The Ethereum network is gearing up for one of its most significant scaling steps yet, with the Fusaka mainnet activation tentatively set for November 5, 2025. The plan comes after rigorous devnet testing, phased blob capacity rollout strategies, and critical alignment among client teams on readiness & risk management.
Path to Fusaka Mainnet
During the All Core Developers Consensus (ACDC) Call #162, developers finalized a phased schedule leading to the November mainnet launch.
Key dates include:
- September 1, 2025 – Client releases for Holesky & Sepolia
- September 8, 2025 – Bug bounty launch
- September 15, 2025 – Holesky fork
- September 22, 2025 – Sepolia fork
- October 1, 2025 – Mainnet client release & Hoodi fork
- October 8, 2025 – Hoodi fork activation
- November 5, 2025 – Fusaka mainnet target
Developers cautioned that even small delays at this stage could cascade into a multi-month push due to the year-end holiday season.
Testing using Devnets & Non-Finality Scenarios
Fusaka Devnet-3 achieved 100% validator participation during stress tests simulating:
- Validator outages (full nodes & supernodes)
- Bandwidth throttling to 1 Mbps for 30% of the network
- Network splits & re-merges using Tyler’s Chaos Tool
On August 8, 2025, Devnet-4 launched, designed to replicate 10% of mainnet scale in a high-intensity single-day run to evaluate blob throughput and client stability under load.
Addressing Timeline Risks
Concerns have been raised by developers, including Matthew Keil, about pending code merges, incomplete private mempool testing, and the absence of a spec freeze.
Mitigation measures include:
- Forking Holesky with non-master branches to decouple client release cycles
- Launching Devnet-5 after Holesky for final pre-mainnet testing
- Maintaining parallel testing to avoid bottlenecks
Client teams like Prysm, Nimbus, and Teku have expressed confidence in meeting the September fork deadlines while continuing testing efforts.
The Fusaka mainnet’s planned November 5 launch marks a pivotal milestone in Ethereum’s scaling journey, built on months of coordinated testing and phased rollout strategies. With rigorous devnet simulations, non-finality stress testing, and careful risk mitigation, core developers aim to deliver a smooth and stable upgrade. The timeline balances ambitious capacity goals with the caution needed to avoid network instability during expansion.
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