BigInt Conversion Error with @reown/walletkit on React Native Hermes

[xwartz]

Describe the bug

After migrating from @walletconnect/web3wallet to @reown/walletkit v1.2.7, our React Native app crashes with BigInt conversion errors when running on Hermes JavaScript engine. The app fails to initialize WalletKit and throws "Cannot convert BigInt to number" and "Maximum call stack size exceeded" errors.

SDK Version (if relevant)

• Client: JS (React Native)
• Version: @reown/walletkit@1.2.7

To Reproduce
Steps to reproduce the behavior:

1. Create a React Native app with Hermes enabled (RN 0.71.x)
2. Install @reown/walletkit@1.2.7 and related WalletConnect dependencies
3. Import and initialize WalletKit:

   import { WalletKit } from '@reown/walletkit'
   import { Core } from '@walletconnect/core'
   
   const signClient = await WalletKit.init({
     core: new Core({
       projectId: 'your-project-id',
       relayUrl: 'wss://relay.walletconnect.com'
     }),
     metadata: {
       name: 'Test App',
       description: 'Test',
       url: 'https://test.com',
       icons: []
     }
   })

4. See error: TypeError: Cannot convert BigInt to number, js engine: hermes

Expected behavior
WalletKit should initialize successfully on React Native Hermes, just like the previous @walletconnect/web3wallet did. The migration should be seamless without BigInt-related crashes.

Screenshots
Error logs:

ERROR ❌ BigInt polyfill error: {"error": "Maximum call stack size exceeded (native stack depth)", "value": "0x6c44198c4a475817", "valueType": "string"}
ERROR ❌ BigInt polyfill error: {"error": "Maximum call stack size exceeded", "value": 4294967295, "valueType": "number"}

Desktop (please complete the following information):

• OS: macOS
• Development Environment: React Native CLI
• Version: React Native 0.71.x

Smartphone (please complete the following information):

• Device: iPhone/Android simulators and physical devices
• OS: iOS 15+/Android API 21+
• JavaScript Engine: Hermes
• Version: React Native 0.71.x

Additional context

• The previous @walletconnect/web3wallet worked perfectly with the same setup
• We've tried implementing comprehensive BigInt polyfills using big-integer library, but the errors persist
• The issue appears to be internal to how @reown/walletkit handles BigInt operations
• This is a blocking issue preventing React Native developers from upgrading to the latest WalletConnect SDK
• Specific problematic values include large hex strings and numbers exceeding safe integer limits
• The error occurs during WalletKit initialization, not during specific wallet operations

Migration context:
Before (Working):

import { Web3Wallet } from '@walletconnect/web3wallet'
signClient = await Web3Wallet.init({ core, metadata })

After (Crashing):

import { WalletKit } from '@reown/walletkit'
signClient = await WalletKit.init({ core, metadata })

[linear]

WK-700 BigInt Conversion Error with @reown/walletkit on React Native Hermes

[ignaciosantise]

hey @xwartz 👋 The library is being used in projects with newer versions of react native and we are not having issues with Big Integers, so this might be an issue with Hermes on RN 0.71.x

How did you polyfill the bigint manually?

Can you try adding this before importing @reown/walletkit?

const BigInt = require('big-integer');

Object.assign(global, {
  BigInt: BigInt
});

import { WalletKit } from '@reown/walletkit'

[xwartz]

Thanks for the response. We already have big-integer polyfill implemented in our project since we've been using @walletconnect/web3wallet for a while.

Here's our current BigInt polyfill setup in our shim.js:

// because RN 0.71 JSC engine doesn't support BigInt, so manually polyfill it
const patchedBigInt = require('big-integer')

if (typeof BigInt === 'undefined') {
  global.BigInt = patchedBigInt
}

This polyfill has been working fine with @walletconnect/web3wallet@1.15.0. However, when we try to migrate to @reown/walletkit, we encounter the error:

TypeError: Cannot convert BigInt to number, js engine: hermes

The issue seems to be that the new @reown/walletkit library has different BigInt usage patterns that aren't fully compatible with the big-integer polyfill approach that worked with the previous WalletConnect libraries.

[ignaciosantise]

@xwartz can you share a minimal reproducible example so i can repro locally? I've just created a sample project using react native 0.71 and i had no issues initializing WalletKit. I didn't have to polyfill BigInt either.

  "dependencies": {
    "@react-native-async-storage/async-storage": "^1.24.0",
    "@react-native-community/netinfo": "^11.4.1",
    "@reown/walletkit": "^1.2.8",
    "@walletconnect/react-native-compat": "^2.21.4",
    "fast-text-encoding": "^1.0.6",
    "react": "18.2.0",
    "react-native": "0.71.0",
    "react-native-get-random-values": "^1.11.0"
  },

Also remember to import react-native-compat before using walletkit:

import '@walletconnect/react-native-compat';
import {WalletKit} from '@reown/walletkit';
import {Core} from '@walletconnect/core';