diff --git a/packages/models-library/src/models_library/api_schemas_webserver/groups.py b/packages/models-library/src/models_library/api_schemas_webserver/groups.py
index d595447c3d3..3b2b77199fb 100644
--- a/packages/models-library/src/models_library/api_schemas_webserver/groups.py
+++ b/packages/models-library/src/models_library/api_schemas_webserver/groups.py
@@ -2,6 +2,7 @@
 from typing import Annotated, Any, Self, TypeVar
 
 from common_library.basic_types import DEFAULT_FACTORY
+from models_library.groups import EVERYONE_GROUP_ID
 from pydantic import (
     AnyHttpUrl,
     AnyUrl,
@@ -14,16 +15,16 @@
     model_validator,
 )
 
-from ..basic_types import IDStr
 from ..emails import LowerCaseEmailStr
 from ..groups import (
     AccessRightsDict,
     Group,
+    GroupID,
     GroupMember,
     StandardGroupCreate,
     StandardGroupUpdate,
 )
-from ..users import UserID
+from ..users import UserID, UserNameID
 from ..utils.common_validators import create__check_only_one_is_set__root_validator
 from ._base import InputSchema, OutputSchema
 
@@ -55,7 +56,7 @@ class GroupAccessRights(BaseModel):
 
 
 class GroupGet(OutputSchema):
-    gid: int = Field(..., description="the group ID")
+    gid: GroupID = Field(..., description="the group ID")
     label: str = Field(..., description="the group name")
     description: str = Field(..., description="the group description")
     thumbnail: AnyUrl | None = Field(
@@ -114,7 +115,7 @@ def from_model(cls, group: Group, access_rights: AccessRightsDict) -> Self:
                     "accessRights": {"read": True, "write": False, "delete": False},
                 },
                 {
-                    "gid": "0",
+                    "gid": "1",
                     "label": "All",
                     "description": "Open to all users",
                     "accessRights": {"read": True, "write": True, "delete": True},
@@ -214,7 +215,7 @@ class MyGroupsGet(OutputSchema):
                     },
                 ],
                 "all": {
-                    "gid": "0",
+                    "gid": EVERYONE_GROUP_ID,
                     "label": "All",
                     "description": "Open to all users",
                     "accessRights": {"read": True, "write": False, "delete": False},
@@ -228,13 +229,11 @@ class GroupUserGet(BaseModel):
     # OutputSchema
 
     # Identifiers
-    id: Annotated[
-        str | None, Field(description="the user id", coerce_numbers_to_str=True)
-    ] = None
-    user_name: Annotated[IDStr, Field(alias="userName")]
+    id: Annotated[UserID | None, Field(description="the user's id")] = None
+    user_name: Annotated[UserNameID, Field(alias="userName")]
     gid: Annotated[
-        str | None,
-        Field(description="the user primary gid", coerce_numbers_to_str=True),
+        GroupID | None,
+        Field(description="the user primary gid"),
     ] = None
 
     # Private Profile
@@ -296,7 +295,7 @@ class GroupUserAdd(InputSchema):
     """
 
     uid: UserID | None = None
-    user_name: Annotated[IDStr | None, Field(alias="userName")] = None
+    user_name: Annotated[UserNameID | None, Field(alias="userName")] = None
     email: Annotated[
         LowerCaseEmailStr | None,
         Field(
diff --git a/packages/models-library/src/models_library/groups.py b/packages/models-library/src/models_library/groups.py
index e79928574a6..368f01523ea 100644
--- a/packages/models-library/src/models_library/groups.py
+++ b/packages/models-library/src/models_library/groups.py
@@ -13,6 +13,9 @@
 EVERYONE_GROUP_ID: Final[int] = 1
 
 
+__all__: tuple[str, ...] = ("GroupID",)
+
+
 class GroupTypeInModel(str, enum.Enum):
     """
     standard: standard group, e.g. any group that is not a primary group or special group such as the everyone group
diff --git a/services/web/server/VERSION b/services/web/server/VERSION
index 5c4503b7043..564edf82ddf 100644
--- a/services/web/server/VERSION
+++ b/services/web/server/VERSION
@@ -1 +1 @@
-0.49.0
+0.50.0
diff --git a/services/web/server/setup.cfg b/services/web/server/setup.cfg
index 0e40e2535ee..9a74fe46b3d 100644
--- a/services/web/server/setup.cfg
+++ b/services/web/server/setup.cfg
@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 0.49.0
+current_version = 0.50.0
 commit = True
 message = services/webserver api version: {current_version} → {new_version}
 tag = False
diff --git a/services/web/server/src/simcore_service_webserver/api/v0/openapi.yaml b/services/web/server/src/simcore_service_webserver/api/v0/openapi.yaml
index fe6f65828b9..d27cbd9537e 100644
--- a/services/web/server/src/simcore_service_webserver/api/v0/openapi.yaml
+++ b/services/web/server/src/simcore_service_webserver/api/v0/openapi.yaml
@@ -2,7 +2,7 @@ openapi: 3.1.0
 info:
   title: simcore-service-webserver
   description: Main service with an interface (http-API & websockets) to the web front-end
-  version: 0.49.0
+  version: 0.50.0
 servers:
 - url: ''
   description: webserver
@@ -10033,8 +10033,10 @@ components:
       properties:
         gid:
           type: integer
+          exclusiveMinimum: true
           title: Gid
           description: the group ID
+          minimum: 0
         label:
           type: string
           title: Label
@@ -10116,10 +10118,12 @@ components:
       properties:
         id:
           anyOf:
-          - type: string
+          - type: integer
+            exclusiveMinimum: true
+            minimum: 0
           - type: 'null'
           title: Id
-          description: the user id
+          description: the user's id
         userName:
           type: string
           maxLength: 100
@@ -10127,7 +10131,9 @@ components:
           title: Username
         gid:
           anyOf:
-          - type: string
+          - type: integer
+            exclusiveMinimum: true
+            minimum: 0
           - type: 'null'
           title: Gid
           description: the user primary gid
diff --git a/services/web/server/src/simcore_service_webserver/groups/_groups_api.py b/services/web/server/src/simcore_service_webserver/groups/_groups_api.py
index 9b9e712df54..18491ec60bf 100644
--- a/services/web/server/src/simcore_service_webserver/groups/_groups_api.py
+++ b/services/web/server/src/simcore_service_webserver/groups/_groups_api.py
@@ -258,14 +258,11 @@ async def add_user_in_group(
         )
         new_by_user_id = user.id
 
-    if not new_by_user_id:
-        msg = "Missing new user in arguments"
-        raise GroupsError(msg=msg)
-
     return await _groups_db.add_new_user_in_group(
         app,
         user_id=user_id,
         group_id=group_id,
         new_user_id=new_by_user_id,
+        new_user_name=new_by_user_name,
         access_rights=access_rights,
     )
diff --git a/services/web/server/tests/unit/with_dbs/01/groups/test_groups_handlers_crud.py b/services/web/server/tests/unit/with_dbs/01/groups/test_groups_handlers_crud.py
index 5adaf33d9af..684f8726089 100644
--- a/services/web/server/tests/unit/with_dbs/01/groups/test_groups_handlers_crud.py
+++ b/services/web/server/tests/unit/with_dbs/01/groups/test_groups_handlers_crud.py
@@ -85,7 +85,7 @@ async def test_list_user_groups_and_try_modify_organizations(
         key=by_gid,
     ) == sorted(standard_groups, key=by_gid)
 
-    for group in standard_groups:
+    for i, group in enumerate(standard_groups):
         # try to delete a group
         url = client.app.router["delete_group"].url_for(gid=f"{group['gid']}")
         response = await client.delete(f"{url}")
@@ -93,7 +93,15 @@ async def test_list_user_groups_and_try_modify_organizations(
 
         # try to add some user in the group
         url = client.app.router["add_group_user"].url_for(gid=f"{group['gid']}")
-        response = await client.post(f"{url}", json={"uid": logged_user["id"]})
+
+        if i % 2 == 0:
+            # by user-id
+            params = {"uid": logged_user["id"]}
+        else:
+            # by user name
+            params = {"userName": logged_user["name"]}
+
+        response = await client.post(f"{url}", json=params)
         await assert_status(response, status.HTTP_403_FORBIDDEN)
 
         # try to modify the user in the group