Ethereum's Fusaka Upgrade: Scaling the Base Layer to Unify L2 Fragmentation

Ethereum’s Fusaka upgrade, a major hard fork aimed at enhancing scalability and data availability, is set to activate on the mainnet on December 3, 2025, following a phased rollout across testnets. The upgrade introduces a doubling of blob capacity from current limits of 6/9 blobs per block to 14/21, achieved through two Blob Parameter Only (BPO) forks scheduled for December 17 and January 7, 2026. This expansion is designed to reduce transaction costs and improve throughput for Layer 2 (L2) rollups, which rely on off-chain data storage to scale Ethereum’s networktitle1^[1].

The Fusaka upgrade includes 11–12 Ethereum Improvement Proposals (EIPs), with a focus on backend infrastructure rather than user-facing features. A key innovation is the implementation of PeerDAS (Peer Data Availability Sampling) via EIP-7594, which allows validator nodes to verify data by sampling subsets of blob data instead of downloading entire blocks. This reduces bandwidth and storage requirements while maintaining security guarantees, enabling more efficient L2 adoptiontitle1^[1]. The upgrade also introduces bounded base fees for blob transactions (EIP-7918) to stabilize costs for data-heavy applications and enhances spam resistance to mitigate network attackstitle1^[1].

The rollout follows a four-phase testnet schedule beginning October 1 on Holesky, followed by Sepolia on October 14 and Hoodi on October 28. Each testnet will validate the BPO fork sequence, which automates blob capacity increases without requiring manual intervention. The staggered approach allows developers to monitor performance and address potential bottlenecks before mainnet deploymenttitle1^[1]. Node operators face preparation deadlines from September 25 (Holesky) to November 3 (mainnet), ensuring infrastructure readinesstitle1^[1].

The upgrade addresses growing pressure to scale Ethereum’s base layer amid criticism of L2 fragmentation. While L2 solutions have enabled higher throughput, they have also created isolated chains with limited interoperability. Fusaka’s infrastructure improvements aim to bolster base layer capacity while supporting continued L2 growth. Recent validator queue delays—over 43 days for exits—highlight network scalability challenges, though Vitalik Buterin has defended these as necessary for securitytitle2^[2].

Long-term scalability efforts include proposed gas limit increases from 45 million to 150 million (EIP-7935) and a 100x gas limit expansion over two years (EIP-9698), which could push Ethereum’s transaction throughput to 2,000 transactions per second. These initiatives align with broader industry trends, such as the Open Intents Framework, which seeks to unify cross-chain interoperability and combat $21 billion in multichain crimetitle1^[1].

The Ethereum Foundation’s strategy emphasizes incremental scaling through non-breaking optimizations, such as cell-level messaging and pipelining, to improve bandwidth efficiency. Future upgrades, including PeerDAS v2 and FullDAS research, aim to further scale data availability (DA) throughput while preserving decentralization. These efforts position Ethereum to compete with high-performance blockchains like Solana, which has attracted institutional interest through projects like Solmate, a $300 million digital asset treasury focused on staking and infrastructuretitle6^[6].