diff --git a/extensions/synology-chat/src/client.loopback.test.ts b/extensions/synology-chat/src/client.loopback.test.ts
index 689e5f65239c..bf3959825254 100644
--- a/extensions/synology-chat/src/client.loopback.test.ts
+++ b/extensions/synology-chat/src/client.loopback.test.ts
@@ -13,7 +13,9 @@ describe("Synology Chat user_list loopback", () => {
     if (server) {
       await new Promise<void>((resolve, reject) => {
         server?.close((err) => (err ? reject(err) : resolve()));
+        server?.closeAllConnections?.();
       });
+      server = undefined;
     }
   });
 
@@ -71,4 +73,80 @@ describe("Synology Chat user_list loopback", () => {
       `fetchChatUsers: user_list response exceeded ${USER_LIST_RESPONSE_MAX_BYTES} bytes, using cached data`,
     );
   });
+
+  it("bounds a dripping user_list body with a wall-clock deadline", async () => {
+    let requestCount = 0;
+    server = http.createServer((_req, res) => {
+      requestCount += 1;
+      res.on("error", () => {});
+      res.writeHead(200, {
+        "Content-Type": "application/json",
+        "Transfer-Encoding": "chunked",
+      });
+      if (requestCount === 1) {
+        res.end(
+          JSON.stringify({
+            success: true,
+            data: { users: [{ user_id: 21, username: "cached", nickname: "drip-user" }] },
+          }),
+        );
+        return;
+      }
+      // Keep sending bytes so ClientRequest socket-idle alone would never fire.
+      const dripTimer = setInterval(() => {
+        if (res.writableEnded || res.destroyed) {
+          return;
+        }
+        res.write("x");
+      }, 20);
+      res.on("close", () => clearInterval(dripTimer));
+      res.write("x");
+    });
+    server.on("clientError", (_err, socket) => socket.destroy());
+    server.listen(0, "127.0.0.1");
+    await once(server, "listening");
+
+    const address = server.address();
+    if (!address || typeof address === "string") {
+      throw new Error("expected loopback server address");
+    }
+    const incomingUrl =
+      `http://127.0.0.1:${address.port}/webapi/entry.cgi?` +
+      "api=SYNO.Chat.External&method=chatbot&version=2";
+    const now = vi.spyOn(Date, "now");
+    now.mockReturnValue(1_700_000_100_000);
+
+    await expect(
+      resolveLegacyWebhookNameToChatUserId({
+        incomingUrl,
+        mutableWebhookUsername: "drip-user",
+      }),
+    ).resolves.toBe(21);
+
+    now.mockReturnValue(1_700_000_100_000 + 10 * 60 * 1000);
+    const warnings: string[] = [];
+    const timeoutMs = 250;
+    const nativeSetTimeout = globalThis.setTimeout;
+    const timeoutSpy = vi.spyOn(globalThis, "setTimeout");
+    timeoutSpy.mockImplementationOnce(((
+      callback: (...args: unknown[]) => void,
+      _delay?: number,
+      ...args: unknown[]
+    ) => nativeSetTimeout(callback, timeoutMs, ...args)) as typeof setTimeout);
+    const startedAt = performance.now();
+    await expect(
+      resolveLegacyWebhookNameToChatUserId({
+        incomingUrl,
+        mutableWebhookUsername: "drip-user",
+        log: { warn: (...args) => warnings.push(args.map(String).join(" ")) },
+      }),
+    ).resolves.toBe(21);
+    const elapsedMs = performance.now() - startedAt;
+
+    expect(requestCount).toBe(2);
+    expect(timeoutSpy).toHaveBeenCalledWith(expect.any(Function), 15_000);
+    expect(warnings).toContain("fetchChatUsers: request timed out, using cached data");
+    expect(elapsedMs).toBeGreaterThanOrEqual(timeoutMs - 50);
+    expect(elapsedMs).toBeLessThan(timeoutMs + 1_500);
+  });
 });
diff --git a/extensions/synology-chat/src/client.ts b/extensions/synology-chat/src/client.ts
index 93be42c289ae..29bf0a39b4e8 100644
--- a/extensions/synology-chat/src/client.ts
+++ b/extensions/synology-chat/src/client.ts
@@ -19,6 +19,8 @@ import { z } from "zod";
 const MIN_SEND_INTERVAL_MS = 500;
 /** user_list JSON can be larger than inbound webhook pre-auth payloads. */
 const USER_LIST_RESPONSE_MAX_BYTES = 1 * 1024 * 1024;
+/** Wall-clock budget for user_list fetch including response body. */
+const USER_LIST_REQUEST_TIMEOUT_MS = 15_000;
 let lastSendTime = 0;
 let sendQueue: Promise<void> = Promise.resolve();
 
@@ -161,14 +163,21 @@ async function fetchChatUsers(
   if (cached && now - cached.cachedAt < CACHE_TTL_MS) {
     return cached.users;
   }
-
   return new Promise((resolve) => {
     let settled = false;
+    let deadlineTimer: ReturnType<typeof setTimeout> | undefined;
+    const clearDeadline = () => {
+      if (deadlineTimer !== undefined) {
+        clearTimeout(deadlineTimer);
+        deadlineTimer = undefined;
+      }
+    };
     const finish = (users: ChatUser[]) => {
       if (settled) {
         return;
       }
       settled = true;
+      clearDeadline();
       resolve(users);
     };
     let parsedUrl: URL;
@@ -227,14 +236,21 @@ async function fetchChatUsers(
         })();
       })
       .on("error", (err) => {
+        if (settled) {
+          return;
+        }
         log?.warn(`fetchChatUsers: HTTP error — ${err instanceof Error ? err.message : err}`);
         finish(cached?.users ?? []);
       });
-    req.setTimeout?.(15_000, () => {
+    // Use a wall-clock deadline, not ClientRequest.setTimeout. Node's socket
+    // idle timer resets on every data chunk, so a slow drip can hang user_list
+    // past the intended budget while body reads have no separate idle bound.
+    deadlineTimer = setTimeout(() => {
       log?.warn("fetchChatUsers: request timed out, using cached data");
       req.destroy?.();
       finish(cached?.users ?? []);
-    });
+    }, USER_LIST_REQUEST_TIMEOUT_MS);
+    deadlineTimer.unref?.();
   });
 }