fix(02-bot-skeleton-initdata-security): WR-02 fail-closed /telegram/webhook — unarmed WEBHOOK_SECRET rejects (constant 500, category-only log) before grammY's accept-everything compare

bot/test/webhook.test.mjs

@@ -13,7 +13,7 @@
  * live Bot API. Armed-secret behavior is verified by the live smokes in
  * plan 02-03 instead.
  *
- * Cases (WR-01 body cap, T-02-01 gate):
+ * Cases (WR-01 body cap, WR-02 fail-closed gate, T-02-01 gate):
  *   WK1  POST valid initData under the cap → 200 {token: uuid};
  *        exactly two TTL-carrying KV writes (900 s)
  *   WK2  POST an over-cap (4 KB+) but VALIDLY SIGNED initData → 413
@@ -24,6 +24,9 @@
  *   WK3  declared-length 999999 + unreadable body stream → 413 resolved
  *        WITHOUT pulling the stream (the pre-read check refuses to buffer)
  *   WK4  GET /api/session → 405 (the cap logic never runs on GET)
+ *   WK5  unarmed WEBHOOK_SECRET → /telegram/webhook rejects CLOSED with a
+ *        constant 500 BEFORE grammY's compareSecretToken (which would
+ *        accept every request once the secret is undefined — WR-02)
  */
 import { strict as assert } from "node:assert";
 import { createHmac } from "node:crypto";
@@ -185,3 +188,17 @@ test("WK4 GET /api/session → 405", async () => {
   const res = await handler(req, makeEnv(makeKV()), {});
   assert.equal(res.status, 405);
 });
+
+/* ————— WK5 — WR-02 fail-closed webhook gate ————— */
+
+test("WK5 unarmed WEBHOOK_SECRET ('') → webhook rejects CLOSED with a constant 500, no bot run, no KV touch", async () => {
+  const env = { BOT_TOKEN: TEST_TOKEN, WEBHOOK_SECRET: "", chat_sessions: undefined };
+  const req = () => new Request("https://host/telegram/webhook", { method: "POST", body: '{\"update_id\":1}' });
+  const res1 = await handler(req(), env, {});
+  const res2 = await handler(req(), env, {});
+  assert.equal(res1.status, 500, "missing binding must fail closed, not fall through to grammY's accept-everything compare");
+  assert.equal(res2.status, 500, "the rejection is constant across calls");
+  assert.equal(await res1.text(), "Server misconfigured");
+  assert.equal(await res2.text(), "Server misconfigured");
+  assert.ok(env.chat_sessions === undefined, "the guard fired before any storage or bot wiring was needed");
+});