Ethereum undergoes major mainnet upgrade tomorrow – here’s why you should be wary of ETH’s “sloping sidetrack”

Ethereum’s Fusaka upgrade goes live on December 3rd and introduces a series of changes aimed at increasing rollup throughput, tightening the gas market, and adding native support for passkey-style signatures.

This fork introduces PeerDAS data availability sampling, doubles the default block gas limit, and prepares the network for blob-only parameter expansions scheduled for later this month and in January.

Fusaka is named after the star Fulu (“auxiliary road”) and the city of Osaka (“slope or hill”), continuing Ethereum’s convention of pairing stars with cities.

Editor’s note: “Sloping side road” is a playful nod to the Fulu + Osaka mashup and is not an official translation.

Data availability gains scaling tier

The central technical change is PeerDAS, formalized in EIP-7694. This protocol allows nodes to verify the presence of BLOB data by sampling a small portion of the BLOB rather than downloading the entire BLOB.

This removes the scaling bottleneck introduced by EIP-4844 and creates a path to boost blob throughput by approximately an order of magnitude over time.

Because rollups compress user transactions into blobs and post them to Ethereum’s base layer, increasing blob capacity reduces layer 2 transaction fees.

Fusaka also increased the default gas limit per block to 60 million gas from the 30 million gas configuration set after the merge.

This increase doubles the L1 block gas budget, providing more room for both standard transactions and BLOB processing.

Two subsequent “Blob parameters only” forks (BPO1 on December 9th and BPO2 on January 7th) adjust blob parameters without additional code changes, further expanding capacity.

Rewiring the BLOB fee market

EIP-7918 ties BLOB’s minimum base price to running gas, preventing BLOB prices from crashing near zero while L1 gas remains expensive.

This change keeps the data availability market economically rational even as usage fluctuates. Previously, blob fees could diverge significantly from execution costs, creating arbitrage opportunities and distorting the economics of rollups.

A related set of Ethereum Improvement Proposals (EIPs) tightens some heavy-duty opcodes and transaction limits. EIPs are 7823, 7825, 7883, and 7934.

This proposal places limits on ModExp’s precompiled input size, increases gas costs, introduces caps on transaction gas limits, and enforces RLP block size limits. These constraints reduce the surface area for denial of service attacks and make worst-case client workloads more predictable.

Developer tools and encryption hooks

EIP-7939 introduces the count-leading-zeros opcode that makes bit manipulation, integer logarithm, and randomness logic cheaper and simpler on-chain.

This addition will benefit DeFi protocols and crypto contracts that rely on efficient bitwise operations.

Deterministic proposer lookahead, as specified in EIP-7917, gives validators a fixed schedule for who proposes blocks.

MEV relay and staking operators can use more accurate timelines to coordinate more safely and efficiently, reducing uncertainty in block production workflows.

EIP-7951 adds native precompilation of the secp256r1 curve, the same encryption standard used by Apple Secure Enclave, Android Keystore, and WebAuthn.

Wallets and smart account schemes will now be able to verify passkey-style signatures directly on Ethereum, enabling FaceID and TouchID authentication flows without the need for custom bridges or circuits.

Precompilation eliminates a major pain point for consumer applications that rely on biometric hardware.

Instant and gradual deployment

Fusaka will be activated at block height on December 3rd, and the first blob parameter adjustment will occur 6 days later. BPO2 will land on January 7th, completing its first capacity expansion.

The gradual rollout allows node operators and rollup teams to monitor blob usage and client performance before the next parameter is increased.

This upgrade does not introduce any consensus layer changes to staking or validator incentives. All changes target execution layer throughput, gas mechanics, and developer primitives.

Validators running the updated client will process the new opcodes and blob logic without changing their staking configuration.

Fusaka represents the most throughput-focused upgrade to Ethereum since the introduction of BLOBs in EIP-4844 in March 2024. This fork doubles block gas capacity, expands data availability sampling, and adds encryption hooks for mainstream authentication hardware.

This combination allows Ethereum to absorb higher rollup activity without proportionally increasing fees, and provides developers with new primitives for on-chain computation and user onboarding.