diff --git a/tests/test_optimization_compatibility.py b/tests/test_optimization_compatibility.py
new file mode 100644
index 00000000..0eeebaa7
--- /dev/null
+++ b/tests/test_optimization_compatibility.py
@@ -0,0 +1,108 @@
+"""Contracts shared by the configuration, tariff and optimizer PRs."""
+
+from types import SimpleNamespace
+from unittest.mock import Mock
+
+import pytest
+
+from akkudoktoreos.optimization.genetic.geneticparams import GeneticEnergyManagementParameters
+from akkudoktoreos.optimization.genetic0.genetic0params import Genetic0EnergyManagementParameters
+from akkudoktoreos.optimization.optimization import OptimizationAlgorithm
+
+
+@pytest.mark.parametrize(
+    "model", [GeneticEnergyManagementParameters, Genetic0EnergyManagementParameters]
+)
+@pytest.mark.parametrize("tariff", [0.00008, [0.00008, -0.00002]])
+def test_energy_parameter_aliases_preserve_wh_prices(model, tariff):
+    raw = {
+        "pv_prognose_wh": [250.0, 0.0],
+        "gesamtlast": [125.0, 125.0],
+        "strompreis_euro_pro_wh": [0.0003, -0.0001],
+        "einspeiseverguetung_euro_pro_wh": tariff,
+        "preis_euro_pro_wh_akku": 0.00005,
+    }
+    params = model.model_validate(raw)
+    data = params.model_dump(mode="json")
+    pairs = {
+        "pv_prognose_wh": "pv_forecast_wh",
+        "gesamtlast": "total_load",
+        "strompreis_euro_pro_wh": "electricity_price_per_wh",
+        "einspeiseverguetung_euro_pro_wh": "feed_in_tariff_per_wh",
+        "preis_euro_pro_wh_akku": "price_per_wh_battery",
+    }
+    for deprecated, canonical in pairs.items():
+        assert data[deprecated] == data[canonical] == raw[deprecated]
+    assert (
+        model.model_validate({pairs[k]: v for k, v in raw.items()}).model_dump(mode="json") == data
+    )
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("algorithm", list(OptimizationAlgorithm))
+async def test_algorithm_result_endpoint_keeps_solution_types_separate(monkeypatch, algorithm):
+    from akkudoktoreos.server import eos
+
+    genetic, genetic0 = object(), object()
+    fake = SimpleNamespace(
+        genetic_solution=Mock(return_value=genetic),
+        genetic0_solution=Mock(return_value=genetic0),
+    )
+    monkeypatch.setattr(eos, "get_ems", lambda: fake)
+    monkeypatch.setattr(
+        eos,
+        "get_config",
+        lambda: SimpleNamespace(optimization=SimpleNamespace(algorithms=["GENETIC", "GENETIC0"])),
+    )
+    result = await eos.fastapi_energy_management_optimization_solution_algorithm_get(algorithm)
+    if algorithm == OptimizationAlgorithm.GENETIC:
+        assert result is genetic
+        fake.genetic_solution.assert_called_once_with()
+        fake.genetic0_solution.assert_not_called()
+    else:
+        assert result is genetic0
+        fake.genetic0_solution.assert_called_once_with()
+        fake.genetic_solution.assert_not_called()
+
+
+@pytest.mark.parametrize("algorithm", ["genetic", "genetic0"])
+def test_device_maps_feed_algorithm_specific_converters(algorithm):
+    from akkudoktoreos.devices.devices import DevicesCommonSettings
+
+    settings = DevicesCommonSettings.model_validate(
+        {
+            "batteries": {"storage": {"capacity_wh": 12000, "max_charge_power_w": 3200}},
+            "electric_vehicles": {"car": {"capacity_wh": 60000, "max_charge_power_w": 7000}},
+            "inverters": {"inverter": {"battery_id": "storage", "max_power_w": 5000}},
+            "home_appliances": {
+                "washer": {
+                    "consumption_wh": 1800,
+                    "duration_h": 2,
+                    "num_cycles": 2,
+                    "min_cycle_gap_h": 1,
+                }
+            },
+        }
+    )
+    battery = getattr(settings.batteries["storage"], "to_" + algorithm + "_pv_bat_param")()
+    ev = getattr(settings.electric_vehicles["car"], "to_" + algorithm + "_ev_bat_param")()
+    inverter = getattr(settings.inverters["inverter"], "to_" + algorithm + "_param")()
+    appliance = getattr(settings.home_appliances["washer"], "to_" + algorithm + "_param")()
+    assert (battery.device_id, ev.device_id, inverter.device_id, appliance.device_id) == (
+        "storage",
+        "car",
+        "inverter",
+        "washer",
+    )
+    assert battery.capacity_wh == 12000
+    assert battery.max_charge_power_w == 3200
+    assert ev.capacity_wh == 60000
+    assert ev.max_charge_power_w == 7000
+    assert inverter.max_power_wh == 5000
+    assert inverter.battery_id == "storage"
+    assert appliance.consumption_wh == 1800
+    assert appliance.duration_h == 2
+    assert settings.batteries["storage"].measurement_key_soc_factor == "storage-soc-factor"
+    if algorithm == "genetic":
+        assert appliance.num_cycles == 2
+        assert appliance.min_cycle_gap_h == 1