FUE-T09: grace-shift *_today daily reset past local midnight + dedicated 00:00:10 publish

alembic_app/versions/20260625_14_meter_uuid.py

@@ -0,0 +1,104 @@
+"""add uuid column to meter table
+
+Adds a stable ``uuid`` (UUID v4 string) column to the ``meter`` table so that
+each meter epoch has a durable identity anchor suitable for use as an HA
+Discovery ``unique_id``.
+
+**Migration strategy (SQLite-safe)**:
+
+SQLite does not support adding a NOT NULL + UNIQUE column to a non-empty table
+in a single ``ALTER TABLE ADD COLUMN`` statement (adding a NOT NULL column
+without a default value is rejected if the table already has rows).  The
+safe approach used here is:
+
+  1. Add ``uuid`` as a **nullable** column (SQLite allows this).
+  2. **Back-fill** every existing ``meter`` row with a distinct ``str(uuid4())``
+     value.  Each row gets its *own* random UUID — not a shared value — so the
+     subsequent UNIQUE constraint is satisfied.
+  3. Use ``batch_alter_table`` (which re-creates the table under the hood in
+     SQLite) to alter the column to ``NOT NULL`` and add a UNIQUE constraint.
+
+**Idempotency**: only rows where ``uuid IS NULL`` are back-filled; rows that
+already have a uuid (e.g. from a repeated upgrade after a partial failure) are
+left untouched.
+
+**Audit**: after back-fill, the count of rows with ``uuid IS NULL`` must be
+exactly zero; if not, the migration raises ``RuntimeError`` and rolls back.
+
+**Data safety**: this migration is additive only — no existing rows are deleted
+or overwritten; it only adds a new column and fills it in.
+
+Revision ID: 20260625_14_meter_uuid
+Revises: 20260625_13_meter_table
+Create Date: 2026-06-25 00:00:00.000000
+"""
+
+import uuid as _uuid
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+revision: str = "20260625_14_meter_uuid"
+down_revision: Union[str, None] = "20260625_13_meter_table"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    conn = op.get_bind()
+
+    # ------------------------------------------------------------------ #
+    # 1. Add uuid as a nullable column.                                    #
+    # ------------------------------------------------------------------ #
+    with op.batch_alter_table("meter", schema=None) as batch_op:
+        batch_op.add_column(
+            sa.Column("uuid", sa.String(length=36), nullable=True)
+        )
+
+    # ------------------------------------------------------------------ #
+    # 2. Back-fill: assign a distinct UUID to every row that has           #
+    #    uuid IS NULL.  Each row gets its own random value so that the     #
+    #    subsequent UNIQUE constraint is satisfied.                        #
+    # ------------------------------------------------------------------ #
+    rows = conn.execute(sa.text("SELECT id FROM meter WHERE uuid IS NULL")).fetchall()
+    for (meter_id,) in rows:
+        new_uuid = str(_uuid.uuid4())
+        conn.execute(
+            sa.text("UPDATE meter SET uuid = :uuid WHERE id = :mid"),
+            {"uuid": new_uuid, "mid": meter_id},
+        )
+
+    # ------------------------------------------------------------------ #
+    # 3. Audit: verify no rows remain with uuid IS NULL.                   #
+    # ------------------------------------------------------------------ #
+    null_count_row = conn.execute(
+        sa.text("SELECT COUNT(*) FROM meter WHERE uuid IS NULL")
+    ).fetchone()
+    null_count: int = null_count_row[0] if null_count_row else 0
+
+    if null_count != 0:
+        raise RuntimeError(
+            f"meter.uuid back-fill audit failed: {null_count} meter row(s) still have "
+            "uuid IS NULL after back-fill.  Migration aborted to protect data integrity."
+        )
+
+    # ------------------------------------------------------------------ #
+    # 4. Alter column to NOT NULL + UNIQUE (requires batch on SQLite).     #
+    #    batch_alter_table re-creates the table, so the UNIQUE constraint  #
+    #    and NOT NULL are applied atomically.                              #
+    # ------------------------------------------------------------------ #
+    with op.batch_alter_table("meter", schema=None) as batch_op:
+        batch_op.alter_column(
+            "uuid",
+            existing_type=sa.String(length=36),
+            nullable=False,
+        )
+        batch_op.create_unique_constraint("uq_meter_uuid", ["uuid"])
+
+
+def downgrade() -> None:
+    # Drop the UNIQUE constraint and the uuid column (batch on SQLite).
+    with op.batch_alter_table("meter", schema=None) as batch_op:
+        batch_op.drop_constraint("uq_meter_uuid", type_="unique")
+        batch_op.drop_column("uuid")

app/api/routes/api/meters.py

@@ -79,6 +79,24 @@ router = APIRouter(prefix="/api/energy", tags=["api-energy-meters"])
 # ---------------------------------------------------------------------------
 
 
+def _trigger_discovery_republish(session: Session) -> None:
+    """Call publish_discovery after a meter write operation (best-effort).
+
+    No-op if MQTT / discovery is not enabled or the broker is not connected
+    (publish_discovery guards internally).  All errors are swallowed so that a
+    discovery failure never breaks the API response.
+
+    Must be called **after** db.commit() so that publish_discovery sees the
+    final committed state of the meter table when it rebuilds the catalog.
+    """
+    try:
+        from app.services.ha_discovery import publish_discovery
+
+        publish_discovery(session)
+    except Exception:
+        logger.exception("_trigger_discovery_republish: publish_discovery raised an error")
+
+
 def _get_meter_or_404(db: Session, meter_id: int) -> Meter:
     """Return the meter with the given id or raise 404."""
     meter: Optional[Meter] = db.get(Meter, meter_id)
@@ -217,6 +235,11 @@ def declare_energy_meter(
     db.commit()
     db.refresh(new_meter)
 
+    # Trigger HA discovery re-publish so the new active meter's energy-cost
+    # device/sensor configuration is pushed to Home Assistant.  Best-effort:
+    # failures are logged and swallowed; the API response is not affected.
+    _trigger_discovery_republish(db)
+
     logger.info(
         "POST /api/energy/meters: declared %r meter id=%d label=%r started_at=%s",
         body.commodity,
@@ -294,6 +317,11 @@ def patch_energy_meter(
     db.commit()
     db.refresh(meter)
 
+    # Trigger HA discovery re-publish so label renames on the active meter
+    # propagate to the HA device name.  Best-effort: failures are logged and
+    # swallowed; the API response is not affected.
+    _trigger_discovery_republish(db)
+
     logger.info(
         "PATCH /api/energy/meters/%d: updated meter label=%r started_at=%s",
         meter_id,

app/integrations/expose.py

@@ -27,6 +27,7 @@ from __future__ import annotations
 
 import logging
 from dataclasses import dataclass, field
+from datetime import timedelta
 from typing import Any, Callable, Optional, Protocol
 
 from sqlalchemy.orm import Session
@@ -369,16 +370,44 @@ register_provider(_modbus_provider)
 # Energy Cost provider
 # ---------------------------------------------------------------------------
 
+# *_today 当日窗口翻天的宽限：本地午夜后 5 秒才切到新的一天，避免在 00:00:0x 把
+# 归零后的值发出去、被慢几秒的 HA 钟记成前一天的 23:59:59（归错小时桶）。
+_TODAY_RESET_GRACE = timedelta(seconds=5)
+
 
 def _energy_cost_provider(session: Session) -> list[ExposableEntity]:
     """Enumerate ExposableEntity objects for the energy cost subsystem.
 
-    Produces 4 sensor entities grouped under a single HA device "Energy Cost":
+    Produces 6 sensor entities grouped under a single HA device whose identity
+    is anchored to the **current active electricity meter**:
 
     - ``buy_price_now``         — current effective buy price (EUR/kWh or local currency).
     - ``sell_price_now``        — current effective sell price (EUR/kWh or local currency).
-    - ``import_cost_total``     — cumulative import cost (total_increasing, monetary).
+    - ``import_cost_total``     — cumulative import cost (total, monetary).
-    - ``export_revenue_total``  — cumulative export revenue (total_increasing, monetary).
+    - ``export_revenue_total``  — cumulative export revenue (total, monetary).
+    - ``import_cost_today``     — today's import cost (total_increasing, monetary).
+    - ``export_revenue_today``  — today's export revenue (total_increasing, monetary).
+
+    Active meter requirement
+    ------------------------
+    **If no active electricity meter exists, the provider returns ``[]``.**
+    No energy-cost entities are exposed to HA until a meter has been declared.
+    This prevents spurious sensor creation with an undefined device identity.
+
+    HA device identity (换表 → 新 sensor)
+    --------------------------------------
+    ``identifiers[1]`` is set to the active meter's **uuid** (not the fixed
+    string ``"energy-cost"``).  ``ha_discovery.py`` uses ``identifiers[1]`` as
+    the MQTT node_id and as part of the ``unique_id`` for every entity.
+    Declaring a new active electricity meter produces a new uuid → new node_id /
+    unique_id → HA creates a brand-new sensor, cleanly isolating post-swap data.
+
+    Entity key stability
+    --------------------
+    Entity keys remain the fixed stable strings (``"energy.buy_price_now"`` etc.),
+    **not** derived from the meter uuid.  The ``exposed_entity_toggle`` table uses
+    keys as its primary handle; keeping them stable means toggled-on entities stay
+    enabled after a meter swap without requiring the user to re-tick them.
 
     Current-price algorithm (source-agnostic, with fallback)
     ---------------------------------------------------------
@@ -399,8 +428,9 @@ def _energy_cost_provider(session: Session) -> list[ExposableEntity]:
     Cumulative totals
     -----------------
     ``SUM(import_cost)`` and ``SUM(export_revenue)`` over **all non-degraded**
-    ``energy_cost_period`` rows.  Degraded rows carry 0 costs and are excluded
+    ``energy_cost_period`` rows within the current meter's window.  Degraded rows
-    to avoid double-counting when they are later overwritten by real values.
+    carry 0 costs and are excluded to avoid double-counting when they are later
+    overwritten by real values.
 
     Currency
     --------
@@ -414,16 +444,37 @@ def _energy_cost_provider(session: Session) -> list[ExposableEntity]:
       - ``"energy.sell_price_now"``
       - ``"energy.import_cost_total"``
       - ``"energy.export_revenue_total"``
+      - ``"energy.import_cost_today"``
+      - ``"energy.export_revenue_today"``
 
     DeviceInfo identifiers
     ----------------------
-    **Two-element tuple** ``("energy-cost", "energy-cost")`` so that
+    **Two-element tuple** ``("energy-cost", meter.uuid)`` so that
-    ``ha_discovery.py``'s ``entity.device.identifiers[1]`` is always valid
+    ``ha_discovery.py``'s ``entity.device.identifiers[1]`` resolves to the
-    (the service uses index [1] as the node_id throughout).
+    meter uuid (used as the MQTT node_id and unique_id seed throughout).
     """
-    from app.models.energy import EnergyCostPeriod  # local import to avoid circular
+    from app.models.energy import EnergyCostPeriod, Meter  # local import to avoid circular
+    from sqlalchemy import select
 
-    # --- Determine currency and representative pricing from the latest non-degraded row ---
+    # --- Require an active electricity meter; return [] if none exists ---
+    # Using an inline query (ended_at IS NULL) rather than a service-layer helper
+    # to avoid a new public dependency and remain consistent with the value_getter
+    # implementations below (which use the same inline pattern).
+    active_meter: Meter | None = session.execute(
+        select(Meter)
+        .where(
+            Meter.commodity == "electricity",
+            Meter.ended_at.is_(None),
+        )
+        .limit(1)
+    ).scalar_one_or_none()
+
+    if active_meter is None:
+        # No active electricity meter → do not expose any energy-cost entities.
+        # HA will not see these sensors until a meter is declared.
+        return []
+
+    # --- Determine currency from the latest non-degraded row ---
 
     latest_period: EnergyCostPeriod | None = (
         session.query(EnergyCostPeriod)
@@ -436,13 +487,15 @@ def _energy_cost_provider(session: Session) -> list[ExposableEntity]:
     if latest_period is not None and latest_period.currency:
         currency = latest_period.currency
 
-    # --- Shared DeviceInfo (2-element identifiers — required by ha_discovery.py [1] access) ---
+    # --- Shared DeviceInfo anchored to the active meter's uuid ---
+    # identifiers[1] = meter.uuid drives the MQTT node_id and unique_id in
+    # ha_discovery.py.  Swapping the meter produces a new uuid → new HA sensor.
     # provides_availability=False: the energy-cost device has only sensors and no
     # online/offline heartbeat, so its entities must be "always available" in HA.
     # (Otherwise HA shows them unavailable despite state being published.)
     device_info = DeviceInfo(
-        identifiers=("energy-cost", "energy-cost"),
+        identifiers=("energy-cost", active_meter.uuid),
-        name="Energy Cost",
+        name=active_meter.label,
         provides_availability=False,
     )
 
@@ -687,7 +740,11 @@ def _energy_cost_provider(session: Session) -> list[ExposableEntity]:
                 return None
 
             # Today's window in UTC, using monkeypatch-safe module attribute calls.
-            today_local = _tz_mod.local_now().date()
+            # Grace: subtract _TODAY_RESET_GRACE so that in the first 5 seconds after
+            # local midnight the getter still returns yesterday's window.  This prevents
+            # a "归零后的值" from being published while HA's clock (which may lag a few
+            # seconds) would stamp it as 23:59:59 of the previous day.
+            today_local = (_tz_mod.local_now() - _TODAY_RESET_GRACE).date()
             tomorrow_local = today_local + _td(days=1)
             today_start_utc = _tz_mod.local_midnight_utc(today_local)
             tomorrow_start_utc = _tz_mod.local_midnight_utc(tomorrow_local)
@@ -724,7 +781,8 @@ def _energy_cost_provider(session: Session) -> list[ExposableEntity]:
             if not versions:
                 return None
 
-            today_local = _tz_mod.local_now().date()
+            # Grace: same logic as import_cost_today — see that getter's comment.
+            today_local = (_tz_mod.local_now() - _TODAY_RESET_GRACE).date()
             tomorrow_local = today_local + _td(days=1)
             today_start_utc = _tz_mod.local_midnight_utc(today_local)
             tomorrow_start_utc = _tz_mod.local_midnight_utc(tomorrow_local)

app/main.py

@@ -7,6 +7,7 @@ from fastapi import FastAPI, HTTPException, Request
 from fastapi.responses import FileResponse
 from fastapi.staticfiles import StaticFiles
 from apscheduler.schedulers.background import BackgroundScheduler
+from apscheduler.triggers.cron import CronTrigger
 from apscheduler.triggers.interval import IntervalTrigger
 from sqlalchemy.orm import Session
 
@@ -36,6 +37,7 @@ from app.services.modbus_poll import poll_all_enabled_devices, BASE_POLL_TICK_SE
 from app.services.ha_discovery import publish_discovery, publish_states
 from app.services.tibber_prices import refresh_prices
 from app.services.energy_cost import compute_closed_periods
+from app.services.timezone import local_tz
 from scripts.app_db_adopt import AppDatabaseAdoptionError, validate_app_runtime_db
 
 logger = logging.getLogger(__name__)
@@ -159,6 +161,20 @@ def _run_scheduled_ha_state_publish() -> None:
         session.close()
 
 
+def _run_midnight_state_publish() -> None:
+    """本地午夜后不久专门发布一次状态，让 *_today 的每日归零稳稳落在午夜之后
+    （对 HA 钟慢几秒鲁棒）。best-effort：失败仅记日志，不影响调度器。"""
+    session_local = get_session_local()
+    session = session_local()
+    try:
+        from app.services.ha_discovery import publish_states
+        publish_states(session)
+    except Exception:
+        logger.exception("_run_midnight_state_publish: failed (non-fatal)")
+    finally:
+        session.close()
+
+
 def ensure_auth_db_ready() -> None:
     session_local = get_session_local()
     session: Session = session_local()
@@ -233,6 +249,17 @@ async def lifespan(_: FastAPI):
         max_instances=1,
         coalesce=True,
     )
+    # Dedicated midnight publish: fire at local 00:00:10 so *_today grace (5 s) has
+    # already elapsed and the day-rolled value is pushed to HA immediately, rather
+    # than waiting for the next 60-second ha-state-publish sweep.
+    scheduler.add_job(
+        _run_midnight_state_publish,
+        trigger=CronTrigger(hour=0, minute=0, second=10, timezone=local_tz()),
+        id="midnight-today-publish",
+        replace_existing=True,
+        max_instances=1,
+        coalesce=True,
+    )
     scheduler.start()
 
     # MQTT: connect using DB-merged runtime settings so broker configured via UI

app/models/energy.py

@@ -11,6 +11,7 @@ Six tables:
 
 from __future__ import annotations
 
+import uuid as _uuid
 from datetime import datetime
 
 from sqlalchemy import Boolean, DateTime, Float, ForeignKey, Integer, String
@@ -20,6 +21,10 @@ from sqlalchemy.types import JSON
 from app.db import Base
 
 
+def _uuid4_str() -> str:
+    return str(_uuid.uuid4())
+
+
 class Meter(Base):
     """One physical electricity meter's installation epoch.
 
@@ -47,6 +52,11 @@ class Meter(Base):
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
 
+    # Stable internal identity — used as HA Discovery unique_id anchor.
+    uuid: Mapped[str] = mapped_column(
+        String(36), unique=True, nullable=False, default=_uuid4_str
+    )
+
     # Human-readable label for this physical meter (e.g. address, serial, tariff zone).
     label: Mapped[str] = mapped_column(String(255), nullable=False)
 

app/services/energy_cost.py

@@ -123,6 +123,10 @@ _READING_MAX_STALENESS = timedelta(minutes=_PERIOD_MINUTES)
 # degraded to prevent negative costs or grossly inflated charges.
 _MAX_DELTA_KWH = Decimal("100")
 
+# 每日固定费/税补在"本地午夜后多久"才结算入账。延后到 01:05 是为了让累计成本的
+# 整天阶跃落在新一天、且避开 01:00 整点（HA 长期统计的小时桶边界）。
+_SETTLEMENT_OFFSET = timedelta(hours=1, minutes=5)
+
 # DSMR payload register keys (cumulative kWh, JSON string values).
 _KEY_D1 = "electricity_delivered_1"   # delivered low-tariff  (dal / _1)
 _KEY_D2 = "electricity_delivered_2"   # delivered high-tariff (normal / _2)
@@ -764,7 +768,8 @@ def summarize(session: Session, start: datetime, end: datetime) -> dict[str, Any
     days = _to_decimal(str(total_seconds)) / _to_decimal("86400")
 
     # --- Fixed costs and credits: Principle C cross-version whole-day counting ---
-    today_local: _date = local_now().date()
+    _now_local = local_now()
+    today_local: _date = _now_local.date()
 
     # --- Compute [first_counted, last_counted] local date range (inclusive) ---
     #
@@ -811,8 +816,16 @@ def summarize(session: Session, start: datetime, end: datetime) -> dict[str, Any
     else:
         last_counted = local_end_date - _td(days=1)
 
-    # Cap: only elapsed or today's days.
+    # Settlement cap: "today" is only counted once the local clock has passed the
-    last_counted = min(last_counted, today_local)
+    # settlement offset since midnight (01:05).  This defers the daily standing-charge
+    # step from 00:00 to 01:05, ensuring the cumulative-cost adiabatic jump lands
+    # inside the new calendar day and avoids the HA 01:00 hourly-bucket boundary.
+    _today_midnight_utc = _lmu(today_local)
+    if _now_local >= _today_midnight_utc + _SETTLEMENT_OFFSET:
+        settled_cap = today_local
+    else:
+        settled_cap = today_local - _td(days=1)
+    last_counted = min(last_counted, settled_cap)
 
     # If the range is empty (first_counted > last_counted), no days are counted.
 

scripts/app_db_adopt.py

@@ -15,7 +15,7 @@ if str(PROJECT_ROOT) not in sys.path:
 
 from app.config import get_settings
 
-APP_BASELINE_REVISION = "20260625_13_meter_table"
+APP_BASELINE_REVISION = "20260625_14_meter_uuid"
 
 
 class AppDatabaseAdoptionError(RuntimeError):

tests/test_api_meters.py

@@ -72,6 +72,24 @@ def _declare_payload(**overrides) -> dict:
 # ---------------------------------------------------------------------------
 
 
+@pytest.fixture(autouse=True)
+def mock_publish_discovery():
+    """Auto-mock publish_discovery for all tests in this module.
+
+    The meters API now calls _trigger_discovery_republish (best-effort) after
+    every successful write.  publish_discovery is lazy-imported inside that
+    helper, so we patch it at its canonical source path
+    (app.services.ha_discovery.publish_discovery).  Tests that need to assert
+    the call receive this fixture explicitly; all others benefit from the
+    isolation it provides (no live MQTT broker required).
+    """
+    with patch(
+        "app.services.ha_discovery.publish_discovery",
+        return_value=None,
+    ) as mock:
+        yield mock
+
+
 @pytest.fixture()
 def meters_client(auth_database):
     """TestClient + SQLAlchemy engine for Meter API tests."""
@@ -660,3 +678,78 @@ def test_patch_started_at_earlier_updates_boundary(meters_client):
         if ended is not None and ended.tzinfo is None:
             ended = ended.replace(tzinfo=UTC)
         assert ended == t1_earlier
+
+
+# ---------------------------------------------------------------------------
+# FUE-T06: HA discovery re-publish triggered after meter writes
+# ---------------------------------------------------------------------------
+
+
+def test_declare_meter_triggers_publish_discovery(meters_client, mock_publish_discovery):
+    """POST /api/energy/meters triggers publish_discovery after successful commit."""
+    client, _ = meters_client
+    _login(client)
+
+    t0 = datetime(2025, 1, 1, 0, 0, 0, tzinfo=UTC)
+    with patch("app.api.routes.api.meters.recompute_range", return_value=0):
+        resp = client.post(
+            "/api/energy/meters",
+            json=_declare_payload(label="Discovery Meter", started_at=t0.isoformat()),
+            headers={"X-CSRF-Token": _CSRF},
+        )
+    assert resp.status_code == 201
+    # publish_discovery must have been called exactly once after the declare.
+    mock_publish_discovery.assert_called_once()
+
+
+def test_patch_meter_triggers_publish_discovery(meters_client, mock_publish_discovery):
+    """PATCH /api/energy/meters/{id} triggers publish_discovery after successful commit."""
+    client, _ = meters_client
+    _login(client)
+
+    t0 = datetime(2025, 1, 1, 0, 0, 0, tzinfo=UTC)
+    with patch("app.api.routes.api.meters.recompute_range", return_value=0):
+        resp = client.post(
+            "/api/energy/meters",
+            json=_declare_payload(label="Original Label", started_at=t0.isoformat()),
+            headers={"X-CSRF-Token": _CSRF},
+        )
+    meter_id = resp.json()["id"]
+    # Reset call count: the POST above also called publish_discovery.
+    mock_publish_discovery.reset_mock()
+
+    resp = client.patch(
+        f"/api/energy/meters/{meter_id}",
+        json={"label": "Renamed Label"},
+        headers={"X-CSRF-Token": _CSRF},
+    )
+    assert resp.status_code == 200
+    # publish_discovery must have been called exactly once after the PATCH.
+    mock_publish_discovery.assert_called_once()
+
+
+def test_declare_meter_succeeds_when_publish_discovery_raises(meters_client):
+    """publish_discovery raising an exception must NOT cause POST declare to return 500.
+
+    The _trigger_discovery_republish helper is best-effort: it swallows all
+    exceptions so that a broken MQTT / discovery layer never breaks the API.
+    """
+    client, _ = meters_client
+    _login(client)
+
+    t0 = datetime(2025, 1, 1, 0, 0, 0, tzinfo=UTC)
+    with (
+        patch("app.api.routes.api.meters.recompute_range", return_value=0),
+        patch(
+            "app.services.ha_discovery.publish_discovery",
+            side_effect=RuntimeError("MQTT broker unreachable"),
+        ),
+    ):
+        resp = client.post(
+            "/api/energy/meters",
+            json=_declare_payload(label="Best Effort Meter", started_at=t0.isoformat()),
+            headers={"X-CSRF-Token": _CSRF},
+        )
+    # The meter must be created successfully despite the discovery failure.
+    assert resp.status_code == 201
+    assert resp.json()["label"] == "Best Effort Meter"

tests/test_energy_cost.py

@@ -1199,10 +1199,16 @@ def _ams_midnight(year: int, month: int, day: int) -> datetime:
 
 
 class TestSummarizePrincipleC:
-    """Principle C whole-day counting with pinned Europe/Amsterdam timezone."""
+    """Principle C whole-day counting with pinned Europe/Amsterdam timezone.
+
+    Tests that assert a specific "today" (e.g. June 25) must also pin
+    ``local_now`` via *pinned_now* to remain deterministic as wall-clock
+    time advances.  Tests that only care about windows entirely in the past
+    or entirely in the future do not need to pin ``local_now``.
+    """
 
     # Effective_from: June 1 CEST local midnight = May 31 22:00 UTC.
-    # Today local = June 25 CEST (since today is 2026-06-25).
+    # Reference "today" pinned in individual tests = June 25 CEST.
 
     def _make_single_version_contract(self, session: Session, *, effective_from_utc: datetime) -> None:
         """Create an active manual contract with a single version."""
@@ -1210,10 +1216,27 @@ class TestSummarizePrincipleC:
         _make_version(session, contract, _MANUAL_VALUES, effective_from=effective_from_utc)
         session.commit()
 
-    def _run_summarize_ams(self, session: Session, start_utc: datetime, end_utc: datetime) -> dict:
+    def _run_summarize_ams(
-        """Run summarize with Europe/Amsterdam local_tz monkeypatched."""
+        self,
+        session: Session,
+        start_utc: datetime,
+        end_utc: datetime,
+        *,
+        pinned_now: datetime | None = None,
+    ) -> dict:
+        """Run summarize with Europe/Amsterdam local_tz monkeypatched.
+
+        If *pinned_now* is given, also patches ``app.services.energy_cost.local_now``
+        to that fixed value, making settlement-offset logic deterministic
+        regardless of wall-clock time.
+        """
         from unittest.mock import patch
+        import app.services.energy_cost as _ec
+
         with patch.object(tz_module, "local_tz", return_value=_ams()):
+            if pinned_now is not None:
+                with patch.object(_ec, "local_now", return_value=pinned_now):
+                    return summarize(session, start_utc, end_utc)
             return summarize(session, start_utc, end_utc)
 
     def test_today_window_counts_1_day(self, energy_db: Session) -> None:
@@ -1259,7 +1282,10 @@ class TestSummarizePrincipleC:
     def test_this_month_window_counts_25_days(self, energy_db: Session) -> None:
         """This Month (June 1 → July 1 local) counts 25 elapsed days (June 1..25).
 
-        Today = June 25 local, so June 26–30 are not yet elapsed.
+        Pins ``local_now`` to June 25 noon AMS so the test is deterministic
+        regardless of the actual wall-clock date.  June 25 is well past the
+        01:05 settlement offset, so ``settled_cap = June 25``.
+        Today = June 25 local, so June 26–30 are not yet elapsed → 25 days.
         Matches table row: 6/1→7/1 (This Month) → 25 days.
         """
         eff_utc = _ams_midnight(2026, 6, 1)
@@ -1267,7 +1293,9 @@ class TestSummarizePrincipleC:
 
         start = _ams_midnight(2026, 6, 1)
         end = _ams_midnight(2026, 7, 1)
-        result = self._run_summarize_ams(energy_db, start, end)
+        # Pin local_now to June 25 2026 noon AMS (well past 01:05 settlement).
+        pinned_now = datetime(2026, 6, 25, 12, 0, 0, tzinfo=_ams())
+        result = self._run_summarize_ams(energy_db, start, end, pinned_now=pinned_now)
 
         daily_fixed = (9.87 + 9.87) / 30
         daily_credit = 600.0 / 365
@@ -1304,8 +1332,9 @@ class TestSummarizePrincipleC:
     def test_partial_future_window_caps_at_today(self, energy_db: Session) -> None:
         """A window partially in the future caps at today (only elapsed days counted).
 
+        Pins ``local_now`` to June 25 noon AMS so the test is deterministic.
         Window: June 25 → June 28 local (4 dates, but June 26/27 are future).
-        Today = June 25 → only 1 day elapsed (June 25).
+        Today = June 25 → settled_cap = June 25 → only 1 day elapsed (June 25).
         Matches table row: 6/25→6/28 → 1 day.
         """
         eff_utc = _ams_midnight(2026, 6, 1)
@@ -1313,7 +1342,9 @@ class TestSummarizePrincipleC:
 
         start = _ams_midnight(2026, 6, 25)
         end = _ams_midnight(2026, 6, 28)
-        result = self._run_summarize_ams(energy_db, start, end)
+        # Pin local_now to June 25 2026 noon AMS (well past 01:05 settlement).
+        pinned_now = datetime(2026, 6, 25, 12, 0, 0, tzinfo=_ams())
+        result = self._run_summarize_ams(energy_db, start, end, pinned_now=pinned_now)
 
         daily_fixed = (9.87 + 9.87) / 30
         daily_credit = 600.0 / 365
@@ -1366,7 +1397,11 @@ class TestSummarizePrincipleC:
         start = _ams_midnight(2026, 6, 1)
         end = _ams_midnight(2026, 7, 1)
         from unittest.mock import patch
+        import app.services.energy_cost as _ec
+        # Pin local_now to June 25 2026 noon AMS: today=June 25, settled_cap=June 25.
+        pinned_now = datetime(2026, 6, 25, 12, 0, 0, tzinfo=_ams())
         with patch.object(tz_module, "local_tz", return_value=_ams()):
+            with patch.object(_ec, "local_now", return_value=pinned_now):
                 result = summarize(energy_db, start, end)
 
         # V1: 24 days × (6+6)/30; V2: 1 day × (12+12)/30
@@ -1408,11 +1443,15 @@ class TestSummarizePrincipleC:
         _make_version(energy_db, contract, _VALUES_V2, effective_from=v2_from)
         energy_db.commit()
 
-        # Window = June 25 only (today, 1 day elapsed at V2 rate)
+        # Window = June 25 only (today, 1 day elapsed at V2 rate).
+        # Pin local_now to June 25 noon AMS: today=June 25, settled_cap=June 25.
         start = _ams_midnight(2026, 6, 25)
         end = _ams_midnight(2026, 7, 1)
         from unittest.mock import patch
+        import app.services.energy_cost as _ec
+        pinned_now = datetime(2026, 6, 25, 12, 0, 0, tzinfo=_ams())
         with patch.object(tz_module, "local_tz", return_value=_ams()):
+            with patch.object(_ec, "local_now", return_value=pinned_now):
                 result = summarize(energy_db, start, end)
 
         # Only 1 day at V2 rate
@@ -1434,13 +1473,11 @@ class TestSummarizePrincipleC:
           within the day start_utc falls.  June 24 is the anchor day → its charge is counted.
 
         Window: [June 24 07:18 UTC (= 09:18 CEST), June 26 22:00 UTC (= June 27 00:00 CEST)).
-        Today local = June 25 (2026-06-25).
+        Pins local_now to June 25 noon AMS → today=June 25, settled_cap=June 25.
         first_counted = June 24 (anchor day, previously dropped).
         last_counted = min(June 26, June 25) = June 25.
         n_days = June 25 - June 24 + 1 = 2.
         """
-        from unittest.mock import patch
-
         eff_utc = _ams_midnight(2026, 6, 1)
         self._make_single_version_contract(energy_db, effective_from_utc=eff_utc)
 
@@ -1449,8 +1486,9 @@ class TestSummarizePrincipleC:
         # end = June 26 22:00 UTC = June 27 00:00 CEST (past today June 25, capped)
         end_utc = datetime(2026, 6, 26, 22, 0, 0, tzinfo=_UTC)
 
-        with patch.object(tz_module, "local_tz", return_value=_ams()):
+        # Pin local_now to June 25 noon AMS: today=June 25, settled_cap=June 25.
-            result = self._run_summarize_ams(energy_db, anchor_utc, end_utc)
+        pinned_now = datetime(2026, 6, 25, 12, 0, 0, tzinfo=_ams())
+        result = self._run_summarize_ams(energy_db, anchor_utc, end_utc, pinned_now=pinned_now)
 
         daily_fixed = (9.87 + 9.87) / 30
         daily_credit = 600.0 / 365
@@ -2409,3 +2447,266 @@ class TestMeterAwareComputePeriod:
         assert row.degraded is False, "All-zero deltas must not trigger the D6 guard"
         assert row.import_cost == 0.0
         assert row.net_cost == 0.0
+
+
+# ---------------------------------------------------------------------------
+# FUE-T08. summarize — settlement offset (local 01:05)
+# ---------------------------------------------------------------------------
+
+
+class TestSummarizeSettlementOffset:
+    """FUE-T08: daily fixed-fee/heffingskorting settled after local 01:05.
+
+    Reference date: June 26, 2026 AMS (CEST = UTC+2).
+      - AMS midnight June 26  = June 25 22:00 UTC
+      - Settlement threshold  = June 25 22:00 + 01:05 = June 25 23:05 UTC
+                              = June 26 01:05 AMS
+      - "before offset" now   = June 26 00:30 AMS = June 25 22:30 UTC
+      - "after  offset" now   = June 26 01:10 AMS = June 25 23:10 UTC
+
+    All tests monkeypatch both local_tz (Europe/Amsterdam) and
+    ``app.services.energy_cost.local_now`` to be fully deterministic.
+    """
+
+    # UTC instants used as "now":
+    # June 25 22:30 UTC = June 26 00:30 AMS (before settlement threshold 23:05 UTC)
+    _NOW_BEFORE = datetime(2026, 6, 25, 22, 30, 0, tzinfo=UTC)
+    # June 25 23:10 UTC = June 26 01:10 AMS (after settlement threshold 23:05 UTC)
+    _NOW_AFTER = datetime(2026, 6, 25, 23, 10, 0, tzinfo=UTC)
+
+    def _setup_single_version_contract(self, session: Session) -> None:
+        """Insert a manual contract effective Jan 1 2026 (covers all test dates)."""
+        c = _make_contract(session, kind="manual", active=True)
+        _make_version(session, c, _MANUAL_VALUES, effective_from=_ams_midnight(2026, 1, 1))
+        session.commit()
+
+    def _run(
+        self,
+        session: Session,
+        start_utc: datetime,
+        end_utc: datetime,
+        *,
+        now_utc: datetime,
+    ) -> dict:
+        """Run summarize with AMS timezone and pinned local_now.
+
+        *now_utc* is converted to AMS before being used as the ``local_now``
+        return value, so ``.date()`` yields the correct AMS local date.
+        """
+        from unittest.mock import patch
+        import app.services.energy_cost as _ec
+
+        now_ams = now_utc.astimezone(_ams())
+        with patch.object(tz_module, "local_tz", return_value=_ams()):
+            with patch.object(_ec, "local_now", return_value=now_ams):
+                return summarize(session, start_utc, end_utc)
+
+    # --- AC1: before 01:05 → today not settled → fixed_costs/credits == 0 ---
+
+    def test_today_window_before_offset_yields_zero(self, energy_db: Session) -> None:
+        """AC1: At local 00:30 (before 01:05), today's window → credits == 0 and fixed_costs == 0.
+
+        Window: [June 26 AMS midnight, June 27 AMS midnight).
+        now = June 26 00:30 AMS (before 01:05) → settled_cap = June 25.
+        first_counted = June 26 > last_counted = June 25 → 0 days.
+        """
+        self._setup_single_version_contract(energy_db)
+        start = _ams_midnight(2026, 6, 26)   # June 25 22:00 UTC
+        end = _ams_midnight(2026, 6, 27)     # June 26 22:00 UTC
+
+        result = self._run(energy_db, start, end, now_utc=self._NOW_BEFORE)
+
+        assert result["fixed_costs"] == 0.0, (
+            "AC1: before settlement offset, today's fixed_costs must be 0; "
+            f"got {result['fixed_costs']}"
+        )
+        assert result["credits"] == 0.0, (
+            "AC1: before settlement offset, today's credits must be 0; "
+            f"got {result['credits']}"
+        )
+
+    # --- AC2: >= 01:05 → today settled → 1 day fixed/credits ---
+
+    def test_today_window_after_offset_yields_one_day(self, energy_db: Session) -> None:
+        """AC2: At local 01:10 (>= 01:05), today's window → 1 day of fixed/credits.
+
+        Window: [June 26 AMS midnight, June 27 AMS midnight).
+        now = June 26 01:10 AMS (after 01:05) → settled_cap = June 26.
+        first_counted = June 26 = last_counted → 1 day.
+        """
+        self._setup_single_version_contract(energy_db)
+        start = _ams_midnight(2026, 6, 26)
+        end = _ams_midnight(2026, 6, 27)
+
+        result = self._run(energy_db, start, end, now_utc=self._NOW_AFTER)
+
+        daily_fixed = (9.87 + 9.87) / 30
+        daily_credit = 600.0 / 365
+        assert abs(result["fixed_costs"] - daily_fixed) < 1e-9, (
+            "AC2: after settlement offset, today's fixed_costs must equal 1 day; "
+            f"expected {daily_fixed:.6f}, got {result['fixed_costs']}"
+        )
+        assert abs(result["credits"] - daily_credit) < 1e-9, (
+            "AC2: after settlement offset, today's credits must equal 1 day; "
+            f"expected {daily_credit:.6f}, got {result['credits']}"
+        )
+
+    # --- AC3a: cumulative window, before offset → today (June 26) not counted ---
+
+    def test_cumulative_before_offset_excludes_today(self, energy_db: Session) -> None:
+        """AC3: Cumulative window at 00:30 (before offset) excludes today from count.
+
+        Window: [June 24 AMS midnight, June 26 00:30 AMS).
+          first_counted = June 24.
+          last_counted (from window) = June 26 (lmu(June 26) = June 25 22:00 < 22:30).
+          settled_cap = June 25 (before offset) → min(June 26, June 25) = June 25.
+          Counted: June 24 + June 25 = 2 days (today June 26 excluded).
+        """
+        self._setup_single_version_contract(energy_db)
+        start = _ams_midnight(2026, 6, 24)   # June 23 22:00 UTC
+        end = self._NOW_BEFORE               # June 25 22:30 UTC = June 26 00:30 AMS
+
+        result = self._run(energy_db, start, end, now_utc=self._NOW_BEFORE)
+
+        daily_fixed = (9.87 + 9.87) / 30
+        daily_credit = 600.0 / 365
+        assert abs(result["fixed_costs"] - daily_fixed * 2) < 1e-9, (
+            "AC3 before offset: today (June 26) must not be counted; expected 2 days; "
+            f"got {result['fixed_costs']}"
+        )
+        assert abs(result["credits"] - daily_credit * 2) < 1e-9, (
+            "AC3 before offset: credits must be 2 days; "
+            f"got {result['credits']}"
+        )
+
+    # --- AC3b: cumulative window, after offset → today (June 26) counted ---
+
+    def test_cumulative_after_offset_includes_today(self, energy_db: Session) -> None:
+        """AC3: Cumulative window at 01:10 (after offset) includes today.
+
+        Window: [June 24 AMS midnight, June 26 01:10 AMS).
+          first_counted = June 24.
+          last_counted (from window) = June 26 (lmu(June 26) < 23:10 UTC).
+          settled_cap = June 26 (after offset) → last_counted = June 26.
+          Counted: June 24 + June 25 + June 26 = 3 days.
+        """
+        self._setup_single_version_contract(energy_db)
+        start = _ams_midnight(2026, 6, 24)   # June 23 22:00 UTC
+        end = self._NOW_AFTER               # June 25 23:10 UTC = June 26 01:10 AMS
+
+        result = self._run(energy_db, start, end, now_utc=self._NOW_AFTER)
+
+        daily_fixed = (9.87 + 9.87) / 30
+        daily_credit = 600.0 / 365
+        assert abs(result["fixed_costs"] - daily_fixed * 3) < 1e-9, (
+            "AC3 after offset: today (June 26) must be counted; expected 3 days; "
+            f"got {result['fixed_costs']}"
+        )
+        assert abs(result["credits"] - daily_credit * 3) < 1e-9, (
+            "AC3 after offset: credits must be 3 days; "
+            f"got {result['credits']}"
+        )
+
+    # --- AC4: past days always fully counted regardless of offset ---
+
+    def test_past_days_always_counted_regardless_of_offset(self, energy_db: Session) -> None:
+        """AC4: Past days (all before today) are fully counted even before 01:05.
+
+        Window: [June 20 AMS midnight, June 26 AMS midnight) — all before today.
+        now = June 26 00:30 AMS (before offset) → settled_cap = June 25.
+        last_counted (from window) = June 25 (lmu(June 26) = end_utc, not <).
+        min(June 25, June 25) = June 25 → 6 days (June 20-25), all past.
+        """
+        self._setup_single_version_contract(energy_db)
+        start = _ams_midnight(2026, 6, 20)   # June 19 22:00 UTC
+        end = _ams_midnight(2026, 6, 26)     # June 25 22:00 UTC
+
+        result = self._run(energy_db, start, end, now_utc=self._NOW_BEFORE)
+
+        daily_fixed = (9.87 + 9.87) / 30
+        daily_credit = 600.0 / 365
+        # June 20-25 = 6 days, all past — unaffected by settlement offset.
+        assert abs(result["fixed_costs"] - daily_fixed * 6) < 1e-9, (
+            "AC4: past days must be fully counted regardless of settlement offset; "
+            f"expected 6 days = {daily_fixed * 6:.6f}, got {result['fixed_costs']}"
+        )
+        assert abs(result["credits"] - daily_credit * 6) < 1e-9, (
+            "AC4: past credits must be 6 days; "
+            f"got {result['credits']}"
+        )
+
+    # --- AC5: cross-version segments still correct with settlement offset ---
+
+    def test_cross_version_with_settlement_offset(self, energy_db: Session) -> None:
+        """AC5: Cross-version day split is correct when settlement offset is active.
+
+        V1 covers June 24; V2 covers June 25+.
+        Window: [June 24 AMS midnight, June 26 01:10 AMS).
+        After offset (01:10) → settled_cap = June 26 → 3 days: V1=1, V2=2.
+
+        V1: network_fee=6, management_fee=6 → daily_fixed = 12/30
+            heffingskorting=300           → daily_credit = 300/365
+        V2: network_fee=12, management_fee=12 → daily_fixed = 24/30
+            heffingskorting=600            → daily_credit = 600/365
+
+        Expected:
+          fixed_costs = 1×(12/30) + 2×(24/30) = 0.4 + 1.6 = 2.0
+          credits     = 1×(300/365) + 2×(600/365) = 1500/365
+        """
+        _VALUES_V1 = {
+            "energy": {"buy": {"normal": 0.10, "dal": 0.10},
+                       "sell": {"normal": 0.05, "dal": 0.05},
+                       "energy_tax": 0.0, "ode": 0.0},
+            "standing": {"network_fee": 6.0, "management_fee": 6.0},
+            "credits": {"heffingskorting": 300.0},
+        }
+        _VALUES_V2 = {
+            "energy": {"buy": {"normal": 0.20, "dal": 0.20},
+                       "sell": {"normal": 0.08, "dal": 0.08},
+                       "energy_tax": 0.0, "ode": 0.0},
+            "standing": {"network_fee": 12.0, "management_fee": 12.0},
+            "credits": {"heffingskorting": 600.0},
+        }
+        v1_from = _ams_midnight(2026, 6, 24)   # June 23 22:00 UTC
+        v2_from = _ams_midnight(2026, 6, 25)   # June 24 22:00 UTC
+
+        c = _make_contract(energy_db, kind="manual", active=True)
+        _make_version(energy_db, c, _VALUES_V1, effective_from=v1_from, effective_to=v2_from)
+        _make_version(energy_db, c, _VALUES_V2, effective_from=v2_from)
+        energy_db.commit()
+
+        start = _ams_midnight(2026, 6, 24)   # June 23 22:00 UTC
+        end = self._NOW_AFTER               # June 25 23:10 UTC = June 26 01:10 AMS
+
+        result = self._run(energy_db, start, end, now_utc=self._NOW_AFTER)
+
+        expected_fixed = 1 * 12 / 30 + 2 * 24 / 30    # V1: 1 day, V2: 2 days
+        expected_credits = 1 * 300 / 365 + 2 * 600 / 365
+        assert abs(result["fixed_costs"] - expected_fixed) < 1e-9, (
+            f"AC5: cross-version fixed_costs wrong; expected {expected_fixed}, "
+            f"got {result['fixed_costs']}"
+        )
+        assert abs(result["credits"] - expected_credits) < 1e-9, (
+            f"AC5: cross-version credits wrong; expected {expected_credits}, "
+            f"got {result['credits']}"
+        )
+
+    # --- AC6: return dict key-set unchanged ---
+
+    def test_return_dict_keys_unchanged(self, energy_db: Session) -> None:
+        """AC6: summarize() return dict keys are unchanged by the settlement offset."""
+        self._setup_single_version_contract(energy_db)
+        start = _ams_midnight(2026, 6, 26)
+        end = _ams_midnight(2026, 6, 27)
+
+        result = self._run(energy_db, start, end, now_utc=self._NOW_AFTER)
+
+        expected_keys = {
+            "currency", "metered_import", "metered_export", "metered_net",
+            "fixed_costs", "credits", "total_payable", "period_count",
+            "degraded_count", "days",
+        }
+        assert set(result.keys()) == expected_keys, (
+            f"AC6: summarize() key set changed; expected {expected_keys}, "
+            f"got {set(result.keys())}"
+        )

tests/test_energy_models.py

@@ -798,7 +798,7 @@ def test_meter_columns(energy_db):
     inspector = inspect(energy_db)
     columns = {col["name"]: col for col in inspector.get_columns("meter")}
 
-    non_nullable = {"id", "label", "commodity", "started_at", "reason", "created_at"}
+    non_nullable = {"id", "uuid", "label", "commodity", "started_at", "reason", "created_at"}
     nullable = {"ended_at", "note"}
 
     for col_name in non_nullable:
@@ -810,11 +810,20 @@ def test_meter_columns(energy_db):
         assert columns[col_name]["nullable"], f"{col_name} should be nullable"
 
 
+def test_meter_uuid_unique_constraint(energy_db):
+    """meter.uuid must have a unique constraint."""
+    inspector = inspect(energy_db)
+    unique_constraints = inspector.get_unique_constraints("meter")
+    unique_cols = [col for uc in unique_constraints for col in uc["column_names"]]
+    assert "uuid" in unique_cols, "meter.uuid must have a unique constraint"
+
+
 def test_meter_orm_metadata():
     """Meter must be registered in Base.metadata with correct field types."""
     assert "meter" in Base.metadata.tables, "meter not in Base.metadata"
     table = Base.metadata.tables["meter"]
     assert "id" in table.columns
+    assert "uuid" in table.columns
     assert "label" in table.columns
     assert "commodity" in table.columns
     assert "started_at" in table.columns
@@ -824,6 +833,14 @@ def test_meter_orm_metadata():
     assert "created_at" in table.columns
 
 
+def test_meter_uuid_unique_in_metadata():
+    """Meter.uuid must be declared unique and not nullable in ORM metadata."""
+    table = Base.metadata.tables["meter"]
+    col = table.columns["uuid"]
+    assert col.unique, "Meter.uuid must be declared unique in ORM metadata"
+    assert not col.nullable, "Meter.uuid must be NOT NULL in ORM metadata"
+
+
 def test_meter_insert_and_retrieve(energy_db):
     """A Meter row can be inserted and retrieved with all fields intact."""
     now = datetime.now(tz=timezone.utc)

tests/test_expose_catalog.py

@@ -205,27 +205,58 @@ def test_register_provider_direct_call():
 def test_build_catalog_empty_with_no_devices(expose_db):
     """build_catalog with no enabled modbus devices must contain no modbus entities.
 
-    The energy_cost provider is always registered and always produces its 6 entities
+    FUE-T05: the energy_cost provider now requires an active electricity meter.
-    (4 original + 2 daily) regardless of device state, so the catalog will not be empty.
+    Without one, it returns [] and the catalog contains no energy entities.
-    This test checks that no *modbus* entities are present when there are no enabled
+    With one, it produces 6 entities.
-    modbus devices.
+
+    This test verifies both cases:
+    1. No modbus devices → no modbus entities.
+    2. No active meter → no energy entities (provider returns []).
+    3. After inserting an active meter → 6 energy entities present.
     """
     from app.integrations.expose import build_catalog
 
+    # Case: no modbus devices, no active meter → catalog is empty.
     with Session(expose_db) as session:
         catalog = build_catalog(session)
 
-    # The modbus provider finds no enabled devices → no modbus entities.
-    # The energy_cost provider always produces 6 entities, so the catalog is non-empty.
     modbus_entities = [e for e in catalog if e.entity.key.startswith("modbus.")]
     assert modbus_entities == [], (
         "Expected no modbus entities when no modbus devices are enabled"
     )
 
-    # The 6 energy_cost entities should always be present (4 original + 2 daily).
+    # No active electricity meter → energy-cost provider returns [] → no energy entities.
-    energy_keys = {e.entity.key for e in catalog if e.entity.key.startswith("energy.")}
+    energy_keys_no_meter = {e.entity.key for e in catalog if e.entity.key.startswith("energy.")}
-    assert len(energy_keys) == 6, (
+    assert len(energy_keys_no_meter) == 0, (
-        f"Expected exactly 6 energy_cost entities (4 original + 2 daily), got {energy_keys!r}"
+        f"Expected 0 energy_cost entities (no active meter), got {energy_keys_no_meter!r}"
+    )
+
+    # Insert an active electricity meter → provider should now produce 6 entities.
+    from datetime import datetime, timezone
+    now = datetime.now(tz=timezone.utc)
+    with Session(expose_db) as session:
+        from app.models.energy import Meter
+        m = Meter(
+            label="Test Meter for catalog",
+            commodity="electricity",
+            started_at=now,
+            ended_at=None,
+            reason="initial",
+            note=None,
+            created_at=now,
+        )
+        session.add(m)
+        session.commit()
+
+    with Session(expose_db) as session:
+        catalog_with_meter = build_catalog(session)
+
+    energy_keys_with_meter = {
+        e.entity.key for e in catalog_with_meter if e.entity.key.startswith("energy.")
+    }
+    assert len(energy_keys_with_meter) == 6, (
+        f"Expected exactly 6 energy_cost entities (4 original + 2 daily) with active meter, "
+        f"got {energy_keys_with_meter!r}"
     )
 
 

tests/test_meters.py

@@ -381,6 +381,43 @@ class TestDeclareMeter:
         assert fetched.commodity == "gas"
         assert fetched.note == "Rotameter serial XYZ"
 
+    def test_declare_meter_generates_uuid(self, session: Session):
+        """declare_meter must auto-generate a non-empty uuid via ORM default."""
+        import re
+        UUID4_RE = re.compile(
+            r"^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$",
+            re.IGNORECASE,
+        )
+
+        m = declare_meter(
+            session,
+            label="Meter with UUID",
+            started_at=_T0,
+            reason="initial",
+        )
+        session.commit()
+
+        fetched = session.get(Meter, m.id)
+        assert fetched is not None
+        assert fetched.uuid is not None, "uuid must not be None after declare_meter"
+        assert fetched.uuid != "", "uuid must not be empty"
+        assert UUID4_RE.match(fetched.uuid), (
+            f"uuid {fetched.uuid!r} does not look like a valid UUID v4"
+        )
+
+    def test_declare_meter_each_gets_distinct_uuid(self, session: Session):
+        """Each declared meter must receive a distinct UUID (not duplicated)."""
+        m1 = declare_meter(session, label="M1", started_at=_T0, reason="initial")
+        session.commit()
+
+        t1 = _T0 + timedelta(days=10)
+        m2 = declare_meter(session, label="M2", started_at=t1, reason="meter_swap")
+        session.commit()
+
+        assert m1.uuid != m2.uuid, (
+            f"Two declared meters must have distinct UUIDs; both got {m1.uuid!r}"
+        )
+
 
 # ---------------------------------------------------------------------------
 # 5. Different commodities are independent