MetaMask - RPC Error: Unsupported non-optional capabilities: paymasterService

[miguelmota]

According to the thirdweb docs I should be able to use paymaster with MetaMask. From docs:

Using EIP-7702 with External Wallets (EIP-5792)
Don’t want to embed an in-app wallet? No problem. EIP-5792 lets you tap into the same 7702 capabilities from any external wallet—like Metamask and Coinbase Wallet —via the sendCalls RPC method.

Sponsoring Gas & Batching Transactions

The useSendCalls React hook (or the plain sendCalls function in vanilla TypeScript) lets you bundle multiple calls into one and attach a paymaster so your dApp covers the gas:

import { useSendCalls } from "thirdweb/react";

const { mutate: sendCalls, data: bundleId } = useSendCalls();
await sendCalls({
client,
 calls: [sendTx1, sendTx2],
 capabilities: {
   paymasterService: {
     url: `https://${CHAIN.id}.bundler.thirdweb.com/${client.clientId}`,
   },
 },
});

This enabled single signature, gas-free, batched execution on exernal wallets like Metamask!

---

I tried the code in a sample react app (gist) and on Sepolia, using MetaMask Version 12.17.3 and get the error:

inpage.js:1 MetaMask - RPC Error: Unsupported non-optional capabilities: paymasterService {code: 5700, message: 'Unsupported non-optional capabilities: paymasterService', stack: '{\n  "code": 5700,\n  "message": "Unsupported non-op…fbeogaeaoehlefnkodbefgpgknn/common-2.js:1:1391130'}

---

Any ideas on why paymaster doesn't work with MetaMask?

[linear]

TOOL-4601 MetaMask - RPC Error: Unsupported non-optional capabilities: paymasterService

[joaquim-verges]

@miguelmota for EIP5792, you should always check the exposed capabilities of the wallet you're interacting with.

you can call useCapabilities() in react or getCapabilities() in TS with a given wallet, like shown here: https://playground.thirdweb.com/connect/account-abstraction/5792

for metamask, you'll see that they don't support the paymaster capability, only 'atomic' which is multi tx batching

[miguelmota]

@joaquim-verges Thanks for the clarification, I was confused by the wording in the docs since it implied MetaMask supported paymaster capability.