diff --git a/src/app/api/affiliates/offers/[id]/apply/route.test.ts b/src/app/api/affiliates/offers/[id]/apply/route.test.ts
new file mode 100644
index 00000000..48fc87d0
--- /dev/null
+++ b/src/app/api/affiliates/offers/[id]/apply/route.test.ts
@@ -0,0 +1,98 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import { NextRequest } from "next/server";
+import { POST } from "./route";
+
+const mockGetAuthContext = vi.fn();
+vi.mock("@/lib/auth/get-user", () => ({
+  getAuthContext: (...args: unknown[]) => mockGetAuthContext(...args),
+}));
+
+const mockCheckRateLimit = vi.fn();
+vi.mock("@/lib/rate-limit", () => ({
+  checkRateLimit: (...args: unknown[]) => mockCheckRateLimit(...args),
+  getRateLimitIdentifier: () => "rate-key",
+  rateLimitExceeded: () => new Response("rate limited", { status: 429 }),
+}));
+
+vi.mock("@/lib/affiliates/tracking", () => ({
+  generateTrackingCode: () => "alice-test123",
+}));
+
+const mockFrom = vi.fn();
+vi.mock("@/lib/supabase/service", () => ({
+  createServiceClient: () => ({
+    from: (...args: unknown[]) => mockFrom(...args),
+  }),
+}));
+
+function makeRequest() {
+  return new NextRequest("http://localhost/api/affiliates/offers/offer-1/apply", {
+    method: "POST",
+    body: "{}",
+  });
+}
+
+function makeParams(id = "offer-1") {
+  return { params: Promise.resolve({ id }) };
+}
+
+function makeSingleResponse(data: unknown) {
+  return {
+    select: () => ({
+      eq: () => ({
+        eq: () => ({
+          single: () => Promise.resolve({ data, error: null }),
+        }),
+        single: () => Promise.resolve({ data, error: null }),
+      }),
+    }),
+  };
+}
+
+describe("POST /api/affiliates/offers/[id]/apply", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    mockCheckRateLimit.mockReturnValue({ allowed: true });
+    mockGetAuthContext.mockResolvedValue({
+      user: { id: "affiliate-1", authMethod: "session" },
+    });
+    delete process.env.NEXT_PUBLIC_APP_URL;
+  });
+
+  it("returns the existing tracking URL when an approved affiliate reapplies", async () => {
+    mockFrom.mockImplementation((table: string) => {
+      if (table === "affiliate_offers") {
+        return makeSingleResponse({
+          id: "offer-1",
+          seller_id: "seller-1",
+          status: "active",
+          slug: "test-offer",
+        });
+      }
+
+      if (table === "affiliate_applications") {
+        return makeSingleResponse({
+          id: "application-1",
+          status: "approved",
+          tracking_code: "alice-test123",
+        });
+      }
+
+      return {};
+    });
+
+    const res = await POST(makeRequest(), makeParams());
+
+    expect(res.status).toBe(409);
+    await expect(res.json()).resolves.toEqual({
+      error: "Already approved",
+      application: {
+        id: "application-1",
+        status: "approved",
+        tracking_code: "alice-test123",
+      },
+      tracking_code: "alice-test123",
+      tracking_url: "https://ugig.net/ref/alice-test123",
+    });
+  });
+});
diff --git a/src/app/api/affiliates/offers/[id]/apply/route.ts b/src/app/api/affiliates/offers/[id]/apply/route.ts
index ddfdc71b..2ced42a0 100644
--- a/src/app/api/affiliates/offers/[id]/apply/route.ts
+++ b/src/app/api/affiliates/offers/[id]/apply/route.ts
@@ -2,11 +2,13 @@ import { NextRequest, NextResponse } from "next/server";
 import { getAuthContext } from "@/lib/auth/get-user";
 import { createServiceClient } from "@/lib/supabase/service";
 import { checkRateLimit, rateLimitExceeded, getRateLimitIdentifier } from "@/lib/rate-limit";
+import { generateTrackingCode } from "@/lib/affiliates/tracking";
 
-// eslint-disable-next-line @typescript-eslint/no-explicit-any
 type AnySupabase = any;
-import { generateTrackingCode } from "@/lib/affiliates/tracking";
 
+function trackingUrl(trackingCode: string): string {
+  return `${process.env.NEXT_PUBLIC_APP_URL || "https://ugig.net"}/ref/${trackingCode}`;
+}
 
 /**
  * POST /api/affiliates/offers/[id]/apply - Apply to become an affiliate for an offer
@@ -46,7 +48,7 @@ export async function POST(
     // Check if already applied
     const { data: existing } = await (admin as AnySupabase)
       .from("affiliate_applications")
-      .select("id, status")
+      .select("id, status, tracking_code")
       .eq("offer_id", id)
       .eq("affiliate_id", auth.user.id)
       .single();
@@ -55,6 +57,8 @@ export async function POST(
       return NextResponse.json({
         error: `Already ${existing.status}`,
         application: existing,
+        tracking_code: existing.tracking_code,
+        tracking_url: existing.tracking_code ? trackingUrl(existing.tracking_code) : null,
       }, { status: 409 });
     }
 
@@ -127,7 +131,7 @@ export async function POST(
     return NextResponse.json({
       application,
       tracking_code: trackingCode,
-      tracking_url: `${process.env.NEXT_PUBLIC_APP_URL || "https://ugig.net"}/ref/${trackingCode}`,
+      tracking_url: trackingUrl(trackingCode),
     }, { status: 201 });
   } catch {
     return NextResponse.json({ error: "An unexpected error occurred" }, { status: 500 });