In a fresh milestone, Pectra has been activated on Arbitrum, Ethereum’s leading layer-2 network. A new upgrade, ArbOS 40 “Callisto,” unlocks powerful new primitives for account abstraction, zk tooling and developer UX.
Announced via a recent tweet, ArbOS 40 “Callisto” is now live on Arbitrum One and Nova. This upgrade brings new capabilities from Ethereum’s Pectra hard fork, including EIP-7702 (Account Abstraction), EIP-2537 (BLS Precompile), EIP-2935 (Block Hash Access) and a minor Stylus fix for devs.
EIP-7702 brings more account abstraction to Arbitrum chains. Externally Owned Accounts (EOAs) can temporarily include executable code during a transaction. This enables account abstraction-like features such as delegation, batching, transaction sponsorship and sub-key permission control.
Pectra is now live on Arbitrum!
Builders can now access one-click swaps, gas sponsorships, and more
More UX. More innovation. Arbitrum Everywhere pic.twitter.com/Kksgl6DKma
— Arbitrum (@arbitrum) June 18, 2025
ArbOS 40 also integrates EIP 2537 (native BLS precompiles). This EIP introduces precompiles on the BLS12-381 curve, boosting efficiency and security.
The update also introduces EIP-2935, which adds access to recent block hashes on L2 and improves Trustless messaging, Oracle syncing and L2 stateless clients. This allows for more accessible and trustless historical data retrieval for Arbitrum chains.
ArbOS 40 also includes a fix to the Stylus VM’s handling of nonexistent contracts in cache lookups. This makes developer workflows smoother for Rust builders on Arbitrum.
Ethereum Pectra upgrade
The Pectra network upgrade was activated on the Ethereum mainnet on May 7, 2025, at epoch 364032. The Pectra upgrade, which followed last year’s Dencun upgrade, added functionality to augment Ethereum accounts, improve the validator experience and support L2 scalability.
EIP-7702 was a significant step toward universal account abstraction by allowing users to upgrade their Externally Owned Accounts (EOAs) with smart contract capability. Pectra’s three new EIPs, 7251, 7002 and 6110, also improved the validator experience.
The main change in Pectra is EIP-7691, which doubles Ethereum’s blob throughput. Blobs, introduced with the Dencun upgrade, are ephemeral data storage units that L2s can employ to send compressed transaction data and proofs to Ethereum L1.
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