Python SDK - Multi-Agent Transactions

Multi-agent transactions allow multiple accounts to participate in the logic of a Move contract.

This can be used to require multiple parties agree to a transaction before executing or to use resources from multiple accounts.

Writing Multi-Agent Transactions

Creating and executing a multi-agent transaction follows a similar flow to the regular transaction flow, but with several notable differences.

1. Build a raw transaction, then wrap it in MultiAgentRawTransaction with each additional signer.

   Note

   Replace the function below with an entry function that actually requires multiple signers. coin::transfer is shown only to demonstrate the API.

   raw_txn = await aptos.transaction.build(
       sender=alice.address,
       payload=TransactionPayload(payload),
   )
   multi_agent_txn = MultiAgentRawTransaction(raw_txn, [bob.address])

2. Sign once for each signer.

   alice_auth = multi_agent_txn.sign(alice.private_key)
   bob_auth = multi_agent_txn.sign(bob.private_key)

3. Combine the signatures with a MultiAgentAuthenticator.

   authenticator = Authenticator(
       MultiAgentAuthenticator(
           sender=alice_auth,
           secondary_signers=[(bob.address, bob_auth)],
       )
   )

4. Submit the signed transaction.

   txn_hash = await aptos.transaction.submit(SignedTransaction(raw_txn, authenticator))

5. Wait for the transaction to resolve.

   result = await aptos.transaction.wait_for_transaction(txn_hash)

Python Multi-Agent Code Sample

import asyncio

from aptos_sdk.v2 import Account, Aptos, AptosConfig, Network
from aptos_sdk.v2.bcs import Serializer
from aptos_sdk.v2.errors import TransactionFailedError
from aptos_sdk.v2.transactions import (
    Authenticator,
    EntryFunction,
    MultiAgentAuthenticator,
    MultiAgentRawTransaction,
    SignedTransaction,
    TransactionArgument,
    TransactionPayload,
)
from aptos_sdk.v2.types import StructTag, TypeTag


async def main():
    async with Aptos(AptosConfig(network=Network.DEVNET)) as aptos:
        alice = Account.generate()
        bob = Account.generate()

        await asyncio.gather(
            aptos.faucet.fund_account(alice.address, 100_000_000),
            aptos.faucet.fund_account(bob.address, 10_000_000),
        )

        payload = EntryFunction.natural(
            "0x1::coin",
            "transfer",
            [TypeTag(StructTag.from_str("0x1::aptos_coin::AptosCoin"))],
            [
                TransactionArgument(bob.address, Serializer.struct),
                TransactionArgument(5_000, Serializer.u64),
            ],
        )
        raw_txn = await aptos.transaction.build(
            sender=alice.address,
            payload=TransactionPayload(payload),
        )
        multi_agent_txn = MultiAgentRawTransaction(raw_txn, [bob.address])

        alice_auth = multi_agent_txn.sign(alice.private_key)
        bob_auth = multi_agent_txn.sign(bob.private_key)
        authenticator = Authenticator(
            MultiAgentAuthenticator(
                sender=alice_auth,
                secondary_signers=[(bob.address, bob_auth)],
            )
        )

        txn_hash = await aptos.transaction.submit(SignedTransaction(raw_txn, authenticator))
        try:
            result = await aptos.transaction.wait_for_transaction(txn_hash)
            print(f"Success: {result['success']}")
        except TransactionFailedError as err:
            print(f"Expected without a multi-signer entry function: {err}")


asyncio.run(main())

Common Errors

NUMBER_OF_SIGNER_ARGUMENTS_MISMATCH - This happens when you are attempting to do multi-agent signing for a function which does not require that number of accounts. For example, if you try using multiple signatures for a 0x1::aptos_account::transfer function - it only expects one address, and so produces an error when more than one is provided.