diff --git a/.github/actions/install-node-dependencies/action.yml b/.github/actions/install-node-dependencies/action.yml
index 916baf446b7..e2b13ac21c0 100644
--- a/.github/actions/install-node-dependencies/action.yml
+++ b/.github/actions/install-node-dependencies/action.yml
@@ -2,6 +2,10 @@ name: Install Node dependencies
 description: Installs the Node toolchain and repository dependencies for CI jobs, with optional Electron archive caching.
 
 inputs:
+  cache-pnpm-store:
+    description: Restore or save the pnpm download store; verification and native caches are independent.
+    required: false
+    default: 'true'
   cache-pnpm-verification:
     description: Restore pnpm's policy-checked lockfile verification record.
     required: false
@@ -69,7 +73,7 @@ runs:
       uses: actions/setup-node@v6
       with:
         node-version-file: package.json
-        cache: ${{ github.event_name != 'pull_request' && 'pnpm' || '' }}
+        cache: ${{ github.event_name != 'pull_request' && inputs.cache-pnpm-store != 'false' && 'pnpm' || '' }}
         cache-dependency-path: ${{ inputs.cache-dependency-path }}
         package-manager-cache: false
 
@@ -79,7 +83,7 @@ runs:
       uses: actions/setup-node@v6
       with:
         node-version: ${{ inputs.node-version }}
-        cache: ${{ github.event_name != 'pull_request' && 'pnpm' || '' }}
+        cache: ${{ github.event_name != 'pull_request' && inputs.cache-pnpm-store != 'false' && 'pnpm' || '' }}
         cache-dependency-path: ${{ inputs.cache-dependency-path }}
         package-manager-cache: false
 
@@ -87,8 +91,10 @@ runs:
     - name: Resolve pnpm download store
       id: pnpm-store
       if: >-
-        github.event_name == 'pull_request' &&
-        (runner.os != 'Windows' || runner.arch != 'X64' || !contains(inputs.cache-dependency-path, 'mobile/pnpm-lock.yaml'))
+        github.event_name == 'pull_request' && inputs.cache-pnpm-store != 'false' &&
+        (runner.os != 'Windows' ||
+        !(runner.arch == 'X64' && contains(inputs.cache-dependency-path, 'mobile/pnpm-lock.yaml')) &&
+        !((runner.arch == 'X64' || runner.arch == 'ARM64') && inputs.cache-dependency-path == 'pnpm-lock.yaml'))
       shell: bash
       env:
         LOCKFILE_HASH: ${{ hashFiles(inputs.cache-dependency-path) }}
@@ -100,11 +106,13 @@ runs:
         printf 'arch=%s\n' "$(node -p 'require("node:os").arch()')" >> "$GITHUB_OUTPUT"
 
     # Match setup-node's key and path so existing default-branch stores remain reusable.
-    # Hosted Windows x64 mixed installs cost less than restoring their root/mobile store.
+    # Measured Windows installs cost less than unpacking their download store.
     - name: Restore pnpm download store without saving
       if: >-
-        github.event_name == 'pull_request' &&
-        (runner.os != 'Windows' || runner.arch != 'X64' || !contains(inputs.cache-dependency-path, 'mobile/pnpm-lock.yaml'))
+        github.event_name == 'pull_request' && inputs.cache-pnpm-store != 'false' &&
+        (runner.os != 'Windows' ||
+        !(runner.arch == 'X64' && contains(inputs.cache-dependency-path, 'mobile/pnpm-lock.yaml')) &&
+        !((runner.arch == 'X64' || runner.arch == 'ARM64') && inputs.cache-dependency-path == 'pnpm-lock.yaml'))
       uses: actions/cache/restore@v5
       with:
         path: ${{ steps.pnpm-store.outputs.path }}
diff --git a/.github/workflows/node-server-tests.yml b/.github/workflows/node-server-tests.yml
index 081f22d4046..dad53d33f47 100644
--- a/.github/workflows/node-server-tests.yml
+++ b/.github/workflows/node-server-tests.yml
@@ -154,6 +154,7 @@ jobs:
       - uses: ./.github/actions/install-node-dependencies
         with:
           native-runtime: ${{ runner.os == 'Windows' && 'node' || 'none' }}
+          cache-pnpm-store: ${{ runner.os != 'Windows' }}
       # Linux release slots come from the floor and Alpine lanes; this slot serves local tests.
       - uses: ./.github/actions/prepare-orcad-prebuilds
         id: orcad-prebuild
diff --git a/.github/workflows/ssh-windows-hosts.yml b/.github/workflows/ssh-windows-hosts.yml
index cd77ee87b67..8afae35ca12 100644
--- a/.github/workflows/ssh-windows-hosts.yml
+++ b/.github/workflows/ssh-windows-hosts.yml
@@ -109,6 +109,7 @@ jobs:
         id: dependencies
         with:
           native-runtime: node
+          cache-pnpm-store: 'false'
       # The deploy materializes rung A from this template; only this runner's slot exists here.
       # The process-tree addon carries the launcher that starts the relay outside sshd's job; the
       # orcad slot and the relay both stage it, and a standard-user host has no other launch route.
diff --git a/config/scripts/ci-dependency-download-cache.test.mjs b/config/scripts/ci-dependency-download-cache.test.mjs
index 584c37f6740..6f2ec4f4d05 100644
--- a/config/scripts/ci-dependency-download-cache.test.mjs
+++ b/config/scripts/ci-dependency-download-cache.test.mjs
@@ -11,7 +11,9 @@ describe('CI dependency download caches', () => {
   it('scopes desktop stores to the root lockfile and lets mixed installs opt in', () => {
     expect(action.inputs['cache-dependency-path'].default).toBe('pnpm-lock.yaml')
     for (const step of action.runs.steps.filter((step) => step.uses === 'actions/setup-node@v6')) {
-      expect(step.with.cache).toBe("${{ github.event_name != 'pull_request' && 'pnpm' || '' }}")
+      expect(step.with.cache).toBe(
+        "${{ github.event_name != 'pull_request' && inputs.cache-pnpm-store != 'false' && 'pnpm' || '' }}"
+      )
       expect(step.with['cache-dependency-path']).toBe('${{ inputs.cache-dependency-path }}')
       expect(step.with['package-manager-cache']).toBe(false)
     }
@@ -30,13 +32,13 @@ describe('CI dependency download caches', () => {
     ])
   })
 
-  it('restores PR stores except measured Windows mixed installs, without a post-job save', () => {
+  it('restores PR stores except measured Windows installs, without a post-job save', () => {
     const resolve = action.runs.steps.find((step) => step.id === 'pnpm-store')
     const restore = action.runs.steps.find(
       (step) => step.name === 'Restore pnpm download store without saving'
     )
     expect(resolve.if).toBe(
-      "github.event_name == 'pull_request' && (runner.os != 'Windows' || runner.arch != 'X64' || !contains(inputs.cache-dependency-path, 'mobile/pnpm-lock.yaml'))"
+      "github.event_name == 'pull_request' && inputs.cache-pnpm-store != 'false' && (runner.os != 'Windows' || !(runner.arch == 'X64' && contains(inputs.cache-dependency-path, 'mobile/pnpm-lock.yaml')) && !((runner.arch == 'X64' || runner.arch == 'ARM64') && inputs.cache-dependency-path == 'pnpm-lock.yaml'))"
     )
     expect(restore.if).toBe(resolve.if)
     expect(restore.uses).toBe('actions/cache/restore@v5')
@@ -69,36 +71,111 @@ describe('CI dependency download caches', () => {
     ['Windows x64 mixed PR', 'pull_request', 'Windows', 'X64', true, false, ''],
     ['Windows ARM64 mixed PR', 'pull_request', 'Windows', 'ARM64', true, true, ''],
     ['Windows x86 mixed PR', 'pull_request', 'Windows', 'X86', true, true, ''],
-    ['Windows x64 root-only PR', 'pull_request', 'Windows', 'X64', false, true, ''],
+    ['Windows x64 root-only PR', 'pull_request', 'Windows', 'X64', false, false, ''],
+    ['Windows ARM64 root-only PR', 'pull_request', 'Windows', 'ARM64', false, false, ''],
+    ['Windows x86 root-only PR', 'pull_request', 'Windows', 'X86', false, true, ''],
+    ['Windows x64 custom PR', 'pull_request', 'Windows', 'X64', 'cloud/pnpm-lock.yaml', true, ''],
+    [
+      'Windows ARM64 custom PR',
+      'pull_request',
+      'Windows',
+      'ARM64',
+      'cloud/pnpm-lock.yaml',
+      true,
+      ''
+    ],
+    ['Windows ARM64 root-only push', 'push', 'Windows', 'ARM64', false, false, 'pnpm'],
+    [
+      'Windows ARM64 root-only manual run',
+      'workflow_dispatch',
+      'Windows',
+      'ARM64',
+      false,
+      false,
+      'pnpm'
+    ],
+    ['Explicit Linux PR opt-out', 'pull_request', 'Linux', 'X64', false, false, '', 'false'],
+    ['Explicit Windows push opt-out', 'push', 'Windows', 'ARM64', false, false, '', 'false'],
+    [
+      'Explicit Windows manual opt-out',
+      'workflow_dispatch',
+      'Windows',
+      'X64',
+      false,
+      false,
+      '',
+      'false'
+    ],
+    [
+      'Explicit custom-store opt-out',
+      'pull_request',
+      'Windows',
+      'X64',
+      'cloud/pnpm-lock.yaml',
+      false,
+      '',
+      'false'
+    ],
+    ['Windows x64 root-only push', 'push', 'Windows', 'X64', false, false, 'pnpm'],
     ['Linux x64 mixed PR', 'pull_request', 'Linux', 'X64', true, true, ''],
     ['Linux ARM64 mixed PR', 'pull_request', 'Linux', 'ARM64', true, true, ''],
     ['macOS ARM64 mixed PR', 'pull_request', 'macOS', 'ARM64', true, true, ''],
     ['Windows x64 mixed push', 'push', 'Windows', 'X64', true, false, 'pnpm'],
     ['Windows x64 mixed manual run', 'workflow_dispatch', 'Windows', 'X64', true, false, 'pnpm']
-  ])('%s keeps its scoped store policy', (_name, event, os, arch, mixed, restore, cache) => {
-    const context = {
-      github: { event_name: event },
-      runner: { os, arch },
-      inputs: {
-        'cache-dependency-path': mixed ? 'pnpm-lock.yaml\nmobile/pnpm-lock.yaml' : 'pnpm-lock.yaml'
-      },
-      contains: (value, search) => value.toLowerCase().includes(search.toLowerCase())
-    }
-    const evaluate = (expression) =>
-      runInNewContext(
-        expression.replaceAll('inputs.cache-dependency-path', 'inputs["cache-dependency-path"]'),
-        context
-      )
-    for (const step of action.runs.steps.filter(
-      (step) =>
-        step.id === 'pnpm-store' || step.name === 'Restore pnpm download store without saving'
-    )) {
-      expect(evaluate(step.if)).toBe(restore)
-    }
-    for (const step of action.runs.steps.filter((step) => step.uses === 'actions/setup-node@v6')) {
-      expect(evaluate(step.with.cache.slice(3, -2))).toBe(cache)
-      expect(step.with['package-manager-cache']).toBe(false)
+  ])(
+    '%s keeps its scoped store policy',
+    (_name, event, os, arch, mixed, restore, cache, storeCache = 'true') => {
+      const context = {
+        github: { event_name: event },
+        runner: { os, arch },
+        inputs: {
+          'cache-pnpm-store': storeCache,
+          'cache-dependency-path':
+            typeof mixed === 'string'
+              ? mixed
+              : mixed
+                ? 'pnpm-lock.yaml\nmobile/pnpm-lock.yaml'
+                : 'pnpm-lock.yaml'
+        },
+        contains: (value, search) => value.toLowerCase().includes(search.toLowerCase())
+      }
+      const evaluate = (expression) =>
+        runInNewContext(
+          expression
+            .replaceAll('inputs.cache-dependency-path', 'inputs["cache-dependency-path"]')
+            .replaceAll('inputs.cache-pnpm-store', 'inputs["cache-pnpm-store"]'),
+          context
+        )
+      for (const step of action.runs.steps.filter(
+        (step) =>
+          step.id === 'pnpm-store' || step.name === 'Restore pnpm download store without saving'
+      )) {
+        expect(evaluate(step.if)).toBe(restore)
+      }
+      for (const step of action.runs.steps.filter(
+        (step) => step.uses === 'actions/setup-node@v6'
+      )) {
+        expect(evaluate(step.with.cache.slice(3, -2))).toBe(cache)
+        expect(step.with['package-manager-cache']).toBe(false)
+      }
     }
+  )
+
+  it('opts Windows server consumers out while preserving the main warmer store writer', () => {
+    const installer = './.github/actions/install-node-dependencies'
+    const persistence = workflow('node-server-tests').jobs.persistence.steps.find(
+      (step) => step.uses === installer
+    )
+    const ssh = workflow('ssh-windows-hosts').jobs.hosts.steps.find(
+      (step) => step.uses === installer
+    )
+    const warmer = workflow('ci-cache-warmup').jobs['warm-windows'].steps.find(
+      (step) => step.uses === installer
+    )
+    expect(action.inputs['cache-pnpm-store'].default).toBe('true')
+    expect(persistence.with['cache-pnpm-store']).toBe("${{ runner.os != 'Windows' }}")
+    expect(ssh.with['cache-pnpm-store']).toBe('false')
+    expect(warmer.with['cache-pnpm-store']).toBeUndefined()
   })
 
   it('restores Windows packaging downloads from the release cache without a PR upload', () => {
diff --git a/config/scripts/mobile-release-shell-switch-workflow.test.mjs b/config/scripts/mobile-release-shell-switch-workflow.test.mjs
index f6f05c779eb..aa6917acb3c 100644
--- a/config/scripts/mobile-release-shell-switch-workflow.test.mjs
+++ b/config/scripts/mobile-release-shell-switch-workflow.test.mjs
@@ -122,7 +122,7 @@ const REVIEWED_COMPUTED_PATHS = [
   '${{ steps.pnpm-store.outputs.path }}',
   // Only pnpm's lockfile-verified.jsonl record, never Metro transforms.
   '${{ steps.verification-cache.outputs.path }}',
-  "${{ github.event_name != 'pull_request' && 'pnpm' || '' }} store"
+  "${{ github.event_name != 'pull_request' && inputs.cache-pnpm-store != 'false' && 'pnpm' || '' }} store"
 ]
 
 /** Every step a workflow runs, descending into the repository's own composite actions. */
diff --git a/config/scripts/pr-workflow-parallelism.test.mjs b/config/scripts/pr-workflow-parallelism.test.mjs
index 611dd974b79..43e8784f185 100644
--- a/config/scripts/pr-workflow-parallelism.test.mjs
+++ b/config/scripts/pr-workflow-parallelism.test.mjs
@@ -289,7 +289,8 @@ describe('PR workflow parallelism', () => {
     expect(steps[pnpmIndex].uses).toBe('pnpm/setup@v2')
     expect(steps[pnpmIndex].with.version).toBeUndefined()
     expect(steps[pnpmIndex].with.install).toBe(false)
-    const saveOutsidePrs = "${{ github.event_name != 'pull_request' && 'pnpm' || '' }}"
+    const saveOutsidePrs =
+      "${{ github.event_name != 'pull_request' && inputs.cache-pnpm-store != 'false' && 'pnpm' || '' }}"
     expect(steps[nodeIndex].with.cache).toBe(saveOutsidePrs)
     expect(steps[nodeIndex].if).toBe("inputs.node-version == ''")
     expect(steps[requestedNodeIndex].if).toBe("inputs.node-version != ''")
@@ -304,7 +305,7 @@ describe('PR workflow parallelism', () => {
     )
     expect(steps[restoreIndex].uses).toBe('actions/cache/restore@v5')
     expect(steps[restoreIndex].if).toBe(
-      "github.event_name == 'pull_request' && (runner.os != 'Windows' || runner.arch != 'X64' || !contains(inputs.cache-dependency-path, 'mobile/pnpm-lock.yaml'))"
+      "github.event_name == 'pull_request' && inputs.cache-pnpm-store != 'false' && (runner.os != 'Windows' || !(runner.arch == 'X64' && contains(inputs.cache-dependency-path, 'mobile/pnpm-lock.yaml')) && !((runner.arch == 'X64' || runner.arch == 'ARM64') && inputs.cache-dependency-path == 'pnpm-lock.yaml'))"
     )
   })
 
diff --git a/docs/reference/ci-runner-efficiency.md b/docs/reference/ci-runner-efficiency.md
index 77b6479804b..f72fa3f2d26 100644
--- a/docs/reference/ci-runner-efficiency.md
+++ b/docs/reference/ci-runner-efficiency.md
@@ -76,6 +76,41 @@ request reuse only following an exact prepared native-cache hit; manual SSH and
 all release builders retain fresh compilation. Subsequent staging checks still
 run. Hosted validation and the reuse interval remain to be measured.
 
+## Windows root download stores: registry installs finish sooner
+
+Three paired samples on each Windows architecture compared the existing exact
+main download-store restore with a fresh registry install. Each treatment used a
+fresh dependency tree, store and pnpm metadata, with registry-first ordering in
+sample 2. Both restored the same policy-checked verification record before timing.
+All six pairs used Node 24.21.0 and pnpm 12.8.1; manifest digests and installed
+lockfile digests matched, and both retained frozen, script-free installation.
+
+| Runner        | Cached totals (seconds)     | Registry totals (seconds)   | Paired median saving |
+| ------------- | --------------------------- | --------------------------- | -------------------- |
+| Windows x64   | 26.820 / 28.885 / 27.751    | 13.644 / 14.126 / 12.908    | 14.759 seconds       |
+| Windows ARM64 | 216.540 / 288.492 / 189.342 | 119.856 / 238.562 / 115.611 | 73.731 seconds       |
+
+The x64 samples are the three successful Windows 2022 jobs in
+[run 37064549378](https://github.com/stablyai/orca/actions/runs/37064549378).
+Its ARM cleanup guard rejected pnpm's setup-owned store path before measurement;
+those incomplete ARM jobs are excluded. The corrected
+[ARM-only run](https://github.com/stablyai/orca/actions/runs/37065220916) passed all
+three samples. Earlier rejected measurements also stopped before installation
+because an optional config file was absent; none count toward these timings.
+
+Intervals include actual store lookup/restore, inter-step overhead and root
+installation. Checkout, toolchain setup, tree/store reset, verification-record
+restoration and native preparation are excluded. ARM variation is substantial;
+these samples do not measure whole-workflow, queue or billing savings.
+
+Root-only Windows x64/ARM64 PR installs now skip the download-store restore.
+The existing x64 mixed-install exception remains. An explicit store opt-out also
+lets Windows headless persistence and SSH jobs avoid the archive on main or
+manual runs. Frozen installs, verification records, native caches and every
+qualification check remain. Other lockfile sets and platforms keep their
+existing policy. Default non-PR writers, including the warmer, still seed stores
+for direct setup-node consumers and workflows that run package scripts.
+
 ## October 1 Windows and dependency cache follow-up
 
 [PR #24355](https://github.com/stablyai/orca/pull/24355) merged at `197ea3a3`.