refactor!: Make create_tracker required on AIConfig (no default)

AIConfig.create_tracker is now a required field with no default value.
The SDK client always injects a real tracker factory, so any direct
construction of AIConfig subclasses must now provide one explicitly.
This eliminates the entire class of null-safety issues around tracker
factories. Reverts the RuntimeError guard in Judge.evaluate() since
it is no longer needed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jsonbailey

packages/ai-providers/server-ai-langchain/tests/test_langchain_provider.py

@@ -530,6 +530,7 @@ def sync_tool(x: str = '') -> str:
         cfg = AIAgentConfig(
             key='n',
             enabled=True,
+            create_tracker=MagicMock(),
             model=ModelConfig(
                 name='gpt-4',
                 parameters={'tools': [{'name': 'my_tool', 'type': 'function', 'parameters': {}}]},
@@ -552,6 +553,7 @@ async def async_tool(x: str = '') -> str:
         cfg = AIAgentConfig(
             key='n',
             enabled=True,
+            create_tracker=MagicMock(),
             model=ModelConfig(
                 name='gpt-4',
                 parameters={'tools': [{'name': 'my_tool', 'type': 'function', 'parameters': {}}]},

packages/ai-providers/server-ai-langchain/tests/test_langgraph_agent_graph_runner.py

@@ -12,9 +12,11 @@
 
 def _make_graph(enabled: bool = True) -> AgentGraphDefinition:
     graph_tracker = MagicMock()
+    node_tracker = MagicMock()
     root_config = AIAgentConfig(
         key='root-agent',
         enabled=enabled,
+        create_tracker=MagicMock(return_value=node_tracker),
         model=ModelConfig(name='gpt-4'),
         provider=ProviderConfig(name='openai'),
         instructions='You are a helpful assistant.',

packages/ai-providers/server-ai-langchain/tests/test_langgraph_callback_handler.py

@@ -462,6 +462,7 @@ def test_flush_skips_node_without_tracker():
     node_config_no_tracker = AIAgentConfig(
         key='no-track',
         enabled=True,
+        create_tracker=lambda: None,
         model=ModelConfig(name='gpt-4', parameters={}),
         provider=ProviderConfig(name='openai'),
         instructions='',

packages/sdk/server-ai/src/ldai/agent_graph/__init__.py

@@ -4,10 +4,10 @@
 
 from ldclient import Context
 
-from ldai.models import AIAgentConfig, AIAgentGraphConfig, Edge
+from ldai.models import AIAgentConfig, AIAgentConfigDefault, AIAgentGraphConfig, Edge
 from ldai.tracker import AIGraphTracker
 
-DEFAULT_FALSE = AIAgentConfig(key="", enabled=False)
+DEFAULT_FALSE = AIAgentConfigDefault(enabled=False)
 
 
 class AgentGraphNode:

packages/sdk/server-ai/src/ldai/judge/__init__.py

@@ -71,11 +71,6 @@ async def evaluate(
             judge_result.sampled = True
 
             tracker = self._ai_config.create_tracker()
-            if tracker is None:
-                raise RuntimeError(
-                    "AIConfig.create_tracker returned None. "
-                    "Ensure the config was obtained from the client rather than constructed directly."
-                )
             messages = self._construct_evaluation_messages(input_text, output_text)
             assert self._evaluation_response_structure is not None
 

packages/sdk/server-ai/src/ldai/models.py

@@ -167,12 +167,16 @@ def _base_to_dict(self) -> Dict[str, Any]:
 class AIConfig:
     """
     Base AI Config interface without mode-specific fields.
+
+    Instances are always created by the SDK client, which injects a real
+    ``create_tracker`` factory.  User code should never need to construct
+    this directly — use the ``*Default`` variants for default values.
     """
     key: str
     enabled: bool
+    create_tracker: Callable[[], Any]
     model: Optional[ModelConfig] = None
     provider: Optional[ProviderConfig] = None
-    create_tracker: Callable[[], Any] = lambda: None
 
     def _base_to_dict(self) -> Dict[str, Any]:
         """

packages/sdk/server-ai/tests/test_agent_graph.py

@@ -2,6 +2,8 @@
 from ldclient import Config, Context, LDClient
 from ldclient.integrations.test_data import TestData
 
+from unittest.mock import MagicMock
+
 from ldai import (
     LDAIClient,
     AIAgentGraphConfig,
@@ -268,13 +270,17 @@ def test_agent_graph_build_nodes(ldai_client: LDAIClient):
         ai_graph_config,
         {
             "customer-support-agent": AIAgentConfig(
-                key="customer-support-agent", enabled=True
+                key="customer-support-agent", enabled=True, create_tracker=MagicMock(),
+            ),
+            "personalized-agent": AIAgentConfig(
+                key="personalized-agent", enabled=True, create_tracker=MagicMock(),
             ),
-            "personalized-agent": AIAgentConfig(key="personalized-agent", enabled=True),
             "multi-context-agent": AIAgentConfig(
-                key="multi-context-agent", enabled=True
+                key="multi-context-agent", enabled=True, create_tracker=MagicMock(),
+            ),
+            "minimal-agent": AIAgentConfig(
+                key="minimal-agent", enabled=True, create_tracker=MagicMock(),
             ),
-            "minimal-agent": AIAgentConfig(key="minimal-agent", enabled=True),
         },
     )
 

packages/sdk/server-ai/tests/test_judge.py

@@ -83,8 +83,7 @@ def _make_judge_config(
         model=model or ModelConfig('gpt-4'),
         provider=provider or ProviderConfig('openai'),
     )
-    if tracker is not None:
-        kwargs['create_tracker'] = lambda: tracker
+    kwargs['create_tracker'] = (lambda: tracker) if tracker is not None else MagicMock()
     return AIJudgeConfig(**kwargs)
 
 
@@ -372,6 +371,7 @@ def test_to_dict_includes_evaluation_metric_key(self):
         config = AIJudgeConfig(
             key='test-judge',
             enabled=True,
+            create_tracker=MagicMock(),
             evaluation_metric_key='$ld:ai:judge:relevance',
             messages=[LDMessage(role='system', content='You are a judge.')],
         )
@@ -386,6 +386,7 @@ def test_to_dict_handles_none_evaluation_metric_key(self):
         config = AIJudgeConfig(
             key='test-judge',
             enabled=True,
+            create_tracker=MagicMock(),
             evaluation_metric_key=None,
             messages=[LDMessage(role='system', content='You are a judge.')],
         )