fix(config): keep validator_pixel_safety_net and planner_validation overrides

artemis/config/llm.py

@@ -182,6 +182,12 @@ def _expand_default_into_nodes(config_dict: dict) -> dict:
                     node_cfg[k] = v
         result[node] = node_cfg
 
+    # Optional judge nodes: only set when declared, otherwise get_agent()
+    # falls back to lightweight_judge_default().
+    for node in ("validator_pixel_safety_net", "planner_validation"):
+        if node in nodes_override:
+            result[node] = {**default_model_cfg, **nodes_override[node]}
+
     utils_dict: dict[str, Any] = {}
     for util in all_utils_nodes:
         util_cfg = dict(default_model_cfg)

tests/unit/config/test_llm_judge_nodes.py

@@ -0,0 +1,54 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""The optional judge nodes declared under ``nodes`` survive config expansion."""
+
+from artemis.config.llm import LLMConfig, _expand_default_into_nodes, lightweight_judge_default
+
+_DEFAULT = {
+    "provider": "openai",
+    "model": "gpt-main",
+    "fallback": {"provider": "openai", "model": "gpt-fallback"},
+}
+
+
+def _parse(nodes: dict) -> LLMConfig:
+    return LLMConfig.model_validate(
+        _expand_default_into_nodes({"default": _DEFAULT, "nodes": nodes})
+    )
+
+
+def test_declared_judge_nodes_are_kept():
+    cfg = _parse(
+        {
+            "validator_pixel_safety_net": {"model": "gpt-judge", "temperature": 0.0},
+            "planner_validation": {"model": "gpt-judge", "temperature": 0.0},
+        }
+    )
+
+    for node in ("validator_pixel_safety_net", "planner_validation"):
+        judge = cfg.get_agent(node)
+        assert judge.provider == "openai"
+        assert judge.model == "gpt-judge"
+        assert judge.temperature == 0.0
+        # Unset keys come from the default, including the fallback.
+        assert judge.fallback.model == "gpt-fallback"
+
+
+def test_undeclared_judge_nodes_fall_back_to_the_lightweight_default():
+    cfg = _parse({})
+
+    assert cfg.validator_pixel_safety_net is None
+    assert cfg.planner_validation is None
+    assert cfg.get_agent("planner_validation") == lightweight_judge_default()