python.defaultInterpreterPath fails to resolve ${workspaceFolder} correctly on Windows and may duplicate the workspace path

[SuSuSoo]

Environment data

• Python Environments extension version: 1.20.1
• Python extension (ms-python.python) version: 2026.4.0
• VS Code version (Help -> About): 1.108.0 (user setup)
• VS Code commit: 94e8ae2b28cb5cc932b86e1070569c4463565c37
• VS Code date: 2026-01-08T13:53:10.781Z
• Electron: 39.2.7
• ElectronBuildId: 12953945
• Chromium: 142.0.7444.235
• Node.js: 22.21.1
• V8: 14.2.231.21-electron.0
• OS and version: Windows_NT x64 10.0.19044
• Python version (& distribution if applicable, e.g. Anaconda): CPython 3.11.13
• Environment manager in use (venv / conda / pyenv / poetry / pipenv / system / uv / other): uv
• Shell (bash / zsh / fish / pwsh / cmd / other): pwsh
• Remote / container scenario (none / WSL / SSH Remote / Dev Container / Codespaces): none
• Workspace type (single folder / multi-root / mono-repo): single folder
• Is this a regression? If yes, last known working extension version: likely related to earlier ${workspaceFolder} resolution regressions, but I do not have a confirmed last known good version

Repro Steps

1. Create a Windows workspace with a local virtual environment, for example:

   D:\Dev\AlexM\Workspace\Python\forum-crawler\
     .vscode\
       settings.json
     .venv\
       Scripts\
         python.exe
     pyproject.toml
     uv.lock
   

2. Put the following in the workspace .vscode/settings.json:

   {
     "python.defaultInterpreterPath": "${workspaceFolder}\\.venv\\Scripts\\python.exe",
     "python.terminal.activateEnvironment": true
   }

3. Make sure the interpreter file actually exists at:

   D:\Dev\AlexM\Workspace\Python\forum-crawler\.venv\Scripts\python.exe
   

4. Open the folder in VS Code and reload the window.

5. Observe that a startup warning appears saying that the default interpreter path could not be resolved.

6. Open Settings UI and search for python.defaultInterpreterPath.

7. Confirm that:

   • the User tab shows the user-level value
   • the Workspace tab shows the workspace override
   • the Workspace tab displays the exact configured value:

   ${workspaceFolder}\.venv\Scripts\python.exe
   

8. Replace the workspace setting with the equivalent absolute path:

   {
     "python.defaultInterpreterPath": "D:\\Dev\\AlexM\\Workspace\\Python\\forum-crawler\\.venv\\Scripts\\python.exe",
     "python.terminal.activateEnvironment": true
   }

9. Reload the window again.

10. Observe that the warning disappears immediately.

Expected behavior

If python.defaultInterpreterPath is configured at workspace scope as:

"${workspaceFolder}\\.venv\\Scripts\\python.exe"

and the interpreter file exists, the path should resolve successfully and no warning should be shown.

The workspace-relative form should behave the same as the equivalent absolute path.

Actual behavior

On startup, VS Code shows a warning equivalent to:

Default interpreter path '${workspaceFolder}\.venv\Scripts\python.exe' could not be resolved:
Could not resolve interpreter path '${workspaceFolder}\.venv\Scripts\python.exe'

Important detail:

• the workspace setting is clearly present and visible in the Workspace settings UI
• the target interpreter file exists
• the error message still contains the literal ${workspaceFolder} token instead of an expanded absolute path
• replacing the exact same value with an absolute path removes the warning immediately

This makes it look like the workspace setting is being read correctly, but ${workspaceFolder} is not being expanded in at least one interpreter resolution path.

After reviewing the logs, there also seems to be a second symptom: in addition to the unexpanded variable case, at least one code path constructs a malformed interpreter path by duplicating the workspace folder name before .venv\Scripts\python.exe.

Logs

Excerpts from the "Python Environments" output:

2026-06-17T01:18:44.510+08:00 [info] Discovered env: D:\Dev\AlexM\Workspace\Python\forum-crawler\.venv\Scripts\python.exe
2026-06-17T01:18:45.757+08:00 [error] [pet] Failed to execute Python to resolve info "D:\Dev\AlexM\Workspace\Python\forum-crawler\forum-crawler\.venv\Scripts\python.exe": The system cannot find the path specified. (os error 3)
2026-06-17T01:18:45.758+08:00 [warning] [priorityChain] D:\Dev\AlexM\Workspace\Python\forum-crawler defaultInterpreterPath '${workspaceFolder}\forum-crawler\.venv\Scripts\python.exe' unresolvable, falling back to auto-discovery
2026-06-17T01:18:45.830+08:00 [info] Resolved Python Environment C:\Users\AlexM\AppData\Roaming\uv\python\cpython-3.11.13-windows-x86_64-none\python.exe
2026-06-17T01:18:45.850+08:00 [info] [interpreterSelection] forum-crawler: forum-crawler (3.11.13) (source: autoDiscovery)
2026-06-17T01:18:45.873+08:00 [error] [pet] Failed to execute Python to resolve info "C:\Users\AlexM\AppData\Local\Programs\VSCode\${workspaceFolder}\forum-crawler\.venv\Scripts\python.exe": The system cannot find the path specified. (os error 3)
2026-06-17T01:18:45.874+08:00 [warning] [priorityChain:global] defaultInterpreterPath '${workspaceFolder}\forum-crawler\.venv\Scripts\python.exe' unresolvable, falling back to auto-discovery

Excerpts from the "Python" output:

2026-06-17T01:18:39.801+08:00 [info] Python interpreter path: .\.venv\Scripts\python.exe
2026-06-17T01:18:44.835+08:00 [warning] Identifier for virt-virtualenv failed to identify D:\Dev\AlexM\Workspace\Python\forum-crawler\forum-crawler\.venv\Scripts\python.exe [Error: ENOENT: no such file or directory, scandir 'D:\Dev\AlexM\Workspace\Python\forum-crawler\forum-crawler\.venv\Scripts']
2026-06-17T01:18:44.896+08:00 [info] > .\forum-crawler\.venv\Scripts\python.exe -I C:\Users\AlexM\.vscode\extensions\ms-python.python-2026.4.0-win32-x64\python_files\get_output_via_markers.py C:\Users\AlexM\.vscode\extensions\ms-python.python-2026.4.0-win32-x64\python_files\interpreterInfo.py
2026-06-17T01:18:45.000+08:00 [error] Command failed: D:\Dev\AlexM\Workspace\Python\forum-crawler\forum-crawler\.venv\Scripts\python.exe ...
2026-06-17T01:18:45.054+08:00 [info] > .\.venv\Scripts\python.exe -I C:\Users\AlexM\.vscode\extensions\ms-python.python-2026.4.0-win32-x64\python_files\get_output_via_markers.py C:\Users\AlexM\.vscode\extensions\ms-python.python-2026.4.0-win32-x64\python_files\interpreterInfo.py

These logs suggest two closely related problems:

1. `${workspaceFolder}` is not expanded in at least one resolution path.
2. Another path appears to incorrectly append the workspace folder name again, producing `...\forum-crawler\forum-crawler\.venv\Scripts\python.exe` instead of `...\forum-crawler\.venv\Scripts\python.exe`.

Despite the warning, the correct interpreter is still discovered and selected later through auto-discovery.

Additional context

• This does not appear to be a missing-Python or missing-interpreter problem. The interpreter exists and is executable.

• This also does not appear to be a case where workspace settings are ignored. The Workspace settings UI shows the workspace override correctly.

• The most important signal is that the warning message still contains the literal ${workspaceFolder} token. That suggests the setting is read, but variable expansion fails in at least one path.

• The logs add another important signal: the extension first discovers the correct local interpreter, but later tries to resolve a malformed path with a duplicated workspace segment, e.g. ...\forum-crawler\forum-crawler\.venv\Scripts\python.exe.

• In other words, this no longer looks like only a warning-message bug. It looks like an actual path composition / resolution bug, followed by fallback to auto-discovery.

• Current workaround:

  {
    "python.defaultInterpreterPath": "D:\\Dev\\AlexM\\Workspace\\Python\\forum-crawler\\.venv\\Scripts\\python.exe"
  }

  This works, but it defeats the portability benefits of ${workspaceFolder} in checked-in workspace settings.

• This seems related to earlier ${workspaceFolder} / defaultInterpreterPath issues, but I am filing this as a fresh report because the behavior is still reproducible and the previous discussion was closed.

• VS Code About information used for this report:

  • Version: 1.108.0 (user setup)
  • Commit: 94e8ae2b28cb5cc932b86e1070569c4463565c37
  • Date: 2026-01-08T13:53:10.781Z
  • Electron: 39.2.7
  • ElectronBuildId: 12953945
  • Chromium: 142.0.7444.235
  • Node.js: 22.21.1
  • V8: 14.2.231.21-electron.0
  • OS: Windows_NT x64 10.0.19044