fix infeasable na home-01

backend/tests/test_planning_dispatch_milp.py

@@ -1243,6 +1243,48 @@ class AutoPassiveSelfConsumptionTests(unittest.TestCase):
         )
         self.assertEqual(len(results), 2)
 
+    def test_negative_buy_in_horizon_does_not_block_all_grid_import(self) -> None:
+        """Jeden slot buy<0 nesmí z min(buy) udělat všechny sloty expensive_import (gi=0 pro dům)."""
+        base = datetime(2026, 5, 22, 13, 15, tzinfo=timezone.utc)
+        slots = [
+            PlanningSlot(
+                interval_start=base + timedelta(minutes=15 * i),
+                buy_price=-0.54 if i == 15 else (0.8 + i * 0.05),
+                sell_price=-0.06 if i < 3 else 2.0,
+                pv_a_forecast_w=0,
+                pv_b_forecast_w=max(0, 5000 - i * 100) if i < 25 else 0,
+                load_baseline_w=5316 if i < 10 else 3392,
+                ev1_connected=False,
+                ev2_connected=False,
+                allow_charge=(i == 15 or i < 3),
+                allow_discharge_export=False,
+                charge_acquisition_buy_czk_kwh=0.94,
+                future_sell_opportunity_czk_kwh=5.5,
+            )
+            for i in range(20)
+        ]
+        battery = _battery(uc_wh=64_000.0, min_pct=12.0, arb_pct=20.0)
+        battery.planner_terminal_soc_value_factor = 0.0
+        battery.planner_discharge_floor_percent = 5.0
+        hp = SimpleNamespace(rated_heating_power_w=0, tuv_min_temp_c=45.0, tuv_target_temp_c=55.0)
+        grid = SimpleNamespace(max_import_power_w=17_000, max_export_power_w=13_500)
+        vehicles = [
+            SimpleNamespace(max_charge_power_w=0, battery_capacity_kwh=1.0, default_target_soc_pct=80.0),
+            SimpleNamespace(max_charge_power_w=0, battery_capacity_kwh=1.0, default_target_soc_pct=80.0),
+        ]
+        results, _, _ = solve_dispatch(
+            slots,
+            battery,
+            hp,
+            grid,
+            [None, None],
+            vehicles,
+            float(battery.soc_max_wh),
+            50.0,
+            operating_mode="AUTO",
+        )
+        self.assertEqual(len(results), 20)
+
 
 class AutoPassiveNoLoadFollowingDischargeTests(unittest.TestCase):
     """AUTO bez allow_discharge_export: žádný export do sítě (Deye PASSIVE)."""