chore(frontend): regenerate API schema after sell_fee docstring change

d07a083 changed the /api/energy/prices docstring (sell now deducts sell_fee)
and refreshed openapi/openapi.json, but frontend/src/api/schema.d.ts was not
regenerated, so CI's "check codegen is in sync" step failed. Comment-only diff.

app/api/routes/api/energy.py

@@ -169,7 +169,7 @@ def get_prices(
 
         Response ``points`` carries per-slot:
         - ``buy  = total``              (Tibber all-inclusive price)
-        - ``sell = total − energy_tax − sell_adjust``  (from active version values)
+        - ``sell = total − energy_tax − sell_fee − sell_adjust``  (from active version values)
         - ``level``                     (Tibber price level, may be null)
 
         ``tariff`` is null.
@@ -222,7 +222,8 @@ def get_prices(
         )
         rows = list(reversed(db.execute(stmt).scalars().all()))
 
-        # Derive sell price per-point using version values (energy_tax + sell_adjust).
+        # Derive sell price per-point using version values
+        # (energy_tax + sell_fee + sell_adjust).
         from decimal import Decimal
 
         def _d(v: Any) -> Decimal:
@@ -230,12 +231,13 @@ def get_prices(
 
         energy = version.values.get("energy", {}) if version.values else {}
         energy_tax = _d(energy.get("energy_tax", 0))
+        sell_fee = _d(energy.get("sell_fee", 0))
         sell_adjust = _d(energy.get("sell_adjust", 0))
 
         points = []
         for row in rows:
             total = _d(row.total)
-            sell = float(total - energy_tax - sell_adjust)
+            sell = float(total - energy_tax - sell_fee - sell_adjust)
             points.append(
                 PricePointSchema(
                     starts_at=_as_utc(row.starts_at),

app/integrations/pricing/profiles.py

@@ -123,6 +123,7 @@ class ManualProfile(BaseModel):
 class TibberEnergySpec(BaseModel):
     source: str  # must be "tibber_api"
     energy_tax: FieldSpec  # subtracted from total to derive sell price
+    sell_fee: FieldSpec  # verkoopvergoeding (feed-in fee); always subtracted from sell; default 0.0248
     sell_adjust: FieldSpec  # additional sell-price adjustment; default 0
 
 
@@ -268,10 +269,13 @@ def _fill_defaults_manual(values: dict[str, Any], profile: ManualProfile) -> dic
 
 
 def _fill_defaults_tibber(values: dict[str, Any], profile: TibberProfile) -> dict[str, Any]:
-    """Return a copy of *values* with sell_adjust and management_fee defaults applied."""
+    """Return a copy of *values* with sell_fee, sell_adjust and management_fee defaults applied."""
     filled = dict(values)
 
     energy = dict(filled.get("energy", {}))
+    # Apply default for sell_fee (default=0.0248) if absent.
+    if "sell_fee" not in energy and profile.energy.sell_fee.default is not None:
+        energy["sell_fee"] = profile.energy.sell_fee.default
     # Apply default for sell_adjust (default=0) if absent.
     if "sell_adjust" not in energy and profile.energy.sell_adjust.default is not None:
         energy["sell_adjust"] = profile.energy.sell_adjust.default
@@ -347,6 +351,7 @@ def _validate_tibber_values(values: dict[str, Any], profile: TibberProfile) -> d
 
     # Required energy fields.
     _require_numeric("energy", "energy_tax", energy)
+    _require_numeric("energy", "sell_fee", energy)
     _require_numeric("energy", "sell_adjust", energy)
     # Required standing fields.
     _require_numeric("standing", "management_fee", standing)
@@ -361,9 +366,10 @@ def validate_values(kind: str, values: dict[str, Any]) -> dict[str, Any]:
     """Validate a contract-values dict against the named profile structure.
 
     Fields that carry a ``default`` in the profile (e.g. ``ode``,
-    ``sell_adjust``, tibber ``management_fee``) are silently filled in when
-    absent from *values*.  Fields with no default that are absent, or fields
-    whose value is not a number, cause a ``ProfileValidationError``.
+    ``sell_fee``, ``sell_adjust``, tibber ``management_fee``) are silently
+    filled in when absent from *values*.  Fields with no default that are
+    absent, or fields whose value is not a number, cause a
+    ``ProfileValidationError``.
 
     Parameters
     ----------

app/integrations/pricing/profiles/tibber.yaml

@@ -2,9 +2,10 @@ kind: tibber
 label: Tibber 动态电价（15 分钟）
 
 energy:
-  source: tibber_api              # buy = total (from API); sell = total − energy_tax − sell_adjust
+  source: tibber_api              # buy = total (from API); sell = total − energy_tax − sell_fee − sell_adjust
   energy_tax:  { unit: EUR/kWh }  # subtracted from total to derive sell price (incl. VAT)
-  sell_adjust: { unit: EUR/kWh, default: 0 }  # additional sell-price adjustment (residual spread)
+  sell_fee:    { unit: EUR/kWh, default: 0.0248 }  # verkoopvergoeding (feed-in fee, incl. VAT); always subtracted from sell
+  sell_adjust: { unit: EUR/kWh, default: 0 }  # manual sell-price adjustment; net-metering: set = −energy_tax to refund the tax
 
 standing:                         # fixed charges; UI fills per month, engine prorates to days
   management_fee: { unit: EUR/month, default: 5.99 }

app/integrations/pricing/strategies.py

@@ -209,12 +209,23 @@ def _tibber_strategy(
         query on ``starts_at``.
 
     Formula (§3.4):
-    - ``buy  = total`` (Tibber's all-inclusive price, already includes tax)
-    - ``sell = total − energy_tax − sell_adjust``
+    - ``buy  = total`` (Tibber's all-inclusive price; already includes energy
+      tax, VAT and the buy-side ``inkoopvergoeding``)
+    - ``sell = total − energy_tax − sell_fee − sell_adjust``
     - ``import_cost   = (Δd1 + Δd2) × buy``
     - ``export_revenue = (Δr1 + Δr2) × sell``
     - ``net_cost = import_cost − export_revenue``
 
+    ``sell_fee`` models Tibber's per-kWh **verkoopvergoeding** (feed-in fee,
+    €0.0248/kWh incl. VAT since 2026-01-01).  It is always deducted from the
+    feed-in payout: even under the net-metering (saldering) scheme, Tibber pays
+    ``total − verkoopvergoeding`` per returned kWh (Tibber NL: "€0,28 − €0,0248
+    = €0,2552").  ``total`` already contains the equal buy-side
+    ``inkoopvergoeding``, so the two fees do **not** cancel — the feed-in price
+    sits ``sell_fee`` below the buy price.  ``sell_adjust`` is a separate manual
+    correction: under net metering it carries back the refunded energy tax
+    (``sell_adjust = −energy_tax``), leaving ``sell = total − sell_fee``.
+
     Tibber does not differentiate tariff slots (dal vs normal) — the 15-minute
     API price applies to the full delivered/returned volume.
 
@@ -248,11 +259,12 @@ def _tibber_strategy(
 
     energy = values.get("energy", {})
     energy_tax = _to_decimal(energy.get("energy_tax", 0))
+    sell_fee = _to_decimal(energy.get("sell_fee", 0))
     sell_adjust = _to_decimal(energy.get("sell_adjust", 0))
 
     total = _to_decimal(price_row.total)
     buy = total
-    sell = total - energy_tax - sell_adjust
+    sell = total - energy_tax - sell_fee - sell_adjust
 
     total_delivered = deltas.d1 + deltas.d2
     total_returned = deltas.r1 + deltas.r2
@@ -269,6 +281,7 @@ def _tibber_strategy(
         "buy": str(buy),
         "sell": str(sell),
         "energy_tax": str(energy_tax),
+        "sell_fee": str(sell_fee),
         "sell_adjust": str(sell_adjust),
     }
 

docs/design/m6-tibber-dynamic-energy.md

@@ -118,8 +118,9 @@ credits:
 kind: tibber
 label: Tibber 动态电价（15 分钟）
 energy:
-  source: tibber_api             # buy = total; sell = total − energy_tax − sell_adjust
+  source: tibber_api             # buy = total; sell = total − energy_tax − sell_fee − sell_adjust
   energy_tax:   { unit: EUR/kWh }
+  sell_fee:     { unit: EUR/kWh, default: 0.0248 }  # verkoopvergoeding, always subtracted
   sell_adjust:  { unit: EUR/kWh, default: 0 }
 standing:
   management_fee: { unit: EUR/month, default: 5.99 }
@@ -164,7 +165,7 @@ credits:
   1. 取各寄存器在 `t0`/`t1` 的值（`recorded_at ≤ 边界` 的最后一行，Decimal），算 **per-register 差**：`Δd1,Δd2,Δr1,Δr2`。
   2. 取 active 合同**在 t0 生效的版本** + 其 strategy：
      - `manual`：`import_cost = Δd1×(buy_dal) + Δd2×(buy_normal)`（`buy_x = energy_buy_x + energy_tax + ode`）；`export_revenue = Δr1×sell_dal + Δr2×sell_normal`。
-     - `tibber`：取覆盖 t0 的 `tibber_price`（`starts_at ≤ t0` 最近一条）；`buy = total`、`sell = total − energy_tax − sell_adjust`；`import_cost = (Δd1+Δd2)×buy`、`export_revenue = (Δr1+Δr2)×sell`。
+     - `tibber`：取覆盖 t0 的 `tibber_price`（`starts_at ≤ t0` 最近一条）；`buy = total`、`sell = total − energy_tax − sell_fee − sell_adjust`（`sell_fee`=verkoopvergoeding，默认 0.0248，见下修正说明）；`import_cost = (Δd1+Δd2)×buy`、`export_revenue = (Δr1+Δr2)×sell`。
   3. `net_cost = import_cost − export_revenue`；**upsert** `energy_cost_period`，**快照**当时用的价 + `contract_version_id`。
 - 缺价/缺数据：跳过或标 `degraded`，留待重算。**不做净计量**（进出口分开累加）。
 
@@ -240,7 +241,7 @@ credits:
 
 1. **两层电价模型**：profile YAML 定结构（仓库、固定、UI 不可编辑）+ `EnergyContract`(+版本) 存数值（UI 填、版本化）+ strategy 按 kind 出价。仿 M5。
 2. **kind 不叫 "fixed"**：`manual`（人工填、可双费率、可带时段）/ `tibber`（API 动态）；合同 `name` UI 自由填。
-3. **买价**：tibber = API `total`（全包，已证 total=energy+tax）；manual = `energy_buy_档 + energy_tax`。**卖价**：tibber = `total − energy_tax − sell_adjust`；manual = `sell_档`（回送价，无能源税）。均含 VAT。
+3. **买价**：tibber = API `total`（全包，已证 total=energy+tax；含 inkoopvergoeding）；manual = `energy_buy_档 + energy_tax`。**卖价**：tibber = `total − energy_tax − sell_fee − sell_adjust`（`sell_fee`=verkoopvergoeding 默认 0.0248）；manual = `sell_档`（回送价，无能源税）。均含 VAT。
 4. **双费率**：manual 用 `delivered_1/2`、`returned_1/2` 分 dal/normal 计价（`_1`=dal/低、`_2`=normal/高）；tibber 求和、15min 价不分档。
 5. **两层费用**：每 15min `energy_cost_period` 只算计量电费（不可变、快照价）；日/月/年汇总再加固定费（按月→天）− heffingskorting（按年→天）。
 6. **回送阶梯罚金（terugleverkosten）不做**：按自然年累计、用户住不到年底算不准——不算、不记、不加功能（留痕见 §10）。
@@ -475,7 +476,7 @@ Phase D（API + 前端）
 ## 13. 待确认 / TODO（拿到真实 token + 账单后钉死，均已落成配置/默认值，不阻塞实现）
 
 1. **买价**：✅ tibber = API `total`（demo 已证 total=energy+tax）；manual = energy_buy_档 + energy_tax。无待办。
-2. **卖价残差（tibber）**：`sell = total − energy_tax − sell_adjust`，`sell_adjust` 默认 0（买卖费相等抵消）。真实账单确认后若有残差再调。
+2. **卖价残差（tibber）**：~~`sell = total − energy_tax − sell_adjust`，`sell_adjust` 默认 0（买卖费相等抵消）~~ → **已修正（2026-07，见 references §3.1）**：`total` 含 inkoopvergoeding，净计量回送 = `total − verkoopvergoeding`，两费**不抵消**。公式改为 `sell = total − energy_tax − sell_fee − sell_adjust`，新增 `sell_fee`（默认 0.0248，始终扣除）；`sell_adjust` 净计量期设 `−energy_tax`。真实账单确认后若有残差再调 `sell_fee`。
 3. **双费率寄存器映射**：`_1`=dal/低、`_2`=normal/高（NL 惯例）——接价前用真实数据确认别接反（差价小但要对）。
 4. **能源税年值**：manual/tibber 的 `energy_tax` 默认 ~0.1108（2026 第一档含 VAT），按当年实际值核。
 5. **Tibber 15min + 币种**：✅ 查询/分辨率已 demo 证实；仍需合同生效后用**真实 token** 确认 NL 返回真 15 分钟价 + 币种 EUR。

docs/references/Tibber-and-NL-Energy-Pricing.md

@@ -113,16 +113,26 @@ curl -s -X POST https://api.tibber.com/v1-beta/gql \
 > "De verkoopvergoeding van 2,48 cent is gelijk aan de inkoopvergoeding die je bij je afgenomen stroom betaalt."
 > （卖侧 verkoopvergoeding 2.48 分 = 买侧 inkoopvergoeding。）
 
-→ **买卖服务费相等（均 €0.0248/kWh）**，在买卖里一进一出**相互抵消**。
+→ **买卖服务费金额相等（均 €0.0248/kWh），但两者对住户都是成本、不互相抵消**：
+- 买侧 inkoopvergoeding 已经**包含在 Tibber API 的 `total` 里**（见下 §3.1 的实证拆解），买电按 `total` 计价即已含它。
+- 卖侧 verkoopvergoeding 则是从回送价里**额外扣掉**的一笔——所以回送价 = `total − 0.0248`，比买价低 0.0248/kWh。
+- ⚠️ **早期版本误判为"一进一出抵消 → 回送=total"**，这是错的：`total` 里那笔 inkoopvergoeding 不会退回来充抵 verkoopvergoeding。代码里用 `energy.sell_fee`（默认 0.0248）建模这笔卖侧费用。
 
 ---
 
 ## 3. 净计量（saldering）、回送（teruglevering）、负电价、2027
 
-### 3.1 回送价（净计量期内，文档原文）
+### 3.1 回送价（净计量期内，文档原文 + 实证）
 > "Op het moment dat je teruglevert geven we je per kWh de beursprijs die op dat moment geldt …, inclusief energiebelasting en inkoopvergoeding plus de btw minus de verkoopvergoeding."
 
-即净计量期内回送价 = `beursprijs + energiebelasting + inkoopvergoeding + btw − verkoopvergoeding`。因 inkoopvergoeding = verkoopvergoeding 抵消 → **= 全额零售价**（spot+能源税+VAT），正是 saldering "回送 1 度 = 用 1 度"的本质。
+> **Worked example（Tibber NL 原文）**："Stel dat tussen 14:00 en 14:15 de totale stroomprijs €0,28 per kWh incl. is, dan krijg je €0,28 − €0,0248 verkoopvergoeding = **€0,2552** per teruggeleverde kWh terug."
+
+即净计量期内回送价 = `beursprijs + energiebelasting + inkoopvergoeding + btw − verkoopvergoeding`，而官方例子直接写成 **`回送价 = totale stroomprijs − verkoopvergoeding = total − 0.0248`**。能源税**退回**（留在 total 里没动），只有 verkoopvergoeding 这 0.0248 被扣。
+
+**✅ 实证（本项目生产库，2026-07-20 三个刻钟）**：按 21% VAT 拆 `total`：`total = 现货×1.21 + energiebelasting(0.11085) + inkoopvergoeding(0.0248)`，三段解出的 inkoop 都精确等于 **0.0248**。→ **我们存的 `tibber_price.total` 就是官方 "totale stroomprijs"（含 inkoopvergoeding 的买价）**，因此：
+- 买价 `buy = total`（已含 inkoopvergoeding，正确）。
+- 净计量回送价 `sell = total − verkoopvergoeding = total − 0.0248`。
+- ⚠️ 所以 saldering 下"回送 1 度"仍比"用 1 度"少 0.0248——**不是完全 1:1**。代码用 `sell_fee` 建模这笔扣减，`sell_adjust` 只负责在净计量期把能源税补回（`sell_adjust = −energy_tax`）。
 
 ### 3.2 年末盈余 / 取消净计量后（文档原文，Scenario 2）
 > "Voor de overproductie van 500 kWh heb je recht op de beursprijs en de inkoopvergoeding, maar heb je geen recht op de energiebelasting. … ontvang je nog een factuur van ons voor de te veel uitgekeerde belastingen …"
@@ -146,9 +156,11 @@ curl -s -X POST https://api.tibber.com/v1-beta/gql \
 
 > spot 取 API `energy`；`total = energy + tax`（全包）。**买价直接用 `total`**，卖价从 `total` 扣掉卖电不交的能源税。
 
-- **Tibber 动态合同**（post-2027 口径）：
-  - 买价 `buy = price.total`
-  - 卖价 `sell = price.total − energy_tax_per_kwh − sell_adjust`（`sell_adjust` 默认 0；含 VAT 归己；买卖费抵消已隐含在 total 里）
+- **Tibber 动态合同**：
+  - 买价 `buy = price.total`（含 energy_tax + VAT + inkoopvergoeding）
+  - 卖价 `sell = price.total − energy_tax − sell_fee − sell_adjust`
+    - `sell_fee`：verkoopvergoeding（卖侧上网费，默认 **0.0248**，含 VAT），**始终扣除**——即使净计量期也扣（见 §3.1）。
+    - `sell_adjust`：手动修正项（默认 0）。**净计量期**设为 `−energy_tax`（把能源税补回），得 `sell = total − sell_fee`；**2027 取消净计量后**设为 0，得 `sell = total − energy_tax − sell_fee`（无能源税、纯市场价再扣上网费）。
 - **固定合同（manual，双费率）**：
   - 买价 `buy_档 = energy_buy_档 + energy_tax`（档 ∈ {normal, dal}）
   - 卖价 `sell_档 = sell_档`（回送价，**无能源税**）
@@ -242,7 +254,7 @@ extra_device_timestamp, extra_device_delivered           # 燃气表（m³，每
 ## 8. 待真实数据核对（合同生效后用真实 token / 账单）
 
 1. **真实 token 复核**：跑 §1.4 的 15 分钟 curl，确认 NL 返回**真** 15 分钟价（非重复小时价）+ 币种 EUR。
-2. **卖价残差**：确认 `total` 里 purchase fee 是否被卖侧 sales fee 完全抵掉、回送 VAT 口径 → 调 `sell_adjust`（默认 0）。
+2. ~~**卖价残差**：确认 `total` 里 purchase fee 是否被卖侧 sales fee 完全抵掉~~ → **已核实（2026-07）**：`total` 含 inkoopvergoeding（0.0248），净计量回送价 = `total − verkoopvergoeding(0.0248)`，两费**不抵消**；代码以 `sell_fee`（默认 0.0248）建模。仍待真实账单核对 `sell_fee` / VAT 口径的最终残差。
 3. **双费率寄存器映射**：确认 `_1`=dal/`_2`=normal 没接反（差价小但要对）。
 4. **能源税年值**：按当年实际值与年用电档位核 `energy_tax`。
 5. **固定合同数值**：回送两档价、电网费、heffingskorting 待用户从账单填。

frontend/src/api/schema.d.ts

@@ -261,7 +261,7 @@ export interface paths {
          *
          *         Response ``points`` carries per-slot:
          *         - ``buy  = total``              (Tibber all-inclusive price)
-         *         - ``sell = total − energy_tax − sell_adjust``  (from active version values)
+         *         - ``sell = total − energy_tax − sell_fee − sell_adjust``  (from active version values)
          *         - ``level``                     (Tibber price level, may be null)
          *
          *         ``tariff`` is null.

frontend/src/energy/TibberPrices.test.tsx

@@ -6,10 +6,14 @@
  * 2. Empty state (no active contract / no kind).
  * 3. Renders tibber chart when tibber kind data is available.
  * 4. Shows tariff table for manual kind.
+ * 5. Marks the currently active price slot (dot + caption).
+ * 6. Hovering past midnight resolves tomorrow's slot, not today's (regression).
+ * 7. buildChartRows: unique X keys across midnight.
+ * 8. findActiveSlotIndex: which slot is currently active.
  */
 
-import { describe, it, expect, vi, beforeEach } from 'vitest'
-import { screen, waitFor } from '@testing-library/react'
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+import { screen, waitFor, fireEvent } from '@testing-library/react'
 import { renderWithProviders } from '../test-utils'
 
 // ---------------------------------------------------------------------------
@@ -42,7 +46,107 @@ vi.mock('../api/client', () => ({
 // Import component
 // ---------------------------------------------------------------------------
 
-import { TibberPrices } from './TibberPrices'
+import { TibberPrices, buildChartRows, findActiveSlotIndex } from './TibberPrices'
+
+// ---------------------------------------------------------------------------
+// Chart size harness
+//
+// jsdom reports every element as 0x0, so Recharts renders an empty plot and no
+// pointer interaction is possible. These helpers hand the chart a fixed size:
+// - the ResponsiveContainer gets 800x300 from its bounding rect + a ResizeObserver
+//   that reports the same size,
+// - the chart wrapper reports 800x260 (the height the component asks for), which
+//   is what Recharts uses to translate clientX/clientY into chart coordinates,
+// - everything else stays 0x0 so the legend does not eat the whole plot area.
+// ---------------------------------------------------------------------------
+
+const CHART_W = 800
+const CONTAINER_H = 300
+const CHART_H = 260
+
+function fakeRect(width: number, height: number): DOMRect {
+  return {
+    x: 0,
+    y: 0,
+    left: 0,
+    top: 0,
+    right: width,
+    bottom: height,
+    width,
+    height,
+    toJSON: () => {},
+  } as DOMRect
+}
+
+const originalResizeObserver = globalThis.ResizeObserver
+const offsetWidthDescriptor = Object.getOwnPropertyDescriptor(
+  HTMLElement.prototype,
+  'offsetWidth',
+)
+const offsetHeightDescriptor = Object.getOwnPropertyDescriptor(
+  HTMLElement.prototype,
+  'offsetHeight',
+)
+
+function installChartSize() {
+  vi.spyOn(Element.prototype, 'getBoundingClientRect').mockImplementation(function (this: Element) {
+    if (this.classList.contains('recharts-responsive-container')) {
+      return fakeRect(CHART_W, CONTAINER_H)
+    }
+    if (this.classList.contains('recharts-wrapper')) return fakeRect(CHART_W, CHART_H)
+    return fakeRect(0, 0)
+  })
+
+  // Recharts divides rect size by offset size to undo CSS transform scaling;
+  // matching them keeps the scale factor at 1.
+  Object.defineProperty(HTMLElement.prototype, 'offsetWidth', {
+    configurable: true,
+    value: CHART_W,
+  })
+  Object.defineProperty(HTMLElement.prototype, 'offsetHeight', {
+    configurable: true,
+    value: CHART_H,
+  })
+
+  globalThis.ResizeObserver = class implements ResizeObserver {
+    private readonly cb: ResizeObserverCallback
+    constructor(cb: ResizeObserverCallback) {
+      this.cb = cb
+    }
+    observe() {
+      this.cb(
+        [{ contentRect: { width: CHART_W, height: CONTAINER_H } } as ResizeObserverEntry],
+        this,
+      )
+    }
+    unobserve() {}
+    disconnect() {}
+  }
+}
+
+function restoreChartSize() {
+  globalThis.ResizeObserver = originalResizeObserver
+  if (offsetWidthDescriptor) {
+    Object.defineProperty(HTMLElement.prototype, 'offsetWidth', offsetWidthDescriptor)
+  }
+  if (offsetHeightDescriptor) {
+    Object.defineProperty(HTMLElement.prototype, 'offsetHeight', offsetHeightDescriptor)
+  }
+}
+
+/** Hourly price points, one per hour starting at `startUtc`, with unique prices. */
+function hourlyPoints(startUtc: number, count: number) {
+  return Array.from({ length: count }, (_, i) => ({
+    starts_at: new Date(startUtc + i * 3600_000).toISOString(),
+    buy: 0.1 + i / 1000,
+    sell: 0.05 + i / 1000,
+    level: 'NORMAL',
+  }))
+}
+
+function tooltipText(): string {
+  return document.querySelector('.recharts-tooltip-wrapper')?.textContent ?? ''
+}
 
 // ---------------------------------------------------------------------------
 // Tests
@@ -50,6 +154,10 @@ import { TibberPrices } from './TibberPrices'
 
 describe('TibberPrices', () => {
   beforeEach(() => vi.clearAllMocks())
+  afterEach(() => {
+    vi.restoreAllMocks()
+    restoreChartSize()
+  })
 
   it('renders loading state initially', () => {
     mockGet.mockImplementation(() => new Promise(() => {}))
@@ -135,4 +243,146 @@ describe('TibberPrices', () => {
     expect(screen.getByTestId('tariff-sell-normal')).toHaveTextContent('0.0900')
     expect(screen.getByTestId('tariff-sell-dal')).toHaveTextContent('0.0900')
   })
+
+  it('marks the currently active price slot with a dot and a caption', async () => {
+    installChartSize()
+
+    const SLOT_MS = 15 * 60 * 1000
+    // Start of the quarter-hour slot that contains "now".
+    const currentSlot = Math.floor(Date.now() / SLOT_MS) * SLOT_MS
+
+    mockGet.mockResolvedValue({
+      data: {
+        kind: 'tibber',
+        currency: 'EUR',
+        points: [
+          { starts_at: new Date(currentSlot - SLOT_MS).toISOString(), buy: 0.11, sell: 0.05 },
+          { starts_at: new Date(currentSlot).toISOString(), buy: 0.2431, sell: 0.1102 },
+          { starts_at: new Date(currentSlot + SLOT_MS).toISOString(), buy: 0.31, sell: 0.15 },
+        ],
+        tariff: null,
+      },
+    })
+
+    renderWithProviders(<TibberPrices />)
+
+    await waitFor(() => {
+      expect(screen.getByTestId('tibber-current-price')).toBeInTheDocument()
+    })
+
+    const marker = screen.getByTestId('tibber-current-price')
+    expect(marker).toHaveTextContent('0.2431')
+    expect(marker).toHaveTextContent('0.1102')
+
+    // One dot on the buy line, one on the sell line — visible without hovering.
+    await waitFor(() => {
+      expect(document.querySelectorAll('.recharts-reference-dot')).toHaveLength(2)
+    })
+  })
+
+  it('resolves the hovered slot past midnight to tomorrow, not today', async () => {
+    installChartSize()
+
+    // 26 hourly points starting at 2020-01-01T00:00Z, so "00:00" and "01:00"
+    // each appear twice. Fixed past dates keep the "now" marker out of range.
+    const points = hourlyPoints(Date.UTC(2020, 0, 1), 26)
+
+    mockGet.mockResolvedValue({
+      data: { kind: 'tibber', currency: 'EUR', points, tariff: null },
+    })
+
+    renderWithProviders(<TibberPrices />)
+
+    await waitFor(() => expect(screen.getByTestId('tibber-chart')).toBeInTheDocument())
+    expect(screen.queryByTestId('tibber-current-price')).not.toBeInTheDocument()
+
+    const wrapper = document.querySelector('.recharts-wrapper')
+    expect(wrapper).not.toBeNull()
+
+    // Right edge of the plot area = the last slot (day 2, 01:00, buy 0.1250).
+    fireEvent.mouseMove(wrapper!, { clientX: 770, clientY: CHART_H / 2 })
+
+    await waitFor(() => expect(tooltipText()).toContain('0.1250'))
+
+    // Label carries the date, so day 2 is distinguishable from day 1.
+    expect(tooltipText()).toContain('1/2/2020')
+    expect(tooltipText()).toContain('0.0750')
+
+    // The active dots must sit on the hovered point (right half of the plot).
+    // The bug put them on day 1's identically-labelled slot near the left edge.
+    const dots = Array.from(document.querySelectorAll('.recharts-active-dot circle'))
+    expect(dots).toHaveLength(2)
+    for (const dot of dots) {
+      expect(Number(dot.getAttribute('cx'))).toBeGreaterThan(CHART_W / 2)
+    }
+  })
+})
+
+// ---------------------------------------------------------------------------
+// buildChartRows
+// ---------------------------------------------------------------------------
+
+describe('buildChartRows', () => {
+  it('keeps X-axis keys unique across midnight', () => {
+    // Same local time-of-day on two consecutive days: as "HH:mm" labels these
+    // collided, which made Recharts resolve the hovered point to the first match
+    // (today) instead of the hovered one (tomorrow).
+    const rows = buildChartRows([
+      { starts_at: '2026-07-26T22:00:00Z', buy: 0.1, sell: 0.05 },
+      { starts_at: '2026-07-27T22:00:00Z', buy: 0.2, sell: 0.06 },
+    ])
+
+    expect(rows).toHaveLength(2)
+    expect(new Set(rows.map((r) => r.ts)).size).toBe(2)
+  })
+
+  it('sorts rows by slot start and parses naive timestamps as UTC', () => {
+    const rows = buildChartRows([
+      { starts_at: '2026-07-27T02:00:00', buy: 0.3, sell: 0.07 },
+      { starts_at: '2026-07-27T01:00:00Z', buy: 0.2, sell: 0.06 },
+      { starts_at: '2026-07-27T00:00:00Z', buy: 0.1, sell: 0.05 },
+    ])
+
+    expect(rows.map((r) => r.buy)).toEqual([0.1, 0.2, 0.3])
+    expect(rows.map((r) => r.ts)).toEqual([
+      '2026-07-27T00:00:00.000Z',
+      '2026-07-27T01:00:00.000Z',
+      '2026-07-27T02:00:00.000Z',
+    ])
+  })
+})
+
+// ---------------------------------------------------------------------------
+// findActiveSlotIndex
+// ---------------------------------------------------------------------------
+
+describe('findActiveSlotIndex', () => {
+  const rows = buildChartRows([
+    { starts_at: '2026-07-27T00:00:00Z', buy: 0.1, sell: 0.05 },
+    { starts_at: '2026-07-27T00:15:00Z', buy: 0.2, sell: 0.06 },
+    { starts_at: '2026-07-27T00:30:00Z', buy: 0.3, sell: 0.07 },
+  ])
+
+  const at = (iso: string) => new Date(iso).getTime()
+
+  it('returns the slot containing now', () => {
+    expect(findActiveSlotIndex(rows, at('2026-07-27T00:20:00Z'))).toBe(1)
+  })
+
+  it('returns the slot at its exact start boundary', () => {
+    expect(findActiveSlotIndex(rows, at('2026-07-27T00:15:00Z'))).toBe(1)
+  })
+
+  it('returns null before the first slot', () => {
+    expect(findActiveSlotIndex(rows, at('2026-07-26T23:59:00Z'))).toBeNull()
+  })
+
+  it('stays on the last slot until its inferred end, then returns null', () => {
+    expect(findActiveSlotIndex(rows, at('2026-07-27T00:44:00Z'))).toBe(2)
+    expect(findActiveSlotIndex(rows, at('2026-07-27T00:45:00Z'))).toBeNull()
+  })
+
+  it('returns null for empty data', () => {
+    expect(findActiveSlotIndex([], Date.now())).toBeNull()
+  })
 })

frontend/src/energy/TibberPrices.tsx

@@ -2,13 +2,15 @@
  * TibberPrices — price curve visualization.
  *
  * - Fetches today + tomorrow price range using useEnergyPrices.
- * - For tibber kind: Recharts LineChart showing buy/sell prices over time.
+ * - For tibber kind: Recharts LineChart showing buy/sell prices over time,
+ *   with the currently active price slot marked by a dot.
  * - For manual kind: shows tariff table (buy_dal, buy_normal, sell_dal, sell_normal).
  * - Handles: no active contract, empty data, loading, error.
  *
  * Recharts imports are isolated to this file only.
  */
 
+import { useEffect, useMemo, useState } from 'react'
 import {
   Stack,
   Text,
@@ -29,10 +31,20 @@ import {
   CartesianGrid,
   Tooltip,
   Legend,
+  ReferenceDot,
   ResponsiveContainer,
 } from 'recharts'
 import { useEnergyPrices } from './hooks'
-import { formatLocalTime } from '../utils/datetime'
+import { formatLocalDate, formatLocalTime, parseBackendTimestamp } from '../utils/datetime'
+
+const BUY_COLOR = '#2196f3'
+const SELL_COLOR = '#4caf50'
+
+/** Slot length assumed for the very last point, when no next point bounds it. */
+const FALLBACK_SLOT_MS = 60 * 60 * 1000
+
+/** How often the "current price" marker re-evaluates which slot is active. */
+const NOW_TICK_MS = 30 * 1000
 
 // ---------------------------------------------------------------------------
 // Time range helpers
@@ -51,34 +63,121 @@ function getTomorrowEnd(): string {
   return d.toISOString()
 }
 
+// ---------------------------------------------------------------------------
+// Chart data helpers
+// ---------------------------------------------------------------------------
+
+export interface PricePoint {
+  starts_at: string
+  buy: number
+  sell: number
+  level?: string | null
+}
+
+export interface ChartRow {
+  /**
+   * X-axis category key — the full instant, NOT a "HH:mm" label.
+   *
+   * Must be unique per slot: Recharts resolves the hovered point by *value*
+   * (findEntryInArray on the axis dataKey), so a repeated key makes the tooltip
+   * and the active dot snap back to the first match. With "HH:mm" labels, every
+   * time of day appears twice in a today+tomorrow range, which pinned the dot on
+   * today once the cursor passed midnight. Formatting to HH:mm happens in the
+   * tick / tooltip formatters instead.
+   */
+  ts: string
+  /** Slot start as epoch ms; NaN when starts_at is unparseable. */
+  tsMs: number
+  buy: number
+  sell: number
+}
+
+/** Map API price points to chart rows with unique X keys, sorted by slot start. */
+export function buildChartRows(points: PricePoint[]): ChartRow[] {
+  return points
+    .map((p) => {
+      const d = parseBackendTimestamp(p.starts_at)
+      const tsMs = d.getTime()
+      return {
+        ts: Number.isFinite(tsMs) ? d.toISOString() : p.starts_at,
+        tsMs,
+        buy: p.buy,
+        sell: p.sell,
+      }
+    })
+    .sort((a, b) => {
+      // Unparseable timestamps sort last so the ascending scan below can stop early.
+      if (!Number.isFinite(a.tsMs)) return Number.isFinite(b.tsMs) ? 1 : 0
+      if (!Number.isFinite(b.tsMs)) return -1
+      return a.tsMs - b.tsMs
+    })
+}
+
+/**
+ * Index of the row whose slot contains `nowMs`, or null when now is outside the
+ * fetched range. A slot ends where the next one starts; the last row has no next
+ * slot, so it falls back to the series spacing (quarter-hourly for Tibber).
+ */
+export function findActiveSlotIndex(rows: ChartRow[], nowMs: number): number | null {
+  let idx = -1
+  for (let i = 0; i < rows.length; i += 1) {
+    if (!Number.isFinite(rows[i].tsMs) || rows[i].tsMs > nowMs) break
+    idx = i
+  }
+  if (idx < 0) return null
+
+  const spacing = rows.length > 1 ? rows[1].tsMs - rows[0].tsMs : NaN
+  const slotMs = Number.isFinite(spacing) && spacing > 0 ? spacing : FALLBACK_SLOT_MS
+  const slotEnd = idx + 1 < rows.length ? rows[idx + 1].tsMs : rows[idx].tsMs + slotMs
+  return nowMs < slotEnd ? idx : null
+}
+
+/** Ticking clock so the active-slot marker follows slot boundaries while open. */
+function useNowMs(intervalMs = NOW_TICK_MS): number {
+  const [now, setNow] = useState(() => Date.now())
+  useEffect(() => {
+    const id = setInterval(() => setNow(Date.now()), intervalMs)
+    return () => clearInterval(id)
+  }, [intervalMs])
+  return now
+}
+
 // ---------------------------------------------------------------------------
 // Tibber chart
 // ---------------------------------------------------------------------------
 
 interface TibberChartProps {
-  points: Array<{ starts_at: string; buy: number; sell: number; level?: string | null }>
+  points: PricePoint[]
   currency: string
 }
 
 function TibberChart({ points, currency }: TibberChartProps) {
-  const data = points.map((p) => ({
-    time: formatLocalTime(p.starts_at),
-    buy: p.buy,
-    sell: p.sell,
-  }))
+  const data = useMemo(() => buildChartRows(points), [points])
+  const nowMs = useNowMs()
+  const activeIndex = findActiveSlotIndex(data, nowMs)
+  const activeRow = activeIndex == null ? null : data[activeIndex]
 
   return (
     <Stack gap="xs" data-testid="tibber-chart">
+      <Group gap="xs" justify="space-between" align="baseline">
         <Title order={6} c="dimmed">
           Price curve ({currency})
         </Title>
+        {activeRow && (
+          <Text size="xs" c="dimmed" data-testid="tibber-current-price">
+            Now {formatLocalTime(activeRow.ts)} · buy {activeRow.buy.toFixed(4)} · sell{' '}
+            {activeRow.sell.toFixed(4)}
+          </Text>
+        )}
+      </Group>
       <ResponsiveContainer width="100%" height={260}>
         <LineChart data={data} margin={{ top: 4, right: 16, left: 0, bottom: 4 }}>
           <CartesianGrid strokeDasharray="3 3" />
           <XAxis
-            dataKey="time"
+            dataKey="ts"
             tick={{ fontSize: 10 }}
             interval="preserveStartEnd"
+            tickFormatter={(v: string) => formatLocalTime(v)}
           />
           <YAxis
             tick={{ fontSize: 10 }}
@@ -89,12 +188,17 @@ function TibberChart({ points, currency }: TibberChartProps) {
             formatter={(val: any) =>
               [`${typeof val === 'number' ? val.toFixed(4) : String(val)} ${currency}`, undefined]
             }
+            labelFormatter={(label) =>
+              typeof label === 'string'
+                ? `${formatLocalDate(label)} ${formatLocalTime(label)}`
+                : label
+            }
           />
           <Legend />
           <Line
             type="monotone"
             dataKey="buy"
-            stroke="#2196f3"
+            stroke={BUY_COLOR}
             dot={false}
             strokeWidth={2}
             name="Buy"
@@ -102,11 +206,32 @@ function TibberChart({ points, currency }: TibberChartProps) {
           <Line
             type="monotone"
             dataKey="sell"
-            stroke="#4caf50"
+            stroke={SELL_COLOR}
             dot={false}
             strokeWidth={2}
             name="Sell"
           />
+          {/* Currently active price slot, marked by default (no hover needed). */}
+          {activeRow && (
+            <ReferenceDot
+              x={activeRow.ts}
+              y={activeRow.buy}
+              r={4}
+              fill={BUY_COLOR}
+              stroke="#fff"
+              strokeWidth={2}
+            />
+          )}
+          {activeRow && (
+            <ReferenceDot
+              x={activeRow.ts}
+              y={activeRow.sell}
+              r={4}
+              fill={SELL_COLOR}
+              stroke="#fff"
+              strokeWidth={2}
+            />
+          )}
         </LineChart>
       </ResponsiveContainer>
     </Stack>

openapi/openapi.json

@@ -701,7 +701,7 @@
           "api-energy"
         ],
         "summary": "Get Prices",
-        "description": "Return the price curve for the active contract.\n\n**Tibber contracts** (kind=\"tibber\"):\n    Fetches ``tibber_price`` rows within ``[start, end]``, ordered ascending\n    by ``starts_at``.  At most ``limit`` rows are returned (most recent first\n    within the window, then reversed to ascending order — identical to the\n    modbus readings pattern).\n\n    Response ``points`` carries per-slot:\n    - ``buy  = total``              (Tibber all-inclusive price)\n    - ``sell = total − energy_tax − sell_adjust``  (from active version values)\n    - ``level``                     (Tibber price level, may be null)\n\n    ``tariff`` is null.\n\n**Manual contracts** (kind=\"manual\"):\n    ``points`` is empty.  ``tariff`` carries the four effective prices\n    derived using the billing engine formula:\n    - ``buy_dal    = energy.buy.dal    + energy_tax + ode``\n    - ``buy_normal = energy.buy.normal + energy_tax + ode``\n    - ``sell_dal   = energy.sell.dal``\n    - ``sell_normal = energy.sell.normal``\n\n**No active contract**: returns kind=null, currency=\"EUR\", points=[], tariff=null (200).",
+        "description": "Return the price curve for the active contract.\n\n**Tibber contracts** (kind=\"tibber\"):\n    Fetches ``tibber_price`` rows within ``[start, end]``, ordered ascending\n    by ``starts_at``.  At most ``limit`` rows are returned (most recent first\n    within the window, then reversed to ascending order — identical to the\n    modbus readings pattern).\n\n    Response ``points`` carries per-slot:\n    - ``buy  = total``              (Tibber all-inclusive price)\n    - ``sell = total − energy_tax − sell_fee − sell_adjust``  (from active version values)\n    - ``level``                     (Tibber price level, may be null)\n\n    ``tariff`` is null.\n\n**Manual contracts** (kind=\"manual\"):\n    ``points`` is empty.  ``tariff`` carries the four effective prices\n    derived using the billing engine formula:\n    - ``buy_dal    = energy.buy.dal    + energy_tax + ode``\n    - ``buy_normal = energy.buy.normal + energy_tax + ode``\n    - ``sell_dal   = energy.sell.dal``\n    - ``sell_normal = energy.sell.normal``\n\n**No active contract**: returns kind=null, currency=\"EUR\", points=[], tariff=null (200).",
         "operationId": "get_prices_api_energy_prices_get",
         "parameters": [
           {

openapi/openapi.yaml

@@ -527,9 +527,9 @@ paths:
         \ (most recent first\n    within the window, then reversed to ascending order\
         \ — identical to the\n    modbus readings pattern).\n\n    Response ``points``\
         \ carries per-slot:\n    - ``buy  = total``              (Tibber all-inclusive\
-        \ price)\n    - ``sell = total − energy_tax − sell_adjust``  (from active\
-        \ version values)\n    - ``level``                     (Tibber price level,\
-        \ may be null)\n\n    ``tariff`` is null.\n\n**Manual contracts** (kind=\"\
+        \ price)\n    - ``sell = total − energy_tax − sell_fee − sell_adjust``  (from\
+        \ active version values)\n    - ``level``                     (Tibber price\
+        \ level, may be null)\n\n    ``tariff`` is null.\n\n**Manual contracts** (kind=\"\
         manual\"):\n    ``points`` is empty.  ``tariff`` carries the four effective\
         \ prices\n    derived using the billing engine formula:\n    - ``buy_dal \
         \   = energy.buy.dal    + energy_tax + ode``\n    - ``buy_normal = energy.buy.normal\

tests/test_api_energy.py

@@ -363,13 +363,65 @@ def test_prices_tibber_contract_returns_points(energy_client):
     starts_at_list = [p["starts_at"] for p in body["points"]]
     assert starts_at_list == sorted(starts_at_list)
 
-    # Check buy/sell calculations: buy=total=0.245, sell=total-energy_tax-sell_adjust=0.245-0.1108-0.0
+    # Check buy/sell calculations: buy=total=0.245, sell=total-energy_tax-sell_fee-sell_adjust
+    # (this version has no sell_fee/sell_adjust → both default to 0 at read time).
     for p in body["points"]:
         assert abs(p["buy"] - 0.245) < 1e-6
         assert abs(p["sell"] - (0.245 - 0.1108)) < 1e-4
         assert p["level"] == "NORMAL"
 
 
+def test_prices_tibber_sell_reflects_sell_fee(energy_client):
+    """/prices sell price deducts sell_fee (verkoopvergoeding), net-metering config."""
+    client, engine, _app = energy_client
+    _login(client)
+
+    # Net-metering version: sell_adjust = −energy_tax (refund tax), sell_fee = 0.0248.
+    now = datetime.now(UTC)
+    with Session(engine) as session:
+        contract = EnergyContract(
+            name="Tibber NetMeter",
+            kind="tibber",
+            active=True,
+            currency="EUR",
+            created_at=now,
+            updated_at=now,
+        )
+        session.add(contract)
+        session.flush()
+        session.add(
+            EnergyContractVersion(
+                contract_id=contract.id,
+                effective_from=now - timedelta(days=30),
+                effective_to=None,
+                values={
+                    "energy": {
+                        "energy_tax": 0.1108,
+                        "sell_fee": 0.0248,
+                        "sell_adjust": -0.1108,
+                    },
+                    "standing": {"management_fee": 5.99, "network_fee": 25.0},
+                    "credits": {"heffingskorting": 600.0},
+                },
+                created_at=now,
+            )
+        )
+        session.commit()
+    _make_tibber_prices(engine, count=3)
+
+    start = (datetime.now(UTC) - timedelta(hours=2)).isoformat()
+    end = (datetime.now(UTC) + timedelta(hours=2)).isoformat()
+    resp = client.get("/api/energy/prices", params={"start": start, "end": end})
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["kind"] == "tibber"
+    assert len(body["points"]) == 3
+    # sell = 0.245 − 0.1108 − 0.0248 − (−0.1108) = 0.245 − 0.0248 = 0.2202
+    for p in body["points"]:
+        assert abs(p["buy"] - 0.245) < 1e-6
+        assert abs(p["sell"] - 0.2202) < 1e-4
+
+
 def test_prices_tibber_limit_caps_results(energy_client):
     client, engine, _app = energy_client
     _login(client)

tests/test_pricing_profiles.py

@@ -137,6 +137,11 @@ class TestLoadProfileTibber:
         profile = load_profile("tibber")
         assert profile.energy.sell_adjust.default == 0
 
+    def test_sell_fee_has_default_verkoopvergoeding(self) -> None:
+        profile = load_profile("tibber")
+        assert profile.energy.sell_fee.unit == "EUR/kWh"
+        assert profile.energy.sell_fee.default == 0.0248
+
     def test_management_fee_has_default(self) -> None:
         profile = load_profile("tibber")
         assert profile.standing.management_fee.default is not None
@@ -350,6 +355,19 @@ class TestValidateValuesTibber:
         filled = validate_values("tibber", values)
         assert filled["energy"]["sell_adjust"] == 0
 
+    def test_sell_fee_default_applied_when_absent(self) -> None:
+        values = {
+            "energy": {
+                "energy_tax": 0.1108,
+                "sell_adjust": 0.0,
+                # sell_fee absent — has default 0.0248 (verkoopvergoeding)
+            },
+            "standing": {"management_fee": 5.99, "network_fee": 9.87},
+            "credits": {"heffingskorting": 600.0},
+        }
+        filled = validate_values("tibber", values)
+        assert filled["energy"]["sell_fee"] == 0.0248
+
     def test_management_fee_default_applied_when_absent(self) -> None:
         values = {
             "energy": {"energy_tax": 0.1108, "sell_adjust": 0.0},

tests/test_pricing_strategies.py

@@ -6,7 +6,7 @@ Acceptance criteria covered
 2. Manual strategy: dual-tariff import/export/net calculated correctly (hand-verified).
 3. Manual strategy: Decimal precision — no float binary rounding errors.
 4. Tibber strategy: queries the most recent TibberPrice with starts_at ≤ t0.
-5. Tibber strategy: buy=total, sell=total−energy_tax−sell_adjust.
+5. Tibber strategy: buy=total, sell=total−energy_tax−sell_fee−sell_adjust.
 6. Tibber strategy: negative total → negative export_revenue (not clamped).
 7. Tibber strategy: raises TibberPriceNotFoundError when no matching row exists.
 8. ``register_strategy`` / ``get_strategy`` round-trip works.
@@ -371,6 +371,68 @@ class TestTibberStrategy:
         # sell = 0.25 - 0.10 - 0.02 = 0.13; export_revenue = 2 × 0.13 = 0.26
         assert result["export_revenue"] == Decimal("2") * Decimal("0.13")
 
+    def test_sell_deducts_sell_fee(self, tibber_db) -> None:
+        """verkoopvergoeding (sell_fee) is subtracted from the feed-in price.
+
+        Under net metering the energy tax is refunded (sell_adjust = −energy_tax),
+        so sell should equal total − sell_fee. Verifies the fee is a first-class,
+        always-deducted term and does NOT cancel against the buy-side inkoopvergoeding
+        that is already baked into total.
+        """
+        t0 = _ts(10, 0)
+        with Session(tibber_db) as session:
+            _insert_tibber_price(session, starts_at=_ts(9, 45), total=0.3073)
+            session.commit()
+
+        # Net-metering config: sell_adjust = −energy_tax refunds the tax;
+        # sell_fee = 0.0248 (Tibber verkoopvergoeding) is still deducted.
+        values = {
+            "energy": {
+                "energy_tax": 0.11085,
+                "sell_fee": 0.0248,
+                "sell_adjust": -0.11085,
+            },
+            "standing": {"management_fee": 5.99, "network_fee": 9.87},
+            "credits": {"heffingskorting": 600.0},
+        }
+        with Session(tibber_db) as session:
+            deltas = PeriodDeltas(
+                d1=Decimal("0"), d2=Decimal("0"),
+                r1=Decimal("0"), r2=Decimal("1"),
+            )
+            result = self._call(deltas, t0, session, values=values)
+
+        # sell = 0.3073 − 0.11085 − 0.0248 − (−0.11085) = 0.3073 − 0.0248 = 0.2825
+        expected_sell = (
+            Decimal("0.3073") - Decimal("0.11085") - Decimal("0.0248") - Decimal("-0.11085")
+        )
+        assert expected_sell == Decimal("0.2825")
+        assert result["export_revenue"] == Decimal("1") * expected_sell
+        assert result["pricing"]["sell_fee"] == "0.0248"
+        assert Decimal(result["pricing"]["sell"]) == Decimal("0.2825")
+
+    def test_sell_fee_absent_defaults_to_zero(self, tibber_db) -> None:
+        """A version without sell_fee (pre-migration) reads it as 0 — no silent deduction."""
+        t0 = _ts(10, 0)
+        with Session(tibber_db) as session:
+            _insert_tibber_price(session, starts_at=_ts(9, 45), total=0.25)
+            session.commit()
+
+        values = {
+            "energy": {"energy_tax": 0.10, "sell_adjust": 0.0},  # no sell_fee key
+            "standing": {"management_fee": 5.99, "network_fee": 9.87},
+            "credits": {"heffingskorting": 600.0},
+        }
+        with Session(tibber_db) as session:
+            deltas = PeriodDeltas(
+                d1=Decimal("0"), d2=Decimal("0"),
+                r1=Decimal("0"), r2=Decimal("1"),
+            )
+            result = self._call(deltas, t0, session, values=values)
+        # sell = 0.25 − 0.10 − 0 − 0 = 0.15
+        assert result["export_revenue"] == Decimal("0.15")
+        assert result["pricing"]["sell_fee"] == "0"
+
     def test_uses_most_recent_price_before_t0(self, tibber_db) -> None:
         """Correct row: starts_at ≤ t0, most recent wins."""
         t0 = _ts(10, 0)