feat(modbus): add DDSU666 profile and select read function code per profile

- Add CHINT DDSU666 profile (ddsu666.yaml): FC03 holding registers, voltage/
  current/active power (kW)/reactive power (kvar)/PF/frequency, import+export
  active energy. Word/byte order left at big-endian as a documented best guess
  (manual has no float example) — to be confirmed on-device.
- Add DDSU666-Modbus-Protocol.md reference extracted from the official manual,
  plus the source PDF (parity with the SDM120 reference).
- Generalize driver.read_blocks to dispatch FC03 (holding) or FC04 (input)
  based on a function_code argument (default 4, SDM120 behaviour unchanged);
  the code is validated before any connection is attempted.
- Wire profile.function_code through the CLI read command, the background
  poller, and the device /test endpoint — previously the profile field was
  declared but never honoured (read path was hardcoded to FC04).
- Tests: default -> FC04, function_code=3 -> FC03 holding, invalid FC rejected
  before connecting.

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)
@@ -185,9 +203,10 @@ def declare_energy_meter(
 
     **Retroactive recompute**: if ``started_at`` is in the past, billing
     records from that point forward are re-judged via ``recompute_range`` to
-    reflect the new meter attribution.  The response includes the count of
-    recomputed periods in ``recomputed_periods`` (not part of ``MeterResponse``
-    — the recompute is transparent; callers should re-fetch costs if needed).
+    reflect the new meter attribution.  The recompute is transparent — the
+    response body is the created meter (``MeterResponse``) only and does **not**
+    include a recompute count; callers should re-fetch costs if they need the
+    updated totals.
     """
     started_at_utc = _localize_started_at(body.started_at)
 
@@ -216,6 +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,
@@ -293,6 +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/api/routes/api/modbus.py

@@ -488,6 +488,7 @@ def test_read(
             device.port,
             device.unit_id,
             [{"start": b.start, "count": b.count} for b in profile.blocks],
+            function_code=profile.function_code,
         )
         payload: dict[str, Any] = decode_profile(profile, registers)
         return ModbusTestReadResponse(ok=True, payload=payload)

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).
-    - ``export_revenue_total``  — cumulative export revenue (total_increasing, monetary).
+    - ``import_cost_total``     — cumulative import cost (total, 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
-    to avoid double-counting when they are later overwritten by real values.
+    ``energy_cost_period`` rows within the current meter's window.  Degraded rows
+    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
-    ``ha_discovery.py``'s ``entity.device.identifiers[1]`` is always valid
-    (the service uses index [1] as the node_id throughout).
+    **Two-element tuple** ``("energy-cost", meter.uuid)`` so that
+    ``ha_discovery.py``'s ``entity.device.identifiers[1]`` resolves to the
+    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"),
-        name="Energy Cost",
+        identifiers=("energy-cost", active_meter.uuid),
+        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/integrations/modbus/driver.py

@@ -1,8 +1,11 @@
 """Modbus TCP driver — thin wrapper around pymodbus.
 
 This module provides a single public function ``read_blocks`` that performs
-one or more FC04 (Read Input Registers) block reads against a Modbus TCP
-gateway and returns a flat ``dict[register_address -> 16-bit_value]`` map.
+one or more block reads against a Modbus TCP gateway — using either FC04
+(Read Input Registers) or FC03 (Read Holding Registers), selected per call
+via the ``function_code`` argument — and returns a flat
+``dict[register_address -> 16-bit_value]`` map.  The function code comes from
+the device profile (e.g. SDM120 uses FC04, DDSU666 uses FC03).
 
 Design decisions
 ----------------
@@ -80,9 +83,10 @@ def read_blocks(
     unit_id: int,
     blocks: Sequence[Block],
     *,
+    function_code: int = 4,
     timeout: float = 3.0,
 ) -> dict[int, int]:
-    """Read one or more contiguous register blocks via FC04 (input registers).
+    """Read one or more contiguous register blocks via FC03 or FC04.
 
     Parameters
     ----------
@@ -96,6 +100,11 @@ def read_blocks(
         Sequence of ``{"start": int, "count": int}`` dicts describing the
         contiguous register ranges to read.  ``count`` is the number of
         16-bit registers (not bytes).
+    function_code:
+        Modbus read function code: ``4`` for FC04 (Read Input Registers,
+        default — SDM120) or ``3`` for FC03 (Read Holding Registers —
+        DDSU666 and other devices that expose measurements as holding
+        registers).  Comes from the device profile's ``function_code`` field.
     timeout:
         TCP connect/read timeout in seconds (default 3 s).
 
@@ -107,12 +116,21 @@ def read_blocks(
 
     Raises
     ------
+    ModbusDriverError
+        If ``function_code`` is neither 3 nor 4 (validated before any
+        connection is attempted).
     ModbusConnectionError
         If the TCP connection to the gateway fails.
     ModbusResponseError
         If the gateway returns a Modbus exception frame or an unexpected
         number of registers.
     """
+    if function_code not in (3, 4):
+        raise ModbusDriverError(
+            f"Unsupported read function code FC{function_code:02d} "
+            f"(only FC03 holding-register and FC04 input-register reads are supported)"
+        )
+
     client = ModbusTcpClient(host, port=port, timeout=timeout)
     try:
         connected = client.connect()
@@ -125,7 +143,7 @@ def read_blocks(
         for block in blocks:
             start: int = block["start"]
             count: int = block["count"]
-            _read_block(client, unit_id, start, count, registers)
+            _read_block(client, unit_id, start, count, registers, function_code=function_code)
 
         return registers
 
@@ -145,10 +163,19 @@ def _read_block(
     start: int,
     count: int,
     result: dict[int, int],
+    *,
+    function_code: int,
 ) -> None:
-    """Read one block and merge into *result*.  Raises on any error."""
+    """Read one block and merge into *result*.  Raises on any error.
+
+    ``function_code`` is assumed already validated to be 3 or 4 by the caller
+    (``read_blocks``); 3 dispatches FC03 (holding) and 4 dispatches FC04 (input).
+    """
     try:
-        response = client.read_input_registers(start, count=count, device_id=unit_id)
+        if function_code == 3:
+            response = client.read_holding_registers(start, count=count, device_id=unit_id)
+        else:  # function_code == 4 (input registers)
+            response = client.read_input_registers(start, count=count, device_id=unit_id)
     except ConnectionException as exc:
         raise ModbusConnectionError(
             f"Lost connection while reading registers 0x{start:04X}+{count}: {exc}"

app/integrations/modbus/profiles/ddsu666.yaml

@@ -0,0 +1,82 @@
+name: ddsu666
+description: CHINT DDSU666 single-phase smart meter
+function_code: 3          # holding registers (FC03) — DDSU666 has NO input registers (no FC04)
+word_order: big           # high register first — ASSUMED; verify with a known voltage reading
+byte_order: big           # high byte first within each register (confirmed by manual CRC example)
+
+# NOTE: the manual gives no worked float-decode example, so word_order is a best-guess
+# (standard big-endian, high register first, matching sdm120).  After wiring the meter,
+# read 0x2000 (voltage) — it should decode to ~230 V.  If it decodes to garbage, the
+# device uses the opposite word order and this profile (and the decoder) need adjusting.
+# Byte order is confirmed big-endian from the manual (Appendix A, Table A.4: 0x1388 -> 13 88).
+
+blocks:
+  # Instantaneous quantities 0x2000–0x200F: voltage, current, P, Q, (rsv), PF, (rsv), Freq.
+  # 16 contiguous registers — single bulk read.  (DDSU666 manual Table 9.)
+  - { start: 0x2000, count: 0x0010 }
+  # Active energy — import (0x4000) and export (0x400A) read as two small blocks rather
+  # than one span, to avoid touching the undocumented/reserved 0x4002–0x4009 gap.
+  - { start: 0x4000, count: 0x0002 }
+  - { start: 0x400A, count: 0x0002 }
+
+metrics:
+  # Addresses are the raw Modbus protocol addresses (hex) from DDSU666 manual Table 9,
+  # read via FC03.  Each float32 occupies two consecutive 16-bit registers.
+
+  - key: voltage
+    address: 0x2000        # U — Voltage (V)
+    type: float32
+    unit: "V"
+    device_class: voltage
+    ha_component: sensor
+
+  - key: current
+    address: 0x2002        # I — Current (A)
+    type: float32
+    unit: "A"
+    device_class: current
+    ha_component: sensor
+
+  - key: active_power
+    address: 0x2004        # P — Active power.  Manual unit is kW (NOT W like sdm120).
+    type: float32
+    unit: "kW"
+    device_class: power
+    ha_component: sensor
+
+  - key: reactive_power
+    address: 0x2006        # Q — Reactive power (kvar)
+    type: float32
+    unit: "kvar"
+    device_class: reactive_power
+    ha_component: sensor
+
+  - key: power_factor
+    address: 0x200A        # PF — Power factor (dimensionless)
+    type: float32
+    unit: ""
+    device_class: power_factor
+    ha_component: sensor
+
+  - key: frequency
+    address: 0x200E        # Freq — Frequency (Hz)
+    type: float32
+    unit: "Hz"
+    device_class: frequency
+    ha_component: sensor
+
+  - key: import_energy
+    address: 0x4000        # Ep — positive/forward active energy (kWh)
+    type: float32
+    unit: "kWh"
+    device_class: energy
+    state_class: total_increasing
+    ha_component: sensor
+
+  - key: export_energy
+    address: 0x400A        # -Ep — reverse active energy (kWh)
+    type: float32
+    unit: "kWh"
+    device_class: energy
+    state_class: total_increasing
+    ha_component: sensor

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)
@@ -678,15 +682,33 @@ def summarize(session: Session, start: datetime, end: datetime) -> dict[str, Any
                       + fixed_costs              -- per-day standing charges, cross-version
                       - credits                  -- per-day heffingskorting, cross-version
 
-    **Fixed-cost / credit counting — Principle C**:
-    Only *already-elapsed* whole local calendar days are counted.  For each
-    local calendar date D in the window ``[start_local_date, min(end_local_date,
-    tomorrow_local))``, the contract version whose rate covers D (the one whose
-    effective_from local-date ≤ D < next version's effective_from local-date) is
-    used.  Days that have not yet started in local time (D > today_local) are
-    never counted.  This is cross-version: if the active contract has V1 from
-    June 1 and V2 from June 25, querying June 1–30 uses V1 for days 1-24 and V2
-    for day 25.  Switching versions never resets the counter.
+    **Fixed-cost / credit counting — Principle C (symmetric begin/end)**:
+    Both the local calendar day in which *start* falls and the local calendar
+    day in which *end* falls are counted as full days.  Fixed charges
+    (network_fee, management_fee) and the energy-tax credit (heffingskorting)
+    are assessed on a "service-is-active" basis — if the meter was online on a
+    given calendar day, the full day's charge/credit applies, regardless of
+    whether the window starts at midnight or mid-morning.
+
+    For each local calendar date D in the range
+    ``[local_date(start), min(local_date(end), today_local)]``:
+    - D ≤ today_local (only elapsed / today days count as "whole days").
+    - The contract version whose effective_from local-date ≤ D is used.
+    - This is cross-version: if V1 is from June 1 and V2 from June 25,
+      querying June 1–30 uses V1 for days 1-24 and V2 for day 25.
+
+    The end-day (last_counted) is included when the end's local midnight falls
+    strictly before end_utc; combined with the always-counted start day this
+    makes the begin/end handling symmetric.  A short same-day window therefore
+    counts its single local day.  A window contributes 0 days only when the
+    counted range is empty (first_counted > last_counted) — e.g. a window lying
+    entirely in the future, since last_counted is capped at today_local.
+
+    Daily getters (``*_today``) use windows exactly aligned to local midnight,
+    so their ``first_counted`` is always today — unaffected by this fix.
+
+    Days that have not yet started in local time (D > today_local) are
+    never counted.  Switching versions never resets the counter.
 
     **Timezone note**: the ``days`` field in the returned dict still represents
     the window length in calendar days (total_seconds / 86400), for backward
@@ -746,29 +768,46 @@ 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) ---
     #
-    # We count local calendar day D if its LOCAL MIDNIGHT falls within [start_utc, end_utc)
-    # AND D ≤ today_local (only elapsed / today days count as "whole days").
+    # Both the window-start day and the window-end day are counted as complete
+    # local calendar days, regardless of whether the window starts/ends at midnight.
     #
-    # Semantics: "A day D is counted when its local midnight has arrived (D ≤ today)
-    # AND the local midnight is within the billing window."
+    # Principle C (symmetric begin/end):
+    #   • first_counted = local calendar date of start_utc  (start day always counted)
+    #   • last_counted  = local calendar date of end_utc    (end day counted if its
+    #                     local midnight is strictly before end_utc)
+    #   • Both are then capped at today_local (only elapsed / today days count).
     #
-    # This means a sub-day window [10:00, 10:30) UTC that doesn't contain any
-    # local midnight contributes 0 days, while a window [22:00 UTC, 23:00 UTC) that
-    # contains CEST midnight (= 22:00 UTC) contributes 1 day.
+    # Why symmetric? Fixed charges (network_fee, management_fee) and energy-tax credits
+    # (heffingskorting) are assessed on a "service-is-active" basis, not on how many
+    # hours the service was actually running within that calendar day.  If the meter
+    # anchor (started_at) falls at 09:18 on June 24, the full June 24 standing charge
+    # and credit still apply because the service was online for that day.
     #
-    # Implementation: compute the first and last local date whose midnight is in range.
+    # Previous asymmetric behaviour: a start_utc that was *later* than the local
+    # midnight of local_start_date caused first_counted to be bumped to the *next*
+    # day, silently dropping the anchor day's charges/credits.  This was incorrect
+    # for cumulative entities (import_cost_total / export_revenue_total) whose anchor
+    # is often an above-midnight started_at.  The end-side had always been symmetric
+    # (counted if local midnight < end_utc), creating an inconsistency.
+    #
+    # Daily getters (window = [local today 00:00, local tomorrow 00:00)) are
+    # unaffected: local_date(local_midnight_utc(today)) == today, so first_counted
+    # is still today regardless of the fix.
+    #
+    # A short same-day window now counts its single local day (the start day is
+    # always counted, symmetric with the end side).  A window contributes 0 days
+    # only when the counted range is empty (first_counted > last_counted) — e.g. a
+    # window lying entirely in the future, where last_counted is capped at
+    # today_local while first_counted is later.
     from app.services.timezone import local_midnight_utc as _lmu
 
-    local_start_date: _date = local_date(start_utc)
-    # Is the midnight of local_start_date ≥ start_utc?  If not, first midnight is next day.
-    if _lmu(local_start_date) >= start_utc:
-        first_counted: _date = local_start_date
-    else:
-        first_counted = local_start_date + _td(days=1)
+    # Start side: always count the local calendar day in which start_utc falls.
+    first_counted: _date = local_date(start_utc)
 
     local_end_date: _date = local_date(end_utc)
     # Is the midnight of local_end_date < end_utc?  If yes, that day's midnight is in range.
@@ -777,8 +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.
-    last_counted = min(last_counted, today_local)
+    # Settlement cap: "today" is only counted once the local clock has passed the
+    # 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.
 

app/services/modbus_poll.py

@@ -64,6 +64,7 @@ def poll_device(session: Session, device: ModbusDevice) -> ModbusReading | None:
             device.port,
             device.unit_id,
             [{"start": b.start, "count": b.count} for b in profile.blocks],
+            function_code=profile.function_code,
         )
         payload = profiles.decode(profile, registers)
 

docs/references/DDSU666-Modbus-Protocol.md

@@ -0,0 +1,198 @@
+# DDSU666 Modbus 协议（从官方 PDF 提取）
+
+> 来源：`docs/references/DDSU666 Single phase Smart Meter.pdf`
+> （CHINT / 正泰仪表 **DDSU666 Single phase Smart Meter — Operation Manual**，文档号 `ZTY0.464.1224`，版本 **V2**，2020 年 8 月；厂商 Zhejiang Chint Instrument & Meter Co., Ltd.）
+> 本文件是 PDF 的可读化提取，供本项目的 Modbus 采集驱动设计参考。**以官方 PDF 为准**，本文件如有出入以 PDF 为准。
+> 同类文档见 SDM120 的 `SDM120-Modbus-Protocol.md`；两表差异较大，见下方 §6「与 SDM120 的关键差异」。
+
+## 设备速览（来自手册 Table 1 / Table 5）
+
+| 项 | DDSU666（直接接入） | DDSU666-CT（经互感器） |
+| --- | --- | --- |
+| 精度等级 | Active Class B | Active Class C |
+| 参考电压 | 230 V | 230 V |
+| 电流规格 | 0.25–5(80) A | 0.015–1.5(6) A |
+| 表常数 | 800 imp/kWh | 6400 imp/kWh |
+| 接入方式 | 直接接入 | 经电流互感器 |
+
+- 单相电子式电能表，DIN35mm 导轨安装；测量电压、电流、有功/无功功率、频率、功率因数、正/反向有功电能。
+- 电能测量范围 `0～999999.99 kWh`（LCD 只显示 6 位，自动移动小数点）。
+- 通信：RS485，**Modbus-RTU**（也支持 DL/T 645-2007，可切换，见 §5 `0005H ChangeProtocol`）。
+- 手册 Table 1 标注 Frequency Reference = 60Hz，但 LCD 示例又写 `F=50.00Hz`（手册自身不一致）；**实际频率以寄存器 `200EH` 读数为准**，不要把 50/60 写死。
+
+## 0. 本项目的接入方式（重要）
+
+DDSU666 物理层是 **Modbus RTU（RS-485 串口）**，半双工。和 SDM120 一样，本项目通过一个 **Modbus-TCP 网关**接入：
+
+- 后端用 **Modbus TCP**（`IP:port`）连到网关，网关在串口侧转成 RTU 与电表通信。
+- TCP 帧用 MBAP header、**无 CRC**（CRC 由网关在 RTU 侧处理）。本文档里 RTU 帧的 `CRC (Lo/Hi)` 字段在 TCP 模式下不需要我们关心。
+- **Slave Address / Unit ID = 电表的通信地址 Addr**（范围 1–247；面板按键只能设 1–99；见 §5 `0006H`），在 TCP 请求里作为 unit id 传入。
+- 若以后直连串口（RTU），才需要管波特率 / 数据格式 / CRC：**默认串口格式是 8 数据位、无校验、2 停止位（8N2）**，与 SDM120 的 8N1 不同——直连时务必对齐。
+- 电表必须处于 **Modbus 协议模式**（而非 DL/T 645）才能用本协议；可经面板长按切换，或写 `0005H = 2`（见 §5）。
+
+## 1. 协议帧格式（Appendix A）
+
+异步传输，按字节为单位。一帧 10 位字符 = **1 起始位(0) + 8 数据位(无校验) + 2 停止位(1)**（其它格式可定制）。
+
+### 信息帧结构（Table A.1）
+
+| 字段 | 长度 | 说明 |
+| --- | --- | --- |
+| Start（起始） | >3.5 字符静默 | 帧间至少 3.5 字符空闲时间作为分隔 |
+| Address code（地址码） | 1 字节 | 目标从机地址 1–247；每个从机在总线上地址唯一 |
+| Function code（功能码） | 1 字节 | 仅支持 **03H / 10H**（见 §2） |
+| Data（数据域） | n 字节 | 随功能码不同而不同（起始地址、寄存器数、寄存器数据等） |
+| CRC check code（CRC 校验） | 2 字节 | 16-bit CRC（**低字节在前、高字节在后**；多项式 `A001`） |
+| End（结束） | >3.5 字符静默 | 帧间静默 |
+
+> TCP 网关模式下 Start/End 静默与 CRC 由网关处理，本项目不关心。
+
+### 功能码 03H 示例（读寄存器，Table A.3/A.4）
+
+读从机 `01H`、起始地址 `0CH`、2 个寄存器：
+
+- 主机发送：`01 03 00 0C 00 02 04 08`（最后 `04 08` 是 CRC，低字节 `04` 在前）。
+- 从机返回（设 `0CH/0DH` 内容为 `0000H`、`1388H`）：`01 03 04 00 00 13 88 F7 65`
+  - `04` = 字节数；`00 00` = `0CH` 数据；`13 88` = `0DH` 数据；`F7 65` = CRC（低字节 `F7` 在前）。
+
+> **注意**：单个 16-bit 寄存器内是「高字节在前、低字节在后」（Table A.4 里 `0DH` 数据返回 `13 88` = `0x1388`）。这一点对解码浮点的字节序很关键，见 §3。
+
+### 功能码 10H 示例（写多个寄存器，Table A.5/A.6）
+
+向从机 `01H`、起始地址 `00H` 连续写 3 个寄存器 `0002H,1388H,000AH`：
+
+- 主机发送：`01 10 00 00 00 03 06 00 02 13 88 00 0A 9B E9`
+  - `06` = 写入字节数（3 寄存器 × 2 字节）；随后是 3 个寄存器的数据；末尾 `9B E9` CRC。
+- 从机返回：`01 10 00 00 00 03 80 08`（回显起始地址 + 寄存器数 + CRC `80 08`）。
+
+### 异常响应（Table A.7/A.8）
+
+- 异常时返回的 Function Code = **原功能码 + 128**（即最高位置 1，`03H→83H`、`10H→90H`）。
+- 数据为单字节 Error Code：
+
+| Error Code | 含义 | 说明 |
+| --- | --- | --- |
+| `01H` | Illegal function code | 收到的功能码本表不支持 |
+| `02H` | Illegal register address | 寄存器地址超出有效范围 |
+| `03H` | Illegal data value | 数据值超出对应地址的取值范围 |
+
+## 2. 功能码
+
+DDSU666 **只支持两个功能码**（Table A.2）：
+
+| 功能码 | 作用 | 说明 |
+| --- | --- | --- |
+| **03H** | Read register（读寄存器） | 读一个或多个寄存器——**测量值、电量、配置全部走它** |
+| **10H** | Write multiple registers（写多个寄存器） | 向 n 个连续寄存器写 n 个 16-bit 数据（改配置 / 清电量） |
+
+> ⚠️ **DDSU666 没有「输入寄存器 / FC04」概念**——所有数据（包括电压电流功率）都用 **FC 03H** 读保持寄存器。这是它和 SDM120（测量值走 FC04）最大的踩坑差异，见 §6。
+
+## 3. 数据编码
+
+DDSU666 有两类数据：
+
+1. **配置 / 参数寄存器（§5，`0000H`–`0010H`）**：每个 1 个寄存器、`16-bit with symbols`（**16 位有符号整数**）。
+2. **测量 / 电量寄存器（§4，`2000H`+ / `4000H`+）**：每个参数 = **32-bit IEEE-754 单精度浮点**（手册写 “single precision floating decimal”），占 **2 个相邻寄存器**（Length = 2 Word）。
+
+**浮点字节序 / 字序**
+
+- **字节序（byte order）= 大端：寄存器内高字节在前** —— 由 Table A.4 的 `0x1388` 返回为 `13 88` 确认。
+- **字序（word order，两个寄存器谁是高 16 位）**：手册**没有给出浮点解码的实例**，未明确标注。按标准 Modbus 浮点惯例应为**大端字序（高寄存器在前，`ABCD`）**，与本项目 SDM120 驱动一致（`registers_to_float` 用 `>f`，高寄存器在前）。
+- ⚠️ **需上机实测确认**：读 `2000H`（电压）应解出 ~230V 这样的合理值；若解出乱数，多半是字序相反，改成「低寄存器在前」再试。CHINT 同系列（DTSU/DDSU666）现场固件偶有字序差异，**首次接入务必用一个已知量（电压）校验**，不要凭手册想当然。
+
+> Python 解码（大端、高寄存器在前）：`struct.unpack('>f', struct.pack('>HH', hi_reg, lo_reg))[0]`。
+> pymodbus：`BinaryPayloadDecoder.fromRegisters(regs, byteorder=Endian.BIG, wordorder=Endian.BIG)`。
+
+## 4. 测量 / 电量寄存器表（FC 03H 读）
+
+全部为只读、`Float`（32-bit），每项占 **2 个寄存器**。地址为 Modbus 协议原始地址（即帧里的 Start Register Address Hi/Lo），手册用十六进制。
+
+### 4.1 瞬时量（“Electric quantity of the secondary side”，`2000H` 段）
+
+| 地址(hex) | 参数 | 代号 | 单位 | 备注 |
+| --- | --- | --- | --- | --- |
+| `2000H` | 电压 Voltage | U | V | |
+| `2002H` | 电流 Current | I | A | |
+| `2004H` | 有功功率 Active power | P | **kW** | 手册标注 “the unit is KW”——**不是 W** |
+| `2006H` | 无功功率 Reactive power | Q | **kvar** | |
+| `2008H` | （保留 RESERVED） | — | — | 占 2 寄存器，跳过 |
+| `200AH` | 功率因数 Power factor | PF | — | 无量纲 |
+| `200CH` | （保留 RESERVED） | — | — | 占 2 寄存器，跳过 |
+| `200EH` | 频率 Frequency | Freq | Hz | |
+
+### 4.2 电量（“Electrical data of the secondary side”，`4000H` 段）
+
+| 地址(hex) | 参数 | 代号 | 单位 | 备注 |
+| --- | --- | --- | --- | --- |
+| `4000H` | 正向（导入）有功电能 Active in electricity | Ep | kWh | 正向 / forward active energy |
+| `400AH` | 反向（导出）有功电能 Reverse in electricity | -Ep | kWh | 反向 / reverse active energy |
+
+> 手册里 `4000H` 与 `400AH` 之间（`4002H`–`4009H`）未列出，视为保留/未文档化。
+
+**读取分块建议**
+
+- 瞬时量：`2000H`–`200FH` 共 **16 个寄存器连续**，一次块读即可覆盖 U…Freq（含两段 RESERVED，解码时跳过）。
+- 电量：`4000H`（2 寄存器）与 `400AH`（2 寄存器）相距较远，分两小块读，或读 `4000H`–`400BH`（12 寄存器）一次取出后挑用——以网关 / 电表是否允许跨保留地址块读为准，谨慎起见分开读更稳。
+
+### 常用核心子集（日常监控够用）
+
+电压 `2000H`、电流 `2002H`、有功功率 `2004H`（kW）、功率因数 `200AH`、频率 `200EH`、正向有功电能 `4000H`、反向有功电能 `400AH`。
+
+## 5. 配置 / 参数寄存器表（FC 03H 读 / FC 10H 写）（Table 9）
+
+每个 1 个寄存器、**16-bit 有符号整数**。`R/W` 列来自手册。
+
+| 地址(hex) | 代号 | 含义 | R/W | 取值 / 说明 |
+| --- | --- | --- | --- | --- |
+| `0000H` | UCode | 编程密码 Programming password code | R/W | 写配置前的密码字 |
+| `0001H` | REV. | 保留；**实际读出的是版本号** | R | |
+| `0002H` | ClrE | 电能清零 CLr.E | R/W | **写 `1` 清除总电量**（不可逆，慎用） |
+| `0003H`–`0004H` | RESERVED | 保留 | — | |
+| `0005H` | ChangeProtocol | 协议切换 | R/W | **`2` = Modbus-RTU**，`1` = DL/T 645-2007 |
+| `0006H` | Addr | 通信地址 | R/W | 1–247（面板按键仅 1–99） |
+| `0007H`–`000AH` | RESERVED | 保留 | — | |
+| `000BH` | Meter type | 表型 Meter type | R | 只读设备类型标识 |
+| `000CH` | BAud | 通信波特率 | R/W | **`1`=2400bps，`2`=4800bps，`3`=9600bps**（手册寄存器仅列这三档；通信章另提到也支持 1200bps） |
+| `000DH`–`0010H` | RESERVED | 保留 | — | |
+
+> ⚠️ 写 `0002H`（清电量）、`0006H`（改地址）、`000CH`（改波特率）、`0005H`（切协议）都会改变电表状态或通信参数，配错可能**清空累计电量**或**导致通信中断**。本项目默认**只读采集**，不在自动化链路里写电表配置寄存器。
+> 写配置通常需先经 `0000H UCode` 密码字校验；具体密码值手册正文未给出，需向厂商确认或经面板操作。
+
+## 6. 与 SDM120 的关键差异（迁移 / 复用驱动时必看）
+
+本项目已有 SDM120 profile（`app/integrations/modbus/profiles/sdm120.yaml`）。DDSU666 **不能照搬**，主要差异：
+
+| 维度 | SDM120 (Eastron) | DDSU666 (CHINT) |
+| --- | --- | --- |
+| 读测量值功能码 | **FC 04**（输入寄存器 3X） | **FC 03**（保持寄存器，无 FC04） |
+| 测量值起始地址 | `0x0000` 起（30001） | 瞬时量 `0x2000` 起；电量 `0x4000`/`0x400A` |
+| 有功功率单位 | **W**（瓦） | **kW（千瓦）** —— 入库前注意换算 / 单位标注 |
+| 无功功率单位 | VAr | kvar |
+| 配置寄存器格式 | Float（FC03/16） | **16-bit 有符号整数**（FC03/10） |
+| 写功能码 | 16 / 0x10 | 10H（同 0x10） |
+| 串口默认格式 | 8N1（1 停止位） | **8N2（2 停止位）** |
+| 多协议 | 仅 Modbus | Modbus **与 DL/T 645-2007 可切换**（需确保在 Modbus 模式） |
+| 浮点字序 | 大端、高寄存器在前（手册有实例佐证） | 字节序大端已确认；**字序手册无实例，需上机实测** |
+
+## 7. 给本项目采集驱动的要点小结
+
+1. 走 **Modbus TCP 网关**：`ModbusTcpClient(host, port)`，`slave=<Addr>`；电表须在 **Modbus 协议模式**。
+2. 所有读取（测量 + 电量 + 配置）都用 **FC 03H**——**没有 FC04**。
+3. 测量值在 `0x2000` 段、电量在 `0x4000`/`0x400A`，均为 **float32**；解码大端字节序，**字序默认高寄存器在前但务必用电压实测校验**。
+4. **有功功率单位是 kW、无功是 kvar**——与 SDM120 的 W/VAr 不同，新建 profile / 入库映射时单位别抄错。
+5. 配置寄存器（`0x0000`–`0x0010`）是 **16-bit 有符号整数**，不是 float。
+6. 默认**只读**；`0002H` 写 1 会**清空累计电量**、`0006H/000CH/0005H` 会改通信参数，自动化链路里一律不写。
+7. 新建 profile 时这是 `ddsu666` 这一个 register profile 的定义；建议 `function_code: 3`、`word_order: big`（先按大端字序，接入后用电压读数验证）、瞬时量与电量分块读。
+
+## 8. 实测记录（真机验证，2026-06-30）
+
+首次接入一台 **DDSU666 直接接入版（5(80)A）** 实测，确认以下几点：
+
+- **字序大端，确认无误**：电压 / 电流 / 频率 / 电能用「大端、高寄存器在前」解码全部得到合理值（如 233.9 V / 0.055 A / 49.99 Hz），与 §3 的假设一致。`ddsu666.yaml` 的 `word_order: big` / `byte_order: big` **无需修改**，§3 里「字序需上机实测」一项可视为已关闭。
+- **FC03 读通**：所有量走 FC03，profile `ddsu666` 在采集链路（CLI `read` / 设备 `/test` / 后台轮询）中工作正常。
+- **低电流下「瞬时功率读 0、但电能照常累加」**：测试负载仅为一台 PoE 交换机（≈230 V / 0.05 A，真实有功仅几瓦），**远低于本表测量量程下限 Imin≈0.25 A**。此工况下：
+  - 瞬时 `active_power`（`0x2004`）与 `power_factor`（`0x200A`）寄存器返回**全零**（原始 hex `0x0000 0x0000`）；电表 LCD 上功率在 0~3.3 W、PF 在 0~0.6 之间抖动。
+  - 抖动成因 = **低电流测量噪声 + 开关电源（SMPS，无 PFC）畸变电流**（电流为电压峰值附近的窄脉冲、谐波重 → 畸变功率因数天然偏低）。**不是**「采样率与开关频率拍频」：计量芯片 SH79F7019 采样在 kHz 量级，远低于开关电源 50–200 kHz 的开关频率，两者不在一个频段。
+  - 但累计电能 `import_energy`（`0x4000`）**正常累加**（实测 0 → 0.01 kWh）——电表内部积分器在防潜动起始电流（`0.004·Ib`≈0.02 A）之上照常计量。
+  - **结论**：低于量程下限时**瞬时功率 / PF 不可信，但电能计量不丢**；电流进入量程（正常负载）后瞬时量即稳定可信。这是 5(80)A 大量程表对极小负载的固有特性，**非缺陷、非解码问题**。
+- **排错提示**：若日后看到 DDSU666「功率一直 0」，先确认负载电流是否在 Imin 以上——多半是负载太轻而非链路故障；可用 `scripts/modbus_cli probe --fc 3 --address 0x2000 --count 16` 看 `0x2004/0x2005` 原始寄存器是否真为全零佐证。

docs/roadmap.md

@@ -288,11 +288,36 @@ httpx / paho-mqtt / pyyaml / apscheduler 均为 M5 已有依赖，M6 复用，
 
 **动机**：浏览器端走 session cookie 即可，但**脚本 / 设备 / 外部程序调用 API** 需要一种长期有效、可随身携带的凭据。在设置页加一组功能，由 admin **手动签发 long-lived token**，之后用它来调 API。
 
+**本次明确的首要目标 = 给现在裸奔的 ingestion 端点上鉴权**（2026-06-27 与用户确认）：
+
+- `POST /location/record`（`app/api/routes/location.py:18`）——位置记录上报。**目前无任何鉴权**。当前数据经 Home Assistant 转发进来，上 token 后 **HA 侧需携带该 token**；也可由其他客户端直接上报。
+- `POST /poo/record`（`app/api/routes/poo.py:21`）+ `GET /poo/latest`（`poo.py:57`）——小狗排便记录上报 / 最新查询。**目前无任何鉴权**。
+- 这些是设备 / 脚本（非浏览器）端点，session cookie 不适用，正是 long-lived token 的用武之地。（浏览器 CRUD `/api/data/*` 已由 session 保护，不在此列。）
+
 **范围（粗略，待细化）**：
 
 - 设置页新增「API Token」区：生成 / 命名 / 吊销 long-lived token；明文只在**生成时展示一次**，此后只存哈希。
-- 后端支持用该 token 鉴权访问 API（与现有 session cookie 并存，互不影响）。
+- 后端支持用该 token 鉴权访问 API（与现有 session cookie 并存，互不影响）；给上述 ingestion 端点加 token 鉴权依赖。
 - 与 [M3](#m3--开放与移动端远期试水) 的 token 主题相关，但**这条是 Web 设置页手动签发的 PAT 风格**，不依赖移动端 OAuth 流程；两者实现时可复用同一套 token 存储 / 校验。
+- 与下面第 3 条「Session 滑动续期」同属 Authentication 主题（一个是设备/脚本的长期凭据，一个是浏览器短会话体验），实现时鉴权层可一并梳理。
+
+### 3. Session 滑动自动续期（Authentication）
+
+**动机**（2026-06-27 与用户确认）：当前 session 是**绝对过期**——登录即定死、活动不续期，满 TTL 必须重新登录，体验割裂。希望改成**滑动续期（sliding / rolling）**：只要用户还在活动就自动延长，提供"在用就不掉线"的体验。
+
+**现状（实现起点，便于快速拾起）**：
+
+- TTL 默认 **12 小时**：`auth_session_ttl_hours`（`app/config.py:38`；配置页 `app/services/config_page.py:45` 可运行时改）。
+- 登录时**一次性写死**：`create_session` 设 `expires_at = now + ttl`（`app/services/auth.py:94`）+ cookie `max_age = ttl`（`app/api/routes/api/session.py:153`）。
+- 每请求**只读校验、从不延长**：`get_authenticated_session`（`app/services/auth.py:103`）只判断 `expires_at <= now`，过期时仅顺手标 `revoked`。`set_cookie` 只在登录路由调用一次，**无 per-request 中间件**。→ 所以是绝对过期，不是滑动。
+
+**设计要点（待写设计文档时展开）**：
+
+- 校验通过时 bump `expires_at = now + ttl` 并**重发 cookie**（滑动窗口）。
+- **写节流**：不要每个请求都写 DB——仅当剩余寿命已过半（或距上次续期 > N 分钟）才续期，避免高频写放大。
+- **绝对寿命硬顶**：除滑动 TTL 外再设 `created_at + max_lifetime` 上限，防止"永不过期"的会话（安全考量）。
+- 新增配置项：滑动 TTL、绝对寿命上限、续期节流阈值。
+- 注意：改动只对**新逻辑生效**，已存在 session 的 `expires_at` 行为按新校验路径走即可；上线前过校验闸门。
 
 ## Future Ideas（暂不排期，想到先记下）
 

frontend/src/api/schema.d.ts

@@ -591,9 +591,10 @@ export interface paths {
          *
          *     **Retroactive recompute**: if ``started_at`` is in the past, billing
          *     records from that point forward are re-judged via ``recompute_range`` to
-         *     reflect the new meter attribution.  The response includes the count of
-         *     recomputed periods in ``recomputed_periods`` (not part of ``MeterResponse``
-         *     — the recompute is transparent; callers should re-fetch costs if needed).
+         *     reflect the new meter attribution.  The recompute is transparent — the
+         *     response body is the created meter (``MeterResponse``) only and does **not**
+         *     include a recompute count; callers should re-fetch costs if they need the
+         *     updated totals.
          */
         post: operations["declare_energy_meter_api_energy_meters_post"];
         delete?: never;

frontend/src/energy/MeterManager.test.tsx

@@ -258,6 +258,95 @@ describe('MeterManager — declare new meter', () => {
   })
 })
 
+describe('MeterManager — edit meter date initialisation', () => {
+  beforeEach(() => vi.clearAllMocks())
+
+  it('initialises date input from started_at (Z-suffix, UTC midnight → local date)', async () => {
+    // ACTIVE_METER.started_at = '2024-01-15T00:00:00Z' (UTC midnight).
+    // The test suite is pinned to TZ=UTC (via vite.config.ts test.env), so
+    // the local date is deterministically '2024-01-15' on any CI runner.
+    const user = userEvent.setup()
+    mockGet.mockResolvedValue({ data: { items: [ACTIVE_METER], total: 1 } })
+
+    renderWithProviders(<MeterManager />)
+
+    await waitFor(() => expect(screen.getByTestId(`meter-edit-${ACTIVE_METER.id}`)).toBeInTheDocument())
+    await user.click(screen.getByTestId(`meter-edit-${ACTIVE_METER.id}`))
+    await waitFor(() => expect(screen.getByTestId('edit-meter-form')).toBeInTheDocument())
+
+    const dateInput = screen.getByTestId('edit-meter-started-at') as HTMLInputElement
+    expect(dateInput.value).toBe('2024-01-15')
+  })
+
+  it('initialises date input from started_at (naive, no tz marker)', async () => {
+    // A naive timestamp without timezone marker — parseBackendTimestamp appends 'Z'
+    // so it is treated as UTC. With TZ=UTC (pinned in vite.config.ts), the local date
+    // equals the UTC date exactly.
+    const naiveMeter = { ...ACTIVE_METER, started_at: '2024-03-20T00:00:00' }
+    const user = userEvent.setup()
+    mockGet.mockResolvedValue({ data: { items: [naiveMeter], total: 1 } })
+
+    renderWithProviders(<MeterManager />)
+
+    await waitFor(() => expect(screen.getByTestId(`meter-edit-${naiveMeter.id}`)).toBeInTheDocument())
+    await user.click(screen.getByTestId(`meter-edit-${naiveMeter.id}`))
+    await waitFor(() => expect(screen.getByTestId('edit-meter-form')).toBeInTheDocument())
+
+    const dateInput = screen.getByTestId('edit-meter-started-at') as HTMLInputElement
+    expect(dateInput.value).toBe('2024-03-20')
+  })
+
+  it('initialises date input from started_at with explicit UTC offset (+02:00) — regression for old buggy regex', async () => {
+    // The old hand-written regex /[zZ+-]\d*$/ would fail to match '+02:00' (the ':00'
+    // suffix broke the pattern) and would incorrectly append 'Z', producing an Invalid Date.
+    // The new code uses parseBackendTimestamp which uses the correct TZ_MARKER_RE regex
+    // and handles explicit offsets properly.
+    const offsetMeter = { ...ACTIVE_METER, started_at: '2024-01-15T02:00:00+02:00' }
+    // UTC equivalent: 2024-01-15T00:00:00Z → with TZ=UTC (pinned) local date = '2024-01-15'
+    const user = userEvent.setup()
+    mockGet.mockResolvedValue({ data: { items: [offsetMeter], total: 1 } })
+
+    renderWithProviders(<MeterManager />)
+
+    await waitFor(() => expect(screen.getByTestId(`meter-edit-${offsetMeter.id}`)).toBeInTheDocument())
+    await user.click(screen.getByTestId(`meter-edit-${offsetMeter.id}`))
+    await waitFor(() => expect(screen.getByTestId('edit-meter-form')).toBeInTheDocument())
+
+    const dateInput = screen.getByTestId('edit-meter-started-at') as HTMLInputElement
+    // Must not be empty (which would indicate Invalid Date from the old buggy path)
+    expect(dateInput.value).not.toBe('')
+    expect(dateInput.value).toBe('2024-01-15')
+  })
+
+  it('does not include started_at in PATCH body when date is unchanged (round-trip idempotence)', async () => {
+    // Open the edit form and immediately submit without changing any fields except label.
+    // The date should be considered unchanged → no started_at in the PATCH body.
+    const user = userEvent.setup()
+    mockGet.mockResolvedValue({ data: { items: [ACTIVE_METER], total: 1 } })
+    mockPatch.mockResolvedValue({ data: { ...ACTIVE_METER, label: 'New label' } })
+
+    renderWithProviders(<MeterManager />)
+
+    await waitFor(() => expect(screen.getByTestId(`meter-edit-${ACTIVE_METER.id}`)).toBeInTheDocument())
+    await user.click(screen.getByTestId(`meter-edit-${ACTIVE_METER.id}`))
+    await waitFor(() => expect(screen.getByTestId('edit-meter-form')).toBeInTheDocument())
+
+    // Change only label; leave date untouched
+    const labelInput = screen.getByTestId('edit-meter-label')
+    await user.clear(labelInput)
+    await user.type(labelInput, 'New label')
+
+    await user.click(screen.getByTestId('edit-meter-submit'))
+
+    await waitFor(() => {
+      expect(mockPatch).toHaveBeenCalled()
+    })
+
+    const patchBody = mockPatch.mock.calls[0][1].body
+    expect(patchBody).not.toHaveProperty('started_at')
+  })
+})
+
 describe('MeterManager — edit meter', () => {
   beforeEach(() => vi.clearAllMocks())
 

frontend/src/energy/MeterManager.tsx

@@ -38,7 +38,7 @@ import {
   type MeterReason,
 } from './hooks'
 import { ApiError } from '../api/client'
-import { formatLocalDate } from '../utils/datetime'
+import { formatLocalDate, parseBackendTimestamp } from '../utils/datetime'
 
 // ---------------------------------------------------------------------------
 // Helpers
@@ -60,6 +60,19 @@ function toLocalMidnightNaive(dateStr: string): string {
   return `${dateStr}T00:00:00`
 }
 
+/**
+ * Format a Date object as a "YYYY-MM-DD" string using the browser's local timezone.
+ * Used to populate <input type="date"> fields.
+ * Returns '' if the Date is invalid.
+ */
+function toLocalDateInputString(d: Date): string {
+  if (isNaN(d.getTime())) return ''
+  const y = d.getFullYear()
+  const m = String(d.getMonth() + 1).padStart(2, '0')
+  const day = String(d.getDate()).padStart(2, '0')
+  return `${y}-${m}-${day}`
+}
+
 // ---------------------------------------------------------------------------
 // Declare meter form (modal)
 // ---------------------------------------------------------------------------
@@ -204,19 +217,12 @@ interface EditMeterFormProps {
 function EditMeterForm({ meter, onClose, onSaved }: EditMeterFormProps) {
   const [label, setLabel] = useState(meter.label)
   const [note, setNote] = useState(meter.note ?? '')
-  // Convert UTC started_at to a local date string for the <input type="date">.
-  // We parse as UTC (appending Z if needed) and format to "YYYY-MM-DD" in local tz.
-  const initialDateStr = (() => {
-    const iso = meter.started_at.includes('T') && !meter.started_at.match(/[zZ+-]\d*$/)
-      ? meter.started_at + 'Z'
-      : meter.started_at
-    const d = new Date(iso)
-    if (isNaN(d.getTime())) return ''
-    const y = d.getFullYear()
-    const m = String(d.getMonth() + 1).padStart(2, '0')
-    const day = String(d.getDate()).padStart(2, '0')
-    return `${y}-${m}-${day}`
-  })()
+  // Convert started_at to a local date string for the <input type="date">.
+  // parseBackendTimestamp correctly handles naive strings (no tz marker → treated as UTC,
+  // matching the backend's storage convention), Z-suffixed strings, and strings with
+  // explicit offsets like +02:00.  We then extract the local-timezone date components
+  // so the displayed date matches the local wall-clock date of the meter start.
+  const initialDateStr = toLocalDateInputString(parseBackendTimestamp(meter.started_at))
   const [dateStr, setDateStr] = useState(initialDateStr)
   const [error, setError] = useState<string | null>(null)
 

frontend/vite.config.ts

@@ -20,5 +20,13 @@ export default defineConfig({
     environment: 'jsdom',
     globals: true,
     setupFiles: ['./src/test-setup.ts'],
+    env: {
+      // Lock the test timezone to UTC so that date-formatting assertions
+      // (which rely on toLocalDateInputString / getFullYear etc.) produce
+      // deterministic results regardless of the CI runner's local timezone.
+      // All fixture timestamps are UTC midnight, so the expected YYYY-MM-DD
+      // values in MeterManager.test.tsx are correct under UTC.
+      TZ: 'UTC',
+    },
   },
 })

openapi/openapi.json

@@ -1405,7 +1405,7 @@
           "api-energy-meters"
         ],
         "summary": "Declare Energy Meter",
-        "description": "Declare a new meter epoch (swap, home move, or initial declaration).\n\nCloses the current active meter for the given commodity at ``started_at``\nand opens a new active meter.  If no active meter exists, the new meter is\nsimply created without closing anything.\n\n**Validation**: ``started_at`` must be **≥** the current active meter's\nown ``started_at`` (no chronological backdate below the active epoch's\nstart).  Equal timestamps are allowed (replaces the current meter at the\nsame logical moment).  Violation → 422.\n\n**Retroactive recompute**: if ``started_at`` is in the past, billing\nrecords from that point forward are re-judged via ``recompute_range`` to\nreflect the new meter attribution.  The response includes the count of\nrecomputed periods in ``recomputed_periods`` (not part of ``MeterResponse``\n— the recompute is transparent; callers should re-fetch costs if needed).",
+        "description": "Declare a new meter epoch (swap, home move, or initial declaration).\n\nCloses the current active meter for the given commodity at ``started_at``\nand opens a new active meter.  If no active meter exists, the new meter is\nsimply created without closing anything.\n\n**Validation**: ``started_at`` must be **≥** the current active meter's\nown ``started_at`` (no chronological backdate below the active epoch's\nstart).  Equal timestamps are allowed (replaces the current meter at the\nsame logical moment).  Violation → 422.\n\n**Retroactive recompute**: if ``started_at`` is in the past, billing\nrecords from that point forward are re-judged via ``recompute_range`` to\nreflect the new meter attribution.  The recompute is transparent — the\nresponse body is the created meter (``MeterResponse``) only and does **not**\ninclude a recompute count; callers should re-fetch costs if they need the\nupdated totals.",
         "operationId": "declare_energy_meter_api_energy_meters_post",
         "parameters": [
           {

openapi/openapi.yaml

@@ -1125,11 +1125,13 @@ paths:
 
         records from that point forward are re-judged via ``recompute_range`` to
 
-        reflect the new meter attribution.  The response includes the count of
+        reflect the new meter attribution.  The recompute is transparent — the
 
-        recomputed periods in ``recomputed_periods`` (not part of ``MeterResponse``
+        response body is the created meter (``MeterResponse``) only and does **not**
 
-        — the recompute is transparent; callers should re-fetch costs if needed).'
+        include a recompute count; callers should re-fetch costs if they need the
+
+        updated totals.'
       operationId: declare_energy_meter_api_energy_meters_post
       parameters:
       - name: X-CSRF-Token

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):

scripts/modbus_cli.py

@@ -131,6 +131,7 @@ def cmd_read(args: argparse.Namespace) -> None:
 
     print(f"Profile  : {profile.name} — {profile.description}")
     print(f"Gateway  : {host}:{port}  unit_id={unit_id}")
+    print(f"Function : FC{profile.function_code:02d}")
     print(f"Blocks   : {[(b.start, b.count) for b in profile.blocks]}")
     print()
 
@@ -141,7 +142,7 @@ def cmd_read(args: argparse.Namespace) -> None:
     from app.integrations.modbus.driver import read_blocks
 
     try:
-        registers = read_blocks(host, port, unit_id, blocks)
+        registers = read_blocks(host, port, unit_id, blocks, function_code=profile.function_code)
     except ModbusConnectionError as exc:
         print(f"Connection error: {exc}", file=sys.stderr)
         sys.exit(1)

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."""
@@ -543,7 +561,7 @@ def test_patch_meter_no_recompute_when_started_at_not_changed(meters_client):
 
 
 # ---------------------------------------------------------------------------
-# Timeline continuity (integration: no recompute mock)
+# Timeline continuity (recompute mocked to avoid slow computation over empty quarters)
 # ---------------------------------------------------------------------------
 
 
@@ -615,7 +633,7 @@ def test_declare_meter_invalid_reason_returns_422(meters_client):
 
 
 # ---------------------------------------------------------------------------
-# Retroactive recompute: integration (no mock) — window coverage check
+# Retroactive recompute & boundary update (recompute mocked) — window coverage check
 # ---------------------------------------------------------------------------
 
 
@@ -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

@@ -996,35 +996,52 @@ class TestSummarize:
         assert result["period_count"] == 2
         assert result["degraded_count"] == 0
 
-    def test_fixed_costs_zero_for_sub_day_window(self, energy_db: Session) -> None:
-        """Principle C: a 30-minute window within the same local day counts 0 whole days.
+    def test_fixed_costs_one_day_for_sub_day_window(self, energy_db: Session) -> None:
+        """FUE-T01 (symmetric begin/end): a 30-minute window within one local day counts 1 day.
 
-        Fixed costs are only added for elapsed whole local calendar days.
-        A window [10:00, 10:30) UTC stays within the same local calendar date
-        regardless of timezone offset (any UTC-11..UTC+14 range), so no whole
-        day is covered → fixed_costs = 0.
+        Under the symmetric-begin/end fix, fixed charges are assessed on a
+        "service-is-active" basis: if the window falls within a local calendar day,
+        that entire day's charge applies.  The begin side no longer requires a local
+        midnight to fall *inside* the window — the local date of start_utc itself is
+        always counted as the first day.
+
+        Window [10:00, 10:30) UTC in Europe/Amsterdam (CEST = UTC+2):
+          local date of start: June 23 (12:00 CEST)
+          local date of end:   June 23 (12:30 CEST)
+          → first_counted = last_counted = June 23 → 1 day
+          → fixed_costs = (9.87 + 9.87) / 30 × 1
         """
         from zoneinfo import ZoneInfo
+        from unittest.mock import patch
+
         self._setup_two_periods(energy_db)
         # Pin the local timezone so the test is deterministic on any CI host.
-        with __import__("unittest.mock", fromlist=["patch"]).patch.object(
-            tz_module, "local_tz", return_value=ZoneInfo("Europe/Amsterdam")
-        ):
+        with patch.object(tz_module, "local_tz", return_value=ZoneInfo("Europe/Amsterdam")):
             result = summarize(energy_db, _ts(10, 0), _ts(10, 30))
-        assert result["fixed_costs"] == 0.0, (
-            "Sub-day window should contribute 0 whole-day fixed costs under Principle C"
+
+        expected_fixed = (9.87 + 9.87) / 30  # 1 day
+        assert abs(result["fixed_costs"] - expected_fixed) < 1e-9, (
+            f"FUE-T01: sub-day window in one local day should count 1 day of fixed costs; "
+            f"expected {expected_fixed:.6f}, got {result['fixed_costs']}"
         )
 
-    def test_credits_zero_for_sub_day_window(self, energy_db: Session) -> None:
-        """Principle C: a 30-minute window within the same local day counts 0 whole days for credits."""
+    def test_credits_one_day_for_sub_day_window(self, energy_db: Session) -> None:
+        """FUE-T01 (symmetric begin/end): a 30-minute window within one local day counts 1 day of credits.
+
+        Same rationale as test_fixed_costs_one_day_for_sub_day_window.
+        credits = 600.0 / 365 × 1 day.
+        """
         from zoneinfo import ZoneInfo
+        from unittest.mock import patch
+
         self._setup_two_periods(energy_db)
-        with __import__("unittest.mock", fromlist=["patch"]).patch.object(
-            tz_module, "local_tz", return_value=ZoneInfo("Europe/Amsterdam")
-        ):
+        with patch.object(tz_module, "local_tz", return_value=ZoneInfo("Europe/Amsterdam")):
             result = summarize(energy_db, _ts(10, 0), _ts(10, 30))
-        assert result["credits"] == 0.0, (
-            "Sub-day window should contribute 0 whole-day credits under Principle C"
+
+        expected_credits = 600.0 / 365  # 1 day
+        assert abs(result["credits"] - expected_credits) < 1e-9, (
+            f"FUE-T01: sub-day window in one local day should count 1 day of credits; "
+            f"expected {expected_credits:.6f}, got {result['credits']}"
         )
 
     def test_total_payable_formula(self, energy_db: Session) -> None:
@@ -1068,12 +1085,20 @@ class TestSummarize:
         assert result["period_count"] == 0
 
     def test_one_day_summarize_hand_calc(self, energy_db: Session) -> None:
-        """Full 1-day hand-calculation: fixed_costs/30 and credits/365 with 1-day interval.
+        """Full 1-day hand-calculation: fixed_costs/30 and credits/365 with 1-day UTC interval.
 
-        Principle C: the window [2026-06-23 00:00 UTC, 2026-06-24 00:00 UTC) spans
-        exactly one local calendar day in Europe/Amsterdam (CEST=UTC+2: 02:00→02:00).
-        effective_from = June 23 00:00 UTC = June 23 02:00 CEST = local date June 23.
-        Today (2026-06-25) ≥ June 23, so the day is elapsed → 1 day counted.
+        FUE-T01 (symmetric begin/end): the window [2026-06-23 00:00 UTC, 2026-06-24 00:00 UTC)
+        in Europe/Amsterdam (CEST=UTC+2):
+          - local date of start (June 23 00:00 UTC = June 23 02:00 CEST) = June 23
+            → first_counted = June 23 (anchor day always counted)
+          - local midnight of June 24 = June 23 22:00 UTC, which is < end_utc (June 24 00:00 UTC)
+            → last_counted = June 24
+          - today (2026-06-25) ≥ June 24 → cap doesn't apply
+          → 2 local calendar days counted (June 23 + June 24)
+
+        Note: a 1-day UTC window centered at non-midnight UTC spans **two** local days
+        in Amsterdam (CEST=UTC+2) because local midnight (June 23 22:00 UTC) falls
+        inside the window.  This is correct under the symmetric begin/end principle.
         """
         from zoneinfo import ZoneInfo
         from unittest.mock import patch
@@ -1091,12 +1116,18 @@ class TestSummarize:
         with patch.object(tz_module, "local_tz", return_value=ZoneInfo("Europe/Amsterdam")):
             result = summarize(energy_db, start, end)
 
-        # fixed_costs = (9.87 + 9.87) / 30 × 1.0 = 0.658
-        assert abs(result["fixed_costs"] - (9.87 + 9.87) / 30) < 1e-9
-        # credits = 600 / 365
-        assert abs(result["credits"] - 600.0 / 365) < 1e-9
-        # total = 0 + 0.658 − (600/365)
-        expected_total = (9.87 + 9.87) / 30 - 600.0 / 365
+        # 2 local days (June 23 start day + June 24 because local midnight of June 24
+        # = June 23 22:00 UTC falls within [start, end)).
+        n_days = 2
+        assert abs(result["fixed_costs"] - (9.87 + 9.87) / 30 * n_days) < 1e-9, (
+            f"FUE-T01: 1-day UTC window = 2 local days in Amsterdam; "
+            f"expected fixed={((9.87 + 9.87) / 30 * n_days):.6f}, got {result['fixed_costs']}"
+        )
+        assert abs(result["credits"] - 600.0 / 365 * n_days) < 1e-9, (
+            f"FUE-T01: expected credits={600.0 / 365 * n_days:.6f}, got {result['credits']}"
+        )
+        # total = 0 + fixed − credits
+        expected_total = (9.87 + 9.87) / 30 * n_days - 600.0 / 365 * n_days
         assert abs(result["total_payable"] - expected_total) < 1e-9
 
 
@@ -1168,10 +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."""
@@ -1179,10 +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:
-        """Run summarize with Europe/Amsterdam local_tz monkeypatched."""
+    def _run_summarize_ams(
+        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:
@@ -1228,7 +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)
@@ -1236,7 +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
@@ -1273,8 +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)
@@ -1282,7 +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
@@ -1335,8 +1397,12 @@ 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()):
-            result = summarize(energy_db, start, end)
+            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
         expected_fixed = 24 * 12 / 30 + 1 * 24 / 30
@@ -1377,12 +1443,16 @@ 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()):
-            result = summarize(energy_db, start, end)
+            with patch.object(_ec, "local_now", return_value=pinned_now):
+                result = summarize(energy_db, start, end)
 
         # Only 1 day at V2 rate
         expected_fixed = 1 * 24 / 30
@@ -1390,6 +1460,120 @@ class TestSummarizePrincipleC:
         assert abs(result["fixed_costs"] - expected_fixed) < 1e-9
         assert abs(result["credits"] - expected_credits) < 1e-9
 
+    def test_morning_anchor_first_day_counted(self, energy_db: Session) -> None:
+        """FUE-T01: anchor falling above local midnight counts its local day as day 1.
+
+        Bug scenario: meter.started_at = June 24 09:18 local time (07:18 UTC, CEST=UTC+2).
+        Old code: local_date(07:18 UTC) = June 24; _lmu(June 24) = June 23 22:00 UTC;
+          June 23 22:00 UTC < June 24 07:18 UTC → False (22:00 < 07:18? No — 22:00 UTC June 23 is
+          *before* 07:18 UTC June 24; so the condition >= start_utc was False);
+          first_counted bumped to June 25. June 24's charges were silently dropped.
+
+        Fix: first_counted = local_date(start_utc) = June 24 always, regardless of where
+          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)).
+        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.
+        """
+        eff_utc = _ams_midnight(2026, 6, 1)
+        self._make_single_version_contract(energy_db, effective_from_utc=eff_utc)
+
+        # anchor = June 24 07:18 UTC = June 24 09:18 CEST (above local midnight)
+        anchor_utc = datetime(2026, 6, 24, 7, 18, 0, tzinfo=_UTC)
+        # 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)
+
+        # Pin local_now to June 25 noon AMS: today=June 25, settled_cap=June 25.
+        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
+        # June 24 (anchor day) + June 25 (today) = 2 days
+        assert abs(result["fixed_costs"] - daily_fixed * 2) < 1e-9, (
+            f"FUE-T01: morning anchor should count anchor day + today = 2 days of fixed costs; "
+            f"expected {daily_fixed * 2:.6f}, got {result['fixed_costs']}"
+        )
+        assert abs(result["credits"] - daily_credit * 2) < 1e-9, (
+            f"FUE-T01: morning anchor should count anchor day + today = 2 days of credits; "
+            f"expected {daily_credit * 2:.6f}, got {result['credits']}"
+        )
+
+    def test_daily_window_midnight_aligned_unaffected(self, energy_db: Session) -> None:
+        """FUE-T01: the daily getter window [today midnight, tomorrow midnight) is not affected.
+
+        The *_today getters use windows exactly aligned to local midnight:
+          start = local_midnight_utc(today) = June 24 22:00 UTC (for June 25 local)
+          end   = local_midnight_utc(tomorrow) = June 25 22:00 UTC
+
+        With either old or new logic, first_counted = June 25 (today):
+          - Old: local_date(June 24 22:00 UTC in Amsterdam) = June 25;
+                 _lmu(June 25) = June 24 22:00 UTC >= June 24 22:00 UTC → True → first = June 25.
+          - New: first_counted = local_date(June 24 22:00 UTC) = June 25.
+        Both give the same result: 1 day counted.
+
+        This test explicitly verifies daily window behaviour is unchanged.
+        """
+        from unittest.mock import patch
+
+        eff_utc = _ams_midnight(2026, 6, 1)
+        self._make_single_version_contract(energy_db, effective_from_utc=eff_utc)
+
+        # Today's window aligned to local midnight (June 25 CEST = June 24 22:00 UTC).
+        today_start_utc = _ams_midnight(2026, 6, 25)   # June 24 22:00 UTC
+        tomorrow_start_utc = _ams_midnight(2026, 6, 26)  # June 25 22:00 UTC
+
+        with patch.object(tz_module, "local_tz", return_value=_ams()):
+            result = self._run_summarize_ams(energy_db, today_start_utc, tomorrow_start_utc)
+
+        daily_fixed = (9.87 + 9.87) / 30
+        daily_credit = 600.0 / 365
+        # Exactly 1 day counted (June 25 only; June 26 is future, capped).
+        assert abs(result["fixed_costs"] - daily_fixed * 1) < 1e-9, (
+            f"FUE-T01: daily window should count exactly 1 day; "
+            f"expected {daily_fixed:.6f}, got {result['fixed_costs']}"
+        )
+        assert abs(result["credits"] - daily_credit * 1) < 1e-9, (
+            f"FUE-T01: daily window should count exactly 1 day of credits; "
+            f"expected {daily_credit:.6f}, got {result['credits']}"
+        )
+
+    def test_single_day_morning_anchor_counts_one_day(self, energy_db: Session) -> None:
+        """FUE-T01: a window starting mid-morning on a single local day counts that 1 day.
+
+        Window: [June 24 08:00 UTC (= 10:00 CEST), June 24 22:00 UTC (= June 25 00:00 CEST)).
+        Both endpoints resolve to June 24 local (end is exactly midnight of June 25,
+        which is June 24 22:00 UTC, so _lmu(June 25) = June 24 22:00 UTC is NOT < end_utc
+        but equal → last_counted = June 24).
+        first_counted = June 24.
+        n_days = 1.  Today (June 25) is past June 24 → elapsed.
+        """
+        from unittest.mock import patch
+
+        eff_utc = _ams_midnight(2026, 6, 1)
+        self._make_single_version_contract(energy_db, effective_from_utc=eff_utc)
+
+        start_utc = datetime(2026, 6, 24, 8, 0, 0, tzinfo=_UTC)     # 10:00 CEST = mid-morning June 24
+        end_utc = datetime(2026, 6, 24, 22, 0, 0, tzinfo=_UTC)       # = June 25 00:00 CEST midnight
+
+        with patch.object(tz_module, "local_tz", return_value=_ams()):
+            result = self._run_summarize_ams(energy_db, start_utc, end_utc)
+
+        daily_fixed = (9.87 + 9.87) / 30
+        daily_credit = 600.0 / 365
+        # Exactly 1 day: June 24 (start day, counted as full day; elapsed since today is June 25).
+        assert abs(result["fixed_costs"] - daily_fixed * 1) < 1e-9, (
+            f"FUE-T01: mid-morning to midnight window on one day should count 1 day; "
+            f"expected {daily_fixed:.6f}, got {result['fixed_costs']}"
+        )
+        assert abs(result["credits"] - daily_credit * 1) < 1e-9, (
+            f"FUE-T01: mid-morning to midnight window on one day should count 1 day of credits; "
+            f"expected {daily_credit:.6f}, got {result['credits']}"
+        )
+
 
 # ---------------------------------------------------------------------------
 # 8. compute_closed_periods
@@ -2263,3 +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
-    (4 original + 2 daily) regardless of device state, so the catalog will not be empty.
-    This test checks that no *modbus* entities are present when there are no enabled
-    modbus devices.
+    FUE-T05: the energy_cost provider now requires an active electricity meter.
+    Without one, it returns [] and the catalog contains no energy entities.
+    With one, it produces 6 entities.
+
+    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).
-    energy_keys = {e.entity.key for e in catalog if e.entity.key.startswith("energy.")}
-    assert len(energy_keys) == 6, (
-        f"Expected exactly 6 energy_cost entities (4 original + 2 daily), got {energy_keys!r}"
+    # No active electricity meter → energy-cost provider returns [] → no energy entities.
+    energy_keys_no_meter = {e.entity.key for e in catalog if e.entity.key.startswith("energy.")}
+    assert len(energy_keys_no_meter) == 0, (
+        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

tests/test_modbus_driver.py

@@ -217,6 +217,57 @@ class TestReadBlocks:
 
         mock_client.close.assert_called_once()
 
+    @patch("app.integrations.modbus.driver.ModbusTcpClient")
+    def test_default_function_code_uses_fc04_input_registers(
+        self, mock_client_cls: MagicMock
+    ) -> None:
+        """With no function_code given, read_blocks uses FC04 (read_input_registers)."""
+        mock_client = MagicMock()
+        mock_client_cls.return_value = mock_client
+        mock_client.connect.return_value = True
+        mock_client.read_input_registers.return_value = _make_ok_response([0x4366, 0x3334])
+
+        read_blocks("127.0.0.1", 502, 1, [{"start": 0x0000, "count": 2}])
+
+        mock_client.read_input_registers.assert_called_once_with(0x0000, count=2, device_id=1)
+        mock_client.read_holding_registers.assert_not_called()
+
+    @patch("app.integrations.modbus.driver.ModbusTcpClient")
+    def test_function_code_3_uses_fc03_holding_registers(
+        self, mock_client_cls: MagicMock
+    ) -> None:
+        """function_code=3 dispatches FC03 (read_holding_registers), e.g. DDSU666."""
+        mock_client = MagicMock()
+        mock_client_cls.return_value = mock_client
+        mock_client.connect.return_value = True
+        mock_client.read_holding_registers.return_value = _make_ok_response(
+            [0x4366, 0x3334, 0x3F80, 0x0000]
+        )
+
+        blocks = [{"start": 0x2000, "count": 4}]
+        result = read_blocks("127.0.0.1", 502, 1, blocks, function_code=3)
+
+        assert result == {0x2000: 0x4366, 0x2001: 0x3334, 0x2002: 0x3F80, 0x2003: 0x0000}
+        mock_client.read_holding_registers.assert_called_once_with(
+            0x2000, count=4, device_id=1
+        )
+        mock_client.read_input_registers.assert_not_called()
+
+    @patch("app.integrations.modbus.driver.ModbusTcpClient")
+    def test_invalid_function_code_raises_before_connecting(
+        self, mock_client_cls: MagicMock
+    ) -> None:
+        """An unsupported function code is rejected without opening a connection."""
+        mock_client = MagicMock()
+        mock_client_cls.return_value = mock_client
+
+        with pytest.raises(ModbusDriverError, match="Unsupported read function code"):
+            read_blocks("127.0.0.1", 502, 1, [{"start": 0, "count": 2}], function_code=16)
+
+        # No client should have been constructed or connected for a bad FC.
+        mock_client_cls.assert_not_called()
+        mock_client.connect.assert_not_called()
+
     @patch("app.integrations.modbus.driver.ModbusTcpClient")
     def test_unit_id_passed_as_device_id(self, mock_client_cls: MagicMock) -> None:
         """unit_id is forwarded as device_id= keyword argument (pymodbus 3.13.x)."""