diff --git a/bot/package.json b/bot/package.json
index 8a01519..8124490 100644
--- a/bot/package.json
+++ b/bot/package.json
@@ -6,7 +6,7 @@
     "test": "node test/runner.mjs",
     "typecheck": "tsc --noEmit",
     "dev": "wrangler dev",
-    "deploy": "wrangler deploy",
+    "deploy": "wrangler deploy && node scripts/set-webhook.mjs",
     "commands": "node scripts/register-commands.mjs"
   },
   "dependencies": {
diff --git a/bot/scripts/set-webhook.mjs b/bot/scripts/set-webhook.mjs
new file mode 100644
index 0000000..0ed1821
--- /dev/null
+++ b/bot/scripts/set-webhook.mjs
@@ -0,0 +1,70 @@
+#!/usr/bin/env node
+/*
+ * set-webhook.mjs — one-time setWebhook registration (D-16, D-17).
+ * -----------------------------------------------------------------
+ * Points Telegram at the Worker's /telegram/webhook route and arms the
+ * secret-token channel: the `secret_token` value sent here is the one
+ * Telegram echoes back in X-Telegram-Bot-Api-Secret-Token on every update,
+ * which the Worker's webhook adapter constant-time-compares against
+ * env.WEBHOOK_SECRET (T-02-03).
+ *
+ * Inputs come from bot/.dev.vars (gitignored, D-15): BOT_TOKEN,
+ * WEBHOOK_URL, WEBHOOK_SECRET. The bot token is never echoed — on failure
+ * only the API's error_code/description are printed (T-02-04).
+ * Exit 0 only when Telegram answers ok:true.
+ */
+import { readFileSync } from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+function readDevVars() {
+  const devVarsPath = path.join(fileURLToPath(new URL(import.meta.url)), "..", "..", ".dev.vars");
+  let raw = "";
+  try {
+    raw = readFileSync(devVarsPath, "utf8");
+  } catch {
+    return {};
+  }
+  const vars = {};
+  for (const line of raw.split("\n")) {
+    const trimmed = line.trim();
+    if (trimmed.length === 0 || trimmed.startsWith("#")) continue;
+    const eq = trimmed.indexOf("=");
+    if (eq === -1) continue;
+    vars[trimmed.slice(0, eq).trim()] = trimmed.slice(eq + 1).trim();
+  }
+  return vars;
+}
+
+const devVars = readDevVars();
+const token = process.env.BOT_TOKEN ?? devVars.BOT_TOKEN;
+const webhookUrl = process.env.WEBHOOK_URL ?? devVars.WEBHOOK_URL;
+const secret = process.env.WEBHOOK_SECRET ?? devVars.WEBHOOK_SECRET;
+
+const missing = ["BOT_TOKEN", "WEBHOOK_URL", "WEBHOOK_SECRET"].filter(
+  (name) => !{ BOT_TOKEN: token, WEBHOOK_URL: webhookUrl, WEBHOOK_SECRET: secret }[name],
+);
+if (missing.length > 0) {
+  console.error(`Missing ${missing.join(", ")} — set them in bot/.dev.vars (see .dev.vars.example; never commit).`);
+  process.exit(1);
+}
+
+const payload = {
+  url: webhookUrl,
+  secret_token: secret,
+  allowed_updates: ["message"],
+};
+
+const res = await fetch(`https://api.telegram.org/bot${token}/setWebhook`, {
+  method: "POST",
+  headers: { "content-type": "application/json" },
+  body: JSON.stringify(payload),
+});
+const body = await res.json();
+
+if (!body.ok) {
+  console.error(`setWebhook failed: ${body.error_code ?? "?"} ${body.description ?? "unknown error"}`);
+  process.exit(1);
+}
+console.log(`setWebhook ok:true — updates will be delivered to the configured URL with the secret-token header.`);
+process.exit(0);
diff --git a/bot/src/webhook.ts b/bot/src/webhook.ts
new file mode 100644
index 0000000..2ed1018
--- /dev/null
+++ b/bot/src/webhook.ts
@@ -0,0 +1,65 @@
+/*
+ * webhook.ts — the Worker entry (D-11, D-14, D-16, D-17).
+ * --------------------------------------------------------
+ * Routes exactly two paths:
+ *   POST /telegram/webhook  → grammY's webhook adapter (cloudflare-mod) with
+ *     the configured secret token — Telegram's updates must carry
+ *     X-Telegram-Bot-Api-Secret-Token = env.WEBHOOK_SECRET or they are 401'd
+ *     by a constant-time compare BEFORE any bot processing or KV touch
+ *     (T-02-03). The bot is instantiated per request because the token only
+ *     arrives with `env` (research-verified Workers pattern).
+ *   POST /api/session       → the phase's security gate (T-02-01): the caller
+ *     posts a verbatim Telegram.WebApp.initData string; only an HMAC-validated,
+ *     fresh identity obtains a one-time opaque session token (D-06). Rotation
+ *     of any prior token for the chat is mintSession's own invariant (D-07) —
+ *     this endpoint adds no extra branch and no extra write path (T-02-06).
+ * Anything else → 404.
+ *
+ * D-14: the ONLY log statement is category-only (malformed/tampered/stale) —
+ * never the raw payload, never user ids, never timestamps. Rejection
+ * responses carry the category only.
+ * D-17: no secret is ever logged or echoed; the bot token / webhook secret
+ * exist only inside `env` at runtime.
+ */
+import { webhookCallback } from "grammy";
+import type { Env } from "./config.ts";
+import { createBot } from "./bot/bot.ts";
+import { mintSession } from "./kv/sessions.ts";
+import { validateInitData } from "./security/initdata.ts";
+
+export default {
+  async fetch(req: Request, env: Env, _ctx: ExecutionContext): Promise<Response> {
+    const url = new URL(req.url);
+    if (url.pathname === "/telegram/webhook") {
+      const bot = createBot(env); // env-bound token → per-request instantiation
+      const cb = webhookCallback(bot, "cloudflare-mod", undefined, undefined, env.WEBHOOK_SECRET);
+      return cb(req);
+    }
+    if (url.pathname === "/api/session") {
+      return handleSession(req, env);
+    }
+    return new Response("Not found", { status: 404 });
+  },
+} satisfies ExportedHandler<Env>;
+
+/** Phase-2 security gate: initData in, one-time opaque session token out —
+ *  nothing else; unvalidated identities get a category-only 401 (T-02-01). */
+async function handleSession(req: Request, env: Env): Promise<Response> {
+  if (req.method !== "POST") return new Response("Method not allowed", { status: 405 });
+  const raw = await req.text(); // the verbatim Telegram.WebApp.initData string
+  const result = await validateInitData(raw, env.BOT_TOKEN);
+  if (!result.ok) {
+    console.log(`[initdata] rejected: ${result.reason}`); // D-14: category ONLY — no payload, no ids, no timestamps
+    return new Response(JSON.stringify({ error: result.reason }), {
+      status: 401,
+      headers: { "content-type": "application/json" },
+    });
+  }
+  const token = await mintSession(env.chat_sessions, {
+    user_id: result.user.id,
+    chat_id: result.chat?.id ?? result.user.id, // private chat: Telegram conflates; claim surface unchanged (D-08)
+    issued_at: Math.floor(Date.now() / 1000),
+    language_code: result.languageCode,
+  });
+  return new Response(JSON.stringify({ token }), { status: 200, headers: { "content-type": "application/json" } });
+}
diff --git a/bot/wrangler.jsonc b/bot/wrangler.jsonc
index fb6a811..9021db3 100644
--- a/bot/wrangler.jsonc
+++ b/bot/wrangler.jsonc
@@ -3,5 +3,8 @@
   "name": "araharah-bot",
   "main": "src/webhook.ts",
   "compatibility_date": "2026-10-22",
+  // workers_dev: serve on the <name>.<account>.workers.dev URL — the WEBHOOK_URL
+  // target for this phase (Phase 3's custom route/domain may supersede)
+  "workers_dev": true,
   "kv_namespaces": [{ "binding": "chat_sessions", "id": "KV_ID_PLACEHOLDER" }]
 }