fix(proxy): tolerate missing team_id in responses id decrypt

_decrypt_response_id required parts[2] after only checking len(parts) >= 2,
so a two-segment managed id (response_id + user_id, no team) raised
IndexError and broke follow-up /v1/responses calls.

Treat team_id as optional when the third segment is absent.

Fixes #43493

litellm/proxy/hooks/responses_id_security.py

@@ -244,7 +244,9 @@ class ResponsesIDSecurity(CustomLogger):
             return response_id, None, None
 
         if decrypted_value.startswith(SpecialEnums.LITELM_MANAGED_FILE_ID_PREFIX.value):
-            # Expected format: "litellm_proxy:responses_api:response_id:{response_id};user_id:{user_id}"
+            # Formats:
+            # - "litellm_proxy:responses_api:response_id:{id};user_id:{user};team_id:{team}"
+            # - "litellm_proxy:responses_api:response_id:{id};user_id:{user}" (legacy / no team)
             parts: Final = decrypted_value.split(";")
 
             if len(parts) >= 2:
@@ -256,9 +258,11 @@ class ResponsesIDSecurity(CustomLogger):
                 user_id_part: Final = parts[1]
                 user_id: Final = user_id_part.split("user_id:")[-1]
 
-                # Extract team_id from "team_id:{team_id}"
-                team_id_part: Final = parts[2]
-                team_id: Final = team_id_part.split("team_id:")[-1]
+                # Team segment is optional; older two-segment ids omit it.
+                team_id: str | None = None
+                if len(parts) >= 3:
+                    team_id_part: Final = parts[2]
+                    team_id = team_id_part.split("team_id:")[-1]
 
                 return original_response_id, user_id, team_id
             else:

tests/unit/test_responses_id_security.py

@@ -113,6 +113,25 @@ class TestDecryptResponseId:
             assert team_id is None
 
 
+    def test_decrypt_response_id_two_segment_no_team(self, responses_id_security):
+        """Two-segment managed ids (no team_id) must not IndexError on parts[2]."""
+        import litellm.proxy.hooks.responses_id_security as responses_module
+
+        with patch.object(responses_module, "decrypt_value_helper") as mock_decrypt:
+            mock_decrypt.return_value = (
+                f"{SpecialEnums.LITELM_MANAGED_FILE_ID_PREFIX.value}"
+                "response_id:resp_abc;user_id:user-1"
+            )
+
+            original_id, user_id, team_id = responses_id_security._decrypt_response_id(
+                "resp_encrypted_two_segment"
+            )
+
+            assert original_id == "resp_abc"
+            assert user_id == "user-1"
+            assert team_id is None
+
+
 class TestCheckUserAccessToResponseId:
     """Test check_user_access_to_response_id function"""