On December 3, 2025, the Ethereum network activated the Fusaka Upgrade, a structural hard fork that analysts widely regard as the network's most consequential scaling enhancement since the introduction of blobs in Dencun.

Named for the coordinated Fulu (Consensus Layer) and Osaka (Execution Layer), it fundamentally rewrites the data availability logic, directly empowering Layer 2 (L2) rollups and paving the road for the next phase of mass adoption.

The upgrade’s impact is designed to be felt directly by the end-user: significantly cheaper and faster Layer 2 transactions, which are critical for making decentralized applications (dApps) viable for global-scale finance, gaming, and social networks.

The headline feature of the Fusaka upgrade is Peer Data Availability Sampling (PeerDAS), implemented via EIP-7594.4. This innovative mechanism is the key to scaling Ethereum's data throughput without sacrificing its core principle of decentralization.

• Decentralized Verification: Before Fusaka, every full node was required to download and store the entire blob (L2 transaction data chunk) to verify its availability.

• The Sampling Model: PeerDAS utilizes Reed-Solomon-style erasure coding and KZG commitments, enabling nodes to verify data availability by sampling only small, random cells from their peers, rather than downloading the entire dataset.

• The Result: Nodes dramatically reduce their bandwidth and storage requirements, achieving what Vitalik Buterin has described as the necessary infrastructure to scale L2s by up to 8 times while keeping the network accessible to ordinary validators.

• This technological breakthrough enables the network to safely and progressively increase the actual data capacity for rollups.

Fusaka not only delivered PeerDAS but also introduced a new, agile mechanism for scaling: Blob Parameter Only (BPO) Forks (EIP-7892).

This light-touch system allows Ethereum to increase the number of blobs per block without needing a full, heavy hard fork every time.

The initial rollout is scheduled in three sequential events:

1. Mainnet Activation (Dec 3, 2025): The core code changes went live.

2. BPO1 Fork (Dec 9, 2025): The target blob count increased from 6 to 10, and the maximum increased to 15 per block.

3. BPO2 Fork (Jan 7, 2026): The capacity will increase further to a target of 14 and a maximum of 21 blobs per block.

   Stability, Efficiency, and the User Experience

   Fusaka is a comprehensive package of vital EIPs designed to enhance the network's resilience and usability for billions of users.

   To boost L1 throughput, the Increased Gas Limit (EIP-7935) raised the default block gas limit to 60 million.

   To secure this capacity gain, a Transaction Gas Cap (EIP-7825) (approx. 16.78 million) was set per transaction to prevent block-clogging attacks, and the Block Size Limit (EIP-7934) was imposed to improve network resilience.

   Finally, the upgrade improved User Experience via Passkey Support (EIP-7951), enabling hardware-backed security (biometrics) for transactions, and Cheaper ZK Computation (EIP-7939) added the CLZ opcode to the EVM, cutting gas costs for complex Zero-Knowledge proving systems.

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   The Transformative Ecosystem Impact

   The flood of new capacity unlocked by PeerDAS and the Blob Parameter Only (BPO) forks is projected to have a profound impact on the Ethereum ecosystem.

   The most direct consequence is a massive Cost Plunge, with L2 transaction fees expected to drop by 60-95% in the coming weeks and months, fundamentally lowering the barrier to entry for users.

   This transformation will lead to a Shift in L2 Competition, as costs equalize and rivalry moves away from who has the lowest fees toward who offers the best user experience, superior developer toolkits, and deepest ecosystem depth.

Fusaka is not merely an incremental software patch; it is a fundamental shift that empowers the entire L2 ecosystem and prepares Ethereum to meet the demands of a global, high-throughput financial system