diff --git a/netx_api/ume_topology_world_graph.py b/netx_api/ume_topology_world_graph.py
index 2f2e045..de37aa4 100644
--- a/netx_api/ume_topology_world_graph.py
+++ b/netx_api/ume_topology_world_graph.py
@@ -525,6 +525,9 @@ def get_flat_view_graph(
     )
     if region_folder_ids is not None:
         q = q.filter(TopoFabricNode.region_folder_id.in_(list(region_folder_ids)))
+
+    truncated = False
+    reason = ""
     if sbn_id.strip():
         sid = sbn_id.strip()
         # Attr JSON filter is rare; keep Python filter but only after a bounded fetch.
@@ -535,16 +538,34 @@ def get_flat_view_graph(
             if str((n.attrs or {}).get("ume_sbn_id") or "") == sid
             or str(n.region_folder_id or "") == sid
         ]
+        if len(nodes) > WORLD_NODE_SOFT_CAP:
+            nodes = nodes[:WORLD_NODE_SOFT_CAP]
+            truncated = True
+            reason = "too_many_viewport_nodes"
     else:
-        # Cap in SQL so we never hydrate 15k ORM rows for a single browser canvas.
-        nodes = q.order_by(TopoFabricNode.id.asc()).limit(WORLD_NODE_SOFT_CAP + 1).all()
-
-    truncated = False
-    reason = ""
-    if len(nodes) > WORLD_NODE_SOFT_CAP:
-        nodes = nodes[:WORLD_NODE_SOFT_CAP]
-        truncated = True
-        reason = "too_many_viewport_nodes"
+        # Cap so we never hydrate 15k ORM rows. Stride across world-order so the
+        # overview is spread out (id-prefix order clumps one corner of the map).
+        id_rows = (
+            q.with_entities(TopoFabricNode.id)
+            .order_by(TopoFabricNode.world_x.asc(), TopoFabricNode.world_y.asc())
+            .all()
+        )
+        total = len(id_rows)
+        if total <= WORLD_NODE_SOFT_CAP:
+            pick_ids = [str(r[0]) for r in id_rows]
+        else:
+            stride = max(1, total // WORLD_NODE_SOFT_CAP)
+            pick_ids = [str(r[0]) for r in id_rows[::stride][:WORLD_NODE_SOFT_CAP]]
+            truncated = True
+            reason = "too_many_viewport_nodes"
+        nodes = (
+            db.query(TopoFabricNode).filter(TopoFabricNode.id.in_(pick_ids)).all()
+            if pick_ids
+            else []
+        )
+        # Preserve world-order for stable layout / fitView.
+        order = {nid: i for i, nid in enumerate(pick_ids)}
+        nodes.sort(key=lambda n: order.get(str(n.id), 0))
 
     fids = [n.id for n in nodes]
     fid_set = set(fids)
diff --git a/web/src/pages/TopologyPage.tsx b/web/src/pages/TopologyPage.tsx
index 1e24e12..2c1c4d0 100644
--- a/web/src/pages/TopologyPage.tsx
+++ b/web/src/pages/TopologyPage.tsx
@@ -1095,6 +1095,8 @@ export function TopologyPage() {
   const dirtyRef = useRef(false);
   const appliedMapIdRef = useRef("");
   const appliedGraphFpRef = useRef("");
+  /** Fit once after graph hydrate — world coords are far outside the default viewport. */
+  const pendingFitRef = useRef(false);
   const nodesRef = useRef<Node<NeNodeData>[]>([]);
   const historyRef = useRef<HistorySnap[]>([]);
   const redoRef = useRef<HistorySnap[]>([]);
@@ -1337,7 +1339,10 @@ export function TopologyPage() {
     return { drill, flatView };
   }, [activeRegion]);
 
-  const isWorldFlatCanvas = isWorldFlatViewName(activeView?.name);
+  const isWorldFlatCanvas =
+    isWorldFlatViewName(activeView?.name) ||
+    isWorldFlatViewName(graphQuery.data?.view?.name) ||
+    Boolean(graphQuery.data?.view?.filter?.world_flat);
 
   // Resolve World drill view id for shortcuts; do not auto-open canvas.
   useEffect(() => {
@@ -1587,11 +1592,34 @@ export function TopologyPage() {
       pendingEdgeCreatesRef.current = new Set();
       clearDirty();
       bumpHistory();
-      // Do not auto-fit on canvas switch — user clicks 适应画布.
+      // World / large canvases use absolute coords far outside the default RF
+      // viewport — without an initial fit the canvas looks empty after load.
+      pendingFitRef.current = nextNodes.length > 0;
     }
     historyLockRef.current = false;
   }, [canvasMode, mapId, graphQuery.data, edgeDefaults, setNodes, setEdges, clearDirty, bumpHistory]);
 
+  useEffect(() => {
+    if (!pendingFitRef.current || !nodes.length) return;
+    let cancelled = false;
+    let tries = 0;
+    const run = () => {
+      if (cancelled) return;
+      const inst = rfRef.current;
+      if (!inst) {
+        if (tries++ < 20) window.setTimeout(run, 50);
+        return;
+      }
+      pendingFitRef.current = false;
+      inst.fitView({ ...FIT_VIEW_OPTS, duration: 200 });
+    };
+    const t = window.setTimeout(run, 40);
+    return () => {
+      cancelled = true;
+      window.clearTimeout(t);
+    };
+  }, [nodes, mapId]);
+
   useEffect(() => {
     setEdges((eds) => eds.map((e) => withEdgeVisual(e, edgeDefaults)));
   }, [edgeDefaults, setEdges]);
@@ -3495,13 +3523,15 @@ export function TopologyPage() {
   const truncateBannerText = useMemo(() => {
     if (!graphTruncated) return "";
     // World map soft-caps viewport nodes; the banner is noise there.
-    if (isWorldFlatViewName(activeView?.name)) return "";
+    if (isWorldFlatViewName(activeView?.name) || Boolean(graphQuery.data?.view?.filter?.world_flat)) {
+      return "";
+    }
     if (truncateReason === "membership_cap") return t("topology.truncatedMembership");
     if (truncateReason === "membership_frozen") return t("topology.truncatedFrozen");
     if (truncateReason === "too_many_view_nodes") return t("topology.truncatedNodes");
     if (truncateReason === "too_many_edges") return t("topology.truncatedEdges");
     return t("topology.truncatedGeneric");
-  }, [graphTruncated, truncateReason, activeView?.name, t]);
+  }, [graphTruncated, truncateReason, activeView?.name, graphQuery.data?.view?.filter?.world_flat, t]);
   const activeLeafName = useMemo(() => {
     if (!mapId) return "";
     if (activeView?.name) return activeView.name;
@@ -4822,7 +4852,7 @@ export function TopologyPage() {
                   connectionLineStyle={{ stroke: "#38bdf8", strokeWidth: 2 }}
                   defaultEdgeOptions={{ type: "straight", labelShowBg: false }}
                   proOptions={{ hideAttribution: true }}
-                  minZoom={0.05}
+                  minZoom={isWorldFlatCanvas ? 0.005 : 0.05}
                   maxZoom={4}
                   nodesDraggable={toolBehavior.nodesDraggable}
                   nodesConnectable={toolBehavior.nodesConnectable}