Ethereum Fusaka Upgrade Set for December 3 Mainnet Launch, Blob Capacity to Double

Ethereum developers confirmed the Fusaka upgrade will activate on mainnet on December 3, 2025, following a systematic testnet rollout beginning on October 1 on Holesky.

The major hard fork will implement around 11-12 Ethereum Improvement Proposals targeting scalability, node efficiency, and data availability improvements without adding new user-facing features.

According to Christine Kim, the upgrade introduces a phased blob capacity expansion through Blob Parameter Only forks occurring two weeks after Fusaka activation.

Initially maintaining current blob limits of 6/9 target/max, the first BPO fork will increase capacity to 10/15 blobs one week later.

A second BPO fork will further expand limits to 14/21 blobs, more than doubling total capacity within two weeks.

Important decisions were made on today's Ethereum developer call, ACDC #165. Developers confirmed the public testnet schedule and BPO hard fork schedule for Fusaka.

Let's get into it. pic.twitter.com/mNrYMYyDj2

Fusaka prioritizes backend protocol improvements over user-facing features, focusing on making Ethereum faster and less resource-intensive.

The upgrade includes PeerDAS implementation through EIP-7594, allowing validator nodes to verify data by sampling small pieces rather than downloading entire blobs.

This reduces bandwidth and storage requirements while enhancing Layer 2 rollup scalability.

The upgrade builds on recent gas limit increases from 30 million to 45 million gas, with ongoing discussions for further expansion.

EIP-7935 proposes increasing limits to 150 million gas, potentially enabling significantly higher transaction throughput.

These improvements complement broader scalability efforts, including EIP-9698, which suggests a 100x gas limit increase over two years to reach 2,000 transactions per second.

Fusaka removes the previously planned EVM Object Format redesign to reduce complexity while maintaining focus on essential infrastructure improvements.

The upgrade introduces bounded base fees for blob transactions via EIP-7918, creating more predictable transaction costs for data-heavy applications.

Enhanced spam resistance and security improvements strengthen network resilience against scalability bottlenecks and attacks.

The Fusaka rollout follows a conservative four-phase approach across Ethereum testnets before mainnet deployment.

Holesky upgrade occurs October 1, followed by Sepolia on October 14 and Hoodi on October 28.

Each testnet will undergo the complete BPO fork sequence to validate the blob capacity expansion mechanism.

BPO forks activate automatically based on predetermined epochs rather than requiring separate hard fork processes.

On mainnet, the first BPO fork launches December 17, increasing blob capacity to 10/15 target/max.

The second BPO fork activates January 7, 2026, reaching the final capacity of 14/21 blobs. This automated approach enables flexible blob scaling without requiring full network upgrades.

At a high-level, here's what developers agreed should be the schedule for Fusaka moving forward:

October 1: Holesky upgrade
October 14: Sepolia upgrade
October 28: Hoodi upgrade
December 3: Mainnet upgrade

Notably, node operators face release deadlines ranging from September 25 for Holesky to November 3 for mainnet preparation.

The staggered timeline, according to the developers, allows comprehensive testing while giving infrastructure providers sufficient preparation time.

Speculatively, the developers use this backward-compatible approach to ensure smooth transitions with minimal disruption to existing applications.

PeerDAS implementation reduces node resource demands, potentially increasing network decentralization by lowering barriers for smaller operators.

The technology enables more efficient data availability sampling, crucial for supporting growing Layer 2 rollup adoption.

Overall, these improvements, combined with increased gas limits, will enable Ethereum to handle higher transaction volumes while maintaining security guarantees.

The Fusaka upgrade addresses mounting pressure for Ethereum base layer improvements amid criticism of Layer 2 fragmentation strategies.

Critics argue that reliance on rollups has created isolated chains with limited interoperability, complicating user experiences.

The upgrade’s focus on infrastructure improvements aims to enhance base layer capacity while supporting continued Layer 2 growth.

The recent validator queue controversy particularly highlights ongoing network scalability challenges.

According to a Cryptonews report covered yesterday, currently, over 2M ETH sits in exit queues facing 43-day delays, while entry queues process in just 7 days.

However, Vitalik Buterin defended these delays as essential for network security, comparing validator commitments to military service requiring “friction in quitting.”

The upgrade coincides with growing institutional interest in Ethereum infrastructure, with VanEck predicting that Layer 2 networks could reach $1 trillion market capitalization within six years.

Fusaka’s emphasis on data availability and node efficiency supports Ethereum’s evolution toward seamless cross-chain interoperability.

The upgrade complements initiatives like the Open Intents Framework, where Coinbase Payments recently joined as a core contributor. The initiative, if successful, will address the $21B surge in cross-chain crime.

These coordinated efforts aim to unify the fragmented multichain experience while maintaining Ethereum’s security and decentralization principles.

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