diff --git a/gns3server/compute/base_node.py b/gns3server/compute/base_node.py
index e6ef96e05..e2431ffa0 100644
--- a/gns3server/compute/base_node.py
+++ b/gns3server/compute/base_node.py
@@ -1256,7 +1256,13 @@ class BaseNode:
         desired = {(name, spec.get("link_id", "")): spec for name, spec in markers.items()}
 
         # 1. Remove installed markers that are no longer desired (marker/def delete).
+        # Scope to THIS bridge: the map is node-wide and also holds markers
+        # installed on this node's other links/NIOs. Without this guard,
+        # reconciling one NIO would delete every other link's markers + pcaps
+        # (desired only carries the current NIO's markers) — a regression.
         for key in list(self._marker_filter_bridges):
+            if self._marker_filter_bridges[key] != bridge_name:
+                continue
             if key not in desired:
                 mname, link_id = key
                 installed_bridge = self._marker_filter_bridges.pop(key)
diff --git a/gns3server/compute/iou/iou_vm.py b/gns3server/compute/iou/iou_vm.py
index 5875af365..ff46bb4fb 100644
--- a/gns3server/compute/iou/iou_vm.py
+++ b/gns3server/compute/iou/iou_vm.py
@@ -1291,7 +1291,12 @@ class IOUVM(BaseNode):
         desired = {(name, spec.get("link_id", "")): spec for name, spec in markers.items()}
 
         # 1. Remove installed markers that are no longer desired.
+        # Scope to THIS port's IOL location — the map is node-wide and also
+        # holds markers on this IOU's other ports, which must not be deleted
+        # when reconciling a single NIO (see base_node for the same guard).
         for key in list(self._marker_filter_bridges):
+            if self._marker_filter_bridges[key] != location:
+                continue
             if key not in desired:
                 mname, link_id = key
                 installed_location = self._marker_filter_bridges.pop(key)
diff --git a/tests/compute/test_base_node.py b/tests/compute/test_base_node.py
index f57b71fff..fa8dce6a5 100644
--- a/tests/compute/test_base_node.py
+++ b/tests/compute/test_base_node.py
@@ -410,6 +410,36 @@ async def test_apply_markers_rebuilds_changed_bpf(compute_project, manager):
     assert any("add_packet_filter VPCS-10 m mark" in c and "tcp" in c for c in cmds)  # new added
 
 
+@pytest.mark.asyncio
+async def test_apply_markers_preserves_markers_on_other_bridges(compute_project, manager):
+    # Regression: reconciling one NIO must not delete markers installed on this
+    # node's OTHER bridges/NIOs. _marker_filter_bridges is node-wide, but
+    # `desired` only carries the current NIO's markers — the delete pass must be
+    # scoped to the current bridge, or updating one link wipes every other link's
+    # markers + pcaps.
+    node = VPCSVM("test", "00010203-0405-0607-0809-0a0b0c0d0e0f", compute_project, manager)
+    node._ubridge_send = AsyncioMagicMock()
+    node._ubridge_hypervisor = MagicMock()
+    node._ubridge_hypervisor.is_running.return_value = True
+    # Two links, each with a marker on its own bridge:
+    node._marker_filter_bridges["m", "L1"] = "VPCS-10"
+    node._marker_specs["m", "L1"] = {"bpf": "icmp", "enabled": True}
+    node._marker_filter_bridges["m", "L2"] = "VPCS-20"
+    node._marker_specs["m", "L2"] = {"bpf": "tcp", "enabled": True}
+    # Update only the VPCS-10 NIO; "m" is gone from this link — but the marker
+    # on VPCS-20 (L2) must survive untouched.
+    nio = NIOUDP(1234, "127.0.0.1", 4321)
+    nio.markers = {}
+    with patch("gns3server.compute.marker.marker_manager.MarkerManager") as mm:
+        mm.instance.return_value.unregister = MagicMock()
+        await node._ubridge_apply_markers("VPCS-10", nio)
+    cmds = [c.args[0] for c in node._ubridge_send.call_args_list]
+    assert any("delete_packet_filter VPCS-10 m" in c for c in cmds)   # L1 removed on its bridge
+    assert not any("VPCS-20" in c for c in cmds)                      # other bridge untouched
+    assert ("m", "L1") not in node._marker_filter_bridges
+    assert ("m", "L2") in node._marker_filter_bridges                 # L2 preserved
+
+
 @pytest.mark.asyncio
 async def test_stop_ubridge_clears_marker_bridges(compute_project, manager):
     # uBridge stopping drops every marker filter — the map must clear so the next