fix: align from_dict() defaults with dataclass defaults

src/ml4t/backtest/config.py

@@ -679,8 +679,8 @@ def from_dict(
             fixed_margin_schedule=acct_cfg.get("fixed_margin_schedule"),
             short_cash_policy=ShortCashPolicy(acct_cfg.get("short_cash_policy", "credit")),
             # Execution
-            execution_price=ExecutionPrice(exec_cfg.get("execution_price", "close")),
-            execution_mode=ExecutionMode(exec_cfg.get("execution_mode", "same_bar")),
+            execution_price=ExecutionPrice(exec_cfg.get("execution_price", "open")),
+            execution_mode=ExecutionMode(exec_cfg.get("execution_mode", "next_bar")),
             # Stops
             stop_fill_mode=StopFillMode(stops_cfg.get("stop_fill_mode", "stop_price")),
             stop_level_basis=StopLevelBasis(stops_cfg.get("stop_level_basis", "fill_price")),
@@ -718,7 +718,7 @@ def from_dict(
             next_bar_simple_cash_check=order_cfg.get("next_bar_simple_cash_check", False),
             buying_power_reservation=order_cfg.get("buying_power_reservation", False),
             immediate_fill=order_cfg.get("immediate_fill", False),
-            rebalance_mode=RebalanceMode(order_cfg.get("rebalance_mode", "snapshot")),
+            rebalance_mode=RebalanceMode(order_cfg.get("rebalance_mode", "incremental")),
             rebalance_headroom_pct=order_cfg.get("rebalance_headroom_pct", 1.0),
             missing_price_policy=MissingPricePolicy(order_cfg.get("missing_price_policy", "skip")),
             late_asset_policy=LateAssetPolicy(order_cfg.get("late_asset_policy", "allow")),

tests/test_config_wiring.py

@@ -852,6 +852,43 @@ def test_to_dict_from_dict_roundtrip(self):
         assert restored.immediate_fill is True
 
 
+class TestFromDictDefaultParity:
+    """from_dict({}) must produce the same defaults as BacktestConfig()."""
+
+    def test_empty_dict_matches_constructor_defaults(self):
+        default = BacktestConfig()
+        from_empty = BacktestConfig.from_dict({}, strict=False)
+
+        # Core execution fields that were previously mismatched
+        assert from_empty.execution_mode == default.execution_mode
+        assert from_empty.execution_price == default.execution_price
+        assert from_empty.rebalance_mode == default.rebalance_mode
+
+        # Verify all enum fields match
+        assert from_empty.stop_fill_mode == default.stop_fill_mode
+        assert from_empty.stop_level_basis == default.stop_level_basis
+        assert from_empty.trail_hwm_source == default.trail_hwm_source
+        assert from_empty.initial_hwm_source == default.initial_hwm_source
+        assert from_empty.trail_stop_timing == default.trail_stop_timing
+        assert from_empty.share_type == default.share_type
+        assert from_empty.commission_type == default.commission_type
+        assert from_empty.slippage_type == default.slippage_type
+        assert from_empty.fill_ordering == default.fill_ordering
+        assert from_empty.entry_order_priority == default.entry_order_priority
+        assert from_empty.short_cash_policy == default.short_cash_policy
+        assert from_empty.data_frequency == default.data_frequency
+        assert from_empty.missing_price_policy == default.missing_price_policy
+        assert from_empty.late_asset_policy == default.late_asset_policy
+
+        # Verify key numeric/bool fields match
+        assert from_empty.initial_cash == default.initial_cash
+        assert from_empty.commission_rate == default.commission_rate
+        assert from_empty.slippage_rate == default.slippage_rate
+        assert from_empty.allow_short_selling == default.allow_short_selling
+        assert from_empty.allow_leverage == default.allow_leverage
+        assert from_empty.settlement_delay == default.settlement_delay
+
+
 class TestConfigModelWiring:
     """All commission/slippage enum choices should map to model instances."""