fix(rn-window): handle frame-ready plain string in handleMessage

[albertoelias-crossmint]

Description

Fixes a JSON parse error in React Native WebView transport when receiving the "frame-ready" message from the open-signer frame.

Root cause: EventsService.notifyReady() sends "frame-ready" as a plain string, but RNWebViewTransport.handleMessage() was attempting to parse all incoming messages as JSON.

Solution: Check for the "frame-ready" string before attempting JSON parsing and return early since this message doesn't need to be dispatched to listeners.

Test plan

• Manual testing: Load the email signer in React Native and confirm no JSON parse error appears in logs
• Verify normal JSON messages still parse and dispatch correctly

Human review checklist

• Confirm "frame-ready" messages don't need to be dispatched to listeners (the fix silently drops them)
• Consider if other plain string messages might need similar handling in the future

Package updates

• @crossmint/client-sdk-rn-window: patch (changeset added)

---

Link to Devin run: https://app.devin.ai/sessions/884e19777e1d4fa89a507ff8471ed740
Requested by: Alberto Elias (alberto.elias@paella.dev) (@albertoelias-crossmint)

[devin-ai-integration]

Original prompt from Alberto Elias

## Prompt to Fix React Native WebView JSON Parse Error  
  
**Problem:** The React Native WebView transport in `RNWebViewTransport.handleMessage()` fails when receiving the "frame-ready" message from the open-signer frame because it attempts to parse all messages as JSON, but "frame-ready" is sent as a plain string.  
  
**Files to modify:**  
- `packages/client/rn-window/src/transport/RNWebViewTransport.ts` - Update `handleMessage()` method [1-cite-0](#1-cite-0)   
  
**Root cause:**   
- `EventsService.notifyReady()` in open-signer sends "frame-ready" as plain string [1-cite-1](#1-cite-1)   
- `RNWebViewTransport.handleMessage()` tries to parse all messages as JSON [1-cite-2](#1-cite-2)   
  
**Solution:**  
Modify `handleMessage()` to check for "frame-ready" string before attempting JSON parsing:  
  
```typescript  
public handleMessage = (event: WebViewMessageEvent) => {  
    if (!this.isWebView) {  
        try {  
            const data = event.nativeEvent.data;  
              
            // Handle plain string messages like "frame-ready"  
            if (data === "frame-ready") {  
                // Frame is ready, no need to parse as JSON  
                return;  
            }  
              
            const parsedData = JSON.parse(data);  
            this.dispatchToListeners({  
                type: "message",  
                data: parsedData,  
            });  
        } catch (error) {  
            console.error(  
                "[RNTransport RN] Error parsing/handling WebView message:",  
                error instanceof Error ? error.message : String(error),  
                "Raw data:",  
                event.nativeEvent.data  
            );  
        }  
    }  
};  

Testing:
Verify the fix by:

1. Loading the email signer in React Native
2. Confirming no JSON parse error in logs
3. Ensuring normal JSON messages still parse correctly

You only need to look in the following repo: Crossmint/crossmint-sdk

</details>

[changeset-bot]

🦋 Changeset detected

Latest commit: 8fe02c4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
@crossmint/client-sdk-rn-window	Patch
expo-demo	Patch
@crossmint/client-sdk-react-native-ui	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

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1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
smart-wallet-auth-demo	Ignored			Dec 10, 2025 10:34pm