fix(llmrails): move LLM isolation setup to after KB initialization

The LLM isolation code was called too early in __init__, before all
components were fully initialized. This caused flow matching to fail
when trying to resolve rail flow IDs.

Move _create_isolated_llms_for_actions() call to after KB setup to
ensure all initialization is complete before creating isolated LLMs.

Author: Pouyanpi

nemoguardrails/rails/llm/llmrails.py

@@ -284,6 +284,8 @@ def __init__(
         # We also register the kb as a parameter that can be passed to actions.
         self.runtime.register_action_param("kb", self.kb)
 
+        # detect actions that need isolated LLM instances and create them
+        self._create_isolated_llms_for_actions()
         # Reference to the general ExplainInfo object.
         self.explain_info = None
 
@@ -507,9 +509,6 @@ def _init_llms(self):
 
         self.runtime.register_action_param("llms", llms)
 
-        # detect actions that need isolated LLM instances and create them
-        self._create_isolated_llms_for_actions()
-
     def _create_isolated_llms_for_actions(self):
         """Create isolated LLM copies for all actions that accept 'llm' parameter."""
         if not self.llm:
@@ -525,17 +524,38 @@ def _create_isolated_llms_for_actions(self):
             )
 
             created_count = 0
-            # Get the actions from flows defined in rails config
-            get_action_details = partial(
-                get_action_details_from_flow_id, flows=self.config.flows
-            )
+
             configured_actions_names = []
-            for flow_id in self.config.rails.input.flows:
-                action_name, _ = get_action_details(flow_id)
-                configured_actions_names.append(action_name)
-            for flow_id in self.config.rails.output.flows:
-                action_name, _ = get_action_details(flow_id)
-                configured_actions_names.append(action_name)
+            try:
+                if self.config.flows:
+                    get_action_details = partial(
+                        get_action_details_from_flow_id, flows=self.config.flows
+                    )
+                    for flow_id in self.config.rails.input.flows:
+                        action_name, _ = get_action_details(flow_id)
+                        configured_actions_names.append(action_name)
+                    for flow_id in self.config.rails.output.flows:
+                        action_name, _ = get_action_details(flow_id)
+                        configured_actions_names.append(action_name)
+                else:
+                    # for configurations without flow definitions, use all actions that need LLMs
+                    print(
+                        "No flow definitions found, creating isolated LLMs for all actions requiring them"
+                    )
+                    configured_actions_names = list(actions_needing_llms)
+            except Exception as e:
+                # if flow matching fails, fall back to all actions that need LLMs
+                log.info(
+                    "No flow definitions found, creating isolated LLMs for all actions requiring them"
+                )
+                configured_actions_names = list(actions_needing_llms)
+            except Exception as e:
+                # if flow matching fails, fall back to all actions that need LLMs
+                log.warning(
+                    "Flow matching failed (%s), creating isolated LLMs for all actions requiring them",
+                    e,
+                )
+                configured_actions_names = list(actions_needing_llms)
 
             for action_name in configured_actions_names:
                 if action_name not in actions_needing_llms:

nemoguardrails/rails/llm/utils.py

@@ -13,7 +13,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import json
-from typing import Any, Dict, List, Optional, Tuple, Union
+from typing import Any, Dict, List, Tuple, Union
+
+from nemoguardrails.colang.v1_0.runtime.flows import _normalize_flow_id
 
 
 def get_history_cache_key(messages: List[dict]) -> str:
@@ -61,37 +63,24 @@ def get_history_cache_key(messages: List[dict]) -> str:
 def get_action_details_from_flow_id(
     flow_id: str,
     flows: List[Union[Dict, Any]],
-    prefixes: Optional[List[str]] = None,
 ) -> Tuple[str, Any]:
     """Get the action name and parameters from the flow id.
 
     First, try to find an exact match.
     If not found, then if the provided flow_id starts with one of the special prefixes,
     return the first flow whose id starts with that same prefix.
     """
-    supported_prefixes = [
-        "content safety check output",
-        "topic safety check output",
-    ]
-    if prefixes:
-        supported_prefixes.extend(prefixes)
 
     candidate_flow = None
 
     for flow in flows:
         # If exact match, use it
-        if flow["id"] == flow_id:
+        flow_id = _normalize_flow_id(flow_id)
+    normalized_flow_id = _normalize_flow_id(flow_id)
+    for flow in flows:
+        # If exact match, use it
+        if flow["id"] == normalized_flow_id:
             candidate_flow = flow
-            break
-
-        # If no exact match, check if both the provided flow_id and this flow's id share a special prefix
-        for prefix in supported_prefixes:
-            if flow_id.startswith(prefix) and flow["id"].startswith(prefix):
-                candidate_flow = flow
-                # We don't break immediately here because an exact match would have been preferred,
-                # but since we're in the else branch it's fine to choose the first matching candidate.
-                # TODO:we should avoid having multiple matchin prefixes
-                break
 
         if candidate_flow is not None:
             break

tests/test_llm_isolation.py

@@ -536,3 +536,44 @@ def test_create_isolated_llms_handles_empty_rails_config(self, rails_with_mock_l
         mock_get_action.assert_not_called()
 
         rails.runtime.register_action_param.assert_not_called()
+
+    def test_llm_isolation_timing_with_empty_flows(self, rails_with_mock_llm, caplog):
+        """Test that LLM isolation handles empty flows gracefully during initialization.
+
+        This test reproduces the timing issue where _create_isolated_llms_for_actions()
+        was called before flows were properly loaded. Before the fix, this would fail
+        when trying to resolve rail flow IDs against an empty flows list, causing
+        LLM isolation to fail silently with a warning log.
+        """
+        rails = rails_with_mock_llm
+
+        rails.llm = MockLLM(model_kwargs={}, temperature=0.7)
+
+        # simulate the problematic scenario: rail flows defined but config.flows empty
+        rails.config.rails = Mock()
+        rails.config.rails.input = Mock()
+        rails.config.rails.output = Mock()
+        rails.config.rails.input.flows = [
+            "content safety check input $model=content_safety"
+        ]
+        rails.config.rails.output.flows = [
+            "content safety check output $model=content_safety"
+        ]
+        rails.config.flows = []  # Empty flows list (timing issue scenario)
+
+        rails.runtime = Mock()
+        rails.runtime.action_dispatcher = MockActionDispatcher()
+        rails.runtime.registered_action_params = {}
+        rails.runtime.register_action_param = Mock()
+
+        # before the fix, this would log a warning about failing to create isolated LLMs
+        # after the fix, it should handle empty flows gracefully without the warning
+        rails._create_isolated_llms_for_actions()
+
+        warning_messages = [
+            record.message for record in caplog.records if record.levelname == "WARNING"
+        ]
+        assert not any(
+            "Failed to create isolated LLMs for actions" in msg
+            for msg in warning_messages
+        ), f"Fix failed: Warning still logged: {warning_messages}"

tests/test_rails_llm_utils.py

@@ -145,11 +145,11 @@ def test_get_action_details_from_flow_id_exact_match():
     assert action_params == {"param1": "value1"}
 
 
-def test_get_action_details_from_flow_id_prefix_match():
-    """Test get_action_details_from_flow_id with prefix matching."""
+def test_get_action_details_from_flow_id_content_safety():
+    """Test get_action_details_from_flow_id  ."""
     flows = [
         {
-            "id": "content safety check output with model gpt-4",
+            "id": "content safety check output",
             "elements": [
                 {
                     "_type": "run_action",
@@ -165,17 +165,17 @@ def test_get_action_details_from_flow_id_prefix_match():
     ]
 
     action_name, action_params = get_action_details_from_flow_id(
-        "content safety check output", flows
+        "content safety check output $model=anothe_model_config", flows
     )
     assert action_name == "content_safety_check"
     assert action_params == {"model": "gpt-4"}
 
 
-def test_get_action_details_from_flow_id_topic_safety_prefix():
-    """Test get_action_details_from_flow_id with topic safety prefix."""
+def test_get_action_details_from_flow_id_topic_safety():
+    """Test get_action_details_from_flow_id with topic safety."""
     flows = [
         {
-            "id": "topic safety check output with model claude",
+            "id": "topic safety check output",
             "elements": [
                 {
                     "_type": "run_action",
@@ -191,38 +191,12 @@ def test_get_action_details_from_flow_id_topic_safety_prefix():
     ]
 
     action_name, action_params = get_action_details_from_flow_id(
-        "topic safety check output", flows
+        "topic safety check output $model=claude_model", flows
     )
     assert action_name == "topic_safety_check"
     assert action_params == {"model": "claude"}
 
 
-def test_get_action_details_from_flow_id_custom_prefixes():
-    """Test get_action_details_from_flow_id with custom prefixes."""
-    flows = [
-        {
-            "id": "custom prefix flow with params",
-            "elements": [
-                {
-                    "_type": "run_action",
-                    "_source_mapping": {
-                        "filename": "custom.co",
-                        "line_text": "execute custom_action",
-                    },
-                    "action_name": "custom_action",
-                    "action_params": {"custom": "value"},
-                }
-            ],
-        }
-    ]
-
-    action_name, action_params = get_action_details_from_flow_id(
-        "custom prefix flow", flows, prefixes=["custom prefix"]
-    )
-    assert action_name == "custom_action"
-    assert action_params == {"custom": "value"}
-
-
 def test_get_action_details_from_flow_id_no_match():
     """Test get_action_details_from_flow_id when no flow matches."""
     flows = [
@@ -410,28 +384,6 @@ def test_get_action_details_exact_match_not_colang_2(dummy_flows):
     assert "No run_action element found for flow_id" in str(exc_info.value)
 
 
-def test_get_action_details_prefix_match(dummy_flows):
-    # For a flow_id that starts with the prefix "other_flow",
-    # we expect to retrieve the action details from the flow whose id starts with that prefix.
-    # we expect a result since we are passing the prefixes argument.
-    action_name, action_params = get_action_details_from_flow_id(
-        "other_flow", dummy_flows, prefixes=["other_flow"]
-    )
-    assert action_name == "other_action"
-    assert action_params == {"param2": "value2"}
-
-
-def test_get_action_details_prefix_match_unsupported_prefix(dummy_flows):
-    # For a flow_id that starts with the prefix "other_flow",
-    # we expect to retrieve the action details from the flow whose id starts with that prefix.
-    # but as the prefix is not supported, we expect a ValueError.
-
-    with pytest.raises(ValueError) as exc_info:
-        get_action_details_from_flow_id("other_flow", dummy_flows)
-
-    assert "No action found for flow_id" in str(exc_info.value)
-
-
 def test_get_action_details_no_match(dummy_flows):
     # Tests that a non matching flow_id raises a ValueError
     with pytest.raises(ValueError) as exc_info: