diff --git a/frontend/src/shared/hooks/useLastDashboardId.ts b/frontend/src/shared/hooks/useLastDashboardId.ts
index 6ee67f8d..da83eb63 100644
--- a/frontend/src/shared/hooks/useLastDashboardId.ts
+++ b/frontend/src/shared/hooks/useLastDashboardId.ts
@@ -1,8 +1,8 @@
 import { useEffect, useState, useCallback } from 'react';
 import { useLocation } from 'react-router-dom';
+import { setLastDashboardId } from '@/shared/lastDashboardId';
 
 const STORAGE_KEY = 'openswarm_last_dashboard_id';
-const WINDOW_KEY = '__openswarm_last_dashboard_id';
 
 /** Sticky last-visited dashboard id so Dashboard stays mounted across non-dashboard nav. */
 export function useLastDashboardId(): [string | null, (id: string | null) => void] {
@@ -23,7 +23,7 @@ export function useLastDashboardId(): [string | null, (id: string | null) => voi
       try {
         localStorage.setItem(STORAGE_KEY, match[1]);
       } catch {}
-      (window as any)[WINDOW_KEY] = match[1];
+      setLastDashboardId(match[1]);
     }
   }, [location.pathname, lastId]);
 
@@ -36,11 +36,7 @@ export function useLastDashboardId(): [string | null, (id: string | null) => voi
         localStorage.removeItem(STORAGE_KEY);
       }
     } catch {}
-    if (id) {
-      (window as any)[WINDOW_KEY] = id;
-    } else {
-      delete (window as any)[WINDOW_KEY];
-    }
+    setLastDashboardId(id);
   }, []);
 
   return [lastId, setLastId];
diff --git a/frontend/src/shared/lastDashboardId.ts b/frontend/src/shared/lastDashboardId.ts
new file mode 100644
index 00000000..59da2f46
--- /dev/null
+++ b/frontend/src/shared/lastDashboardId.ts
@@ -0,0 +1,13 @@
+// The dashboard the user is currently on, mirrored to a window global so low-level non-React code (the addBrowserCard reducer) can tag a new browser card with its home dashboard at birth, instead of the card leaking onto every dashboard until the first layout save.
+const WINDOW_KEY = '__openswarm_last_dashboard_id';
+
+export function setLastDashboardId(id: string | null): void {
+  if (typeof window === 'undefined') return;
+  if (id) (window as any)[WINDOW_KEY] = id;
+  else delete (window as any)[WINDOW_KEY];
+}
+
+export function getLastDashboardId(): string | null {
+  if (typeof window === 'undefined') return null;
+  return ((window as any)[WINDOW_KEY] as string) || null;
+}
diff --git a/frontend/src/shared/state/dashboardLayoutSlice.ts b/frontend/src/shared/state/dashboardLayoutSlice.ts
index 32323bc8..77661a7b 100644
--- a/frontend/src/shared/state/dashboardLayoutSlice.ts
+++ b/frontend/src/shared/state/dashboardLayoutSlice.ts
@@ -1,6 +1,7 @@
 import { createSlice, createAsyncThunk, PayloadAction, createAction } from '@reduxjs/toolkit';
 import { launchAndSendFirstMessage } from './agentsSlice';
 import { API_BASE } from '@/shared/config';
+import { getLastDashboardId } from '@/shared/lastDashboardId';
 
 // fetchSession 404/410 strips the layout card to stop AgentChat remount-loop. Matched by string to avoid circular import.
 const fetchSessionRejectedAction = createAction<
@@ -708,6 +709,8 @@ const dashboardLayoutSlice = createSlice({
         width: DEFAULT_BROWSER_CARD_W,
         height: DEFAULT_BROWSER_CARD_H,
         zOrder: state.nextZOrder++,
+        // Born onto the current dashboard so it shows there and only there, never bleeding onto every dashboard while it waits for the first layout save to tag it.
+        dashboard_id: getLastDashboardId() ?? undefined,
       };
       state.pendingFocusBrowserId = id;
     },