All Quai chains are interoperable and composed into a coordinated network. Transactions can be sent from any Quai zone chain to any Quai zone chain, ensuring Quai's usability as a single, composable network.

Cross-chain transactions in Quai are referred to as external transactions (ETXs), and use hash linked references to ensure atomic state transitions across chains. Quai Network uses new EVM opcodes to facilitate ETXs. The braided structure of Quai Network also enables multi-chain smart contracts and cross-chain contract interactions. While contracts can be deployed to a single Quai thread in a similar way that contracts are traditionally deployed on a single-threaded blockchain, developers also have the ability to deploy contracts across multiple or all Quai chains to maintain the operability of dapps across the network.

Double-spend attacks attempting to take advantage of Quai's interoperability are protected by atomic rollbacks, meaning that if a dominant chain rolls back all chains subordinate to it will roll back to the canonical state as well.