uvscem 1.0.2

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uVSCEM

uVSCEM is a VS Code extension installer for restricted environments.

It helps when normal extension installation fails because of proxy issues, controlled outbound access, or air-gapped workflows. It can also export and import offline extension bundles.

What it does

• Reads extension IDs from your devcontainer.json.
• Downloads VSIX packages and marketplace signatures.
• Verifies extension signatures using vsce-sign.
• Installs extensions in a DevContainer-compatible way.
• Supports offline bundles (export and import).

Requirements

• Python 3.10+
• VS Code CLI (code) available in your environment
• Access to your devcontainer.json

Platform support

uVSCEM auto-detects common VS Code runtime environments and can fall back to local CLI discovery on macOS and Windows.

The primary tested target is still Linux, especially DevContainer and VS Code Remote (.vscode-server) environments.

Install

pip install uvscem

You can also use uv or pipx if you prefer.

Quick start (DevContainer)

Add uVSCEM to your container image, then call it from postAttachCommand:

{
  "postAttachCommand": "uvscem install --config-name /path/to/devcontainer.json"
}

This installs (and updates) extensions listed in your config each time the container is attached.

Commands

Install extensions directly:

uvscem install --config-name ./devcontainer.json

Pinning is supported in devcontainer.json using publisher.extension@version:

{
  "customizations": {
    "vscode": {
      "extensions": [
        "dbaeumer.vscode-eslint@3.0.10"
      ]
    }
  }
}

Export an offline bundle:

uvscem export --config-name ./devcontainer.json --bundle-path ./uvscem-offline-bundle

Import an offline bundle without network access:

uvscem import --bundle-path ./uvscem-offline-bundle --strict-offline

Optional manifest authenticity checks:

uvscem export --config-name ./devcontainer.json --manifest-signing-key YOUR_GPG_KEY_ID
uvscem import --bundle-path ./uvscem-offline-bundle --verify-manifest-signature

Proxy note

uVSCEM follows standard proxy environment variables such as HTTP_PROXY, HTTPS_PROXY, and NO_PROXY.

Why this exists

uVSCEM is a practical workaround for known VS Code proxy/devcontainer limitations, including:

• https://github.com/microsoft/vscode/issues/12588
• https://github.com/microsoft/vscode/issues/29910
• https://github.com/orgs/devcontainers/discussions/94

Contributing

Development setup, testing, and release details are in CONTRIBUTING.md.

A big thank you to the following people

• Jossef Harush Kadouri for this GitHub Gist on how to query the undocumented VisualStudio Code Marketplace API, which I used as blueprint for api_client.py.
• Ian McKellar for his blog post "VSCode Remote and the command line" (notable mention: Lazy Ren@Stackoverflow for this answer pointing me in this direction).
• Michael Petrov for this answer on StackOverflow on how to test if a socket is closed in python.