AD-SDL · RyanTheRobothead · Mar 27, 2026 · Mar 27, 2026 · Mar 27, 2026 · Mar 27, 2026
diff --git a/src/madsci_client/madsci/client/node/rest_node_client.py b/src/madsci_client/madsci/client/node/rest_node_client.py
@@ -7,6 +7,7 @@
 from pathlib import Path
 from typing import Any, ClassVar, Optional, Union
 
+import requests
 from madsci.client.event_client import EventClient
 from madsci.client.node.abstract_node_client import (
     AbstractNodeClient,
@@ -439,7 +440,20 @@ def get_action_result_by_name(
             f"{self.url}/action/{action_name}/{action_id}/result",
             timeout=timeout or self.config.timeout_default,
         )
-        rest_response.raise_for_status()
+        try:
+            rest_response.raise_for_status()
+        except requests.HTTPError:
+            if rest_response.status_code >= 500:
+                # Fall back to generic endpoint if typed endpoint returns a
+                # server error (e.g. unpatched nodes returning None for failed
+                # typed actions)
+                self.logger.warning(
+                    "Typed endpoint returned server error; falling back to generic endpoint",
+                    action_name=action_name,
+                    status_code=rest_response.status_code,
+                )
+                return self.get_action_result(action_id, timeout=timeout)
+            raise
 
         # If include_files is False, we can convert directly without fetching files
         if not include_files:

diff --git a/src/madsci_common/madsci/common/types/action_types.py b/src/madsci_common/madsci/common/types/action_types.py
@@ -1041,9 +1041,10 @@ def create_dynamic_model(
 
     # Always override json_result field for proper OpenAPI documentation
     if json_result_type is not None:
-        # Specific type for json_result
+        # Specific type for json_result, wrapped in Optional to allow None
+        # for failed/in-progress actions (fixes 500 errors on typed endpoints)
         fields["json_result"] = (
-            json_result_type,
+            Optional[json_result_type],
             Field(
                 description=f"JSON result data for {action_name} action", default=None
             ),

diff --git a/src/madsci_node_module/tests/test_rest_node_module.py b/src/madsci_node_module/tests/test_rest_node_module.py
@@ -1286,6 +1286,53 @@ def test_mixed_return_maps_to_both_fields(self, enhanced_client):
         assert result["json_result"]["result"] == "success"
         assert result["files"] is not None
 
+    def test_failed_typed_action_returns_200(self, enhanced_test_node, enhanced_client):
+        """Test that a failed typed action returns 200 with FAILED status, not 500.
+
+        Regression test for issue #187: when a typed action (e.g. -> int) fails,
+        the action-specific result endpoint must still return the ActionResult
+        with status=failed, rather than a 500 error from Pydantic rejecting
+        json_result=None against a non-Optional type.
+        """
+
+        def _raise(*_args, **_kwargs):
+            raise RuntimeError("simulated failure")
+
+        # 1. Create the action
+        response = enhanced_client.post("/action/return_int", json={"args": {}})
+        assert response.status_code == 200
+        action_id = response.json()["action_id"]
+
+        # 2. Swap the handler in action_handlers dict so the action fails
+        original = enhanced_test_node.action_handlers["return_int"]
+        enhanced_test_node.action_handlers["return_int"] = _raise
+        try:
+            # 3. Start the action (will fail internally)
+            response = enhanced_client.post(f"/action/return_int/{action_id}/start")
+            assert response.status_code == 200
+
+            # 4. Wait for the action to finish
+            result = None
+            for _ in range(50):
+                response = enhanced_client.get(f"/action/return_int/{action_id}/result")
+                if response.status_code == 200:
+                    result = response.json()
+                    if result.get("status") in ["succeeded", "failed", "error"]:
+                        break
+                time.sleep(0.1)
+        finally:
+            enhanced_test_node.action_handlers["return_int"] = original
+            enhanced_test_node.node_status.errored = False
+
+        # 5. The typed endpoint must return 200, not 500
+        assert response.status_code == 200, (
+            f"Expected 200 but got {response.status_code} — "
+            "typed endpoint likely rejected json_result=None"
+        )
+        assert result is not None
+        assert result["status"] in ["failed", "error"]
+        assert result["json_result"] is None
+
 
 class TestEnhancedBackwardCompatibility:
     """Test that changes maintain backward compatibility."""