diff --git a/libervia/backend/core/core_types.py b/libervia/backend/core/core_types.py
index a59c3150..4e07ec05 100644
--- a/libervia/backend/core/core_types.py
+++ b/libervia/backend/core/core_types.py
@@ -18,7 +18,7 @@
 
 from abc import ABC, abstractmethod
 from collections import namedtuple
-from typing import Any
+from typing import TYPE_CHECKING, Any
 from twisted.internet import defer
 from twisted.python import failure
 from typing_extensions import TypedDict
@@ -30,6 +30,9 @@ from wokkel import disco
 
 from libervia.backend.core import exceptions
 
+if TYPE_CHECKING:
+    from libervia.backend.core.xmpp import LiberviaRosterProtocol
+
 
 EncryptionPlugin = namedtuple(
     "EncryptionPlugin", ("instance", "name", "namespace", "priority", "directed")
@@ -261,6 +264,10 @@ class SatXMPPEntity(ABC):
         raise NotImplementedError
 
 
+class SatXMPPClient(SatXMPPEntity):
+    roster: "LiberviaRosterProtocol"
+
+
 class SatXMPPComponent(SatXMPPEntity):
 
     def is_local(self, jid_: t_jid.JID) -> bool: ...
diff --git a/libervia/backend/core/xmpp.py b/libervia/backend/core/xmpp.py
index 95982a07..bfeaf275 100644
--- a/libervia/backend/core/xmpp.py
+++ b/libervia/backend/core/xmpp.py
@@ -941,7 +941,7 @@ ExtraDict = dict  # TODO
 
 
 @implementer(iwokkel.IDisco)
-class SatXMPPClient(SatXMPPEntity, wokkel_client.XMPPClient):
+class SatXMPPClient(SatXMPPEntity, core_types.SatXMPPClient, wokkel_client.XMPPClient):
     trigger_suffix = ""
     is_component = False
 
@@ -1553,8 +1553,8 @@ class LiberviaRosterProtocol(xmppim.RosterClientProtocol):
         self.host = host
         self.got_roster = defer.Deferred()  # called when roster is received and ready
         # XXX: the two following dicts keep a local copy of the roster
-        self._jids = {}  # map from jids to RosterItem: key=jid value=RosterItem
-        self._groups = {}  # map from groups to jids: key=group value=set of jids
+        self._jids: dict[jid.JID, xmppim.RosterItem] = {}
+        self._groups: dict[str, set[jid.JID]] = {}  # map from groups to jids
 
     def __contains__(self, entity_jid):
         return self.is_jid_in_roster(entity_jid)
@@ -1773,11 +1773,11 @@ class LiberviaRosterProtocol(xmppim.RosterClientProtocol):
         # then we send the bridge signal
         self.host.bridge.contact_deleted(entity.full(), self.parent.profile)
 
-    def get_groups(self):
+    def get_groups(self) -> list[str]:
         """Return a list of groups"""
         return list(self._groups.keys())
 
-    def get_item(self, entity_jid):
+    def get_item(self, entity_jid) -> xmppim.RosterItem | None:
         """Return RosterItem for a given jid
 
         @param entity_jid(jid.JID): jid of the contact
@@ -1786,11 +1786,11 @@ class LiberviaRosterProtocol(xmppim.RosterClientProtocol):
         """
         return self._jids.get(entity_jid, None)
 
-    def get_jids(self):
+    def get_jids(self) -> list[jid.JID]:
         """Return all jids of the roster"""
         return list(self._jids.keys())
 
-    def is_jid_in_roster(self, entity_jid):
+    def is_jid_in_roster(self, entity_jid) -> bool:
         """Return True if jid is in roster"""
         if not isinstance(entity_jid, jid.JID):
             raise exceptions.InternalError(