fix(app): prevent caching of QR session polling responses

apps/app/src/app/api/pick/cache-regression.test.ts

@@ -0,0 +1,11 @@
+// @vitest-environment node
+import { it, expect, vi } from "vitest";
+import { NextRequest } from "next/server";
+vi.mock("./store", () => ({getSession:vi.fn(),setSession:vi.fn()}));
+import { getSession } from "./store";
+import { GET } from "./route";
+it.each([undefined,{status:"scanned"},{status:"picked",prompt:"Private prompt"}] as const)("never caches QR polling", async session => {
+  vi.mocked(getSession).mockReturnValue(session);
+  const r = await GET(new NextRequest("http://localhost/api/pick?sessionId=valid"));
+  expect(r.headers.get("cache-control")).toBe("no-store");
+});

apps/app/src/app/api/pick/route.ts

@@ -1,44 +1,46 @@
 import { NextRequest, NextResponse } from "next/server";
 import { getSession, setSession } from "./store";
 
+const reply = (body: object, status = 200) => NextResponse.json(body, { status, headers: { "Cache-Control": "no-store" } });
+
 /** GET — poll session status (desktop polls this) */
 export async function GET(req: NextRequest) {
   const sessionId = req.nextUrl.searchParams.get("sessionId");
-  if (!sessionId) return NextResponse.json({ error: "missing sessionId" }, { status: 400 });
+  if (!sessionId) return reply({ error: "missing sessionId" }, 400);
 
   const session = getSession(sessionId);
-  if (!session) return NextResponse.json({ status: "waiting" });
+  if (!session) return reply({ status: "waiting" });
 
   // Consume the prompt on first read so duplicate polls don't re-trigger
   if (session.status === "picked" && session.prompt) {
     const prompt = session.prompt;
     setSession(sessionId, { status: "picked" });
-    return NextResponse.json({ status: "picked", prompt });
+    return reply({ status: "picked", prompt });
   }
 
-  return NextResponse.json(session);
+  return reply(session);
 }
 
 /** PUT — mark session as scanned (mobile calls this on page load) */
 export async function PUT(req: NextRequest) {
   const { sessionId } = await req.json();
-  if (!sessionId) return NextResponse.json({ error: "missing sessionId" }, { status: 400 });
+  if (!sessionId) return reply({ error: "missing sessionId" }, 400);
 
   const existing = getSession(sessionId);
   if (!existing || existing.status === "waiting") {
     setSession(sessionId, { status: "scanned" });
   }
 
-  return NextResponse.json({ ok: true });
+  return reply({ ok: true });
 }
 
 /** POST — submit picked prompt (mobile calls this when user picks an option) */
 export async function POST(req: NextRequest) {
   const { sessionId, prompt } = await req.json();
   if (!sessionId || !prompt) {
-    return NextResponse.json({ error: "missing sessionId or prompt" }, { status: 400 });
+    return reply({ error: "missing sessionId or prompt" }, 400);
   }
 
   setSession(sessionId, { status: "picked", prompt });
-  return NextResponse.json({ ok: true });
+  return reply({ ok: true });
 }