diff --git a/src/akkudoktoreos/config/configmigrate.py b/src/akkudoktoreos/config/configmigrate.py
index 431d8181..30291e70 100644
--- a/src/akkudoktoreos/config/configmigrate.py
+++ b/src/akkudoktoreos/config/configmigrate.py
@@ -47,15 +47,20 @@ def _list_to_device_dict(
     """
 
     def _transform(value: Any) -> Any:
-        if not isinstance(value, list):
-            return value  # already a dict or something unexpected – leave as-is
+        if not isinstance(value, (list, dict)):
+            return value
         result: Dict[str, Any] = {}
-        for i, item in enumerate(value):
-            if not isinstance(item, dict):
-                continue
-            key = item.get("device_id") or f"{prefix}{i}"
-            # Ensure device_id is stored inside the dict so Pydantic can validate it
+        entries = enumerate(value) if isinstance(value, list) else value.items()
+        for index, original in entries:
+            if not isinstance(original, dict):
+                raise ValueError("Device settings must be an object")
+            item = dict(original)
+            key = (item.get("device_id") or f"{prefix}{index}") if isinstance(value, list) else index
+            if key in result:
+                raise ValueError(f"Duplicate device_id: {key!r}")
             item.setdefault("device_id", key)
+            if "levelized_cost_of_storage_kwh" in item:
+                item.setdefault("levelized_cost_of_storage_amt_kwh", item.pop("levelized_cost_of_storage_kwh"))
             result[key] = item
         return result
 
@@ -190,7 +195,7 @@ MIGRATION_MAP: Dict[
     "optimization/interval": None,
     "optimization/horizon_hours": "optimization/genetic0/horizon_hours",
     "optimization/ev_available_charge_rates_percent": (
-        "devices/electric_vehicles/0/charge_rates",
+        "devices/electric_vehicles/ev0/charge_rates",
         lambda v: [x / 100 for x in v],
     ),
     "optimization/hours": "optimization/genetic0/horizon_hours",
@@ -288,6 +293,16 @@ def migrate_config_data(config_data: Dict[str, Any]) -> "SettingsEOSDefaults":
         try:
             if transform:
                 old_value = transform(old_value)
+            if old_path == "optimization/ev_available_charge_rates_percent":
+                from akkudoktoreos.devices.settings.batterysettings import BatteriesCommonSettings
+
+                vehicles = new_config.devices.electric_vehicles
+                if not vehicles:
+                    new_config.devices.electric_vehicles = {
+                        "ev0": BatteriesCommonSettings(device_id="ev0")
+                    }
+                device_id = next(iter(new_config.devices.electric_vehicles))
+                new_path = f"devices/electric_vehicles/{device_id}/charge_rates"
             new_config.set_nested_value(new_path, old_value)
             migrated_source_paths.add(old_path.strip("/"))
             mapped_count += 1
diff --git a/src/akkudoktoreos/devices/devices.py b/src/akkudoktoreos/devices/devices.py
index d5c8fa19..71efb4f3 100644
--- a/src/akkudoktoreos/devices/devices.py
+++ b/src/akkudoktoreos/devices/devices.py
@@ -4,7 +4,7 @@ import json
 from typing import Any, Optional, TextIO, cast
 
 from loguru import logger
-from pydantic import Field, computed_field, model_validator
+from pydantic import Field, computed_field, field_validator, model_validator
 
 from akkudoktoreos.config.configabc import ConfigScope, SettingsBaseModel
 from akkudoktoreos.core.cache import CacheFileStore
@@ -113,6 +113,25 @@ class DevicesCommonSettings(SettingsBaseModel):
         },
     )
 
+    @field_validator("batteries", "electric_vehicles", "inverters", "home_appliances", mode="before")
+    @classmethod
+    def validate_device_ids(cls, value: Any) -> Any:
+        """Keep map keys and device identities consistent without mutating callers."""
+        if not isinstance(value, dict):
+            return value
+        result = {}
+        for key, device in value.items():
+            if isinstance(device, dict):
+                device = dict(device)
+                device.setdefault("device_id", key)
+                device_id = device["device_id"]
+            else:
+                device_id = device.device_id
+            if device_id != key:
+                raise ValueError(f"device_id {device_id!r} must match map key {key!r}")
+            result[key] = device
+        return result
+
     @computed_field  # type: ignore[prop-decorator]
     @property
     def measurement_keys(self) -> list[str]:
diff --git a/tests/test_consolidation_config.py b/tests/test_consolidation_config.py
new file mode 100644
index 00000000..6de18949
--- /dev/null
+++ b/tests/test_consolidation_config.py
@@ -0,0 +1,30 @@
+"""Contracts required by the combined EOS configuration."""
+import copy
+import pytest
+from pydantic import ValidationError
+from akkudoktoreos.config.configmigrate import migrate_config_data
+from akkudoktoreos.devices.devices import DevicesCommonSettings
+
+
+def test_device_map_supplies_stable_identity():
+    raw = {"batteries": {"house": {"capacity_wh": 12000}}}
+    a = DevicesCommonSettings.model_validate(raw)
+    b = DevicesCommonSettings.model_validate(raw)
+    assert a.batteries["house"].device_id == b.batteries["house"].device_id == "house"
+    assert "house-soc-factor" in a.measurement_keys
+
+
+def test_device_map_rejects_conflicting_identity():
+    with pytest.raises(ValidationError, match="device_id"):
+        DevicesCommonSettings.model_validate({"batteries": {"house": {"device_id": "other"}}})
+
+
+@pytest.mark.parametrize("as_list", [False, True])
+def test_migration_preserves_lcos_and_input(as_list):
+    battery = {"device_id": "house", "capacity_wh": 12000,
+               "levelized_cost_of_storage_kwh": 0.123}
+    raw = {"devices": {"batteries": [battery] if as_list else {"house": battery}}}
+    original = copy.deepcopy(raw)
+    migrated = migrate_config_data(raw)
+    assert migrated.devices.batteries["house"].levelized_cost_of_storage_amt_kwh == 0.123
+    assert raw == original
diff --git a/tests/testdata/eos_config_andreas_now.json b/tests/testdata/eos_config_andreas_now.json
index 23e80bab..97303bfa 100644
--- a/tests/testdata/eos_config_andreas_now.json
+++ b/tests/testdata/eos_config_andreas_now.json
@@ -19,8 +19,8 @@
             }
         },
         "electric_vehicles": {
-            "0": {
-                "device_id": "__ANY__",
+            "ev0": {
+                "device_id": "ev0",
                 "charge_rates": [
                     0.0,
                     0.375,