diff --git a/csaxs_bec/devices/epics/falcon_csaxs.py b/csaxs_bec/devices/epics/falcon_csaxs.py
index 521aad58..d818cf10 100644
--- a/csaxs_bec/devices/epics/falcon_csaxs.py
+++ b/csaxs_bec/devices/epics/falcon_csaxs.py
@@ -4,6 +4,7 @@ import enum
 import os
 import threading
 import time
+from typing import TYPE_CHECKING
 from typing import Literal
 
 from bec_lib.file_utils import get_full_path
@@ -17,6 +18,9 @@ from ophyd_devices.interfaces.base_classes.psi_device_base import PSIDeviceBase
 
 from csaxs_bec.devices.utils.utils import fetch_scan_info
 
+if TYPE_CHECKING:  # pragma: no cover
+    from bec_lib.devicemanager import DeviceManagerBase, ScanInfo
+
 logger = bec_logger.logger
 
 # NOTE Layout of the written HDF5 file, resolved by the IOC relative to its own working
@@ -82,16 +86,35 @@ class FalconcSAXS(PSIDeviceBase, FalconControl):
 
     file_event = Cpt(FileEventSignal, name="file_event")
 
-    def __init__(self, *args, xml_file_name: str | None = None, **kwargs):
+    def __init__(
+        self,
+        name: str,
+        prefix: str = "",
+        scan_info: "ScanInfo | None" = None,
+        device_manager: "DeviceManagerBase | None" = None,
+        xml_file_name: str | None = None,
+        **kwargs,
+    ):
         """
+        Every deviceConfig key must appear here by name. The device server builds the
+        init kwargs by intersecting the config keys with the class signature's named
+        parameters, so a bare *args/**kwargs signature silently drops 'prefix' and the
+        device is built with empty PV names.
+
         Args:
+            name: device name.
+            prefix: EPICS prefix, e.g. 'X12SA-SITORO:'.
+            scan_info: scan info object.
+            device_manager: BEC device manager.
             xml_file_name: HDF5 layout description, as the IOC resolves it. Defaults to
                 DEFAULT_XML_FILE_NAME; pass "" to use the plugin's built-in layout.
         """
         self._xml_file_name_config = (
             DEFAULT_XML_FILE_NAME if xml_file_name is None else xml_file_name
         )
-        super().__init__(*args, **kwargs)
+        super().__init__(
+            name=name, prefix=prefix, scan_info=scan_info, device_manager=device_manager, **kwargs
+        )
 
     def on_init(self) -> None:
         """Initialize Falcon Sitoro detector"""
diff --git a/tests/tests_devices/test_falcon_csaxs.py b/tests/tests_devices/test_falcon_csaxs.py
index 97ce39b0..156544f9 100644
--- a/tests/tests_devices/test_falcon_csaxs.py
+++ b/tests/tests_devices/test_falcon_csaxs.py
@@ -1,4 +1,5 @@
 # pylint: skip-file
+import inspect
 import os
 import threading
 from typing import Generator
@@ -360,3 +361,32 @@ def test_falcon_accepts_a_valid_layout_silently(mock_det: FalconcSAXS):
     ):
         assert falcon._check_xml_layout(timeout=0.05) is True
         mock_logger.error.assert_not_called()
+
+
+def test_falcon_init_names_every_device_config_key():
+    """The device server drops config keys that are not named parameters.
+
+    bec_server's devicemanager builds the init kwargs by intersecting the deviceConfig
+    keys with the class signature's named parameters. A *args/**kwargs signature
+    therefore silently discards 'prefix', and every PV is built without it -- which
+    presents as 'failed to connect to all signals' rather than as a config error.
+    """
+    params = inspect.signature(FalconcSAXS).parameters
+    for key in ("name", "prefix", "scan_info", "device_manager", "xml_file_name"):
+        assert key in params, f"{key} must be a named parameter or the device server drops it"
+
+
+def test_falcon_keeps_the_configured_prefix():
+    """A prefix passed as the device server passes it must reach the signals."""
+    with patched_device(
+        FalconcSAXS,
+        name="falcon",
+        prefix="X12SA-SITORO:",
+        device_manager=DMMock(),
+        _mock_pv_initial_value=1,
+    ) as dev:
+        try:
+            assert dev.prefix == "X12SA-SITORO:"
+            assert dev.hdf5.file_path.pvname.startswith("X12SA-SITORO:")
+        finally:
+            dev.destroy()