Using Native Atomic Composability

Cross-interface calls go through the gateway contract of the caller's interface. The sections below describe how to initiate a cross-interface call from each interface.

EVM to Michelson

The EVM-to-Michelson gateway is a precompile deployed at:

0xff00000000000000000000000000000000000007

callMichelson

Call a Michelson contract by providing:

Parameter	Type	Description
destination	address	The KT1 contract address on the Michelson interface
entrypoint	string	The target entrypoint name
data	bytes	Michelson-encoded parameters

interface IRuntimeGateway {
    function callMichelson(
        address destination,
        string calldata entrypoint,
        bytes calldata data
    ) external payable;
}

IRuntimeGateway gateway = IRuntimeGateway(
    0xff00000000000000000000000000000000000007
);
gateway.callMichelson(kt1Address, "default", michelsonParams);

The data parameter must be encoded in Michelson binary format. On-chain encoding libraries are available to help construct these payloads from within Solidity contracts.

FA1.2 wrapper

For calling FA1.2 token contracts specifically, a convenience precompile is available at:

0xff00000000000000000000000000000000ffff09

This precompile provides approve and transfer methods that handle Michelson parameter encoding automatically, without requiring manual binary encoding.

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Michelson to EVM

The Michelson-to-EVM gateway is an enshrined contract deployed at:

KT18oDJJKXMKhfE1bSuAPGp92pYcwVDiqsPw

call_evm

Call an EVM contract by providing the same parameters as the EVM-to-Michelson gateway: the destination address, entrypoint selector, and ABI-encoded data. Additionally, it accepts as an optional parameter a callback, which takes the form of a Michelson contract address. This addresses the specifics of Michelson, in which contract calls do not return a value.

ERC-20 wrapper

For calling ERC-20 token contracts specifically, a convenience contract is available at:

KT18oDJJKXMKhfE1bSuAPGp92pYcwVKvCChb

This contract provides approve and transfer methods with a Michelson-friendly interface.

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Return values

Return values from cross-interface calls are encoded in the callee's native format:

• EVM → Michelson: The Michelson return value is ABI-encoded as bytes and returned to the calling Solidity contract. For non-effectful calls (read-only views), use the call_view entry point on the Michelson gateway.
• Michelson → EVM: The EVM return value (ABI-encoded bytes) is passed back to a callback contract specified via the KT1<MERG>%with_result entrypoint. The callback contract must implement handling for the raw bytes.

On-chain libraries for encoding and decoding across runtimes are provided to simplify this.

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Gas and fees

When making a cross-interface call, the caller does not set an explicit gas limit for the callee — the runtime converts the caller's remaining gas automatically using the conversion coefficient. See Resources for details.

Fees for cross-interface transactions follow the same structure as single-interface transactions. The total fee covers execution in both runtimes.