diff --git a/libs/schemas/reasoning.py b/libs/schemas/reasoning.py
index 5008cf3..a658af7 100644
--- a/libs/schemas/reasoning.py
+++ b/libs/schemas/reasoning.py
@@ -1,7 +1,6 @@
 from __future__ import annotations
 from typing import Literal, Optional
-from pydantic import BaseModel, Field
-import json
+from pydantic import BaseModel, Field, computed_field
 
 
 class ReasoningResult(BaseModel):
@@ -16,24 +15,22 @@ class ReasoningResult(BaseModel):
     severity_score: float                            = Field(0.0, ge=0.0, le=1.0)
     alert_id:       Optional[str]                    = None
 
+    @computed_field
     @property
     def confidence_tier(self) -> Literal["high", "medium", "low"]:
-        if self.confidence >= 0.75: return "high"
-        if self.confidence >= 0.50: return "medium"
+        if self.confidence >= 0.75:
+            return "high"
+        if self.confidence >= 0.50:
+            return "medium"
         return "low"
 
+    @computed_field
     @property
     def is_actionable(self) -> bool:
         return self.label == "Suspicious" and self.confidence >= 0.65
 
-    def model_dump_json(self, **kw) -> str:
-        d = self.model_dump(**kw)
-        d["confidence_tier"] = self.confidence_tier
-        d["is_actionable"]   = self.is_actionable
-        return json.dumps(d, default=str)
-
 
 class GroundingResult(BaseModel):
     grounded:        bool
     invented_label:  Optional[str] = None
-    checked_caption: str           = ""
+    checked_caption: str           = ""
\ No newline at end of file
diff --git a/tests/test_reasoning_schema.py b/tests/test_reasoning_schema.py
new file mode 100644
index 0000000..8b18763
--- /dev/null
+++ b/tests/test_reasoning_schema.py
@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+import pytest
+from libs.schemas.reasoning import ReasoningResult
+
+
+@pytest.mark.parametrize(
+    "confidence, expected_tier",
+    [
+        (0.49, "low"),
+        (0.50, "medium"),
+        (0.74, "medium"),
+        (0.75, "high"),
+        (1.0, "high"),
+    ],
+)
+def test_confidence_tier_boundaries(confidence: float, expected_tier: str) -> None:
+    result = ReasoningResult(track_id=1, label="Suspicious", confidence=confidence, reason="test")
+    assert result.confidence_tier == expected_tier
+
+
+@pytest.mark.parametrize(
+    "label, confidence, expected",
+    [
+        ("Suspicious", 0.65, True),
+        ("Suspicious", 0.64, False),
+        ("Normal", 0.99, False),
+        ("Normal", 0.65, False),
+    ],
+)
+def test_is_actionable(label: str, confidence: float, expected: bool) -> None:
+    result = ReasoningResult(track_id=1, label=label, confidence=confidence, reason="test")
+    assert result.is_actionable is expected
+
+
+def test_model_dump_json_mode_includes_computed_fields() -> None:
+    result = ReasoningResult(track_id=1, label="Suspicious", confidence=0.88, reason="test")
+    payload = result.model_dump(mode="json")
+
+    assert payload["confidence_tier"] == "high"
+    assert payload["is_actionable"] is True
\ No newline at end of file