Unity Package Management (headless, via the C# Client API)

Add, remove, upgrade, and discover UPM (Unity Package Manager) packages programmatically with UnityEditor.PackageManager.Client, driven headless from the terminal or CI. Do not hand-edit Packages/manifest.json — the Client API resolves dependencies and compatible versions correctly, whereas manual edits routinely break resolution.

This complements the unity-cli skill (editor install, project creation, build/test): the CLI has no package-management command, so all package work goes through the Editor's C# API.

When to use

• Add / remove / upgrade one or more packages in an existing or freshly-created project.
• Set up a project's packages non-interactively in CI.
• Verify a package id exists, or find its available versions, before depending on it.
• Decide which packages a game actually needs — see references/select-packages.md.

Choosing what to install