diff --git a/framework/py/flwr/supercore/error/base.py b/framework/py/flwr/supercore/error/base.py
index 96dba8e9608a..0301f8ea7c7c 100644
--- a/framework/py/flwr/supercore/error/base.py
+++ b/framework/py/flwr/supercore/error/base.py
@@ -16,15 +16,28 @@
 
 
 from enum import IntEnum
+import json
 
 
 class FlowerError(Exception):
     """Base exception that carries an internal error code and debug message."""
 
-    def __init__(self, code: int, message: str) -> None:
+    def __init__(
+        self, code: int, message: str, public_details: str | None = None,
+    ) -> None:
         super().__init__(message)
         self.code = code
-        self.message = message
+        self.message = message  # Sensitive message
+        self.public_details = public_details
+
+    def to_json(self, public_message: str) -> str:
+        """Convert the error to a JSON string."""
+        return json.dumps({
+            "code": self.code,
+            "public_message": public_message,
+            "public_details": self.public_details,
+        }
+        )
 
 
 class ApiErrorCode(IntEnum):
diff --git a/framework/py/flwr/supercore/error/grpc.py b/framework/py/flwr/supercore/error/grpc.py
index 48510184e9e4..f470f9973b00 100644
--- a/framework/py/flwr/supercore/error/grpc.py
+++ b/framework/py/flwr/supercore/error/grpc.py
@@ -17,6 +17,7 @@
 
 from collections.abc import Iterator
 from contextlib import contextmanager
+import json
 from logging import ERROR
 
 import grpc
@@ -48,7 +49,7 @@ def rpc_error_translator(
 
         msg = f"[{rpc_name}][ApiError:{err.code}] {err.message}"
         log(ERROR, msg)
-        context.abort(grpc_status, public_message)
+        context.abort(grpc_status, err.to_json(public_message))
         raise grpc.RpcError() from None  # Unreachable, but satisfies type checker
     except Exception as err:
         # Let pass through if `context.abort()` is called
diff --git a/framework/py/flwr/superlink/federation/noop_federation_manager.py b/framework/py/flwr/superlink/federation/noop_federation_manager.py
index 305295da8ae5..56bd21add801 100644
--- a/framework/py/flwr/superlink/federation/noop_federation_manager.py
+++ b/framework/py/flwr/superlink/federation/noop_federation_manager.py
@@ -31,6 +31,7 @@
     NOOP_FEDERATION_DESCRIPTION,
     ActionType,
 )
+import json
 from flwr.supercore.error import ApiErrorCode, FlowerError
 from flwr.supercore.typing import ActionContext
 
@@ -47,6 +48,24 @@ def __init__(self, message: str):
         )
 
 
+class EntitlementError(FlowerError):
+    """Exception raised when an account is not entitled to perform an action."""
+
+    def __init__(self, details: str , entitlement_code: int):
+        super().__init__(
+            message=details,
+            public_details=details,
+            code=...,
+        )
+        self.entitlement_code = entitlement_code
+
+    def to_json(self) -> str:
+        """Convert the error into a JSON string."""
+        base_dict = json.loads(super().to_json())
+        base_dict["entitlement_code"] = self.entitlement_code
+        return json.dumps(base_dict)
+
+
 class NoOpFederationManager(FederationManager):
     """No-Op FederationManager implementation."""