diff --git a/backend/main.py b/backend/main.py
index 6640b19..d14f098 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -55,7 +55,7 @@ async def lifespan(app: FastAPI):
     schedule_task.cancel()
 
 
-app = FastAPI(title="StackPilot", version="0.21.1", lifespan=lifespan)
+app = FastAPI(title="StackPilot", version="0.21.2", lifespan=lifespan)
 
 app.add_middleware(
     CORSMiddleware,
diff --git a/backend/services/port_service.py b/backend/services/port_service.py
index eb5465f..fb205c3 100644
--- a/backend/services/port_service.py
+++ b/backend/services/port_service.py
@@ -103,12 +103,21 @@ def host_listening_ports() -> dict[str, set[int]]:
     }
 
 
-def docker_bound_ports() -> dict[tuple[int, str], str]:
-    """Return {(host_port, proto): container_name}."""
-    out: dict[tuple[int, str], str] = {}
+COMPOSE_PROJECT_LABEL = "com.docker.compose.project"
+
+
+def docker_bound_ports() -> dict[tuple[int, str], tuple[str, Optional[str]]]:
+    """Return {(host_port, proto): (container_name, compose_project)}.
+
+    The compose project is taken from the container's compose label so a
+    stack's own running containers can be reliably recognised on re-deploy,
+    regardless of explicit container_name or name separator differences.
+    """
+    out: dict[tuple[int, str], tuple[str, Optional[str]]] = {}
     try:
         client = get_client()
         for c in safe_call(client.containers.list):
+            project = (c.labels or {}).get(COMPOSE_PROJECT_LABEL)
             bindings = (c.attrs.get("NetworkSettings") or {}).get("Ports") or {}
             for container_port, hosts in bindings.items():
                 if not hosts:
@@ -117,7 +126,7 @@ def docker_bound_ports() -> dict[tuple[int, str], str]:
                 for h in hosts:
                     hp = h.get("HostPort")
                     if hp:
-                        out[(int(hp), proto)] = c.name
+                        out[(int(hp), proto)] = (c.name, project)
     except (DockerError, ValueError):
         pass
     return out
@@ -140,10 +149,16 @@ def detect_conflicts(yaml_str: str, ignore_stack: Optional[str] = None) -> list[
         used_by = None
         owner = docker_ports.get((port, proto))
         if owner:
+            owner_name, owner_project = owner
             # A container from the same stack (re-deploy) is not a conflict.
-            if ignore_stack and owner.startswith(f"{ignore_stack}-"):
+            # Match on the compose project label, falling back to the legacy
+            # name-prefix check for containers without the label.
+            if ignore_stack and (
+                owner_project == ignore_stack
+                or owner_name.startswith(f"{ignore_stack}-")
+            ):
                 continue
-            used_by = f"container {owner}"
+            used_by = f"container {owner_name}"
         elif port in host_ports.get(proto, set()):
             used_by = "host process"
         if used_by: