dshworks · lroolle · Sep 18, 2026 · Sep 18, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,17 @@
 # Changelog
 
+## 0.5.3 - 2026-09-18
+
+### Fixed
+
+- **The V4.1 cutover is 2026-09-10 04:00 UTC, as DeepSeek published it.**
+  The release note says "New pricing takes effect at 04:00 UTC on Sept 10,
+  2026" (12:00 Beijing). 0.5.0 guessed 00:00 Beijing from a pattern; 0.5.1
+  guessed 11:00 UTC from when our docs mirror first saw the new pricing page,
+  which lagged the bill by hours. Requests between 04:00 and 11:00 UTC that
+  day were billed at the new Flash price and are now metered at it.
+  `stateVersion` 5.
+
 ## 0.5.2 - 2026-09-18
 
 ### Changed

diff --git a/README.md b/README.md
@@ -167,12 +167,12 @@ by V4.1 Flash and billed at the Flash price, so the meter bills a
 echoes back whatever name you sent, so the echo cannot say which model
 billed; the dispatch time can.
 
-DeepSeek published a date, not an instant. The meter cuts over at
-**2026-09-10 11:00 UTC**: our docs mirror saw the old card on the pricing
-page at 04:50 UTC that day and the new one at 11:27 UTC, and this is the
-last whole hour before the new one was seen, so an error can only
-overstate a bill. A probe at 2026-09-11 17:03 UTC settled on the new card
-to the cent.
+The new price took effect at **2026-09-10 04:00 UTC** (12:00 Beijing),
+as DeepSeek's [release note](https://api-docs.deepseek.com/news/news260910)
+states; the meter cuts over at exactly that instant. The pricing page
+itself lagged by hours, so don't date a price change by when its reference
+page moved. A probe at 2026-09-11 17:03 UTC settled on the new card to the
+cent.
 
 **Weekends have been off-peak all day since 2026-08-22 16:00 UTC**
 (00:00 Beijing, Sunday 23 August), on the *Beijing* calendar — so the
@@ -204,7 +204,7 @@ cheapest token, which is the one an agent sends most of.
 <summary>The retired V4 Flash card, kept to reprice history</summary>
 
 Billed by `deepseek-v4-flash` and `deepseek-v4-flash-vision-exp` until
-**2026-09-10 11:00 UTC**; both names bill as `deepseek-flash` since.
+**2026-09-10 04:00 UTC**; both names bill as `deepseek-flash` since.
 
 | | cache hit | cache miss | output |
 |---|---|---|---|

diff --git a/README.zh.md b/README.zh.md
@@ -127,7 +127,7 @@ DeepSeek 公布的是**两张互相独立的价目表**——国际站按美元
 
 **`deepseek-flash` 即 DeepSeek-V4.1-Flash，自 2026-09-10 起。** 它取代了 V4 Flash 和 V4 Flash Vision Exp（视觉能力已内置），Flash 价格随之下调：空闲时段缓存未命中 ¥1.5 -> ¥1，输出 ¥4.5 -> ¥4，缓存命中 ¥0.05 -> ¥0.02。旧模型名仍可调用，由 V4.1 Flash 提供服务并按 Flash 价格计费，所以切换之后发出的 `deepseek-v4-flash` 请求，电表按 `deepseek-flash` 计费；切换之前的仍按旧价。API 返回的模型名只是回显你发出的名字，看不出实际由谁计费；发出时间可以。
 
-DeepSeek 公布的是日期，不是时刻。电表在 **UTC 2026-09-10 11:00** 切换：我们的文档镜像当天 UTC 04:50 抓到的价格页还是旧价，11:27 抓到新价，这里取看到新价之前最后一个整点，所以误差只会让账单偏高，不会偏低。UTC 2026-09-11 17:03 的账单探测按新价结算，分毫不差。
+新价格于 **北京时间 2026 年 9 月 10 日 12:00**（UTC 04:00）生效，见 DeepSeek 的[发布公告](https://api-docs.deepseek.com/zh-cn/news/news260910)，电表就在这一刻切换。价格页本身晚了好几个小时才更新，所以别用参考页面的变动时间去推断调价时刻。UTC 2026-09-11 17:03 的账单探测按新价结算，分毫不差。
 
 <details>
 <summary>已退役的统一价，保留用于回算历史</summary>
@@ -146,7 +146,7 @@ DeepSeek 公布的是日期，不是时刻。电表在 **UTC 2026-09-10 11:00**
 <details>
 <summary>已退役的 V4 Flash 价目，保留用于回算历史</summary>
 
-`deepseek-v4-flash` 与 `deepseek-v4-flash-vision-exp` 在 **UTC 2026-09-10 11:00** 之前按此计费，之后均按 `deepseek-flash` 计费。
+`deepseek-v4-flash` 与 `deepseek-v4-flash-vision-exp` 在 **UTC 2026-09-10 04:00**（北京时间 12:00）之前按此计费，之后均按 `deepseek-flash` 计费。
 
 | | 缓存命中 | 缓存未命中 | 输出 |
 |---|---|---|---|

diff --git a/docs/index.html b/docs/index.html
diff --git a/docs/pricing.json b/docs/pricing.json
diff --git a/lib/client.js b/lib/client.js
diff --git a/lib/core.js b/lib/core.js
@@ -102,20 +102,18 @@ export const RATES = {
  * DeepSeek-V4.1-Flash model and billed at the Flash price" (pricing page,
  * footnote 1; changelog 2026-09-10). The same release cut the Flash price.
  *
- * The instant is inferred, not published. The changelog gives a date. Our
- * docs mirror (thevibeworks/deepseek-docs) fetched the pricing page with the
- * OLD card at 2026-09-10T04:50Z and the new one at 11:27Z, so the cutover is
- * in that gap; this takes the last whole hour before the new card was seen.
- * An error inside the gap can only overstate a bill, never understate it.
- * The same instant is used by thevibeworks/deepseek-cli, so the two meters
- * agree. A bill probe at 2026-09-11T17:03Z settled on the new card to the
- * cent (¥0.58 billed, ¥0.583 new, ¥0.749 old).
+ * Published, in the release note rather than the changelog: "New pricing
+ * takes effect at 04:00 UTC on Sept 10, 2026" (news260910; "2026 年 9 月 10
+ * 日 12:00 开始生效" in the Chinese one). A bill probe at 2026-09-11T17:03Z
+ * settled on the new card to the cent (¥0.58 billed, ¥0.583 new, ¥0.749 old).
  *
- * 0.5.0 shipped 2026-09-09T16:00Z on the pattern that DeepSeek's price
- * changes land at 00:00 Beijing. The page itself says otherwise: it still
- * carried the old card thirteen hours later.
+ * Two earlier guesses, both wrong and both kept here as the lesson: 0.5.0
+ * took 00:00 Beijing from the pattern of earlier price changes, and 0.5.1
+ * took 11:00 UTC from when our docs mirror first SAW the new pricing page.
+ * The page lagged the bill by hours. Read the vendor's announcement before
+ * inferring anything from its reference pages.
  */
-export const V41_FLASH_FROM = Date.UTC(2026, 8, 10, 11, 0, 0)
+export const V41_FLASH_FROM = Date.UTC(2026, 8, 10, 4, 0, 0)
 
 /**
  * Retired model ids: the rates they billed at while they existed, and the

diff --git a/lib/index.js b/lib/index.js
@@ -73,10 +73,10 @@ export function apply(ctx, config) {
       init,
       apply: foldEvent,
       // 3: 0.5.0 re-attributes retired Flash ids to `deepseek-flash` after the
-      // V4.1 cutover and bills `assistant/attempt`. 4: 0.5.1 moved that
+      // V4.1 cutover and bills `assistant/attempt`. 4, 5: 0.5.1 and 0.5.3 moved that
       // cutover. A fold cached under an older version would keep pricing
       // those requests by the old rule forever.
-      stateVersion: 4,
+      stateVersion: 5,
 
       // Two spellings of one contract. `@deepseek-ai/dsh-session-projection`
       // 0.1.1-rc.1 split the single `schema`/`view` pair into a host-side

diff --git a/package.json b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "@dshworks/dsh-meter",
   "description": "The DeepSeek time-of-use meter for dsh: what this session cost, which tariff is running, when it flips, and the account balance behind it — one line under the composer.",
-  "version": "0.5.2",
+  "version": "0.5.3",
   "license": "MIT",
   "homepage": "https://dsh.works/dsh-meter/",
   "publishConfig": {

diff --git a/tests/ledger.spec.mjs b/tests/ledger.spec.mjs
@@ -132,11 +132,12 @@ describe('the fold', () => {
   })
 
   describe('the V4.1 Flash retirement', () => {
-    /* Weekday off-peak on both sides of the cutover: 2026-09-10 is a
-     * Thursday, and 04:50 (the mirror's last old-card read) and 11:30 UTC
-     * are outside both peak windows. */
-    const oldDays = utc(2026, 9, 10, 4, 50)
-    const newDays = utc(2026, 9, 10, 11, 30)
+    /* Weekday off-peak on both sides of the cutover (2026-09-10 04:00 UTC,
+     * a Thursday): 2026-09-09 12:00 and 2026-09-10 04:50 UTC are outside
+     * both peak windows. 04:50 is when the pricing page still showed the old
+     * card — the bill had already moved. */
+    const oldDays = utc(2026, 9, 9, 12)
+    const newDays = utc(2026, 9, 10, 4, 50)
     const flashSession = at => fold([
       stepStart(at),
       header(at, 'deepseek-v4-flash'),