diff --git a/src/strategy/scenario_engine.py b/src/strategy/scenario_engine.py
index bf84740..59aadf1 100644
--- a/src/strategy/scenario_engine.py
+++ b/src/strategy/scenario_engine.py
@@ -38,8 +38,21 @@ class ScenarioEngine:
     """Evaluates playbook scenarios against real-time market data.
 
     No API calls — pure Python condition matching.
+
+    Expected market_data keys: "rsi", "volume_ratio", "current_price", "price_change_pct".
+    Callers must normalize data source keys to match this contract.
     """
 
+    @staticmethod
+    def _safe_float(value: Any) -> float | None:
+        """Safely cast a value to float. Returns None on failure."""
+        if value is None:
+            return None
+        try:
+            return float(value)
+        except (ValueError, TypeError):
+            return None
+
     def evaluate(
         self,
         playbook: DayPlaybook,
@@ -148,25 +161,37 @@ class ScenarioEngine:
 
         checks: list[bool] = []
 
-        rsi = market_data.get("rsi")
+        rsi = self._safe_float(market_data.get("rsi"))
+        if condition.rsi_below is not None or condition.rsi_above is not None:
+            if "rsi" not in market_data:
+                logger.warning("Condition requires 'rsi' but key missing from market_data")
         if condition.rsi_below is not None:
             checks.append(rsi is not None and rsi < condition.rsi_below)
         if condition.rsi_above is not None:
             checks.append(rsi is not None and rsi > condition.rsi_above)
 
-        volume_ratio = market_data.get("volume_ratio")
+        volume_ratio = self._safe_float(market_data.get("volume_ratio"))
+        if condition.volume_ratio_above is not None or condition.volume_ratio_below is not None:
+            if "volume_ratio" not in market_data:
+                logger.warning("Condition requires 'volume_ratio' but key missing from market_data")
         if condition.volume_ratio_above is not None:
             checks.append(volume_ratio is not None and volume_ratio > condition.volume_ratio_above)
         if condition.volume_ratio_below is not None:
             checks.append(volume_ratio is not None and volume_ratio < condition.volume_ratio_below)
 
-        price = market_data.get("current_price")
+        price = self._safe_float(market_data.get("current_price"))
+        if condition.price_above is not None or condition.price_below is not None:
+            if "current_price" not in market_data:
+                logger.warning("Condition requires 'current_price' but key missing from market_data")
         if condition.price_above is not None:
             checks.append(price is not None and price > condition.price_above)
         if condition.price_below is not None:
             checks.append(price is not None and price < condition.price_below)
 
-        price_change_pct = market_data.get("price_change_pct")
+        price_change_pct = self._safe_float(market_data.get("price_change_pct"))
+        if condition.price_change_pct_above is not None or condition.price_change_pct_below is not None:
+            if "price_change_pct" not in market_data:
+                logger.warning("Condition requires 'price_change_pct' but key missing from market_data")
         if condition.price_change_pct_above is not None:
             checks.append(price_change_pct is not None and price_change_pct > condition.price_change_pct_above)
         if condition.price_change_pct_below is not None:
diff --git a/tests/test_scenario_engine.py b/tests/test_scenario_engine.py
index e440fa0..59163eb 100644
--- a/tests/test_scenario_engine.py
+++ b/tests/test_scenario_engine.py
@@ -139,6 +139,50 @@ class TestEvaluateCondition:
         cond = StockCondition(rsi_above=70.0)
         assert not engine.evaluate_condition(cond, {"rsi": 70.0})
 
+    def test_string_value_no_exception(self, engine: ScenarioEngine) -> None:
+        """String numeric value should not raise TypeError."""
+        cond = StockCondition(rsi_below=30.0)
+        # "25" can be cast to float → should match
+        assert engine.evaluate_condition(cond, {"rsi": "25"})
+        # "35" → should not match
+        assert not engine.evaluate_condition(cond, {"rsi": "35"})
+
+    def test_percent_string_returns_false(self, engine: ScenarioEngine) -> None:
+        """Percent string like '30%' cannot be cast to float → False, no exception."""
+        cond = StockCondition(rsi_below=30.0)
+        assert not engine.evaluate_condition(cond, {"rsi": "30%"})
+
+    def test_decimal_value_no_exception(self, engine: ScenarioEngine) -> None:
+        """Decimal values should be safely handled."""
+        from decimal import Decimal
+
+        cond = StockCondition(rsi_below=30.0)
+        assert engine.evaluate_condition(cond, {"rsi": Decimal("25.0")})
+
+    def test_mixed_invalid_types_no_exception(self, engine: ScenarioEngine) -> None:
+        """Various invalid types should not raise exceptions."""
+        cond = StockCondition(
+            rsi_below=30.0, volume_ratio_above=2.0,
+            price_above=100, price_change_pct_below=-1.0,
+        )
+        data = {
+            "rsi": [25],           # list
+            "volume_ratio": "bad",  # non-numeric string
+            "current_price": {},    # dict
+            "price_change_pct": object(),  # arbitrary object
+        }
+        # Should return False (invalid types → None → False), never raise
+        assert not engine.evaluate_condition(cond, data)
+
+    def test_missing_key_logs_warning(self, engine: ScenarioEngine, caplog) -> None:
+        """Missing market_data key should log a warning."""
+        import logging
+
+        cond = StockCondition(rsi_below=30.0)
+        with caplog.at_level(logging.WARNING):
+            engine.evaluate_condition(cond, {})
+        assert "key missing from market_data" in caplog.text
+
 
 # ---------------------------------------------------------------------------
 # check_global_rules