diff --git a/src/openenv/core/env_client.py b/src/openenv/core/env_client.py
index 7bfd33be2..39bd510e9 100644
--- a/src/openenv/core/env_client.py
+++ b/src/openenv/core/env_client.py
@@ -182,6 +182,7 @@ def __init__(
         )  # Convert MB to bytes
         self._provider = provider
         self._ws: Optional[ClientConnection] = None
+        self._ws_loop: Optional[asyncio.AbstractEventLoop] = None
 
     def __setattr__(self, name: str, value: Any) -> None:
         """Prevent modification of _mode after initialization."""
@@ -200,7 +201,19 @@ async def connect(self) -> "EnvClient":
             ConnectionError: If connection cannot be established
         """
         if self._ws is not None:
-            return self
+            if self._ws_loop is asyncio.get_running_loop():
+                return self
+            # Connected from a different event loop than the one running
+            # now -- e.g. `client = await Client.from_env(...)` inside
+            # `asyncio.run(...)`, then `client.sync()` drives every later
+            # call on `SyncEnvClient`'s own dedicated background loop. The
+            # websocket object is bound to internals of the original loop,
+            # which is typically already closed by the time we get here, so
+            # it cannot be reused (or even cleanly closed) from this loop.
+            # Drop the stale reference and reconnect fresh below rather than
+            # silently no-op-ing onto a dead connection.
+            self._ws = None
+            self._ws_loop = None
 
         # Disable the proxy for localhost connections via the per-connection
         # `proxy` argument rather than mutating the process-global NO_PROXY
@@ -217,6 +230,7 @@ async def connect(self) -> "EnvClient":
                 max_size=self._max_message_size,
                 **connect_kwargs,
             )
+            self._ws_loop = asyncio.get_running_loop()
         except Exception as e:
             raise ConnectionError(f"Failed to connect to {self._ws_url}: {e}") from e
 
@@ -235,6 +249,7 @@ async def disconnect(self) -> None:
             except Exception:
                 pass
             self._ws = None
+            self._ws_loop = None
 
     async def _ensure_connected(self) -> None:
         """Ensure WebSocket connection is established."""
diff --git a/tests/test_core/test_generic_client.py b/tests/test_core/test_generic_client.py
index 9a9121ce6..98632a269 100644
--- a/tests/test_core/test_generic_client.py
+++ b/tests/test_core/test_generic_client.py
@@ -695,6 +695,91 @@ async def fake_ws_connect(*args, **kwargs):
         assert "NO_PROXY" not in os.environ
 
 
+class TestForeignLoopReconnect:
+    """`connect()` must not silently no-op onto a websocket bound to a
+    different (often already-closed) event loop -- e.g. a client connected
+    via `await Client.from_env(...)` inside `asyncio.run(...)`, then driven
+    afterwards through `.sync()`'s own dedicated background loop.
+    """
+
+    @pytest.mark.asyncio
+    async def test_same_loop_reconnect_is_a_noop(self):
+        """Calling connect() again on the loop that created _ws is still a
+        cheap no-op -- only a genuinely different loop should reconnect.
+        """
+        client = GenericEnvClient(base_url="http://localhost:8000")
+
+        async def fake_ws_connect(*args, **kwargs):
+            return MagicMock()
+
+        with patch(
+            "openenv.core.env_client.ws_connect", side_effect=fake_ws_connect
+        ) as mock_connect:
+            await client.connect()
+            await client.connect()
+
+        mock_connect.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_foreign_loop_triggers_reconnect_not_noop(self):
+        """If _ws was bound to a different loop than the one connect() is
+        now running on, connect() must drop the stale reference and
+        establish a fresh connection on the current loop, rather than
+        returning early as if already connected.
+        """
+        client = GenericEnvClient(base_url="http://localhost:8000")
+
+        first_ws = MagicMock()
+
+        async def fake_ws_connect_first(*args, **kwargs):
+            return first_ws
+
+        with patch(
+            "openenv.core.env_client.ws_connect", side_effect=fake_ws_connect_first
+        ):
+            await client.connect()
+
+        assert client._ws is first_ws
+
+        # Simulate "connected on a different loop": the real scenario is two
+        # different asyncio event loops, which isn't practical to spin up
+        # for a unit test, so we directly substitute a sentinel loop object
+        # that isn't the one currently running.
+        client._ws_loop = object()
+
+        second_ws = MagicMock()
+
+        async def fake_ws_connect_second(*args, **kwargs):
+            return second_ws
+
+        with patch(
+            "openenv.core.env_client.ws_connect", side_effect=fake_ws_connect_second
+        ) as mock_connect:
+            await client.connect()
+
+        mock_connect.assert_called_once()
+        assert client._ws is second_ws
+        assert client._ws_loop is asyncio.get_running_loop()
+
+    @pytest.mark.asyncio
+    async def test_disconnect_clears_ws_loop(self):
+        """disconnect() must clear _ws_loop along with _ws so a later
+        connect() on the same loop doesn't think it's still connected.
+        """
+        client = GenericEnvClient(base_url="http://localhost:8000")
+
+        async def fake_ws_connect(*args, **kwargs):
+            return MagicMock()
+
+        with patch("openenv.core.env_client.ws_connect", side_effect=fake_ws_connect):
+            await client.connect()
+
+        await client.disconnect()
+
+        assert client._ws is None
+        assert client._ws_loop is None
+
+
 # ============================================================================
 # Integration Tests (require running server)
 # ============================================================================