fix(synology-chat): deregister stale webhook route before re-registering on restart (#24971)

When the Synology Chat plugin restarts (auto-restart or health monitor),
startAccount is called again without calling the previous stop(). The
HTTP route is still registered, so registerPluginHttpRoute returns a
no-op unregister function and logs "already registered". This triggers
another restart, creating an infinite loop.

Store the unregister function at module level keyed by account+path.
Before registering, check for and call any stale unregister from the
previous start cycle, ensuring a clean slate for route registration.

Fixes #24894

Co-authored-by: Cursor <cursoragent@cursor.com>

extensions/synology-chat/src/channel.ts

@@ -20,6 +20,8 @@ import { createWebhookHandler } from "./webhook-handler.js";
 const CHANNEL_ID = "synology-chat";
 const SynologyChatConfigSchema = buildChannelConfigSchema(z.object({}).passthrough());
 
+const activeRouteUnregisters = new Map<string, () => void>();
+
 export function createSynologyChatPlugin() {
   return {
     id: CHANNEL_ID,
@@ -270,7 +272,16 @@ export function createSynologyChatPlugin() {
           log,
         });
 
-        // Register HTTP route via the SDK
+        // Deregister any stale route from a previous start (e.g. on auto-restart)
+        // to avoid "already registered" collisions that trigger infinite loops.
+        const routeKey = `${accountId}:${account.webhookPath}`;
+        const prevUnregister = activeRouteUnregisters.get(routeKey);
+        if (prevUnregister) {
+          log?.info?.(`Deregistering stale route before re-registering: ${account.webhookPath}`);
+          prevUnregister();
+          activeRouteUnregisters.delete(routeKey);
+        }
+
         const unregister = registerPluginHttpRoute({
           path: account.webhookPath,
           pluginId: CHANNEL_ID,
@@ -278,6 +289,7 @@ export function createSynologyChatPlugin() {
           log: (msg: string) => log?.info?.(msg),
           handler,
         });
+        activeRouteUnregisters.set(routeKey, unregister);
 
         log?.info?.(`Registered HTTP route: ${account.webhookPath} for Synology Chat`);
 
@@ -285,6 +297,7 @@ export function createSynologyChatPlugin() {
           stop: () => {
             log?.info?.(`Stopping Synology Chat channel (account: ${accountId})`);
             if (typeof unregister === "function") unregister();
+            activeRouteUnregisters.delete(routeKey);
           },
         };
       },