[BUG] install-strategy=linked: install does not repair a wrong-but-existing symlink target (silently keeps the wrong version) #9611

Part of #9608.

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

This is not just a request to bump a dependency for a CVE

• This is not solely a request to bump a dependency for a CVE

Current Behavior

Under install-strategy=linked, if a top-level node_modules/<dep> symlink points to a store key that exists on disk but is the wrong version, re-running npm install does not repair it. npm reports success and leaves the dependency resolving to the wrong version. This is the on-disk state an interrupted npm install / npm update can leave behind (the new store entry is extracted, but the symlink is not yet repointed). When the symlink instead points to a non-existent target, npm install / npm ci do repair it — so the problem is specific to a wrong target that happens to exist on disk.

Expected Behavior

npm install should detect that an existing symlink points to the wrong store target and repoint it to the version required by the tree (as the hoisted strategy self-heals an equivalent corruption).

Steps To Reproduce

cd "$(mktemp -d)"
echo 'install-strategy=linked' > .npmrc
cat > package.json <<'EOF'
{ "name": "nat2", "version": "1.0.0",
  "dependencies": { "minimatch": "3.1.0", "glob": "10.3.10" } }
EOF
npm install >/dev/null    # store now has minimatch@3.1.0 (root) AND minimatch@9.x (via glob)

# Simulate an interrupted update: repoint the root symlink at the wrong (but existing) store key
OKEY=$(ls node_modules/.store | grep '^minimatch@9')
rm node_modules/minimatch
ln -s ".store/$OKEY/node_modules/minimatch" node_modules/minimatch

npm install                # exits 0, reports success
readlink node_modules/minimatch
#   .store/minimatch@9.0.9-.../node_modules/minimatch   <-- NOT repaired
grep version node_modules/minimatch/package.json        # -> 9.0.9, expected 3.1.0

Environment

• npm: 12.0.0-pre.1 (latest)
• Node.js: v24.17.0
• OS Name: macOS (Darwin 25.5.0)
• System Model Name: MacBook (arm64)
• npm config:

install-strategy=linked