diff --git a/.github/workflows/update-ecs-runner-qwen.yml b/.github/workflows/update-ecs-runner-qwen.yml
index 004c0677409..864f6832ea4 100644
--- a/.github/workflows/update-ecs-runner-qwen.yml
+++ b/.github/workflows/update-ecs-runner-qwen.yml
@@ -51,18 +51,20 @@ jobs:
           VERSION: '${{ steps.version.outputs.version }}'
         run: |-
           set -euo pipefail
-          global_prefix="$(npm prefix -g)"
-          if [[ -w "${global_prefix}" ]]; then
-            npm install -g "@qwen-code/qwen-code@${VERSION}"
-          else
-            sudo env "NPM_CONFIG_PREFIX=${global_prefix}" npm install -g "@qwen-code/qwen-code@${VERSION}"
-          fi
+          # The runner service resolves the system-wide qwen binary. Do not
+          # carry a runner user's custom npm prefix into the sudo install.
+          (
+            cd "${RUNNER_TEMP:?}"
+            sudo env -u NPM_CONFIG_PREFIX npm install -g --registry=https://registry.npmjs.org "@qwen-code/qwen-code@${VERSION}"
+          )
 
       - name: 'Verify version'
         env:
           VERSION: '${{ steps.version.outputs.version }}'
         run: |-
           set -euo pipefail
-          actual="$(qwen --version)"
+          qwen_path="$(command -v qwen)"
+          actual="$("${qwen_path}" --version)"
+          echo "qwen path: ${qwen_path}"
           echo "qwen version: ${actual}"
           test "${actual}" = "${VERSION}"
diff --git a/scripts/tests/update-ecs-runner-qwen-workflow.test.js b/scripts/tests/update-ecs-runner-qwen-workflow.test.js
index ecfde040b87..e331576a616 100644
--- a/scripts/tests/update-ecs-runner-qwen-workflow.test.js
+++ b/scripts/tests/update-ecs-runner-qwen-workflow.test.js
@@ -13,14 +13,8 @@ describe('ECS runner qwen update workflow', () => {
     'utf8',
   );
 
-  it('updates the npm prefix used by the selected runner', () => {
-    expect(workflow).toContain('global_prefix="$(npm prefix -g)"');
-    expect(workflow).toContain('if [[ -w "${global_prefix}" ]]');
-    expect(workflow).toContain(
-      'sudo env "NPM_CONFIG_PREFIX=${global_prefix}" npm install -g',
-    );
-    expect(workflow).toMatch(
-      /if \[\[ -w "\$\{global_prefix\}" \]\][\s\S]*?then\s*\n\s*npm install -g/,
-    );
+  it('installs without the selected runner npm prefix', () => {
+    expect(workflow).toContain('cd "${RUNNER_TEMP:?}"');
+    expect(workflow).toContain('sudo env -u NPM_CONFIG_PREFIX npm install -g');
   });
 });