diff --git a/extensions/feishu/src/monitor.state.ts b/extensions/feishu/src/monitor.state.ts
index 55b8d0dea5a..3100c1da839 100644
--- a/extensions/feishu/src/monitor.state.ts
+++ b/extensions/feishu/src/monitor.state.ts
@@ -13,8 +13,8 @@ export const httpServers = new Map<string, http.Server>();
 export const botOpenIds = new Map<string, string>();
 export const botNames = new Map<string, string>();
 
-export const FEISHU_WEBHOOK_MAX_BODY_BYTES = 1024 * 1024;
-export const FEISHU_WEBHOOK_BODY_TIMEOUT_MS = 30_000;
+export const FEISHU_WEBHOOK_MAX_BODY_BYTES = 64 * 1024;
+export const FEISHU_WEBHOOK_BODY_TIMEOUT_MS = 5_000;
 
 type WebhookRateLimitDefaults = {
   windowMs: number;
diff --git a/extensions/feishu/src/monitor.webhook-security.test.ts b/extensions/feishu/src/monitor.webhook-security.test.ts
index 957d874cc3a..60b5517e66c 100644
--- a/extensions/feishu/src/monitor.webhook-security.test.ts
+++ b/extensions/feishu/src/monitor.webhook-security.test.ts
@@ -1,3 +1,4 @@
+import { createConnection } from "node:net";
 import { afterEach, describe, expect, it, vi } from "vitest";
 import {
   createFeishuClientMockModule,
@@ -35,6 +36,47 @@ import {
   stopFeishuMonitor,
 } from "./monitor.js";
 
+async function waitForSlowBodyTimeoutResponse(
+  url: string,
+  timeoutMs: number,
+): Promise<{ body: string; elapsedMs: number }> {
+  return await new Promise<{ body: string; elapsedMs: number }>((resolve, reject) => {
+    const target = new URL(url);
+    const startedAt = Date.now();
+    let response = "";
+    const socket = createConnection(
+      {
+        host: target.hostname,
+        port: Number(target.port),
+      },
+      () => {
+        socket.write(`POST ${target.pathname} HTTP/1.1\r\n`);
+        socket.write(`Host: ${target.hostname}\r\n`);
+        socket.write("Content-Type: application/json\r\n");
+        socket.write("Content-Length: 65536\r\n");
+        socket.write("\r\n");
+        socket.write('{"type":"url_verification"');
+      },
+    );
+
+    socket.setEncoding("utf8");
+    socket.on("error", () => {});
+    socket.on("data", (chunk) => {
+      response += chunk;
+      if (response.includes("Request body timeout")) {
+        clearTimeout(failTimer);
+        socket.destroy();
+        resolve({ body: response, elapsedMs: Date.now() - startedAt });
+      }
+    });
+
+    const failTimer = setTimeout(() => {
+      socket.destroy();
+      reject(new Error(`timeout response did not arrive within ${timeoutMs}ms`));
+    }, timeoutMs);
+  });
+}
+
 afterEach(() => {
   clearFeishuWebhookRateLimitStateForTest();
   stopFeishuMonitor();
@@ -91,6 +133,48 @@ describe("Feishu webhook security hardening", () => {
     );
   });
 
+  it("rejects oversized unsigned webhook bodies with 413 before signature verification", async () => {
+    probeFeishuMock.mockResolvedValue({ ok: true, botOpenId: "bot_open_id" });
+    await withRunningWebhookMonitor(
+      {
+        accountId: "payload-too-large",
+        path: "/hook-payload-too-large",
+        verificationToken: "verify_token",
+        encryptKey: "encrypt_key",
+      },
+      monitorFeishuProvider,
+      async (url) => {
+        const response = await fetch(url, {
+          method: "POST",
+          headers: { "content-type": "application/json" },
+          body: JSON.stringify({ payload: "x".repeat(70 * 1024) }),
+        });
+
+        expect(response.status).toBe(413);
+        expect(await response.text()).toBe("Payload too large");
+      },
+    );
+  });
+
+  it("drops slow-body webhook requests within the tightened pre-auth timeout", async () => {
+    probeFeishuMock.mockResolvedValue({ ok: true, botOpenId: "bot_open_id" });
+    await withRunningWebhookMonitor(
+      {
+        accountId: "slow-body-timeout",
+        path: "/hook-slow-body-timeout",
+        verificationToken: "verify_token",
+        encryptKey: "encrypt_key",
+      },
+      monitorFeishuProvider,
+      async (url) => {
+        const result = await waitForSlowBodyTimeoutResponse(url, 15_000);
+        expect(result.body).toContain("408 Request Timeout");
+        expect(result.body).toContain("Request body timeout");
+        expect(result.elapsedMs).toBeLessThan(12_000);
+      },
+    );
+  });
+
   it("rate limits webhook burst traffic with 429", async () => {
     probeFeishuMock.mockResolvedValue({ ok: true, botOpenId: "bot_open_id" });
     await withRunningWebhookMonitor(