diff --git a/docs/lib/content/configuring-npm/package-json.md b/docs/lib/content/configuring-npm/package-json.md
index abb5e362c61e3..c077129719657 100644
--- a/docs/lib/content/configuring-npm/package-json.md
+++ b/docs/lib/content/configuring-npm/package-json.md
@@ -842,6 +842,16 @@ This is a map of package name to version or URL, just like the `dependencies` ob
 The difference is that build failures do not cause installation to fail.
 Running `npm install --omit=optional` will prevent these dependencies from being installed.
 
+For example:
+
+```json
+{
+  "optionalDependencies": {
+    "@npm/foo": "^1.0.0"
+  }
+}
+```
+
 It is still your program's responsibility to handle the lack of the dependency.
 For example, something like this:
 
diff --git a/workspaces/arborist/lib/arborist/build-ideal-tree.js b/workspaces/arborist/lib/arborist/build-ideal-tree.js
index c9d9c308cbc9c..7fecd6759c041 100644
--- a/workspaces/arborist/lib/arborist/build-ideal-tree.js
+++ b/workspaces/arborist/lib/arborist/build-ideal-tree.js
@@ -1351,7 +1351,22 @@ This is a one-time fix-up, please be patient...
     // doesn't satisfy the edge. try to fetch a manifest and build a node from that.
     return this.#fetchManifest(spec, parent, edge)
       .then(
-        pkg => new Node({ name, pkg, parent, installLinks, legacyPeerDeps }),
+        pkg => {
+          // When a proxy/upstream registry returns an incomplete manifest
+          // (e.g. missing version field for platform-specific packages it
+          // hasn't cached), treat it as a load failure so that optional deps
+          // are properly pruned instead of written to the lockfile without
+          // version metadata.  Only apply to registry specs — file: deps
+          // legitimately omit version.
+          if (!pkg.version && spec.registry) {
+            const error = Object.assign(
+              new Error(`incomplete manifest for ${name}, missing version`),
+              { code: 'EINCOMPLETEMANIFEST' }
+            )
+            return this.#failureNode(name, parent, error, edge)
+          }
+          return new Node({ name, pkg, parent, installLinks, legacyPeerDeps })
+        },
         error => this.#failureNode(name, parent, error, edge)
       )
   }
diff --git a/workspaces/arborist/lib/link.js b/workspaces/arborist/lib/link.js
index d200f3d8f8d78..3824dc81ffb3c 100644
--- a/workspaces/arborist/lib/link.js
+++ b/workspaces/arborist/lib/link.js
@@ -109,12 +109,24 @@ class Link extends Node {
   // so this is a no-op
   [_loadDeps] () {}
 
-  // When a Link receives overrides (via edgesIn), forward them to the target node which holds the actual edgesOut.
-  // Without this, overrides stop at the Link and never reach the target's dependency edges.
+  // When a Link receives overrides (via edgesIn), forward them to the target node which holds the actual edgesOut — but only when the OverrideSet has at least one rule that names a dep the target actually depends on.
+  // Without this scope, the link forwards a generic ancestor OverrideSet that has no real effect on the target's edges, but still flips the target to "has overrides", which changes downstream `canReplaceWith` / placement decisions and causes `npm ci` to re-resolve lockfile-pinned edges from the registry.
+  // See npm/cli#9357.
   recalculateOutEdgesOverrides () {
-    if (this.target) {
-      this.target.updateOverridesEdgeInAdded(this.overrides)
+    if (!this.target || !this.overrides) {
+      return
+    }
+    let hasMatchingRule = false
+    for (const rule of this.overrides.ruleset.values()) {
+      if (this.target.edgesOut.has(rule.name)) {
+        hasMatchingRule = true
+        break
+      }
+    }
+    if (!hasMatchingRule) {
+      return
     }
+    this.target.updateOverridesEdgeInAdded(this.overrides)
   }
 
   // links can't have children, only their targets can
diff --git a/workspaces/arborist/lib/shrinkwrap.js b/workspaces/arborist/lib/shrinkwrap.js
index 8cb1814661c6d..ce2c58457098d 100644
--- a/workspaces/arborist/lib/shrinkwrap.js
+++ b/workspaces/arborist/lib/shrinkwrap.js
@@ -909,10 +909,20 @@ class Shrinkwrap {
         if (node.extraneous && !/(^|\/)node_modules\//.test(loc) && loc !== 'node_modules') {
           continue
         }
-        this.data.packages[loc] = Shrinkwrap.metaFromNode(
+        const meta = Shrinkwrap.metaFromNode(
           node,
           this.path,
           this.resolveOptions)
+        // Skip inert nodes — these are optional deps that failed to load
+        // (e.g. 404 from a proxy registry that hasn't cached the package,
+        // or incomplete manifest missing version field).
+        // #pruneFailedOptional marks them inert so they won't be reified;
+        // writing them to the lockfile produces invalid entries like
+        // {"optional": true} that cause "Invalid Version:" errors.
+        if (node.inert && !node.package.version) {
+          continue
+        }
+        this.data.packages[loc] = meta
       }
     } else if (this.#awaitingUpdate.size > 0) {
       for (const loc of this.#awaitingUpdate.keys()) {
diff --git a/workspaces/arborist/test/arborist/build-ideal-tree.js b/workspaces/arborist/test/arborist/build-ideal-tree.js
index 143255a0ec9cd..d6705222ef73e 100644
--- a/workspaces/arborist/test/arborist/build-ideal-tree.js
+++ b/workspaces/arborist/test/arborist/build-ideal-tree.js
@@ -4816,3 +4816,70 @@ t.test('allow-directory=root soft-skips a transitive optional directory dependen
   t.ok(optChild, 'blocked optional transitive is recorded in the tree')
   t.equal(optChild.inert, true, 'blocked optional transitive is marked inert (will not be reified)')
 })
+
+t.test('incomplete manifest from proxy registry prunes optional dep (#9342)', async t => {
+  // When a proxy/upstream registry returns an
+  // incomplete manifest for a platform-specific optional dep it hasn't
+  // cached, the version field is missing.  Our fix in #nodeFromSpec
+  // treats this as EINCOMPLETEMANIFEST load failure so that
+  // #pruneFailedOptional() marks it inert instead of writing a broken
+  // lockfile entry like {"optional": true}.
+  const registry = createRegistry(t, false)
+
+  // parent package with an optional dep
+  const esbuildPack = registry.packument({
+    name: 'esbuild',
+    version: '0.27.7',
+    optionalDependencies: {
+      '@esbuild/aix-ppc64': '0.27.7',
+    },
+  })
+  const esbuildManifest = registry.manifest({ name: 'esbuild', packuments: [esbuildPack] })
+  await registry.package({ manifest: esbuildManifest })
+
+  // simulate proxy registry returning incomplete manifest (no version field)
+  await registry.package({
+    manifest: {
+      _id: '@esbuild/aix-ppc64',
+      _rev: '00-incomplete',
+      name: '@esbuild/aix-ppc64',
+      description: 'incomplete proxy manifest',
+      'dist-tags': { latest: '0.27.7' },
+      versions: {
+        '0.27.7': {
+          _id: '@esbuild/aix-ppc64@0.27.7',
+          name: '@esbuild/aix-ppc64',
+          // NO version field — this is the proxy registry bug
+          dependencies: {},
+          dist: {
+            tarball: 'https://registry.npmjs.org/@esbuild/aix-ppc64/-/aix-ppc64-0.27.7.tgz',
+          },
+        },
+      },
+    },
+  })
+
+  const path = t.testdir({
+    'package.json': JSON.stringify({
+      name: 'test-incomplete-manifest',
+      version: '1.0.0',
+      devDependencies: { esbuild: '^0.27.0' },
+    }),
+  })
+
+  const arb = newArb(path)
+  const tree = await arb.buildIdealTree()
+
+  // esbuild itself should be in the tree
+  t.ok(tree.children.get('esbuild'), 'esbuild is installed')
+  t.equal(tree.children.get('esbuild').version, '0.27.7', 'esbuild has correct version')
+
+  // @esbuild/aix-ppc64 should be marked inert (EINCOMPLETEMANIFEST → loadFailure)
+  // pruneFailedOptional marks it inert so it won't be written to lockfile
+  const aixNodes = [...tree.inventory.query('name', '@esbuild/aix-ppc64')]
+  const aixNode = aixNodes.find(n => n.root === tree)
+  t.ok(aixNode, 'incomplete optional dep node exists in tree')
+  t.equal(aixNode.inert, true, 'incomplete optional dep is marked inert')
+  t.equal(aixNode.errors[0].code, 'EINCOMPLETEMANIFEST',
+    'node has EINCOMPLETEMANIFEST error')
+})
diff --git a/workspaces/arborist/test/link.js b/workspaces/arborist/test/link.js
index f9b7d8eb1d96d..472f33c2f4535 100644
--- a/workspaces/arborist/test/link.js
+++ b/workspaces/arborist/test/link.js
@@ -256,6 +256,51 @@ t.test('recalculateOutEdgesOverrides forwards overrides to target', t => {
   t.end()
 })
 
+t.test('recalculateOutEdgesOverrides does not forward when no rule matches a target dep — npm/cli#9357', t => {
+  // Regression: prior to the fix, Link.recalculateOutEdgesOverrides forwarded the link's full OverrideSet to the target unconditionally.
+  // For a target whose edges are NOT named in any override rule, that flipped target.overrides from undefined to the root's OverrideSet.
+  // Downstream, that "has overrides" state changed canPlaceDep's KEEP-vs-REPLACE decision and made `npm ci` re-resolve lockfile-pinned edges from the registry.
+  // After the fix, propagation is gated on at least one rule whose name matches an edge in target.edgesOut.
+  const root = new Node({
+    path: '/path/to/root',
+    pkg: {
+      name: 'root',
+      dependencies: { foo: '1.0.0' },
+      // override is for "bar", but the linked target only depends on "baz"
+      overrides: { bar: '2.0.0' },
+    },
+    loadOverrides: true,
+  })
+
+  const target = new Node({
+    path: '/path/to/store/foo',
+    pkg: {
+      name: 'foo',
+      version: '1.0.0',
+      dependencies: { baz: '1.0.0' },
+    },
+    root,
+  })
+
+  // eslint-disable-next-line no-new
+  new Link({
+    pkg: { name: 'foo', version: '1.0.0' },
+    path: '/path/to/root/node_modules/foo',
+    realpath: '/path/to/store/foo',
+    target,
+    parent: root,
+  })
+
+  t.ok(root.overrides, 'root has overrides')
+  t.notOk(target.overrides,
+    'target.overrides stays undefined when no rule matches a target dep')
+  const bazEdge = target.edgesOut.get('baz')
+  t.notOk(bazEdge.overrides,
+    'unrelated edge keeps edge.overrides undefined')
+  t.equal(bazEdge.spec, '1.0.0', 'unrelated edge spec is unchanged')
+  t.end()
+})
+
 t.test('link to root path gets root as target', t => {
   const root = new Node({
     path: '/project/root',
diff --git a/workspaces/arborist/test/shrinkwrap.js b/workspaces/arborist/test/shrinkwrap.js
index bcdf50b0f87b0..79389a862caa0 100644
--- a/workspaces/arborist/test/shrinkwrap.js
+++ b/workspaces/arborist/test/shrinkwrap.js
@@ -863,6 +863,141 @@ t.test('load a hidden lockfile', async t => {
   t.equal(data.dependencies, undefined, 'deleted legacy metadata')
 })
 
+t.test('skip inert nodes in commit', async t => {
+  // When a proxy registry returns 404 or incomplete manifests for
+  // platform-specific optional deps, #pruneFailedOptional marks them
+  // inert.  commit() must skip inert nodes — otherwise the lockfile
+  // gets entries like {"optional": true} without version/resolved/integrity
+  // that cause "Invalid Version:" errors on subsequent npm ci.
+  const path = t.testdir({
+    'package.json': JSON.stringify({
+      name: 'proxy-registry-repro',
+      version: '1.0.0',
+      devDependencies: { esbuild: '^0.27.0' },
+    }),
+  })
+  const meta = new Shrinkwrap({ path })
+  meta.data = {
+    lockfileVersion: 3,
+    packages: {},
+  }
+
+  const root = new Node({
+    pkg: {
+      name: 'proxy-registry-repro',
+      version: '1.0.0',
+      devDependencies: { esbuild: '^0.27.0' },
+    },
+    path,
+    realpath: path,
+  })
+
+  // esbuild with full metadata (valid)
+  const esbuild = new Node({
+    pkg: {
+      name: 'esbuild',
+      version: '0.27.7',
+      optionalDependencies: {
+        '@esbuild/linux-x64': '0.27.7',
+        '@esbuild/aix-ppc64': '0.27.7',
+      },
+    },
+    name: 'esbuild',
+    parent: root,
+  })
+  esbuild.dev = true
+
+  // platform dep with full metadata (current platform — valid, NOT inert)
+  const validDep = new Node({
+    pkg: {
+      name: '@esbuild/linux-x64',
+      version: '0.27.7',
+      os: ['linux'],
+      cpu: ['x64'],
+    },
+    name: '@esbuild/linux-x64',
+    parent: root,
+  })
+  validDep.optional = true
+  validDep.dev = true
+
+  // platform dep marked inert (proxy registry 404'd or returned incomplete manifest)
+  // #pruneFailedOptional sets inert=true on these nodes
+  const brokenDep = new Node({
+    pkg: {
+      name: '@esbuild/aix-ppc64',
+      // no version — proxy registry returned 404 or incomplete manifest
+    },
+    name: '@esbuild/aix-ppc64',
+    parent: esbuild,
+  })
+  brokenDep.optional = true
+  brokenDep.dev = true
+  brokenDep.extraneous = false
+  brokenDep.inert = true
+
+  // file: optional dep WITHOUT version (legitimate — NOT inert, should be kept)
+  const fileDep = new Node({
+    pkg: {
+      name: 'my-local-optional',
+      // no version — but this is a file: dep, so it's legitimate
+    },
+    name: 'my-local-optional',
+    parent: root,
+    resolved: 'file:../my-local-optional',
+  })
+  fileDep.optional = true
+  fileDep.extraneous = false
+
+  // local optional dep WITHOUT version or resolved (NOT inert, should be kept)
+  const localDep = new Node({
+    pkg: {
+      name: 'my-disk-optional',
+      // no version, no resolved — loaded from local node_modules
+    },
+    name: 'my-disk-optional',
+    parent: root,
+  })
+  localDep.optional = true
+  localDep.extraneous = false
+
+  meta.tree = root
+  const committed = meta.commit()
+
+  // The valid platform dep should be in the lockfile
+  const validLoc = 'node_modules/@esbuild/linux-x64'
+  t.ok(
+    committed.packages[validLoc],
+    'valid optional dep is included'
+  )
+  t.equal(
+    committed.packages[validLoc].version,
+    '0.27.7',
+    'valid optional dep has version'
+  )
+
+  // The inert dep should NOT be in the lockfile
+  const brokenLoc = 'node_modules/esbuild/node_modules/@esbuild/aix-ppc64'
+  t.notOk(
+    committed.packages[brokenLoc],
+    'inert optional dep is excluded from lockfile'
+  )
+
+  // The file: optional dep WITHOUT version SHOULD be kept (not inert)
+  const fileLoc = 'node_modules/my-local-optional'
+  t.ok(
+    committed.packages[fileLoc],
+    'file: optional dep without version is preserved in lockfile'
+  )
+
+  // The local (resolved=null) optional dep WITHOUT version SHOULD be kept (not inert)
+  const localLoc = 'node_modules/my-disk-optional'
+  t.ok(
+    committed.packages[localLoc],
+    'local optional dep without version is preserved in lockfile'
+  )
+})
+
 t.test('load a fresh hidden lockfile', async t => {
   const sw = await Shrinkwrap.reset({
     path: hiddenLockfileFixture,