fix(common): honor DeepSeek Beijing weekend boundaries

Author: c8dhjp4tyv-bit

common/src/__tests__/freebuff-peak-hours.test.ts

@@ -2,8 +2,10 @@ import { describe, expect, test } from 'bun:test'
 
 import {
   DEEPSEEK_EXPENSIVE_WINDOW_UTC,
+  DEEPSEEK_WEEKEND_OFFPEAK_EFFECTIVE_AT_UTC,
   deepSeekExpensiveWindowEndsAt,
   deepseekPricingWindow,
+  isBeijingWeekend,
   isDeepSeekExpensiveWindow,
 } from '../constants/freebuff-peak-hours'
 
@@ -64,6 +66,38 @@ describe('the expensive window', () => {
   })
 })
 
+describe('the Beijing weekend boundary', () => {
+  test.each([
+    ['2026-08-28T15:00:00Z', false], // Friday 23:00 in Beijing
+    ['2026-08-28T16:00:00Z', true], // Saturday 00:00 in Beijing
+    ['2026-08-30T15:00:00Z', true], // Sunday 23:00 in Beijing
+    ['2026-08-30T16:00:00Z', false], // Monday 00:00 in Beijing
+  ])('%s isBeijingWeekend=%p', (instant, weekend) => {
+    expect(isBeijingWeekend(new Date(instant as string))).toBe(
+      weekend as boolean,
+    )
+  })
+
+  test('does not apply the weekend rule before its effective instant', () => {
+    expect(DEEPSEEK_WEEKEND_OFFPEAK_EFFECTIVE_AT_UTC).toBe(
+      Date.parse('2026-08-22T16:00:00Z'),
+    )
+    expect(deepseekPricingWindow(new Date('2026-08-22T09:59:59Z'))).toBe('peak')
+    expect(isDeepSeekExpensiveWindow(new Date('2026-08-22T02:00:00Z'))).toBe(
+      true,
+    )
+  })
+
+  test('applies the weekend rule from its effective instant onward', () => {
+    expect(deepseekPricingWindow(new Date('2026-08-23T01:30:00Z'))).toBe(
+      'off-peak',
+    )
+    expect(isDeepSeekExpensiveWindow(new Date('2026-08-23T02:00:00Z'))).toBe(
+      false,
+    )
+  })
+})
+
 test.each(['2026-08-29T02:00:00Z', '2026-08-30T02:00:00Z'])(
   '%s uses weekend rates in Beijing',
   (instant) => {

common/src/constants/freebuff-peak-hours.ts

@@ -13,8 +13,8 @@
 /**
  * Peak hours, from api-docs.deepseek.com/quick_start/pricing (read 2026-08-16):
  * "Peak hours are 01:00 - 04:00 and 06:00 - 10:00 UTC (all other hours are
- * off-peak)." These windows apply Monday-Friday Beijing time; weekends are
- * always off-peak.
+ * off-peak)." These windows apply Monday-Friday Beijing time; from
+ * `DEEPSEEK_WEEKEND_OFFPEAK_EFFECTIVE_AT_UTC` onward, weekends are off-peak.
  *
  * Half-open [start, end): 04:00:00 UTC itself is already off-peak. TWO
  * disjoint windows, not one — the 04:00-06:00 gap between them is exactly what
@@ -29,7 +29,17 @@ export const DEEPSEEK_PEAK_HOUR_RANGES_UTC: ReadonlyArray<
 
 export type DeepSeekPricingWindow = 'peak' | 'off-peak'
 
-function isBeijingWeekend(at: Date): boolean {
+/**
+ * The weekend pricing change took effect at 00:00 Beijing time on 2026-08-23.
+ * Keep this as an instant rather than a local date so historical billing and
+ * availability checks use the same boundary in every runtime timezone.
+ */
+export const DEEPSEEK_WEEKEND_OFFPEAK_EFFECTIVE_AT_UTC = Date.parse(
+  '2026-08-22T16:00:00Z',
+)
+
+/** Whether `at` falls on Saturday or Sunday in Beijing time. */
+export function isBeijingWeekend(at: Date): boolean {
   const beijingDay = new Date(at.getTime() + 8 * 60 * 60 * 1000).getUTCDay()
   return beijingDay === 0 || beijingDay === 6
 }
@@ -42,7 +52,12 @@ function isBeijingWeekend(at: Date): boolean {
  * ceiling), and a hidden `new Date()` would make both untestable.
  */
 export function deepseekPricingWindow(at: Date): DeepSeekPricingWindow {
-  if (isBeijingWeekend(at)) return 'off-peak'
+  if (
+    at.getTime() >= DEEPSEEK_WEEKEND_OFFPEAK_EFFECTIVE_AT_UTC &&
+    isBeijingWeekend(at)
+  ) {
+    return 'off-peak'
+  }
   const hour = at.getUTCHours()
   const peak = DEEPSEEK_PEAK_HOUR_RANGES_UTC.some(
     ([startHour, endHour]) => hour >= startHour && hour < endHour,
@@ -86,7 +101,12 @@ export const DEEPSEEK_EXPENSIVE_WINDOW_UTC: readonly [number, number] = [
 /** Whether `at` falls in the window above. Half-open like the peak check, so
  *  the closing hour is already outside it. */
 export function isDeepSeekExpensiveWindow(at: Date): boolean {
-  if (isBeijingWeekend(at)) return false
+  if (
+    at.getTime() >= DEEPSEEK_WEEKEND_OFFPEAK_EFFECTIVE_AT_UTC &&
+    isBeijingWeekend(at)
+  ) {
+    return false
+  }
   const [start, end] = DEEPSEEK_EXPENSIVE_WINDOW_UTC
   const hour = at.getUTCHours()
   return hour >= start && hour < end