[bug] Unhandled stale-session errors: 'No matching key' + setDefaultChain chainChanged fallout

[PaulRBerg]

Link to minimal reproducible example

https://app.sablier.com (public production app repro; not minimal yet)

Steps to Reproduce

1. Open https://app.sablier.com.
2. Connect a wallet through AppKit.
3. Let the tab sit for a while or disconnect/reconnect wallet state.
4. Trigger a network change (including chain switching paths that emit chainChanged).
5. Check browser console.

Summary

We are consistently seeing unhandled promise rejections from WalletConnect/AppKit internals in production:

• No matching key. session topic doesn't exist: <topic>
• TypeError: Cannot read properties of undefined (reading 'setDefaultChain')

The second error appears immediately after stale session-topic validation failures. We traced this to session-event/update processing and chain-change handling (onSessionUpdateRequest/isValidSessionTopic followed by onChainChanged -> setDefaultChain path).

Expected behavior:

• stale/deleted session topics should be handled internally without unhandled rejections
• chainChanged handling should not attempt setDefaultChain on an undefined provider/session state

Actual behavior:

• both errors surface as unhandled rejections and spam prod console/Sentry unless explicitly filtered

List of related npm package versions

• @reown/appkit@1.8.18
• @reown/appkit-adapter-solana@1.8.18
• @reown/appkit-adapter-wagmi@1.8.18
• @walletconnect/universal-provider@2.23.2 (transitive)
• @walletconnect/sign-client@2.23.2 (transitive)
• wagmi@2.19.5
• viem@2.45.2
• next@16.1.6
• react@19.2.4

Node.js Version

v25.6.0

Package Manager

bun@1.3.9

[linear]

REOWN-4467