[BUG] Internal useEnsFallbackConfig causes Wagmi storage pollution and inconsistent chain state

[myxtype]

Issue Description

When using ConnectKit, we discovered a problem of Wagmi storage pollution, which leads to inconsistent chain states. Specifically:

• Multiple Wagmi storage keys appear in the app (e.g., wagmi.store and a custom storage key)
• After a user manually switches the chain, it reverts to the default chain (Ethereum mainnet) upon reloading the page
• Chain state appears inconsistent across different components

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Root Cause

After debugging, we found that the issue originates from the internal useEnsFallbackConfig hook inside ConnectKit (located at packages/connectkit/src/hooks/useEnsFallbackConfig.ts).

The relevant code:

import { http, createConfig } from 'wagmi';
import { mainnet } from 'wagmi/chains';

const ensFallbackConfig = createConfig({
  chains: [mainnet],
  transports: {
    [mainnet.id]: http(),
  },
});

export function useEnsFallbackConfig(): Config | undefined {
  return !useChainIsSupported(1) ? ensFallbackConfig : undefined;
}

This internal configuration:

• Creates a separate Wagmi instance, even when the app already provides a custom Wagmi configuration
• Uses the default storage key, resulting in the coexistence of wagmi.store and the custom storage key
• Interferes with chain state management — when this fallback config is activated, it can override the user’s manually selected chain

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Steps to Reproduce

1. Configure ConnectKit and Wagmi, setting a custom storage key and default chain (e.g., BSC chain with ID 56).

2. Manually connect a wallet and switch to the BSC chain.

3. Refresh or reopen the app.

4. Observe the behavior: the app reconnects to Ethereum mainnet (chain ID 1).

5. Check localStorage:

   • wagmi.store contains chain ID 1
   • Custom storage key contains chain ID 56

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Expected Behavior

• The app should use the user-provided Wagmi configuration and storage settings.
• Chain state should remain consistent and unaffected by any internal fallback config.
• The user’s manual chain selection should be correctly persisted across sessions.