Vitest Explorer fails to initialize on VS Code Insiders 1.139.0 while Stable works

Does this issue occur when all extensions are disabled?: N/A

This issue requires the Vitest Explorer extension to reproduce. However, it also occurs in a clean VS Code Insiders profile with only Vitest Explorer installed.

Version: 1.139.0-insider
Commit: 4fa9fcf245ad90eb1f21fae5ed0511515e068b1d
OS: macOS arm64

Vitest Explorer: 1.52.0
Vitest: 3.2.6
Node.js: 22.23.1

Steps to Reproduce:

1. Open a project containing a valid Vitest configuration in VS Code Insiders.
2. Install the Vitest Explorer extension.
3. Reload the window.
4. Vitest Explorer successfully resolves the configuration and starts the Vitest worker.
5. The WebSocket/RPC connection closes during initialization.
6. Vitest Explorer fails to load the configuration.

Relevant output:

[INFO] [v1.52.0] Vitest extension is activated because Vitest is installed or there is a Vite/Vitest config file in the workspace.
[INFO] [API] Resolving configs: bob-dashboard/vitest.config.js
[API] Spawning on-demand process...
[INFO] [API] Running Vitest v3.2.6 (bob-dashboard/vitest.config.js) with "/Users/youzonglin/.nvm/versions/node/v22.23.1/bin/node .../vitest.explorer-1.52.0/dist/worker.js"
[API] Vitest WebSocket connection closed, cannot call RPC anymore.
[API] On-demand process finished
[Error] There were errors during config load.
[Error] [birpc] rpc is closed, cannot call "getFiles"
[Error] Error: The extension could not load any config.

The same problem occurs when using:

"vitest.shellType": "terminal"

Output:

[TERMINAL] Initiated ws connection via ws://localhost:55105
[TERMINAL] Starting Vitest v3.2.6 (bob-dashboard/vitest.config.js) in the terminal
[API] Vitest v3.2.6 (bob-dashboard/vitest.config.js) terminal process created
[API] Vitest WebSocket connection closed, cannot call RPC anymore.
[Error] [birpc] rpc is closed, cannot call "getFiles"

Expected Result:

Vitest Explorer initializes successfully and displays the tests in the Testing panel.

Actual Result:

The Vitest worker starts, but the WebSocket/RPC connection is immediately closed and the extension reports:

[birpc] rpc is closed, cannot call "getFiles"
The extension could not load any config.

Additional Information:

• The exact same workspace works correctly in VS Code Stable.
• Running Vitest directly works correctly:

npx vitest --config vitest.config.js

• The issue reproduces in a clean VS Code Insiders profile with only Vitest Explorer installed.
• Multiple Vitest Explorer versions were tested and show the same behavior on Insiders.
• Both child_process and terminal modes fail.
• Node is correctly resolved to:

/Users/youzonglin/.nvm/versions/node/v22.23.1/bin/node

• NODE_OPTIONS, HTTP_PROXY, HTTPS_PROXY, ALL_PROXY, and NO_PROXY are not set.

Reproduce with VS Code Insiders 1.139.0, the clean profile, and Vitest Explorer using the listed child_process and terminal modes. Compare the WebSocket/RPC initialization with Stable, starting from the vitest.config.js worker.js flow and the extension-host connection; done when the configuration loads and tests appear in the Testing panel.