Proposal: Galileo Upgrade

Proposal Title: Galileo Update on Scroll Mainnet.

Proposal Type: Governance.

Authors: Ahmed Castro, Filbert Nicholas, Péter Garamvölgyi

Summary

The purpose of this proposal is to inform the Scroll DAO of a proposed protocol upgrade, called Galileo, and to allow projects, users, and developers to prepare. As this is a core protocol upgrade, there is no associated funding request.

Executive Summary

I am Ahmed Castro, part of the Up Labs team. We propose the Galileo upgrade for consideration and execution. This upgrade improves Scroll's sequencer efficiency and integrates significant upcoming changes from Ethereum mainnet.

The following are the primary Galileo changes:

1. Implements the latest Ethereum EVM features.

2. Adopts a more accurate and resilient rollup fee model.

3. Reduces prover cycle consumption by 50%.

Motivation

The motivation for this protocol upgrade is to make Scroll more robust and efficient across the stack. By staying up to date with Ethereum's features and compatibility changes introduced by Fusaka, we ensure EVM developers on Scroll keep having a familiar experience, while simultaneously optimizing the internal sequencer and prover layers.

Execution

The upgrade code is developed by Up Labs. Deployment will be reviewed by the Security Council and executed by Up Labs.

Audit Report

As this upgrade does not modify significant smart contract logic, no external smart contract audits are necessary for this proposal.

An internal audit was conducted by the Up Labs team regarding the Statesless Block Verifier and Scroll REVM. The audit is available here.

Upgrade Timeline

If the proposal passes, the upgrade will be rolled out with the following timeline:

1. November 25th (tentative): Galileo Upgrade on Scroll Sepolia.

2. December 1st (Mon): Submit upgrade to governance proposal.

3. December 4th (Thu): Governance voting begins.

4. December 11th (Thu): Governance voting ends.

5. December 12th (Fri): The Security Council signs the upgrade transaction according to the voting result.

6. December 16th (tentative): Galileo Upgrade on Scroll mainnet.

These network upgrade times are tentative; node operators should keep an eye on the node release page.

Features & Change List

EVM Changes

Scroll will incorporate EVM changes included in the Fusaka upgrade to maintain a high degree of compatibility with Ethereum.

MODEXP Upper Bound & Gas Cost Increase This implements EIP-7823 and EIP-7883. The MODEXP precompile has long been a challenge, and has even been called a prover killer because the high computation required for large numbers is incredibly difficult for ZK provers to handle. By setting an upper bound and a fairer gas cost, the Scroll prover can better predict hardware requirements, even in worst-case scenarios.

secp256r1 Gas Costs Changes This precompile was introduced in Scroll's Euclid upgrade, as RIP-7212, to allow dApps to verify signatures from devices like iPhones, Androids, TEEs, and others. Fusaka introduces this precompile to Ethereum as EIP-7951 with slight changes, specifically to the precompile gas cost. Scroll will adopt these changes to maintain compatibility.

CLZ, a New Opcode: A new Count Leading Zeros CLZ EVM opcode will be introduced, following EIP-7939. This opcode is targeted to save significant proving time in zkVM provers. It will be included in Scroll so developers can use it in new dApps and compile with the latest versions of Solidity.

Fee Calculation Adjustments

Scroll is currently among the rollups with the lowest fees. The Fusaka upgrade introduces blob gas price changes via EIP-7918, and more changes will come through EIP-7892’s BPOs. To remain adaptable to these changes and continue providing low fees, Galileo introduces a new rollup fee structure.

As a reminder, rollup fee is what the sequencer charges to cover DA and proof verification costs, separate from normal execution gas. The new rollup fee for a transaction will be calculated as follows:

Where the components are defined as:

Instead of the previous “penalty over threshold” model, which used a step-function, Galileo’s rollup fee formula will price each transaction based on its actual compressed size, and will apply a quadratic penalty to large transactions. The goal of the penalty term is to disincentivize and prevent attacks that spam the network with large, poorly-compressible transactions. Fees for normal user transactions will remain low.

Prover Optimizations

The Galileo upgrade significantly improves Scroll's stateless execution performance within OpenVM.

Stateless verification of EVM execution requires efficient access to Scroll's state through the Merkle Patricia Trie (MPT). The previous implementation (Feynman) built the trie dynamically during block execution—a computationally intensive process that imposed significant overhead in zkVM cycles.

Galileo introduces an optimized approach using RISC Zero's cached trie. We now construct a partial MPT directly from the block's execution witness. This eliminates on-the-fly trie construction, achieving approximately 50% fewer zkVM cycles, enabling much faster proof generation.

Additionally, our prover stack has been upgraded to OpenVM v1.4.1, which contributes further performance gains across the entire proving pipeline.

Impact on Stakeholders

Most significant Galileo upgrades will occur at the protocol level. However, stakeholders should note the following changes.

Impact on Node Operators

As usual, l2geth node operators will need to upgrade their nodes to follow the Galileo upgrade on Scroll Sepolia and Scroll mainnet. Please keep an eye on the node releases, and contact the Scroll team if you have any questions.

Node operators should also be aware that following Ethereum’s Fusaka upgrade (which introduces EIP-7594 PeerDas), the L1 beacon node will not be able to serve blob data unless it is run as a supernode. For l2geth, it means that the --da.blob.beaconnode flag will only work with a beacon supernode, and node operators are encouraged to specify --da.blob.awss3 as a fallback blob data source.

Impact on Users

Users can expect a different gas fee pricing structure that more accurately reflects the L1 blob fee changes being introduced by Fusaka.

Impact on dApps and Tooling

Developers will be able to use the most recent EVM changes introduced in Fusaka, ensuring full compatibility with the latest Solidity versions.

Developers who use the secp256r1 precompile in their dapps should be aware that the pecompile gas cost will double, and evaluate the impact of this change on their system.

Developers operating their own nodes must ensure they upgrade their clients to support Galileo to fetch correct gas pricing. Developers relying on external node providers can expect this upgrade to be handled directly by their provider.