From 4d995672b1cbde606d2799130e7bf27e650f8169 Mon Sep 17 00:00:00 2001
From: "Alan Z." <shuai.xyz@gmail.com>
Date: Sat, 25 Jul 2026 04:29:58 -0700
Subject: [PATCH] [bug] [python] Propagate config model reconstruction errors
 in Action deserialize (#921)

---
 python/flink_agents/plan/actions/action.py    | 28 ++++++----
 .../plan/tests/resources/action.json          | 11 ++--
 python/flink_agents/plan/tests/test_action.py | 51 +++++++++++++++++++
 3 files changed, 75 insertions(+), 15 deletions(-)

diff --git a/python/flink_agents/plan/actions/action.py b/python/flink_agents/plan/actions/action.py
index c3ad31457..9d57ae7c9 100644
--- a/python/flink_agents/plan/actions/action.py
+++ b/python/flink_agents/plan/actions/action.py
@@ -26,6 +26,9 @@
 from flink_agents.plan.function import Function, JavaFunction, PythonFunction
 
 _CONFIG_TYPE = "__config_type__"
+# Tags a config entry that we serialized from a pydantic model, so on the way
+# back we only rebuild the ones we tagged and leave plain values alone.
+_PYDANTIC_MODEL_MARKER = "__pydantic_model__"
 
 
 class Action(BaseModel):
@@ -70,11 +73,12 @@ def __serialize_config(self, config: Dict[str, Any]) -> Dict[str, Any] | None:
         data[_CONFIG_TYPE] = "python"
         for name, value in config.items():
             if isinstance(value, BaseModel):
-                data[name] = (
-                    inspect.getmodule(value).__name__,
-                    value.__class__.__name__,
-                    value,
-                )
+                data[name] = {
+                    _PYDANTIC_MODEL_MARKER: True,
+                    "module": inspect.getmodule(value).__name__,
+                    "class": value.__class__.__name__,
+                    "value": value,
+                }
             else:
                 data[name] = value
         return data
@@ -95,11 +99,15 @@ def __custom_deserialize(self) -> "Action":
                     self["config"][name] = value["value"]
             return self
         for name, value in config.items():
-            try:
-                module = importlib.import_module(value[0])
-                clazz = getattr(module, value[1])
-                self["config"][name] = clazz.model_validate(value[2])
-            except Exception:  # noqa : PERF203
+            # Rebuild only entries with our marker, so a plain list or dict
+            # value is not treated as a model by mistake. Do not catch errors:
+            # if the class cannot be imported (e.g. missing on the worker),
+            # fail here with the real cause instead of a confusing error later.
+            if isinstance(value, dict) and value.get(_PYDANTIC_MODEL_MARKER):
+                module = importlib.import_module(value["module"])
+                clazz = getattr(module, value["class"])
+                self["config"][name] = clazz.model_validate(value["value"])
+            else:
                 self["config"][name] = value
         return self
 
diff --git a/python/flink_agents/plan/tests/resources/action.json b/python/flink_agents/plan/tests/resources/action.json
index 09393e475..08cdad3fb 100644
--- a/python/flink_agents/plan/tests/resources/action.json
+++ b/python/flink_agents/plan/tests/resources/action.json
@@ -10,10 +10,11 @@
     ],
     "config": {
         "__config_type__": "python",
-        "output_schema": [
-            "flink_agents.api.agents.types",
-            "OutputSchema",
-            {
+        "output_schema": {
+            "__pydantic_model__": true,
+            "module": "flink_agents.api.agents.types",
+            "class": "OutputSchema",
+            "value": {
                 "output_schema": {
                     "names": [
                         "result"
@@ -23,6 +24,6 @@
                     ]
                 }
             }
-        ]
+        }
     }
 }
\ No newline at end of file
diff --git a/python/flink_agents/plan/tests/test_action.py b/python/flink_agents/plan/tests/test_action.py
index f93ee4531..08f0d5dd2 100644
--- a/python/flink_agents/plan/tests/test_action.py
+++ b/python/flink_agents/plan/tests/test_action.py
@@ -120,3 +120,54 @@ def test_action_deserialize_java_shape_config_unwraps_primitives() -> None:
         "rate": 1.5,
         "label": "fast",
     }
+
+
+def test_action_deserialize_python_config_propagates_reconstruction_error() -> None:
+    """A tagged model whose module is missing must fail loudly.
+
+    The entry is marked as a serialized model, so importing a non-existent
+    module raises instead of being silently swallowed.
+    """
+    json_str = json.dumps(
+        {
+            "name": "legal",
+            "exec": {
+                "func_type": "PythonFunction",
+                "module": "flink_agents.plan.tests.test_action",
+                "qualname": "legal_signature",
+            },
+            "trigger_conditions": ["_input_event"],
+            "config": {
+                "__config_type__": "python",
+                "broken": {
+                    "__pydantic_model__": True,
+                    "module": "nonexistent_module_xyz",
+                    "class": "SomeClass",
+                    "value": {},
+                },
+            },
+        }
+    )
+    with pytest.raises(ModuleNotFoundError):
+        Action.model_validate_json(json_str)
+
+
+def test_action_deserialize_python_config_preserves_plain_list() -> None:
+    """A plain user list must survive untouched, not be mistaken for a model."""
+    json_str = json.dumps(
+        {
+            "name": "legal",
+            "exec": {
+                "func_type": "PythonFunction",
+                "module": "flink_agents.plan.tests.test_action",
+                "qualname": "legal_signature",
+            },
+            "trigger_conditions": ["_input_event"],
+            "config": {
+                "__config_type__": "python",
+                "hosts": ["host-a", "host-b", "host-c"],
+            },
+        }
+    )
+    action = Action.model_validate_json(json_str)
+    assert action.config == {"hosts": ["host-a", "host-b", "host-c"]}