diff --git a/app-instance/backend/beaver/tasks/models.py b/app-instance/backend/beaver/tasks/models.py
index 7e2a172..88182c3 100644
--- a/app-instance/backend/beaver/tasks/models.py
+++ b/app-instance/backend/beaver/tasks/models.py
@@ -70,10 +70,12 @@ class ValidationResult:
         if not isinstance(payload, dict):
             return None
         raw_status = payload.get("status")
-        status: ValidationStatus | None = raw_status if raw_status in VALIDATION_STATUSES else None
+        if "status" in payload and raw_status not in VALIDATION_STATUSES:
+            raise ValueError(f"unknown validation status: {raw_status}")
+        status: ValidationStatus | None = raw_status if "status" in payload else None
         return cls(
             status=status,
-            passed=bool(payload.get("passed")) if status is None else None,
+            passed=bool(payload.get("passed")) if "status" not in payload else None,
             score=float(payload.get("score", 0.0) or 0.0),
             issues=[str(item) for item in payload.get("issues") or []],
             missing_requirements=[str(item) for item in payload.get("missing_requirements") or []],
diff --git a/app-instance/backend/tests/unit/test_task_mode_feedback.py b/app-instance/backend/tests/unit/test_task_mode_feedback.py
index dc81dda..d23a756 100644
--- a/app-instance/backend/tests/unit/test_task_mode_feedback.py
+++ b/app-instance/backend/tests/unit/test_task_mode_feedback.py
@@ -439,6 +439,11 @@ def test_validation_result_rejects_unknown_status() -> None:
         ValidationResult(status="pending", score=0.9, validator="test")  # type: ignore[arg-type]
 
 
+def test_validation_result_from_dict_rejects_unknown_explicit_status() -> None:
+    with pytest.raises(ValueError, match="unknown validation status"):
+        ValidationResult.from_dict({"status": "pending", "passed": True, "score": 0.9})
+
+
 def test_validation_result_evidence_gaps_round_trip() -> None:
     validation = ValidationResult(
         status="insufficient_evidence",