diff --git a/nix/host-modules/swarm-grafana/dashboards/agents.json b/nix/host-modules/swarm-grafana/dashboards/agents.json
index c4e80216..02b9ec35 100644
--- a/nix/host-modules/swarm-grafana/dashboards/agents.json
+++ b/nix/host-modules/swarm-grafana/dashboards/agents.json
@@ -1404,6 +1404,80 @@
             }
           }
         }
+      },
+      "panel-46": {
+        "kind": "Panel",
+        "spec": {
+          "id": 46,
+          "title": "Distinct subagents by agent, over time",
+          "description": "mara: \"the subagent should already stamp the agent on the metric. so i want to see count of distinct subagent names per agent name over time\" — it does (claude_code.session.count carries both agent and subagent labels on a subagent's own turns). One line per parent agent: at each point, how many differently-named subagents had at least one turn in the trailing $__rate_interval window. This is a ROLLING distinct count, not a running total — it can go back down once a batch of subagents stops running, same shape as any other rate()-style panel on this board. A true concurrent-right-now count (subagents open at this exact instant, able to rise and fall between scrapes) would need hive-subagent-mcp to publish its own gauge on start/stop; nothing does today, and that's a different, harder ask than this one.",
+          "links": [],
+          "data": {
+            "kind": "QueryGroup",
+            "spec": {
+              "queries": [
+                {
+                  "kind": "PanelQuery",
+                  "spec": {
+                    "query": {
+                      "kind": "DataQuery",
+                      "group": "prometheus",
+                      "version": "v0",
+                      "datasource": {
+                        "name": "@datasourceUid@"
+                      },
+                      "spec": {
+                        "expr": "count by (agent) (count by (agent, subagent) (increase({__name__=\"claude_code.session.count\", hive=~\"$hive\", agent=~\"$agent\", subagent!=\"\"}[$__rate_interval]) > 0))",
+                        "legendFormat": "{{agent}}"
+                      }
+                    },
+                    "refId": "A",
+                    "hidden": false
+                  }
+                }
+              ],
+              "transformations": [],
+              "queryOptions": {}
+            }
+          },
+          "vizConfig": {
+            "kind": "VizConfig",
+            "group": "timeseries",
+            "version": "",
+            "spec": {
+              "options": {
+                "legend": {
+                  "calcs": [],
+                  "displayMode": "list",
+                  "placement": "bottom",
+                  "showLegend": true
+                },
+                "tooltip": {
+                  "mode": "multi",
+                  "sort": "desc"
+                }
+              },
+              "fieldConfig": {
+                "defaults": {
+                  "unit": "short",
+                  "decimals": 0,
+                  "color": {
+                    "mode": "palette-classic"
+                  },
+                  "custom": {
+                    "axisSoftMin": 0,
+                    "drawStyle": "line",
+                    "fillOpacity": 0,
+                    "lineWidth": 1,
+                    "showPoints": "never",
+                    "spanNulls": false
+                  }
+                },
+                "overrides": []
+              }
+            }
+          }
+        }
       }
     },
     "layout": {
@@ -1690,6 +1764,19 @@
                           "name": "panel-45"
                         }
                       }
+                    },
+                    {
+                      "kind": "GridLayoutItem",
+                      "spec": {
+                        "x": 0,
+                        "y": 15,
+                        "width": 24,
+                        "height": 8,
+                        "element": {
+                          "kind": "ElementReference",
+                          "name": "panel-46"
+                        }
+                      }
                     }
                   ]
                 }