diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 38d72a4..6d7a75a 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -194,6 +194,54 @@ jobs:
           pnpm add is-odd
         shell: bash
 
+  standalone_windows_self_update:
+    # Regression guard for the patchPnpmEnv PATH-shadow bug. When
+    # standalone: true on Windows AND the requested pnpm differs from the
+    # bootstrap, the previous patchPnpmEnv prepended node_modules/.bin to
+    # PATH; that directory contains an npm-created pnpm.cmd shim pointing
+    # at the BOOTSTRAP pnpm, which shadowed the self-updated pnpm at
+    # $PNPM_HOME/bin and caused `pnpm install` inside the action to run
+    # under the bootstrap version. Exercising a newer-pnpm-only flag
+    # (`--no-runtime`, added in 11.1.0) makes the regression assertable:
+    # if the bootstrap (11.0.4) handles the install, it errors with
+    # "Unknown option: 'runtime'".
+    name: 'Standalone Windows self-update (PATH regression)'
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
+
+      - name: Set up package.json with a minimal manifest
+        # run_install needs a manifest to install against. Removing the
+        # repo's existing pnpm-lock.yaml avoids frozen-lockfile mismatch.
+        run: |
+          rm -f pnpm-lock.yaml
+          echo '{"name":"sw","private":true,"packageManager":"pnpm@11.1.0"}' > package.json
+        shell: bash
+
+      - name: Run the action
+        uses: ./
+        with:
+          version: 11.1.0
+          standalone: true
+          run_install: |
+            args: ['--no-runtime']
+
+      - name: 'Test: pnpm install completed under the self-updated pnpm'
+        # If the bug recurs, the previous step's run_install will have failed
+        # the job with "Unknown option: 'runtime'", so reaching this step
+        # implies success. Still verify the version on PATH matches request.
+        env:
+          REQUIRED: '11.1.0'
+        run: |
+          set -e
+          actual="$(pnpm --version)"
+          echo "pnpm --version: ${actual}"
+          if [ "${actual}" != "${REQUIRED}" ]; then
+            echo "Expected pnpm ${REQUIRED}, got ${actual}"
+            exit 1
+          fi
+        shell: bash
+
   cache_store_path:
     # Regression guard for #233. When package.json pins a pnpm major that
     # differs from the bootstrap pnpm's major, the bootstrap reports its
diff --git a/dist/index.js b/dist/index.js
index c675785..ecacf49 100644
Binary files a/dist/index.js and b/dist/index.js differ
diff --git a/src/pnpm-install/index.ts b/src/pnpm-install/index.ts
index a3188ad..4702aa2 100644
--- a/src/pnpm-install/index.ts
+++ b/src/pnpm-install/index.ts
@@ -1,11 +1,8 @@
 import { setFailed, startGroup, endGroup } from '@actions/core'
 import { spawnSync } from 'child_process'
 import { Inputs } from '../inputs'
-import { patchPnpmEnv } from '../utils'
 
 export function runPnpmInstall(inputs: Inputs) {
-  const env = patchPnpmEnv(inputs)
-
   for (const options of inputs.runInstall) {
     const args = ['install']
     if (options.recursive) args.unshift('recursive')
@@ -14,11 +11,16 @@ export function runPnpmInstall(inputs: Inputs) {
     const cmdStr = ['pnpm', ...args].join(' ')
     startGroup(`Running ${cmdStr}...`)
 
+    // spawnSync inherits process.env, which already has $PNPM_HOME/bin and
+    // $PNPM_HOME prepended via addPath() in install-pnpm. Do NOT pass a
+    // hand-patched env that adds node_modules/.bin to the front — on
+    // Windows standalone, .bin/pnpm.cmd is an npm shim pointing at the
+    // BOOTSTRAP pnpm, which would shadow the self-updated one and break
+    // newer-pnpm-only behavior.
     const { error, status } = spawnSync('pnpm', args, {
       stdio: 'inherit',
       cwd: options.cwd,
       shell: true,
-      env,
     })
 
     endGroup()
diff --git a/src/pnpm-store-prune/index.ts b/src/pnpm-store-prune/index.ts
index 5b1a2dd..c7a2b35 100644
--- a/src/pnpm-store-prune/index.ts
+++ b/src/pnpm-store-prune/index.ts
@@ -1,7 +1,6 @@
 import { warning, startGroup, endGroup } from '@actions/core'
 import { spawnSync } from 'child_process'
 import { Inputs } from '../inputs'
-import { patchPnpmEnv } from '../utils'
 
 export function pruneStore(inputs: Inputs) {
   if (inputs.runInstall.length === 0) {
@@ -10,10 +9,11 @@ export function pruneStore(inputs: Inputs) {
   }
 
   startGroup('Running pnpm store prune...')
+  // spawnSync inherits process.env (which has the right PATH from addPath
+  // in install-pnpm). See pnpm-install/index.ts for the rationale.
   const { error, status } = spawnSync('pnpm', ['store', 'prune'], {
     stdio: 'inherit',
     shell: true,
-    env: patchPnpmEnv(inputs),
   })
   endGroup()
 
diff --git a/src/utils/index.ts b/src/utils/index.ts
deleted file mode 100644
index 2d83874..0000000
--- a/src/utils/index.ts
+++ /dev/null
@@ -1,10 +0,0 @@
-import path from 'path'
-import process from 'process'
-import { Inputs } from '../inputs'
-
-export const getBinDest = (inputs: Inputs): string => path.join(inputs.dest, 'node_modules', '.bin')
-
-export const patchPnpmEnv = (inputs: Inputs): NodeJS.ProcessEnv => ({
-  ...process.env,
-  PATH: path.join(getBinDest(inputs), 'bin') + path.delimiter + getBinDest(inputs) + path.delimiter + process.env.PATH,
-})