SyntaxError: "[Object Object]" is not valid JSON when parsing event.data

Description
When handling a message event, the following error occurs:
SyntaxError: "[Object Object]" is not valid JSON

This happens at the line:
const parsed = SuperJSON.parse(event.data);

Details

• File: index.js
• Line: 5924
• Stack: Vue DevTools, Vite, SuperJSON
  From the debug panel, event.data is sometimes an object, not a JSON string. When SuperJSON.parse is called on an object, it throws the above error.

Example of problematic data:

event.data = {
  payload: '{"json":{"event":{"event":"shutdown"}}}',
  source: "proxy->server"
}

Steps to Reproduce

1. Trigger a message event where event.data is an object instead of a JSON string.
2. The code tries to parse event.data using SuperJSON.parse.
3. The error is thrown: "[Object Object]" is not valid JSON.

Expected Behavior
The code should check if event.data is a string before parsing, or handle objects appropriately.

Environment

• OS: macOS m3
• Browser: 137.0.7151.120 (arm64)
• Project: Vue DevTools + Vite

Start at index.js line 5924, where event.data is passed to SuperJSON.parse, and inspect the message-event handling around it. Reproduce the case with event.data as the object shown in the issue, then verify that message events with object data no longer throw the reported SyntaxError while string data remains handled correctly.