dynamic registration of watchedFiles does not respect files outside workspace

[Sysix]

Background

Not sure if this is a bug with the LSP-communication, or it is how VS Code works 🤷. Feels still wrong

Project Setup

- /home/project/
  - .vscode/
    - settings.json
- /home/outside-project/
  - watched-file.txt

Opening the project with code /home/project
My extension has a setting where I can define the path for the watched file.
Example: my-extenion.watchingFiles: "/home/outside-project/watched-file.txt"

Issue

My LSP Server tells VS Code to watch for the file outside its project:

2026-05-29 14:22:37.762 [info] [Trace - 2:22:37 PM] Received request 'client/registerCapability - (0)'.
2026-05-29 14:22:37.762 [info] Params: {
    "registrations": [
        {
            "id": "watcher-file:///home/project",
            "method": "workspace/didChangeWatchedFiles",
            "registerOptions": {
                "watchers": [
                    {
                        "globPattern": "/home/outside-project/watched-file.txt",
                        "kind": 7
                    },
                    {
                        "globPattern": {
                            "baseUri": "file:///home/project",
                            "pattern": "**/tsconfig*.json"
                        },
                        "kind": 7
                    }
                ]
            }
        }
    ]
}

But VS Code does never send a workspace/didChangeWatchedFiles notification to the server, when editing the file.
When watched-file.txt is inside /home/project/ it works as expected with the absolute path.

2026-05-29 14:37:07.043 [info] [Trace - 2:37:07 PM] Sending notification 'workspace/didChangeWatchedFiles'.
2026-05-29 14:37:07.043 [info] Params: {
    "changes": [
        {
            "uri": "file:///home/project/watched-file.txt",
            "type": 2
        }
    ]
}

[DavyLandman]

Looks like for out of workspace watches you have to use a relative pattern: https://code.visualstudio.com/api/references/vscode-api#workspace.createFileSystemWatcher (see the "Out of workspace file watching" section in examples).

Maybe an interesting issue to raise in the VS Code repo that it won't detect the file path is outside the repo and rewrite that internally?