[ARBITRUM] [CONSTITUTIONAL] AIP: ArbOS Version 40 Callisto
Type: Constitutional AIP
Abstract
This AIP proposes to upgrade Arbitrum One and Arbitrum Nova to ArbOS 40 “Callisto”. Callisto adds support for relevant Execution Layer (EL) changes from Ethereum’s upcoming Pectra upgrade (H1 2025) and a small Arbitrum Stylus related fix. Among the EL changes include a way for Externally Owned Accounts (EOAs) to execute smart contract code directly from their addresses (via EIP-7702) and new pre-compiles to efficiently perform operations over the BLS12-381 elliptic curve, including those for BLS signature verification (via EIP-2537).
While the goal of the proposed ArbOS 40 “Callisto” upgrade is to eventually be available for adoption by any Arbitrum Chain, this proposal only concerns the Arbitrum One and Arbitrum Nova chains, as these two chains are governed by the Arbitrum DAO. On a high level, an ArbOS upgrade can be interpreted as Arbitrum’s equivalent of a hard fork - more can be read about the subject over in Arbitrum ArbOS upgrades here.
Please note that ArbOS Version 40 “Callisto” is a proposed upgrade that builds upon ArbOS version 32 which has been previously adopted by the ArbitrumDAO - this proposal increments the version number to 40 instead of 33 due to technical details that allow for better Orbit chain customizability as explained here.
Changes that will be included in ArbOS 40 Callisto:
EIP-7702: Set EOA Account code
EIP-7702 introduces a new transaction type that allows Externally Owned Accounts (EOAs) to set executable code adding account-abstraction functionality to EOAs such as delegation, batching, sponsorship, and privilege de-escalation. In terms of batching, multiple operations can be combined (ex. token approval, token spend) in an atomic transaction. Transaction sponsorship or paymaster support can also be extended to EOAs. Discrete permissioning can also be enabled with the use of sub-keys.
EIP-2537: Precompile for BLS12-381 curve operations
This EIP introduces precompiles for performing cryptographic operations on the BLS12-381 curve and focuses on enhancing the efficiency and security of those operations. This cryptographic primitive unlocks 120+ bits of security for operations over the pairing-friendly curves, compared to the existing BN254 precompile which only provides 80 bits of security. BLS signature verification is the primary use case for this EIP, though many other applications that rely on point additions, multiplications, and pairing operations stand to gain from this proposal; examples are zkSNARKS, cross-chain interactions, randomness beacons, and vector commitments.
EIP-2935: Serve historical block hashes from state
This EIP proposes storing a wider window of block hashes in the storage of a dedicated system contract. Bundling historical block hashes within the state enables efficient data retrieval for applications that require extended access to historical block hashes, like stateless clients. If approved, ArbOS 40 will adapt this EIP to the L2 and store the same number of L2 block hashes that are generated in the time it takes for 8192 L1 blocks to be built - this is approximately 27 hours worth of L2 block hashes.
Type: Constitutional AIP
Abstract
This AIP proposes to upgrade Arbitrum One and Arbitrum Nova to ArbOS 40 “Callisto”. Callisto adds support for relevant Execution Layer (EL) changes from Ethereum’s upcoming Pectra upgrade (H1 2025) and a small Arbitrum Stylus related fix. Among the EL changes include a way for Externally Owned Accounts (EOAs) to execute smart contract code directly from their addresses (via EIP-7702) and new pre-compiles to efficiently perform operations over the BLS12-381 elliptic curve, including those for BLS signature verification (via EIP-2537).
While the goal of the proposed ArbOS 40 “Callisto” upgrade is to eventually be available for adoption by any Arbitrum Chain, this proposal only concerns the Arbitrum One and Arbitrum Nova chains, as these two chains are governed by the Arbitrum DAO. On a high level, an ArbOS upgrade can be interpreted as Arbitrum’s equivalent of a hard fork - more can be read about the subject over in Arbitrum ArbOS upgrades here.
Please note that ArbOS Version 40 “Callisto” is a proposed upgrade that builds upon ArbOS version 32 which has been previously adopted by the ArbitrumDAO - this proposal increments the version number to 40 instead of 33 due to technical details that allow for better Orbit chain customizability as explained here.
Changes that will be included in ArbOS 40 Callisto:
EIP-7702: Set EOA Account code
EIP-7702 introduces a new transaction type that allows Externally Owned Accounts (EOAs) to set executable code adding account-abstraction functionality to EOAs such as delegation, batching, sponsorship, and privilege de-escalation. In terms of batching, multiple operations can be combined (ex. token approval, token spend) in an atomic transaction. Transaction sponsorship or paymaster support can also be extended to EOAs. Discrete permissioning can also be enabled with the use of sub-keys.
EIP-2537: Precompile for BLS12-381 curve operations
This EIP introduces precompiles for performing cryptographic operations on the BLS12-381 curve and focuses on enhancing the efficiency and security of those operations. This cryptographic primitive unlocks 120+ bits of security for operations over the pairing-friendly curves, compared to the existing BN254 precompile which only provides 80 bits of security. BLS signature verification is the primary use case for this EIP, though many other applications that rely on point additions, multiplications, and pairing operations stand to gain from this proposal; examples are zkSNARKS, cross-chain interactions, randomness beacons, and vector commitments.
EIP-2935: Serve historical block hashes from state
This EIP proposes storing a wider window of block hashes in the storage of a dedicated system contract. Bundling historical block hashes within the state enables efficient data retrieval for applications that require extended access to historical block hashes, like stateless clients. If approved, ArbOS 40 will adapt this EIP to the L2 and store the same number of L2 block hashes that are generated in the time it takes for 8192 L1 blocks to be built - this is approximately 27 hours worth of L2 block hashes.
Minor Stylus fix to correct caching behavior for contracts that do not exist
Minor Stylus fix to correct caching behavior for contracts that do not exist
Currently, Stylus will cache results from calling account_code and account_code_size for a contract that does not exist. We would like to propose a fix to address this so that the call returns the correct information that properly reflects the latest state of the contract’s code or code size. This change will not increment the Stylus version and so a re-activation of already-deployed Stylus contracts will not be required.
Pectra changes that are not included in the proposed ArbOS 40 Callisto Upgrade
Support and implementation for the following EIPs are not planned to be part of ArbOS 40 Callisto:
- All Ethereum Consensus Layer (CL) Pectra changes (EIP-6610, EIP-7002, EIP-7251, EIP-7549, EIP-7691) because Arbitrum chains do not have a beacon chain and therefore do not have a peer-to-peer layer like Ethereum does.
- EIP-7623: Increase calldata cost: because block size variance is less of a concern on Arbitrum chains. This is because of two reasons. First, Arbitrum chains do not require nodes to send blocks over the network through its peer-to-peer layer and instead rely on the parent chain’s RPC to retrieve block data. Secondly, because Arbitrum block sizes are already limited to ~100KB and so increasing calldata cost is not expected to reduce Arbitrum block sizes.
- EIP-7685: General purpose execution layer requests: because Arbitrum chains do not have a beacon chain and, therefore, there
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Off-Chain Vote
Timeline
Feb 20, 2025Proposal created
Feb 20, 2025Proposal vote started
Feb 26, 2025Proposal vote ended
Mar 26, 2026Proposal updated