diff --git a/app/api/agent/route.ts b/app/api/agent/route.ts
index 14e573b..cabbdcc 100644
--- a/app/api/agent/route.ts
+++ b/app/api/agent/route.ts
@@ -1058,6 +1058,7 @@ function hasInternalCronAuth(req: NextRequest): boolean {
 export async function POST(req: NextRequest): Promise<Response> {
   const body = (await req.clone().json().catch(() => ({}))) as {
     query?: string;
+    demo?: boolean;
     fallback?: boolean;
   };
   const url = new URL(req.url);
@@ -1087,6 +1088,15 @@ export async function POST(req: NextRequest): Promise<Response> {
     );
   }
 
+  const query = (body.query ?? "").trim();
+  const demoMode =
+    body.demo === true ||
+    url.searchParams.get("demo") === "1" ||
+    req.headers.get("x-txlookup-demo") === "1";
+  if (demoMode && query && findFixture(query)) {
+    return handlePost(req);
+  }
+
   const byok = req.cookies.get("txl_byok")?.value;
   if (byok && byok.startsWith("sk-")) {
     return runWithKey(byok, () => handlePost(req));