fix: store asyncio task references to prevent GC mid-execution (#3267)

Python's asyncio event loop holds only weak references to tasks.
Without a strong reference, the garbage collector can destroy a task
while it's awaiting I/O — silently dropping messages. Python 3.12+
made this more aggressive.

Audit of all gateway platform adapters found 6 untracked create_task
calls across 6 files:

Per-message tasks (tracked via _background_tasks set from base class):
- gateway/platforms/webhook.py: handle_message task
- gateway/platforms/sms.py: handle_message task
- gateway/platforms/signal.py: SSE response aclose task

Long-running infrastructure tasks (stored in named instance vars):
- gateway/platforms/slack.py: Socket Mode handler (_socket_mode_task)
- gateway/platforms/discord.py: bot client (_bot_task)
- gateway/platforms/whatsapp.py: message poll loop (_poll_task, 2 sites)

All other adapters (telegram, mattermost, matrix, email, homeassistant,
dingtalk) already tracked their tasks correctly.

Salvaged from PR #3160 by memosr — expanded from 1 file to 6.

gateway/platforms/discord.py

@@ -446,6 +446,7 @@ class DiscordAdapter(BasePlatformAdapter):
         # Persistent typing indicator loops per channel (DMs don't reliably
         # show the standard typing gateway event for bots)
         self._typing_tasks: Dict[str, asyncio.Task] = {}
+        self._bot_task: Optional[asyncio.Task] = None
         # Cap to prevent unbounded growth (Discord threads get archived).
         self._MAX_TRACKED_THREADS = 500
     
@@ -588,7 +589,7 @@ class DiscordAdapter(BasePlatformAdapter):
             self._register_slash_commands()
             
             # Start the bot in background
-            asyncio.create_task(self._client.start(self.config.token))
+            self._bot_task = asyncio.create_task(self._client.start(self.config.token))
             
             # Wait for ready
             await asyncio.wait_for(self._ready_event.wait(), timeout=30)

gateway/platforms/signal.py

@@ -344,7 +344,9 @@ class SignalAdapter(BasePlatformAdapter):
         """Force SSE reconnection by closing the current response."""
         if self._sse_response and not self._sse_response.is_stream_consumed:
             try:
-                asyncio.create_task(self._sse_response.aclose())
+                task = asyncio.create_task(self._sse_response.aclose())
+                self._background_tasks.add(task)
+                task.add_done_callback(self._background_tasks.discard)
             except Exception:
                 pass
             self._sse_response = None

gateway/platforms/slack.py

@@ -72,6 +72,7 @@ class SlackAdapter(BasePlatformAdapter):
         self._handler: Optional[AsyncSocketModeHandler] = None
         self._bot_user_id: Optional[str] = None
         self._user_name_cache: Dict[str, str] = {}  # user_id → display name
+        self._socket_mode_task: Optional[asyncio.Task] = None
 
     async def connect(self) -> bool:
         """Connect to Slack via Socket Mode."""
@@ -119,7 +120,7 @@ class SlackAdapter(BasePlatformAdapter):
 
             # Start Socket Mode handler in background
             self._handler = AsyncSocketModeHandler(self._app, app_token)
-            asyncio.create_task(self._handler.start_async())
+            self._socket_mode_task = asyncio.create_task(self._handler.start_async())
 
             self._running = True
             logger.info("[Slack] Connected as @%s (Socket Mode)", bot_name)

gateway/platforms/sms.py

@@ -265,7 +265,9 @@ class SmsAdapter(BasePlatformAdapter):
         )
 
         # Non-blocking: Twilio expects a fast response
-        asyncio.create_task(self.handle_message(event))
+        task = asyncio.create_task(self.handle_message(event))
+        self._background_tasks.add(task)
+        task.add_done_callback(self._background_tasks.discard)
 
         # Return empty TwiML — we send replies via the REST API, not inline TwiML
         return web.Response(

gateway/platforms/webhook.py

@@ -363,7 +363,9 @@ class WebhookAdapter(BasePlatformAdapter):
         )
 
         # Non-blocking — return 202 Accepted immediately
-        asyncio.create_task(self.handle_message(event))
+        task = asyncio.create_task(self.handle_message(event))
+        self._background_tasks.add(task)
+        task.add_done_callback(self._background_tasks.discard)
 
         return web.json_response(
             {

gateway/platforms/whatsapp.py

@@ -140,6 +140,7 @@ class WhatsAppAdapter(BasePlatformAdapter):
         self._message_queue: asyncio.Queue = asyncio.Queue()
         self._bridge_log_fh = None
         self._bridge_log: Optional[Path] = None
+        self._poll_task: Optional[asyncio.Task] = None
     
     async def connect(self) -> bool:
         """
@@ -198,7 +199,7 @@ class WhatsAppAdapter(BasePlatformAdapter):
                                 print(f"[{self.name}] Using existing bridge (status: {bridge_status})")
                                 self._mark_connected()
                                 self._bridge_process = None  # Not managed by us
-                                asyncio.create_task(self._poll_messages())
+                                self._poll_task = asyncio.create_task(self._poll_messages())
                                 return True
                             else:
                                 print(f"[{self.name}] Bridge found but not connected (status: {bridge_status}), restarting")
@@ -304,7 +305,7 @@ class WhatsAppAdapter(BasePlatformAdapter):
                     print(f"[{self.name}]   If session expired, re-pair: hermes whatsapp")
             
             # Start message polling task
-            asyncio.create_task(self._poll_messages())
+            self._poll_task = asyncio.create_task(self._poll_messages())
             
             self._mark_connected()
             print(f"[{self.name}] Bridge started on port {self._bridge_port}")