Ethereum’s Layer 1 is the foundation of the entire ecosystem as it is responsible for security, settlement, and decentralization. While Layer 2 scaling often dominates the discussion, the upcoming Fusaka upgrade (Q4 2025) introduces critical improvements to Layer 1 itself. These changes enhance throughput, prevent instability, reduce node costs, and ensure Ethereum can scale sustainably while staying decentralized.
- Block Size & Gas Limit Adjustments
- History Expiry & Cryptographic Improvements
- Deterministic Proposer Lookahead & CLZ Opcode
Block Size and Gas Limit Adjustments
The Fusaka upgrade introduces a 16.8M gas cap per transaction (EIP-7825). This prevents oversized transactions from consuming entire blocks and ensures more predictable validation times.
For Layer 1, it improves fairness across users, reduces risks of denial-of-service (DoS) attacks, and allows Ethereum to scale blockspace safely. Fusaka enforces a 10MB block size limit (EIP-7934) to maintain stable block propagation and reduce the risk of forks.
Alongside this, it prioritizes testing for a higher default block gas limit (EIP-7935), which expands throughput and enables more complex on-chain applications. Together, these upgrades balance higher execution capacity with network stability.
History Expiry & Cryptographic Improvements
With EIP-7642 (History Expiry), Ethereum nodes save ~530GB per sync, making node operation faster and more cost-efficient. This keeps decentralization intact by lowering the barrier to run full nodes.
Additionally, EIP-7823 & EIP-7883 introduce upper bounds and updated pricing for ModExp operations, eliminating consensus risks from unbounded cryptography and aligning gas with computational effort. These changes ensure security and sustainability at the protocol level.
Currently, Ethereum supports secp256k1 signatures, but billions of devices use secp256r1 (P-256). With EIP-7951, Fusaka introduces native support for secp256r1, enabling direct signing from smartphones, hardware wallets, and secure enclaves.
Deterministic Proposer Lookahead & CLZ Opcode
EIP-7917 introduces deterministic proposer lookahead, making block proposer schedules predictable. This improves MEV mitigation and enhances fairness in transaction ordering.
Meanwhile, EIP-7939 adds the CLZ opcode, reducing costs for mathematical and cryptographic operations. This especially benefits zero-knowledge proofs and DeFi protocols, making Ethereum’s computation layer leaner and more efficient.
Fusaka upgrade makes Ethereum more accessible to mainstream users and developers, simplifying authentication flows across L1 and L2 ecosystems. It makes blockspace more reliable, cryptography more secure, node operation more efficient, and computation cheaper.
These improvements ensure that Ethereum’s base layer remains robust enough to support massive Layer 2 growth while staying true to decentralization. In essence, Fusaka strengthens the backbone of Ethereum, paving the way for a scalable and sustainable future.
If you find any issues in this blog or notice any missing information, please feel free to reach out at yash@etherworld.co for clarifications or updates.
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