diff --git a/parrot/serve/variable_manager.py b/parrot/serve/variable_manager.py
index 852ed3d..9cb02b5 100644
--- a/parrot/serve/variable_manager.py
+++ b/parrot/serve/variable_manager.py
@@ -253,17 +253,13 @@ def create_var(self, session_id: int, var_name: str) -> SemanticVariable:
         )
 
     def get_var(self, session_id: int, var_id: str) -> SemanticVariable:
-        """Get a Semantic Variable by ID.
+        """Get a session-local Semantic Variable by ID.
 
         Args:
             session_id: int. The session ID.
             var_id: str. The Semantic Variable ID.
         """
 
-        cp_var = self.constant_prefix_namespace.get_var_by_id(var_id)
-        if cp_var is not None:
-            return cp_var
-
         parrot_assert(
             session_id in self.session_namespaces,
             f"Local namespace of {session_id} does not exist.",
diff --git a/tests/serve/test_sv.py b/tests/serve/test_sv.py
index 24b20d6..52aba41 100644
--- a/tests/serve/test_sv.py
+++ b/tests/serve/test_sv.py
@@ -1,3 +1,6 @@
+import pytest
+
+from parrot.exceptions import ParrotCoreUserError
 from parrot.serve.graph import (
     RequestChain,
     ConstantFill,
@@ -22,6 +25,21 @@ def test_content_hash():
     assert var1 == var2
 
 
+def test_constant_prefix_is_not_exposed_through_session_lookup():
+    var_mgr = SemanticVariableManager(constant_prefix_var_timeout=10)
+    owner_session_id = 0
+    other_session_id = 1
+    var_mgr.register_local_var_space(owner_session_id)
+    var_mgr.register_local_var_space(other_session_id)
+
+    prefix_var = var_mgr._get_constant_prefix_var("private system prompt")
+
+    with pytest.raises(ParrotCoreUserError):
+        var_mgr.get_var(owner_session_id, prefix_var.id)
+    with pytest.raises(ParrotCoreUserError):
+        var_mgr.get_var(other_session_id, prefix_var.id)
+
+
 def test_request_chain_hash():
     var_mgr = SemanticVariableManager(constant_prefix_var_timeout=10)