diff --git a/gateway/platforms/signal.py b/gateway/platforms/signal.py
index 1629e08631e5..2a3acbfb3c84 100644
--- a/gateway/platforms/signal.py
+++ b/gateway/platforms/signal.py
@@ -230,9 +230,13 @@ async def connect(self) -> bool:
             resp = await self.client.get(f"{self.http_url}/api/v1/check", timeout=10.0)
             if resp.status_code != 200:
                 logger.error("Signal: health check failed (status %d)", resp.status_code)
+                await self.client.aclose()
+                self.client = None
                 return False
         except Exception as e:
             logger.error("Signal: cannot reach signal-cli at %s: %s", self.http_url, e)
+            await self.client.aclose()
+            self.client = None
             return False
 
         self._running = True
diff --git a/tests/gateway/test_signal_client_leak.py b/tests/gateway/test_signal_client_leak.py
new file mode 100644
index 000000000000..6991dd474448
--- /dev/null
+++ b/tests/gateway/test_signal_client_leak.py
@@ -0,0 +1,120 @@
+"""Tests for Signal httpx client cleanup on failed health check.
+
+When Signal's connect() creates an httpx.AsyncClient and the health check
+then fails (non-200 or network error), both return-False paths must close
+the client to avoid leaking TCP connections and file descriptors.
+"""
+
+import asyncio
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+
+
+def _make_adapter():
+    """Build a minimal SignalAdapter with mocked internals."""
+    from gateway.platforms.signal import SignalAdapter
+
+    adapter = SignalAdapter.__new__(SignalAdapter)
+    adapter.http_url = "http://localhost:8080"
+    adapter.account = "+1234567890"
+    adapter._closing = False
+    adapter._running = False
+    adapter.client = None
+    adapter._phone_lock_identity = None
+    adapter._session_lock_identity = None
+    adapter.platform = MagicMock()
+    adapter.platform.value = "signal"
+    return adapter
+
+
+class TestSignalClientLeakOnHealthCheckFailure:
+    """gateway/platforms/signal.py — connect() health check paths"""
+
+    def test_client_closed_on_non_200_health_check(self):
+        """A non-200 health check should close the httpx client."""
+        adapter = _make_adapter()
+
+        mock_response = MagicMock()
+        mock_response.status_code = 503
+
+        mock_client = AsyncMock()
+        mock_client.get = AsyncMock(return_value=mock_response)
+        mock_client.aclose = AsyncMock()
+
+        async def run():
+            with patch("gateway.platforms.signal.httpx.AsyncClient",
+                       return_value=mock_client):
+                with patch("gateway.status.acquire_scoped_lock",
+                           return_value=(True, None)):
+                    result = await adapter.connect()
+
+            assert result is False
+            mock_client.aclose.assert_called_once()
+            assert adapter.client is None
+
+        asyncio.run(run())
+
+    def test_client_closed_on_connection_error(self):
+        """A connection error during health check should close the client."""
+        adapter = _make_adapter()
+
+        mock_client = AsyncMock()
+        mock_client.get = AsyncMock(side_effect=ConnectionError("refused"))
+        mock_client.aclose = AsyncMock()
+
+        async def run():
+            with patch("gateway.platforms.signal.httpx.AsyncClient",
+                       return_value=mock_client):
+                with patch("gateway.status.acquire_scoped_lock",
+                           return_value=(True, None)):
+                    result = await adapter.connect()
+
+            assert result is False
+            mock_client.aclose.assert_called_once()
+            assert adapter.client is None
+
+        asyncio.run(run())
+
+    def test_client_kept_on_successful_health_check(self):
+        """A 200 health check should keep the client open."""
+        adapter = _make_adapter()
+
+        mock_response = MagicMock()
+        mock_response.status_code = 200
+
+        mock_client = AsyncMock()
+        mock_client.get = AsyncMock(return_value=mock_response)
+        mock_client.aclose = AsyncMock()
+
+        async def run():
+            with patch("gateway.platforms.signal.httpx.AsyncClient",
+                       return_value=mock_client):
+                with patch("gateway.status.acquire_scoped_lock",
+                           return_value=(True, None)):
+                    with patch("asyncio.create_task", return_value=MagicMock()):
+                        result = await adapter.connect()
+
+            assert result is True
+            mock_client.aclose.assert_not_called()
+            assert adapter.client is mock_client
+
+        asyncio.run(run())
+
+
+class TestSourceLineVerification:
+    """Verify signal.py has aclose() on both early-return paths."""
+
+    @staticmethod
+    def _read_source() -> str:
+        import os
+        base = os.path.dirname(os.path.dirname(os.path.dirname(__file__)))
+        with open(os.path.join(base, "gateway", "platforms", "signal.py")) as f:
+            return f.read()
+
+    def test_aclose_present_in_connect(self):
+        src = self._read_source()
+        assert "await self.client.aclose()" in src, (
+            "signal.py connect() missing await self.client.aclose() "
+            "on health check failure paths"
+        )