pnpm/yarn "workspace:" Protocol Not Supported in CI

A package depends on a sibling via the workspace: protocol (e.g. "@acme/ui": "workspace:*"), but the tool installing it does not understand that protocol. Classically this is npm trying to install a pnpm/yarn workspace, or a published package that leaked an unresolved workspace: spec.

What this error means

Install fails with Unsupported URL Type "workspace:" or a "workspace: protocol not supported" message. It happens when the wrong package manager runs the install, or when a tarball published with workspace: ranges is consumed downstream.

npm output

npm error code EUNSUPPORTEDPROTOCOL
npm error Unsupported URL Type "workspace:": workspace:*

Common causes

Wrong package manager for the workspace

The workspace: protocol is a pnpm/yarn/Bun feature. Running npm install over a repo that uses it (without npm workspaces support for that spec) fails to parse it.

Published package leaked workspace: ranges

When publishing, pnpm/yarn rewrite workspace: to real version ranges. If that rewrite was skipped (wrong publish flow), consumers see an unresolved workspace: spec.

How to fix it

Install with the matching package manager

Use the package manager that understands workspace: and the committed lockfile.

Terminal

pnpm install --frozen-lockfile   # pnpm repos
yarn install --immutable         # yarn berry repos

Publish with proper workspace rewriting

Publish via pnpm publish / yarn npm publish, which rewrite workspace:* to concrete versions.
Never npm publish a package that still contains workspace: ranges.
Pin packageManager so CI and publish use the right tool.

How to prevent it

Use one package manager per repo and pin it via packageManager.
Publish with the tool that rewrites workspace: to real ranges.
Commit the correct lockfile and install with --frozen-lockfile/--immutable.