@moon-x/evm-adapter

Chain-aware EVM signing helpers for MoonX ephemeral signers.

The low-level signWithEphemeralSigner primitive in @moon-x/core signs an arbitrary keccak256 digest — which means the integrator is responsible for building the exact bytes to sign (EIP-191 prefixing, EIP-712 hashing, RLP serialization, EIP-7702 auth hashing) and for re-assembling the result into something broadcastable. That's the most security-sensitive and error-prone part of signing, and every integration ends up re-implementing the same viem glue.

This adapter does it for you. You pass intent — a message, typed data, a transaction — and get back a ready-to-use artifact.

Install

pnpm add @moon-x/evm-adapter viem

viem is a peer dependency, so your app's single viem instance is the one used.

Usage

import { createEvmSigner } from "@moon-x/evm-adapter";

const signer = createEvmSigner({
  apiPubHex,        // from provisioning
  apiPrivHex,       // never leaves your backend
  walletId,         // the EVM wallet the agent was provisioned for
  baseUrl,          // wallets backend URL
  secretKey,        // moon_sk_* (server-only; the sign routes are secret-key-only)
});

// EIP-191 personal message → 65-byte 0x signature
const sig = await signer.signMessage("gm");

// EIP-712 typed data → 65-byte 0x signature
const tdSig = await signer.signTypedData(typedData);

// Transaction → wire-ready serialized tx for eth_sendRawTransaction
const rawTx = await signer.signTransaction({
  type: "eip1559",
  chainId: 1,
  nonce: 0,
  to,
  value: 0n,
  maxFeePerGas: 2_000_000_000n,
  maxPriorityFeePerGas: 1_000_000_000n,
  gas: 21_000n,
});

// EIP-7702 authorization → signed authorization for authorizationList
const signedAuth = await signer.signAuthorization(authorization);

Scheme safety

The adapter enforces that the target wallet is ECDSA/secp256k1. Pointing it at an ed25519 (Solana) wallet throws EvmSchemeMismatchError instead of producing a valid-but-wrong signature — use @moon-x/solana-adapter for those.

Escape hatch

For custom chains or digests this adapter doesn't model, drop down to signWithEphemeralSigner from @moon-x/core/sdk and build the digest yourself.