[BUG] install-strategy=linked creates an unnecessary self-link inside every undeclared workspace's node_modules/ #9398

Is there an existing issue for this?

• I have searched the existing issues

This issue exists in the latest npm version

• I am using the latest npm

Current Behavior

When installing a monorepo with --install-strategy=linked, every workspace that is not listed in the root package.json's dependencies / devDependencies / optionalDependencies gets a symlink to itself created inside its own node_modules/ directory, even though the workspace does not declare itself as a dependency.

For example, given a workspace packages/test whose package is named @namespace/test and which is not declared in the root manifest, the following symlink is created:

packages/test/node_modules/@namespace/test -> ..

This symlink is not pointed to by any edge in the dependency graph. It is created as a side effect of how the isolated reifier parks the workspace IsolatedLink node off-root when the workspace is undeclared.

Packages that need to resolve themselves by name rely on Node.js's built-in self-referencing via the exports field instead.

Expected Behavior

No self-link should be created inside an undeclared workspace's node_modules/. The on-disk layout should match the "After" example shown in #9076's description:

packages/a/node_modules/@scope/b -> packages/b   # @scope/a depends on @scope/b

…with no extra packages/<ws>/node_modules/<ws> self-symlink.

Steps To Reproduce

1. Create a monorepo where the root does not list its workspaces as dependencies:

root/
  package.json        # { workspaces: ["packages/*"] } — no dependencies on workspaces
  packages/
    test/package.json # { "name": "@namespace/test", "version": "1.0.0" }
    a/package.json    # { "name": "@namespace/a", "version": "1.0.0", "dependencies": { "abbrev": "^1.0.0" } }

2. Install with the linked strategy:

npm install --install-strategy=linked

3. Inspect the workspace's own node_modules/:

ls -la packages/test/node_modules/

4. Observe the unexpected self-link:

@namespace/test -> ..

Environment

• npm: 12.0.0-pre.0.0 (also reproduces on earlier versions since fix(arborist): do not hoist undeclared workspaces in linked strategy #9076 landed)
• Node.js: v24.15.0
• OS Name: macOS 26.5
• System Model Name: MacBook Pro
• npm config:

install-strategy = "linked"