Installation of mypy 1.18 fails with uv ("Access denied" during cache rename) Windows in enterprise environment

[MarcCharron]

Bug Report

I'm unable to install mypy==1.18.2 using the uv package manager in a Windows enterprise environment.
The installation fails with an “Access denied” error when trying to rename a temporary cache file.

Older versions like mypy==1.3.0 install successfully, so I'm wondering if something changed in the packaging or wheel structure between these versions.

This issue might be related to antivirus or endpoint protection software, but I’d like to confirm whether the Mypy distribution (wheel or source tarball) could trigger stricter Windows file operations or permission issues.

---

To Reproduce

pyproject.toml

[tool.uv]
dev-dependencies = [
    "mypy==1.18.2",
]

Command:

uv sync

---

Expected Behavior

Resolved 52 packages in 837ms
      Built project_xxxxx @ file:///C:/Users/USERXXX/git_local/project_xxxxx
Prepared 1 package in 31ms
Uninstalled 1 package in 45ms
Installed 3 packages in 832ms
~ project_xxxxx==0.1.0 (from file:///C:/Users/USERXXX/git_local/project_xxxxx)
+ mypy==1.3.0
+ mypy-extensions==1.1.0

---

Actual Behavior

Using CPython 3.12.10 interpreter at: C:\Program Files\Python\python.exe
Creating virtual environment at: .venv
  × Failed to download `mypy==1.18.2`
  ├─▶ Failed to read from the distribution cache
  ╰─▶ failed to rename file from C:\Users\USERXXX\AppData\Local\uv\cache\.tmpY0qi9j 
      to C:\Users\USERXXX\AppData\Local\uv\cache\archive-v0\YQY-kdG0vVLvidw-fW6wT: 
      Access denied. (os error 5)
  help: `mypy` (v1.18.2) was included because `project_xxxx:dev` (v0.1.0) depends on `mypy`

---

Environment

• Mypy version: 1.18.2
• Python version: 3.12.10
• OS: Windows 10 Enterprise
• Package manager: uv
• Environment: corporate network (likely antivirus active)

---

Notes

• Installing mypy==1.3.0 works fine with the same setup.
• Installing mypy==1.18.2 via pip also works fine.
• The issue seems specific to the caching or rename step during installation.

---

Thanks in advance for your support! 🙏

[sterliakov]

Seems like this isn't mypy-specific: astral-sh/uv#15108 and astral-sh/uv#1491.

Does the problem go away if you run with UV_LINK_MODE=copy?

[MarcCharron]

I tried with this configuration :

[tool.uv]
native-tls = true
link-mode = "copy"

But it still doesn't work in entreprise environnement (Trellix is running on my computer).

I ask for help on the uv GitHub.

PS : I use uv 0.9.7