c^2) transactions (where c is the calculation per node) on L2s, but not on Ethereum L1,” adding that “if we want to scale to benefit Ethereum L1 as well, beyond what we can achieve through constant factor upgrades like BAL and ePBS, we need mature ZK-EVMs.”
Second, he pointed out the “proposer/builder bottleneck,” where “the builder has to have all the data and build the entire block,” and said “it would be amazing to be able to build distributed blocks.” Third, he pointed out bluntly: “We don’t have a fragmented memory pool. We still need it.”
Despite these reservations, Buterin called Fusaka “a fundamental advancement in blockchain design.” He argued that “the next two years will give us time to refine the PeerDAS mechanism, carefully scale it up while continuing to ensure its stability, use it to scale L2s, and then, when ZK-EVMs are mature, turn it inward to scale Ethereum L1 gas as well.”
He concluded by giving “big congratulations to the researchers and core developers of Ethereum who have worked hard for years to achieve this,” emphasizing that for the Ethereum community, Fusaka is not a routine protocol update but the arrival of a long-promised era of sharding on the mainnet.
At press time, ETH was trading at $3,194.
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