diff --git a/apps/planner/app/components/SessionView.tsx b/apps/planner/app/components/SessionView.tsx
index 77d9517..0c2ea56 100644
--- a/apps/planner/app/components/SessionView.tsx
+++ b/apps/planner/app/components/SessionView.tsx
@@ -4,7 +4,7 @@ import { Link } from "react-router";
 import type { TFunction } from "i18next";
 import * as Sentry from "@sentry/react";
 import { useYjs, type YjsState } from "~/lib/use-yjs";
-import { useRouting } from "~/lib/use-routing";
+import { useRouting, type RouteError } from "~/lib/use-routing";
 import { ProfileSelector } from "~/components/ProfileSelector";
 import { ExportButton } from "~/components/ExportButton";
 import { SaveToJournalButton } from "~/components/SaveToJournalButton";
@@ -25,26 +25,32 @@ const ElevationChart = lazy(() =>
 interface Toast {
   id: number;
   message: string;
+  variant?: "error" | "info";
 }
 
 let toastIdCounter = 0;
 
-function useAwarenessToasts(yjs: YjsState | null, t: TFunction) {
+function useToasts() {
   const [toasts, setToasts] = useState<Toast[]>([]);
+
+  const addToast = useCallback((message: string, variant: Toast["variant"] = "info") => {
+    const id = ++toastIdCounter;
+    setToasts((prev) => [...prev, { id, message, variant }]);
+    setTimeout(() => {
+      setToasts((prev) => prev.filter((toast) => toast.id !== id));
+    }, 4000);
+  }, []);
+
+  return { toasts, addToast };
+}
+
+function useAwarenessToasts(yjs: YjsState | null, t: TFunction, addToast: (message: string) => void) {
   const namesCacheRef = useRef<Map<number, string>>(new Map());
   const initializedRef = useRef(false);
 
   useEffect(() => {
     if (!yjs) return;
 
-    const addToast = (message: string) => {
-      const id = ++toastIdCounter;
-      setToasts((prev) => [...prev, { id, message }]);
-      setTimeout(() => {
-        setToasts((prev) => prev.filter((toast) => toast.id !== id));
-      }, 3000);
-    };
-
     const handleChange = (
       changes: { added: number[]; updated: number[]; removed: number[] },
     ) => {
@@ -100,9 +106,7 @@ function useAwarenessToasts(yjs: YjsState | null, t: TFunction) {
       initializedRef.current = false;
       namesCacheRef.current.clear();
     };
-  }, [yjs, t]);
-
-  return toasts;
+  }, [yjs, t, addToast]);
 }
 
 function ColorModeToggle({ yjs }: { yjs: YjsState }) {
@@ -181,9 +185,23 @@ export function SessionView({ sessionId, callbackUrl, callbackToken, returnUrl,
   const { t } = useTranslation("planner");
   useEffect(() => { Sentry.setTag("session_id", sessionId); }, [sessionId]);
   const yjs = useYjs(sessionId, initialWaypoints);
-  const { computing, routeStats, requestRoute } = useRouting(yjs);
+  const { computing, routeError, routeStats, requestRoute } = useRouting(yjs);
   const [highlightPosition, setHighlightPosition] = useState<[number, number] | null>(null);
-  const toasts = useAwarenessToasts(yjs, t);
+  const { toasts, addToast } = useToasts();
+  useAwarenessToasts(yjs, t, addToast);
+
+  // Show toast on route calculation error
+  const prevErrorRef = useRef<RouteError>(null);
+  useEffect(() => {
+    if (routeError && routeError !== prevErrorRef.current) {
+      const message =
+        routeError === "rate_limit" ? t("rateLimitExceeded") :
+        routeError === "no_route" ? t("noRouteFound") :
+        t("routeError");
+      addToast(message, "error");
+    }
+    prevErrorRef.current = routeError;
+  }, [routeError, addToast, t]);
 
   const handleElevationHover = useCallback((pos: [number, number] | null) => {
     setHighlightPosition(pos);
@@ -258,7 +276,9 @@ export function SessionView({ sessionId, callbackUrl, callbackToken, returnUrl,
           {toasts.map((toast) => (
             <div
               key={toast.id}
-              className="rounded-lg bg-gray-800 px-4 py-2 text-sm text-white shadow-lg animate-[fadeIn_0.2s_ease-out]"
+              className={`rounded-lg px-4 py-2 text-sm text-white shadow-lg animate-[fadeIn_0.2s_ease-out] ${
+                toast.variant === "error" ? "bg-red-600" : "bg-gray-800"
+              }`}
             >
               {toast.message}
             </div>
diff --git a/apps/planner/app/lib/brouter.ts b/apps/planner/app/lib/brouter.ts
index 4b24a34..b772c3c 100644
--- a/apps/planner/app/lib/brouter.ts
+++ b/apps/planner/app/lib/brouter.ts
@@ -61,11 +61,21 @@ export async function computeRoute(request: RouteRequest): Promise<EnrichedRoute
   return mergeGeoJsonSegments(segments);
 }
 
+export class BRouterError extends Error {
+  constructor(
+    message: string,
+    public readonly statusCode: number,
+  ) {
+    super(message);
+    this.name = "BRouterError";
+  }
+}
+
 async function fetchSegment(url: string): Promise<Record<string, unknown>> {
   const response = await fetch(url);
   if (!response.ok) {
     const body = await response.text();
-    throw new Error(`BRouter error (${response.status}): ${body}`);
+    throw new BRouterError(body.trim(), response.status);
   }
   return response.json() as Promise<Record<string, unknown>>;
 }
diff --git a/apps/planner/app/lib/use-routing.ts b/apps/planner/app/lib/use-routing.ts
index 0e1e4df..3283da5 100644
--- a/apps/planner/app/lib/use-routing.ts
+++ b/apps/planner/app/lib/use-routing.ts
@@ -21,11 +21,36 @@ function getWaypointsFromYjs(waypoints: Y.Array<Y.Map<unknown>>): WaypointData[]
   }));
 }
 
+function restoreWaypoints(yjs: YjsState, snapshot: WaypointData[], restoringRef: React.RefObject<boolean>) {
+  restoringRef.current = true;
+  yjs.doc.transact(() => {
+    for (let i = 0; i < snapshot.length && i < yjs.waypoints.length; i++) {
+      const yMap = yjs.waypoints.get(i);
+      const wp = snapshot[i]!;
+      if (yMap) {
+        yMap.set("lat", wp.lat);
+        yMap.set("lon", wp.lon);
+      }
+    }
+    // Remove extra waypoints added since snapshot
+    if (yjs.waypoints.length > snapshot.length) {
+      yjs.waypoints.delete(snapshot.length, yjs.waypoints.length - snapshot.length);
+    }
+  });
+  // Reset after microtask so Yjs observers fire first
+  queueMicrotask(() => { restoringRef.current = false; });
+}
+
+export type RouteError = "no_route" | "failed" | "rate_limit" | null;
+
 export function useRouting(yjs: YjsState | null) {
   const [isHost, setIsHost] = useState(false);
   const [computing, setComputing] = useState(false);
+  const [routeError, setRouteError] = useState<RouteError>(null);
   const [routeStats, setRouteStats] = useState<RouteStats>({});
   const debounceTimer = useRef<ReturnType<typeof setTimeout>>(undefined);
+  const lastGoodWaypointsRef = useRef<WaypointData[] | null>(null);
+  const restoringRef = useRef(false);
 
   // Host election via Yjs awareness
   useEffect(() => {
@@ -56,6 +81,9 @@ export function useRouting(yjs: YjsState | null) {
         points: (yMap.get("points") as Array<{ lat: number; lon: number }>) ?? [],
       })).filter((a) => a.points.length >= 3);
 
+      // Save current waypoints so we can restore on failure
+      const snapshotBeforeCompute = getWaypointsFromYjs(yjs.waypoints);
+
       setComputing(true);
       try {
         const response = await fetch("/api/route", {
@@ -69,13 +97,22 @@ export function useRouting(yjs: YjsState | null) {
         });
 
         if (response.status === 429) {
-          console.warn("[Rate Limit] Route computation rate limit exceeded");
+          setRouteError("rate_limit");
+          restoreWaypoints(yjs, lastGoodWaypointsRef.current ?? snapshotBeforeCompute, restoringRef);
+          return;
+        }
+        if (!response.ok) {
+          const body = await response.json().catch(() => ({}));
+          const code = (body as { code?: string }).code;
+          setRouteError(code === "no_route" ? "no_route" : "failed");
+          restoreWaypoints(yjs, lastGoodWaypointsRef.current ?? snapshotBeforeCompute, restoringRef);
           return;
         }
-        if (!response.ok) return;
 
         const enriched = await response.json();
 
+        setRouteError(null);
+        lastGoodWaypointsRef.current = snapshotBeforeCompute;
         setRouteStats({
           distance: enriched.totalLength || undefined,
           elevationGain: enriched.totalAscend || undefined,
@@ -91,7 +128,8 @@ export function useRouting(yjs: YjsState | null) {
           }
         });
       } catch {
-        // Route computation failed
+        setRouteError("failed");
+        restoreWaypoints(yjs, lastGoodWaypointsRef.current ?? snapshotBeforeCompute, restoringRef);
       } finally {
         setComputing(false);
       }
@@ -101,7 +139,7 @@ export function useRouting(yjs: YjsState | null) {
 
   const requestRoute = useCallback(
     (waypoints: WaypointData[]) => {
-      if (!isHost) return;
+      if (!isHost || restoringRef.current) return;
       if (debounceTimer.current) clearTimeout(debounceTimer.current);
       debounceTimer.current = setTimeout(() => computeRoute(waypoints), 500);
     },
@@ -139,5 +177,5 @@ export function useRouting(yjs: YjsState | null) {
     };
   }, [yjs, isHost, requestRoute]);
 
-  return { isHost, computing, routeStats, requestRoute };
+  return { isHost, computing, routeError, routeStats, requestRoute };
 }
diff --git a/apps/planner/app/routes/api.route.ts b/apps/planner/app/routes/api.route.ts
index 4ab4899..7f7e025 100644
--- a/apps/planner/app/routes/api.route.ts
+++ b/apps/planner/app/routes/api.route.ts
@@ -1,6 +1,6 @@
 import { data } from "react-router";
 import type { Route } from "./+types/api.route";
-import { computeRoute } from "~/lib/brouter";
+import { computeRoute, BRouterError } from "~/lib/brouter";
 import { checkRateLimit } from "~/lib/rate-limit";
 
 export async function action({ request }: Route.ActionArgs) {
@@ -40,7 +40,11 @@ export async function action({ request }: Route.ActionArgs) {
       headers: { "X-RateLimit-Remaining": String(limit.remaining) },
     });
   } catch (e) {
+    if (e instanceof BRouterError && e.statusCode >= 400 && e.statusCode < 500) {
+      // BRouter client error: unroutable waypoints, missing tiles, etc.
+      return data({ error: e.message, code: "no_route" }, { status: 422 });
+    }
     const message = e instanceof Error ? e.message : "Route computation failed";
-    return data({ error: message }, { status: 502 });
+    return data({ error: message, code: "server_error" }, { status: 502 });
   }
 }
diff --git a/packages/i18n/src/locales/de.ts b/packages/i18n/src/locales/de.ts
index 48ad53a..72080a3 100644
--- a/packages/i18n/src/locales/de.ts
+++ b/packages/i18n/src/locales/de.ts
@@ -22,6 +22,8 @@ export default {
     connecting: "Verbinde...",
     loadingMap: "Karte wird geladen...",
     computingRoute: "Route wird berechnet...",
+    routeError: "Routenberechnung fehlgeschlagen. Bitte versuche es erneut.",
+    noRouteFound: "Keine Route gefunden. Versuche den Wegpunkt auf einen Weg zu verschieben.",
     host: "Host",
     connected: "Verbunden",
     saveToJournal: "Im Journal speichern",
diff --git a/packages/i18n/src/locales/en.ts b/packages/i18n/src/locales/en.ts
index 838416e..51af6f7 100644
--- a/packages/i18n/src/locales/en.ts
+++ b/packages/i18n/src/locales/en.ts
@@ -22,6 +22,8 @@ export default {
     connecting: "Connecting...",
     loadingMap: "Loading map...",
     computingRoute: "Computing route...",
+    routeError: "Route calculation failed. Please try again.",
+    noRouteFound: "No route found. Try moving the waypoint to a road or path.",
     host: "Host",
     connected: "Connected",
     saveToJournal: "Save to Journal",