Author: stacymuur
Compiled by: Vernacular Blockchain
Introduction: Why Fusaka is so important now
Ethereum continues to evolve to support more users, more transactions, and more applications while maintaining security and decentralization. Each upgrade addresses a bottleneck in the system. Earlier in 2024, the Dencun upgrade introduced "blobs," a new data format, providing a new way for Layer 2 (L2) rollups to cheaply store data on Ethereum. This was a major milestone, but demand for blobs quickly reached its limit, causing congestion and driving up fees again.
Today, Ethereum launched the Fusaka upgrade on the Holesky testnet as the next step forward.
Fusaka's headline feature is Peer Data Availability Sampling (PeerDAS) , a secure way to scale blob throughput, allowing nodes to verify data without downloading the entire blob. In addition to PeerDAS, Fusaka also improves gas rules, cryptographic tools, and the developer experience. For users, this means Ethereum becomes faster, cheaper, and easier to use, especially for rollups, which millions of users rely on every day.
By launching on Holesky before mainnet, Fusaka provides developers, validators, and application teams with the opportunity to prepare for the next chapter of Ethereum.
From Dencun to Fusaka
To understand the significance of Fusaka, it helps to take a step back. Earlier in 2024, Ethereum released the Dencun upgrade, introducing blobs as a new data format. Blobs allowed rollups to publish bundled data to Ethereum in a cost-effective and secure manner. This breakthrough significantly reduced user fees for networks like Optimism, Arbitrum, and zkSync.
But blob demand grew so rapidly that rollups couldn't always secure blob space, and fees skyrocketed again. Ethereum needed a way to further scale blob throughput without overwhelming regular nodes. That 's exactly what Fusaka, which launched today on Holesky, provides.
PeerDAS Detailed Explanation
At the heart of Fusaka is PeerDAS (Peer Data Availability Sampling, EIP-7594) , a new way for Ethereum nodes to check the true availability of blob data.
Fusaka%20Previous Questions
Until today, nodes had to download the entire blob even if they only needed to confirm its existence. This was secure, but inefficient.
Imagine a library where every member must read every book to verify it's on the shelf. As the number of books increases, this effort becomes unsustainable. Similarly, as more blobs are added to Ethereum blocks, nodes become overwhelmed by the unnecessary weight of data. This limits blob throughput and drives up fees for rollup users during periods of high demand.
How PeerDAS works
PeerDAS uses erasure coding (a mathematical method that splits data into many small pieces). Imagine tearing a giant book into hundreds of chapters - even a small, random subset can prove the existence of the entire book.
Instead of downloading the entire blob, nodes sample a few chunks from their peers. If enough nodes confirm their random sample, the network can guarantee with high probability that the entire blob is available.
It's like a book club where each member randomly checks two or three chapters. If all the samples agree, the group can be confident that the book is intact without anyone having to read the whole thing.
Extensions in the works: Blob parameter only fork
Ethereum will not significantly increase blob capacity all at once. Fusaka introduced the Blob Parameter Only (BPO) fork (EIP-7892) , a method to gradually increase the blob limit after PeerDAS is activated.
On Holesky, the rollout plan is as follows:
October 1, 2025 – Fusaka activated at 08:48 UTC.
October 7, 2025 – BPO1 Increased blob target from 6 to 10 and maximum from 9 to 15.
October 13, 2025 – BPO2 raises target to 14 and maximum to 21.
This gradual approach ensures that performance can be measured at each step and gives node operators time to adapt to the hardware. Rather than a sudden leap, Ethereum scales in controlled, safer increments.
Beyond Blobs: Strengthening Ethereum’s Base Layer
Fusaka is not just about blobs. It also improves Ethereum’s Layer 1 infrastructure:
Gas rules: The default block gas limit is increased to 60 million (EIP-7935), while a single transaction cannot exceed approximately 16.7 million gas (EIP-7825). This prevents large transactions from crowding out other transactions and prepares for future parallel execution.
Cryptography: Optimizations for modular exponential arithmetic (EIP-7883, 7823) improve the performance of complex mathematical operations. A new precompile (EIP-7951) provides native support for P-256 signatures , which are widely used for passkeys and device-level security.
Network: Removed legacy proof-of-stake fields (EIP-7642), saving bandwidth and simplifying client code.
Block encoding: Introducing a block size cap (EIP-7934) to prevent extreme blocks from slowing down propagation.
Together, these changes enhance Ethereum’s resilience and efficiency as activity scales.
Build with Fusaka
Ethereum upgrades also focus on usability. Fusaka introduces features that make developers’ lives easier and users’ lives safer:
Passkeys: With native support for P-256 signatures, the wallet can provide passkey logins directly on Ethereum (available for iPhone, Android devices, and browsers).
Bit-level operations: The new CLZ opcode (EIP-7939) reduces the cost of compression methods and zero-knowledge (zk) circuits.
Transparency : Deterministic Proposer Lookahead (EIP-7917) makes block proposer schedules known in advance, enabling transaction pre-confirmation.
Predictability: Blob Fee Guarantee (EIP-7918) keeps blob fees relatively bounded by execution fees, ensuring stable economics. For developers, these are powerful new tools. For users, they translate into smoother applications, cheaper zk protocols, and more predictable fees.
Testnet rollout: Holesky today, mainnet coming soon
Ethereum upgrades always go through the testnet first before reaching the mainnet. Fusaka’s rollout is phased:
Holesky: Launched on October 1, 2025. BPO1 and BPO2 will follow within two weeks. Holesky will also retire thereafter, marking both a launch and a farewell.
Sepolia: Planned for October 14, 2025.
Hoodi: Planned for October 28, 2025.
Mainnet activation will only be scheduled after all three testnets have been successfully upgraded, currently expected to be in December 2025.
Actual changes
These technological upgrades will cascade outward to real-world benefits:
Rollup users: During peak trading times, blob slots used to fill up quickly, causing fees to rise. With PeerDAS and higher blob capacity, fees will remain more stable.
Node Operators: Validators that upgrade today on Holesky are now compatible with PeerDAS and the new gas rules. Those that do not upgrade will be forked from the chain.
App developers: Wallet teams can cheaply and natively support passkey login.
zk developers: Protocols can use CLZ opcodes to reduce the cost of proving zk circuits.
Security and Governance
Ethereum strikes a balance between innovation and caution. In addition to Fusaka, a bug bounty program has been launched, offering rewards of up to $2 million to encourage pre mainnet testing.
Fusaka also laid out Ethereum’s governance model: developers propose Ethereum Improvement Proposals (EIPs), client teams implement them, and node operators decide by upgrading their software. While Fusaka is expected to be non-contentious, the final decision will always be in the hands of the community.
Outlook: Ethereum after Fusaka
Ethereum's roadmap unfolds in phases: Dencun, Pectra, Fusaka, and beyond. Each upgrade removes a bottleneck and paves the way for the next. Fusaka's importance lies in its ability to safely scale blob throughput, enabling rollups to handle more transactions while maintaining reasonable node requirements.
For users, this means a cheaper and more reliable L2 experience.
For developers, it unlocks tools like passkey authentication and zk efficiencies.
For validators, it proves that Ethereum can scale while remaining decentralized.
in conclusion
The Fusaka upgrade, launched today on Holesky , is more than just another name on the roadmap. It marks the beginning of scaling beyond current blob limits, powered by PeerDAS and secured through a phased fork. It also strengthens Ethereum's foundation in areas such as gas, encryption, and networking.
As Fusaka progressed from the Holesky rollout to Sepolia and Hoodi, and then to mainnet, it demonstrated the Ethereum philosophy of careful, inclusive evolution, and a focus on long-term usability. For millions of users, developers, and validators around the world, Fusaka is a concrete step towards a faster, cheaper, and more practical Ethereum.
Link to this article: https://www.hellobtc.com/kp/du/10/6059.html
Source: https://stacymuur.substack.com/p/ethereum-fusaka-upgrade-live-on-holesky
