diff --git a/src/app/api/v1/buyer-tasks/mark-ready/route.test.ts b/src/app/api/v1/buyer-tasks/mark-ready/route.test.ts
new file mode 100644
index 0000000..f9fd48f
--- /dev/null
+++ b/src/app/api/v1/buyer-tasks/mark-ready/route.test.ts
@@ -0,0 +1,74 @@
+import { describe, it, expect, beforeEach, vi } from "vitest";
+
+vi.mock("@/lib/server/buyer-tasks-service", () => ({
+  markGroupReady: vi.fn(),
+}));
+
+import { POST } from "./route";
+import { markGroupReady } from "@/lib/server/buyer-tasks-service";
+
+function makeRequest(body: unknown) {
+  return new Request("http://test/api/v1/buyer-tasks/mark-ready", {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(body),
+  });
+}
+
+describe("POST /api/v1/buyer-tasks/mark-ready", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("returns result on success", async () => {
+    vi.mocked(markGroupReady).mockResolvedValue({
+      updated: 2,
+      failed: [],
+    });
+
+    const res = await POST(
+      makeRequest({
+        orderId: "order-1",
+        supplierId: "sup-1",
+        items: [{ id: "item-1" }, { id: "item-2" }],
+      }) as never
+    );
+    expect(res.status).toBe(200);
+    const body = await res.json();
+    expect(body.updated).toBe(2);
+    expect(body.failed).toEqual([]);
+  });
+
+  it("returns 400 on missing orderId", async () => {
+    const res = await POST(
+      makeRequest({ supplierId: "sup-1", items: [{ id: "item-1" }] }) as never
+    );
+    expect(res.status).toBe(400);
+  });
+
+  it("returns 400 on missing supplierId", async () => {
+    const res = await POST(
+      makeRequest({ orderId: "order-1", items: [{ id: "item-1" }] }) as never
+    );
+    expect(res.status).toBe(400);
+  });
+
+  it("returns 400 on empty items", async () => {
+    const res = await POST(
+      makeRequest({ orderId: "order-1", supplierId: "sup-1", items: [] }) as never
+    );
+    expect(res.status).toBe(400);
+  });
+
+  it("returns 500 on service error", async () => {
+    vi.mocked(markGroupReady).mockRejectedValue(new Error("PB down"));
+    const res = await POST(
+      makeRequest({
+        orderId: "order-1",
+        supplierId: "sup-1",
+        items: [{ id: "item-1" }],
+      }) as never
+    );
+    expect(res.status).toBe(500);
+  });
+});
diff --git a/src/app/api/v1/buyer-tasks/mark-ready/route.ts b/src/app/api/v1/buyer-tasks/mark-ready/route.ts
new file mode 100644
index 0000000..0deda14
--- /dev/null
+++ b/src/app/api/v1/buyer-tasks/mark-ready/route.ts
@@ -0,0 +1,37 @@
+import { NextRequest, NextResponse } from "next/server";
+import { markGroupReady } from "@/lib/server/buyer-tasks-service";
+
+type Body = {
+  orderId?: string;
+  supplierId?: string;
+  items?: Array<{ id: string }>;
+};
+
+export async function POST(req: NextRequest) {
+  let body: Body;
+  try {
+    body = (await req.json()) as Body;
+  } catch {
+    return NextResponse.json({ error: "Invalid JSON body" }, { status: 400 });
+  }
+
+  if (!body.orderId) {
+    return NextResponse.json({ error: "orderId is required" }, { status: 400 });
+  }
+  if (!body.supplierId) {
+    return NextResponse.json({ error: "supplierId is required" }, { status: 400 });
+  }
+  if (!body.items || body.items.length === 0) {
+    return NextResponse.json({ error: "items must be non-empty" }, { status: 400 });
+  }
+
+  try {
+    const result = await markGroupReady(body.orderId, body.supplierId, body.items);
+    return NextResponse.json(result);
+  } catch (err) {
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : "Failed to mark group ready" },
+      { status: 500 }
+    );
+  }
+}