[rush] strictPeerDependencies are on, but do not complain if internal (inter-subspace) peers are missing

Reproduce the issue with rush update using common/config/rush/pnpm-config.json, subspaces/sdk/pnpm-config.json, and the package-a, package-b, and package-c package.json files. Start by tracing how Rush handles strictPeerDependencies across subspaces and workspace injection. Done means the missing made-up-package peer is reported for both package B and package C.

Summary

Imagine a rush.js managed monorepo, with two subspaces, default and sdk.

strictPeerDependencies are on, in both the global config and both subspace configs.

BUT

Imagine packages A, B, C

Package A has a peerDependency for "madeUpPackage". Package A is in the SDK subspace.

Package B consumes package A. Package B does not have madeUpPackage installed. Package B is in the SDK subspace.

Package C consumes package A. Package C does not have madeUpPackage installed. Package C is in the default subspace.

When I run rush update, only complains on Package C.

But how do I make it complain about missing peer from perspective of package B

Repro steps

Expected result: rush install/update command failed

Actual result: rush install pass correctly

Details

Reproduction Setup

Monorepo Structure

monorepo/
├── rush.json
├── common/
│   └── config/
│       └── rush/
│           └── pnpm-config.json          # Global config
├── subspaces/
│   ├── default/
│   │   └── pnpm-config.json              # Default subspace config
│   └── sdk/
│       └── pnpm-config.json              # SDK subspace config
└── packages/
    ├── package-a/package.json            # SDK subspace - declares peerDependency
    ├── package-b/package.json            # SDK subspace - consumes A, missing peer
    └── package-c/package.json            # default subspace - consumes A, missing peer

Configuration

common/config/rush/pnpm-config.json (Global):

{
    "useWorkspaces": true,
    "strictPeerDependencies": true
   "alwaysInjectDependenciesFromOtherSubspaces": true,
}

subspaces/sdk/pnpm-config.json:

{
    "useWorkspaces": true,
    "strictPeerDependencies": true
}

Package Definitions

packages/package-a/package.json (SDK subspace):

{
    "name": "@myorg/package-a",
    "version": "1.0.0",
    "devDependencies": {
        "made-up-package": "^2.0.0"
    },
    "peerDependencies": {
        "made-up-package": "^2.0.0"
    }
}

packages/package-b/package.json (SDK subspace):

{
    "name": "@myorg/package-b",
    "version": "1.0.0",
    "devDependencies": {
        "@myorg/package-a": "workspace:*"
        // ❌ "made-up-package" is NOT installed - should trigger error
    }
}

packages/package-c/package.json (deafult subspace):

{
    "name": "@myorg/package-c",
    "version": "1.0.0",
    "devDependencies": {
        "@myorg/package-a": "workspace:*"
        // ❌ "made-up-package" is NOT installed - should trigger error
    }
}

Expected Behavior

Running rush update should fail and report missing peer dependencies for both Package B and Package C:

ERR_PNPM_PEER_DEP_ISSUES  Unmet peer dependencies

@myorg/package-b
└─┬ @myorg/package-a
  └── ✕ missing peer made-up-package@^2.0.0

@myorg/package-c
└─┬ @myorg/package-a
  └── ✕ missing peer made-up-package@^2.0.0

Actual Behavior

Running rush update only complains about Package C:

ERR_PNPM_PEER_DEP_ISSUES  Unmet peer dependencies

@myorg/package-c
└─┬ @myorg/package-a
  └── ✕ missing peer made-up-package@^2.0.0

Package B is silently ignored, even though it has the exact same missing peer dependency.

Standard questions

Please answer these questions to help us investigate your issue more quickly:

Question	Answer
@microsoft/rush globally installed version?	5.158.1
rushVersion from rush.json?	5.158.1
pnpmVersion, npmVersion, or yarnVersion from rush.json?	[email protected]
(if pnpm) useWorkspaces from pnpm-config.json?	yes
Operating system?	Mac
Would you consider contributing a PR?	yes
Node.js version (node -v)?	22.13.0