UPDATE

weather/test_farm_weather_api.py

@@ -6,6 +6,8 @@ from unittest.mock import patch
 from django.test import TestCase, override_settings
 from rest_framework.test import APIClient
 
+from rag.failure_contract import RAGServiceError
+
 
 @override_settings(ROOT_URLCONF="weather.urls")
 class FarmWeatherApiTests(TestCase):
@@ -122,3 +124,29 @@ class WaterNeedPredictionApiTests(TestCase):
 
         self.assertEqual(response.status_code, 404)
         self.assertEqual(response.json()["msg"], "Farm not found.")
+
+    @patch("weather.views.apps.get_app_config")
+    def test_water_need_api_returns_structured_failure_for_invalid_llm_json(self, mock_get_app_config):
+        mock_service = SimpleNamespace(
+            get_water_need_prediction=lambda **_kwargs: (_ for _ in ()).throw(
+                RAGServiceError(
+                    error_code="invalid_json",
+                    message="Water need prediction LLM response was not valid JSON.",
+                    source="llm",
+                    retriable=True,
+                    http_status=502,
+                )
+            )
+        )
+        mock_get_app_config.return_value = SimpleNamespace(
+            get_water_need_service=lambda: mock_service
+        )
+
+        response = self.client.post(
+            "/water-need-prediction/",
+            data={"farm_uuid": "550e8400-e29b-41d4-a716-446655440000"},
+            format="json",
+        )
+
+        self.assertEqual(response.status_code, 502)
+        self.assertEqual(response.json()["data"]["error_code"], "invalid_json")