Regression: noConfigScripts appended to PATH without separator (2025.18.0) — bug from #843/#882 returned #1011

Summary

The debugpy extension appends its noConfigScripts directory to the integrated terminal's PATH without a leading semicolon, mangling whichever entry was last in the user's PATH. This appears to be a regression of #843 (closed by #958) and #882 — both closed, but the bug is reproducible on 2025.18.0.

Environment

• VS Code: 1.117.0
• ms-python.debugpy: 2025.18.0-win32-x64
• ms-python.python: 2026.4.0-win32-x64
• OS: Windows 11 Pro 26200
• Shell: PowerShell 7.6.0 (pwsh.exe)

Steps to reproduce

1. On Windows, ensure your user PATH does not end with a trailing semicolon (this is normal — Windows strips them on save). Note the last entry.
2. Open a new integrated terminal in VS Code with the Python extension active.
3. Run $env:Path -split ';' | Select-Object -Last 1.

Expected

The last PATH entry equals the user's PATH final entry, intact. The injected noConfigScripts directory appears as its own separate entry preceding it (or after, separated by ;).

Actual

The user's final PATH entry is concatenated with c:\Users\<me>\.vscode\extensions\ms-python.debugpy-2025.18.0-win32-x64\bundled\scripts\noConfigScripts to form one nonexistent merged directory.

Example from my system, where my final user-PATH entry was C:\Users\<me>\.local\bin:

C:\Users\<me>\.local\binc:\Users\<me>\.vscode\extensions\ms-python.debugpy-2025.18.0-win32-x64\bundled\scripts\noConfigScripts

Get-Command claude (whose exe lives in .local\bin) returns nothing in the integrated terminal but works in any terminal launched outside VS Code, and & "C:\Users\<me>\.local\bin\claude.exe" succeeds — confirming the file is fine and only the PATH entry is mangled.

Diagnostic snippet

$entries = $env:Path -split ';'
$entries[-1]

Output ends in ...\.local\binc:\Users\<me>\.vscode\extensions\ms-python.debugpy-...\noConfigScripts instead of ...\.local\bin.

Workaround

Append a sacrificial trailing entry to user PATH so debugpy's append-without-separator clobbers a throwaway dir instead of a real one. Not a fix — should be addressed upstream by always inserting a ; before the appended path or by appending via a list-aware API rather than string concatenation.

References

• #843 (closed by Fix PATH concatenation without separator in environment variable collection #958, this regression suggests the fix is incomplete or was reverted)
• #882 (closed without resolution; same bug class)
• #609 (related: PATH overwriting concerns)