diff --git a/files/ansible-playbooks/ptsd-migrate.yml b/files/ansible-playbooks/ptsd-migrate.yml
index cc053cc..8c7df9a 100644
--- a/files/ansible-playbooks/ptsd-migrate.yml
+++ b/files/ansible-playbooks/ptsd-migrate.yml
@@ -588,6 +588,31 @@
           esac
       changed_when: false
 
+    # ============================ PHASE 0 (LAST, BEFORE PPP CHECK): IN-PROGRESS MARKER GUARD ============================
+    - name: "PHASE 0 (LAST) | DEV2 check: /tmp/ptst.inprogress marker exists (show-stopper) via wrapper"
+      delegate_to: localhost
+      ansible.builtin.shell: |
+        export DEV2_CMD="test -f /tmp/ptst.inprogress && echo YES || echo NO"
+        {{ dev2_exec_cmd }}
+      args: { executable: /bin/bash }
+      register: dev2_inprogress_marker
+      changed_when: false
+      failed_when: false
+
+    - name: "PHASE 0 (LAST) | Graceful stop if DEV2 in-progress marker is present"
+      when: (dev2_inprogress_marker.stdout | default('') | trim) == "YES"
+      delegate_to: localhost
+      ansible.builtin.debug:
+        msg:
+          - "Show-stopper: DEV2 has /tmp/ptst.inprogress marker present."
+          - "We shall not continue: concurrent work appears to be in progress."
+          - "dev2_conn_final={{ dev2_conn_final }}"
+      changed_when: false
+
+    - name: "PHASE 0 (LAST) | End host if DEV2 in-progress marker is present"
+      when: (dev2_inprogress_marker.stdout | default('') | trim) == "YES"
+      ansible.builtin.meta: end_host
+
 
     # ============================ PHASE 0 (LAST): DEV2 STATE GUARD (OLD PPP EXPECTED) ============================
     - name: "PHASE 0 (LAST) | DEV2 check: ppp0 has IPv4 (old expected) via wrapper"