Ethereum’s Fusaka: What Builders Need to Prepare For

Ethereum’s Fusaka upgrade goes live on 3 December 2025. It is the second major upgrade of the year after Pecta and introduces changes that impact developers, infra providers, rollups, and anyone pushing transactions through an Ethereum RPC or blockchain data API.

Fusaka brings three core shifts:

More L1 throughput: block gas limit rises to ~150M gas, pushing L1 capacity into the 40-60 TPS range

A hard per-transaction gas cap: EIP-7825 limits single tx gas to 2²⁴ = 16,777,216 gas

Smarter data availability economics: PeerDAS + EIP-7918 scale blob capacity while introducing a blob fee floor tied to L1 gas costs

Below is a clean breakdown of what is actually changing and what you should update in your stack.

EIP-7825: The 16.78M Gas Cap

Before Fusaka, a single transaction could consume an entire block. That is incompatible with parallel execution and creates DoS risk.

After Fusaka:
Every transaction is capped at 2²⁴ gas (≈16.78M), independent of the 150M gas block limit.

Who is affected:

-Heavy deployments

-Large batch operations

-Routers/aggregators that chain many calls in one tx

What to do:

-Simulate deployments and batch jobs on Holesky/Sepolia (the cap is already active there)

-Split large operations across multiple transactions

-Update any builder/wallet logic that allows tx gas above 16,777,216

eth_call is unaffected, only confirmed txs enforce the cap.

Block Gas Limit → 150M

Fusaka increases the block gas limit roughly 3x, enabling 40-60 TPS depending on workload.

Impact:

-More room for L2 settlement + normal L1 activity

-More data to index per block

-Higher CPU, bandwidth, and disk requirements for node operators

If you run your own Ethereum nodes or rely on a provider, confirm their Fusaka-ready client versions (Geth, Erigon, Reth, Nethermind, Besu).

PeerDAS + EIP-7918: Blob Capacity Scaling and Fee Floors

Fusaka reshapes Ethereum’s data availability layer, which powers rollups.

PeerDAS

Instead of every node downloading full blob data, validators sample pieces from peers, drastically reducing per-node load. This unlocks higher blob counts (10→14 per block shortly after activation).

EIP-7918: Blob Base Fee Floor

Blob fees can no longer sit near zero while L1 gas is high. They now follow a minimum fee linked to L1 execution cost.

A backtest shows the new rules would have generated:‍

-≈24,641 additional ETH in blob revenue

-Blob prices higher on ≈93% of days since Dencun

This redirects more value to ETH stakers and makes L2 DA costs more predictable, though slightly higher.

Action for rollups and DA-heavy apps:

-Update blob cost models

-Adjust batch sizes

-Monitor blob usage around activation

Verkle Trees and UX-Focused EIPs

Several smaller but impactful improvements land in Fusaka:

Verkle trees → smaller proofs, lighter clients, better mobile UX

EIP-7951 → native P-256 verification for WebAuthn and hardware-secure logins

EIP-7939 → new CLZ opcode for efficient bit operations

If you build wallets, zk systems, AA flows, or mobile clients, these are meaningful upgrades.

EIP-7917: Deterministic Proposer Lookahead & Based Rollups

Validators can now see in advance who will propose future blocks.
This unlocks:

-Preconfirmations

-Based rollups, where Ethereum validators sequence L2 transactions

-New MEV/tip flows that accrue to ETH stakers instead of centralized L2 sequencers

If you operate or design a rollup, expect roadmap conversations around integrating preconfirmations.

Builder Checklist Before Fusaka

Smart Contracts & Scripts

-Ensure no tx exceeds 16,777,216 gas

-Replay heavy operations on Holesky/Sepolia

-Break down deployments or migrations into smaller calls

SDKs, Wallets, Transaction Builders

-Add client-side validation for the new gas cap

-Update gas estimation logic

-Handle failures gracefully once mainnet enforces the rule

Nodes, RPC, and Data APIs

-Benchmark block ingestion assuming 150M gas blocks

-Update to Fusaka-compatible client releases

-Monitor blob usage and fee fluctuations

Rollups & DA Users

-Recalculate DA costs with the blob fee floor

-Test PeerDAS-driven blob throughput increases

-Evaluate based rollup strategy and preconfirmation UX

If you rely on Tatum RPC, Data API, or Notifications, ensure your staging environment points to Fusaka-ready testnets so you can measure gas patterns, blob usage, and indexing performance early.

Final Thoughts

Fusaka realigns Ethereum around three priorities:
scale L1, scale DA, improve UX.

It increases capacity, stabilizes blob pricing, removes harmful “mega-transactions”, and sets the foundation for based rollups. For developers, the main task is updating assumptions, especially around gas ceilings and blob behavior.

If you do that early, your contracts, rollups, and infra should transition smoothly the moment Fusaka hits mainnet.