Replace polling with WebSocket for real-time Signal message reception

Switch from polling /v1/receive every 2s to a persistent WebSocket
connection at ws://.../v1/receive/<number>. Messages now arrive
instantly via the signal-cli-rest-api WebSocket endpoint.

- Add `listen()` generator to SignalClient using websockets library
- Extract `_parse_envelope()` as standalone function
- Replace `run_loop` polling with WebSocket listener + reconnect logic
- Remove `poll_interval` from BotConfig and CLI args
- Add websockets to Nix overlay and pyproject.toml dependencies

https://claude.ai/code/session_01AKXQBuVBsW7J1YbukDiQ7A

overlays/default.nix

@@ -43,6 +43,7 @@
         tinytuya
         typer
         types-requests
+        websockets
       ]
     );
   };

pyproject.toml

@@ -21,6 +21,7 @@ dependencies = [
     "requests",
     "sqlalchemy",
     "typer",
+    "websockets",
 ]
 
 [project.scripts]

python/signal_bot/main.py

@@ -31,6 +31,8 @@ Available commands:
 Send a receipt photo with the message "!inventory" to scan it.\
 """
 
+RECONNECT_DELAY = 5
+
 
 def dispatch(
     message: SignalMessage,
@@ -84,20 +86,19 @@ def run_loop(
     llm: LLMClient,
     registry: DeviceRegistry,
 ) -> None:
-    """Main polling loop."""
+    """Listen for messages via WebSocket, reconnecting on failure."""
     inventory_path = Path(config.inventory_file)
-    logger.info(f"Bot started — polling every {config.poll_interval}s")
+    logger.info("Bot started — listening via WebSocket")
 
     while True:
         try:
-            messages = signal.receive()
-            for message in messages:
+            for message in signal.listen():
                 logger.info(f"Message from {message.source}: {message.message[:80]}")
                 registry.record_contact(message.source, "")
                 dispatch(message, signal, llm, registry, inventory_path)
         except Exception:
-            logger.exception("Error in message loop")
-        time.sleep(config.poll_interval)
+            logger.exception(f"WebSocket error, reconnecting in {RECONNECT_DELAY}s")
+            time.sleep(RECONNECT_DELAY)
 
 
 def main(
@@ -106,7 +107,6 @@ def main(
     llm_host: Annotated[str, typer.Option(envvar="LLM_HOST")],
     llm_model: Annotated[str, typer.Option(envvar="LLM_MODEL")] = "qwen3-vl:32b",
     llm_port: Annotated[int, typer.Option(envvar="LLM_PORT")] = 11434,
-    poll_interval: Annotated[int, typer.Option(help="Seconds between polls")] = 2,
     inventory_file: Annotated[str, typer.Option(envvar="INVENTORY_FILE")] = "/var/lib/signal-bot/van_inventory.json",
     registry_file: Annotated[str, typer.Option(envvar="REGISTRY_FILE")] = "/var/lib/signal-bot/device_registry.json",
     log_level: Annotated[str, typer.Option()] = "INFO",
@@ -119,7 +119,6 @@ def main(
         signal_api_url=signal_api_url,
         phone_number=phone_number,
         llm=llm_config,
-        poll_interval=poll_interval,
         inventory_file=inventory_file,
     )
 

python/signal_bot/models.py

@@ -82,5 +82,4 @@ class BotConfig(BaseModel):
     signal_api_url: str
     phone_number: str
     llm: LLMConfig
-    poll_interval: int = 2
     inventory_file: str = "van_inventory.json"

python/signal_bot/signal_client.py

@@ -2,16 +2,41 @@
 
 from __future__ import annotations
 
+import json
 import logging
-from typing import Any
+from typing import TYPE_CHECKING, Any
 
 import httpx
+import websockets.sync.client
+
+if TYPE_CHECKING:
+    from collections.abc import Generator
 
 from python.signal_bot.models import SignalMessage
 
 logger = logging.getLogger(__name__)
 
 
+def _parse_envelope(envelope: dict[str, Any]) -> SignalMessage | None:
+    """Parse a signal-cli envelope into a SignalMessage, or None if not a data message."""
+    data_message = envelope.get("dataMessage")
+    if not data_message:
+        return None
+
+    attachment_ids = [att["id"] for att in data_message.get("attachments", []) if "id" in att]
+
+    group_info = data_message.get("groupInfo")
+    group_id = group_info.get("groupId") if group_info else None
+
+    return SignalMessage(
+        source=envelope.get("source", ""),
+        timestamp=envelope.get("timestamp", 0),
+        message=data_message.get("message", "") or "",
+        attachments=attachment_ids,
+        group_id=group_id,
+    )
+
+
 class SignalClient:
     """Communicate with signal-cli-rest-api.
 
@@ -25,35 +50,26 @@ class SignalClient:
         self.phone_number = phone_number
         self._client = httpx.Client(base_url=self.base_url, timeout=30)
 
-    def receive(self) -> list[SignalMessage]:
-        """Poll for new messages."""
-        response = self._client.get(f"/v1/receive/{self.phone_number}")
-        response.raise_for_status()
-        envelopes: list[dict[str, Any]] = response.json()
+    def _ws_url(self) -> str:
+        """Build the WebSocket URL from the base HTTP URL."""
+        url = self.base_url.replace("http://", "ws://").replace("https://", "wss://")
+        return f"{url}/v1/receive/{self.phone_number}"
 
-        messages: list[SignalMessage] = []
-        for raw in envelopes:
-            envelope = raw.get("envelope", {})
-            data_message = envelope.get("dataMessage")
-            if not data_message:
-                continue
+    def listen(self) -> Generator[SignalMessage]:
+        """Connect via WebSocket and yield messages as they arrive."""
+        ws_url = self._ws_url()
+        logger.info(f"Connecting to WebSocket: {ws_url}")
 
-            attachment_ids = [att["id"] for att in data_message.get("attachments", []) if "id" in att]
-
-            group_info = data_message.get("groupInfo")
-            group_id = group_info.get("groupId") if group_info else None
-
-            messages.append(
-                SignalMessage(
-                    source=envelope.get("source", ""),
-                    timestamp=envelope.get("timestamp", 0),
-                    message=data_message.get("message", "") or "",
-                    attachments=attachment_ids,
-                    group_id=group_id,
-                ),
-            )
-
-        return messages
+        with websockets.sync.client.connect(ws_url) as ws:
+            for raw in ws:
+                try:
+                    data = json.loads(raw)
+                    envelope = data.get("envelope", {})
+                    message = _parse_envelope(envelope)
+                    if message:
+                        yield message
+                except json.JSONDecodeError:
+                    logger.warning(f"Non-JSON WebSocket frame: {raw[:200]}")
 
     def send(self, recipient: str, message: str) -> None:
         """Send a text message."""