yarn add: Add Dependencies

yarn add installs a package and writes it to package.json.

yarn add is a developer command; CI normally only installs from the committed lockfile.

Common flags

• -D / --dev - devDependency
• -E / --exact - pin exact version
• -P / --peer - peerDependency
• yarn add <pkg>@<tag>

Example

Add a dev tool pinned exactly.

yarn add -D -E vitest

In CI

If CI runs yarn add, it will change the lockfile and break --immutable. Keep dependency changes in PRs, not the build.

Key takeaways

• -D for dev, -E to pin exact.
• CI should not run yarn add.
• Lockfile changes belong in PRs.

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