docs: require frontend codegen alongside the OpenAPI export in the gates

The local gate list only covered `scripts/export_openapi.py` + a clean
`openapi/` diff, but `frontend/src/api/schema.d.ts` is generated from that JSON
and CI re-runs `npm run codegen` with `git diff --exit-code`. d07a083 changed a
route docstring, refreshed openapi.json, and skipped codegen — local green,
remote red on a one-line comment diff. Spell out both steps and note that route
docstrings feed the OpenAPI description too.

Also add AGENTS.md as a symlink to CLAUDE.md so other agent tooling picks up
the same contract.

AGENTS.md

@@ -0,0 +1 @@
+CLAUDE.md

CLAUDE.md

@@ -79,6 +79,23 @@ python scripts/export_openapi.py && git diff --exit-code openapi/   # 改了路
 前端任务（M2）在 `frontend/` 下另跑 `npm run lint && npm run typecheck && npm run test && npm run build`（详见 m2 文档 §8）。
 **不过闸门就不算完成**，不得跳过、不得留红给下一轮。
 
+#### API 契约同步：`openapi/` 与 `schema.d.ts` 是**两步**（v1.4.0 后教训）
+
+**只跑 `export_openapi.py` 不够。** 前端的 `frontend/src/api/schema.d.ts` 是由 `openapi/openapi.json` 二次生成的，CI（`.github/workflows/frontend.yml` 的 *Check codegen is in sync*）会重跑 codegen 并 `git diff --exit-code src/api/schema.d.ts`。漏了第二步 → 本地闸门全绿、远端 CI 红。真出过：`d07a083` 改了 `/api/energy/prices` 的 docstring 并同步了 `openapi.json`，但没重跑 codegen，只差一行注释就把 CI 挂了。
+
+所以**只要动了路由 / Pydantic schema / 路由 docstring**（docstring 也会进 OpenAPI description！），两步都要跑，两个产物都要入库：
+
+```bash
+# 1) 后端契约
+python scripts/export_openapi.py && git diff --exit-code openapi/
+# 2) 前端类型（在 frontend/ 下）
+npm run codegen && git diff --exit-code src/api/schema.d.ts
+```
+
+- 判据：`git diff --exit-code openapi/` 有输出 → **必然**还要跑一次 `npm run codegen`。
+- 反过来也成立：`schema.d.ts` 不要手改，它是生成物。
+- Reviewer 审"动了路由 / schema / 路由 docstring"类任务时，把**这两个产物是否都已重新生成并入库**当作 acceptance 的一部分。
+
 ### 构建上下文完整性（M1 Dockerfile 教训）
 
 `docker build` **不在 pytest/ruff 闸门里**——M1 删了 `alembic_location/poo` 后忘了同步 `Dockerfile` 的 `COPY`，单元闸门全绿却把坏掉的镜像构建一路漏到 release tag。所以：

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 { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
-import { screen, waitFor } from '@testing-library/react'
+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) => ({
+  const data = useMemo(() => buildChartRows(points), [points])
-    time: formatLocalTime(p.starts_at),
+  const nowMs = useNowMs()
-    buy: p.buy,
+  const activeIndex = findActiveSlotIndex(data, nowMs)
-    sell: p.sell,
+  const activeRow = activeIndex == null ? null : data[activeIndex]
-  }))
 
   return (
     <Stack gap="xs" data-testid="tibber-chart">
-      <Title order={6} c="dimmed">
+      <Group gap="xs" justify="space-between" align="baseline">
-        Price curve ({currency})
+        <Title order={6} c="dimmed">
-      </Title>
+          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>