fix(frontend): clear ?subscription=success URL param after showing toast

Replace toastShownRef guard with router.replace(pathname) so the success
toast is not re-shown on page refresh and correctly re-fires on a second
checkout in the same SPA session. Adds test coverage for the behaviour.

autogpt_platform/frontend/src/app/(platform)/profile/(user)/credits/components/SubscriptionTierSection/__tests__/SubscriptionTierSection.test.tsx

@@ -10,12 +10,13 @@ import { SubscriptionTierSection } from "../SubscriptionTierSection";
 
 // Mock next/navigation
 const mockSearchParams = new URLSearchParams();
+const mockRouterReplace = vi.fn();
 vi.mock("next/navigation", async (importOriginal) => {
   const actual = await importOriginal<typeof import("next/navigation")>();
   return {
     ...actual,
     useSearchParams: () => mockSearchParams,
-    useRouter: () => ({ push: vi.fn() }),
+    useRouter: () => ({ push: vi.fn(), replace: mockRouterReplace }),
     usePathname: () => "/profile/credits",
   };
 });
@@ -103,6 +104,7 @@ afterEach(() => {
   mockUseGetSubscriptionStatus.mockReset();
   mockUseUpdateSubscriptionTier.mockReset();
   mockToast.mockReset();
+  mockRouterReplace.mockReset();
   // Reset search params
   mockSearchParams.delete("subscription");
 });
@@ -289,4 +291,18 @@ describe("SubscriptionTierSection", () => {
     expect(screen.queryByText("Pro")).toBeNull();
     expect(screen.queryByText("Business")).toBeNull();
   });
+
+  it("shows success toast and clears URL param when ?subscription=success is present", async () => {
+    mockSearchParams.set("subscription", "success");
+    setupMocks();
+    render(<SubscriptionTierSection />);
+
+    await waitFor(() => {
+      expect(mockToast).toHaveBeenCalledWith(
+        expect.objectContaining({ title: "Subscription upgraded" }),
+      );
+    });
+    // URL param must be stripped so a page refresh doesn't re-trigger the toast
+    expect(mockRouterReplace).toHaveBeenCalledWith("/profile/credits");
+  });
 });

autogpt_platform/frontend/src/app/(platform)/profile/(user)/credits/components/SubscriptionTierSection/useSubscriptionTierSection.ts

@@ -1,5 +1,5 @@
-import { useEffect, useRef, useState } from "react";
-import { useSearchParams } from "next/navigation";
+import { useEffect, useState } from "react";
+import { usePathname, useRouter, useSearchParams } from "next/navigation";
 import {
   useGetSubscriptionStatus,
   useUpdateSubscriptionTier,
@@ -13,8 +13,9 @@ export type SubscriptionStatus = SubscriptionStatusResponse;
 export function useSubscriptionTierSection() {
   const searchParams = useSearchParams();
   const subscriptionStatus = searchParams.get("subscription");
+  const router = useRouter();
+  const pathname = usePathname();
   const { toast } = useToast();
-  const toastShownRef = useRef(false);
   const [tierError, setTierError] = useState<string | null>(null);
 
   const {
@@ -36,22 +37,18 @@ export function useSubscriptionTierSection() {
 
   useEffect(() => {
     if (subscriptionStatus === "success") {
-      if (!toastShownRef.current) {
-        toastShownRef.current = true;
-        refetch();
-        toast({
-          title: "Subscription upgraded",
-          description:
-            "Your plan has been updated. It may take a moment to reflect.",
-        });
-      }
-    } else {
-      // Reset so the toast fires again if the user completes another checkout
-      // during the same mount (e.g. SPA navigation away and back with a new
-      // ?subscription=success param).
-      toastShownRef.current = false;
+      refetch();
+      toast({
+        title: "Subscription upgraded",
+        description:
+          "Your plan has been updated. It may take a moment to reflect.",
+      });
+      // Strip ?subscription=success from the URL so a page refresh does not
+      // re-trigger the toast, and so a second checkout in the same session
+      // correctly fires the toast again.
+      router.replace(pathname);
     }
-  }, [subscriptionStatus, refetch, toast]);
+  }, [subscriptionStatus, refetch, toast, router, pathname]);
 
   async function changeTier(tier: string) {
     setTierError(null);