dsh-python-tempfile-shim

When running Python inside the DSH Windows sandbox (workspace-write mode), CPython creates temporary directories with a 0o700 ACL that grants only owner access. Because the sandbox WRITE_RESTRICTED token excludes the user own SID from the restricting list, the confined process cannot read or write the directories it just created, and pytest tmp_path tests immediately fail with PermissionError (WinError 5). dsh-python-tempfile-shim plugs this gap until an upstream fix ships.

The plugin injects PYTHONPATH at the shell executor resolve layer, so every confined command automatically picks up a lightweight sitecustomize.py shim. That shim makes os.mkdir ignore the mode argument, letting new directories inherit the parent folder ACL which already carries the sandbox workspace and temp write ACEs, instead of CPython owner-only DACL. The fix transparently covers python, pytest, pip, tox, nox, venvs, and all child processes, with no extra tools, environment variables, or model context required, and it leaves the sandbox token, ACEs, and policy boundary completely untouched.

It is intended for anyone running Python development or test suites inside the DSH Windows sandbox. Keep in mind this is a stopgap: once DSH ships its upstream fix, uninstall the plugin, since 0o700 is CPython privacy hardening that unconfined processes should retain.