diff --git a/eval/pricing.json b/eval/pricing.json
index 9bd64bd..a53c6a0 100644
--- a/eval/pricing.json
+++ b/eval/pricing.json
@@ -25,8 +25,8 @@
       }
     },
     {
-      "since": "2026-09-10T11:00:00Z",
-      "label": "V4.1 Flash (changelog 2026-09-10); instant inferred, see src/provider/catalog.ts",
+      "since": "2026-09-10T04:00:00Z",
+      "label": "V4.1 Flash (changelog 2026-09-10); effective 04:00 UTC per the release note, see src/provider/catalog.ts",
       "rates": {
         "flash": { "input_hit": 0.003, "input_miss": 0.15, "output": 0.6 },
         "pro": { "input_hit": 0.022, "input_miss": 0.66, "output": 1.98 }
diff --git a/src/provider/catalog.ts b/src/provider/catalog.ts
index 3e3c984..0c17e7c 100644
--- a/src/provider/catalog.ts
+++ b/src/provider/catalog.ts
@@ -70,11 +70,12 @@ export const CARDS: Card[] = [
   },
   {
     // V4.1 Flash, 2026-09-10: Flash cut on every item, Pro unchanged.
-    // The instant is INFERRED: our docs mirror read the old card at 04:50
-    // UTC and the new one at 11:27 UTC that day. 11:00 is the last whole
-    // hour between, so a call in the gap can only be overstated.
+    // "New pricing takes effect at 04:00 UTC on Sept 10, 2026" -- DeepSeek's
+    // release note (news260910; 12:00 Beijing in the Chinese one). The
+    // pricing page itself still showed the old card at 04:50 UTC, so a date
+    // read off the page lags the bill.
     label: "V4.1",
-    since: new Date("2026-09-10T11:00:00Z"),
+    since: new Date("2026-09-10T04:00:00Z"),
     timeOfUse: true,
     rates: { flash: { inputHit: 0.003, inputMiss: 0.15, output: 0.6 }, pro: V4_PRO },
   },
diff --git a/tests/catalog.test.ts b/tests/catalog.test.ts
index b0e9a92..2314411 100644
--- a/tests/catalog.test.ts
+++ b/tests/catalog.test.ts
@@ -42,12 +42,14 @@ describe("dated cards", () => {
     expect(ratesAt("deepseek-v4-flash", at("2026-09-09T02:00:00Z"))?.inputMiss).toBe(0.44); // Wed peak
   });
 
-  test("V4.1 Flash card from 2026-09-10 11:00 UTC; pro unchanged across it", () => {
-    const before = at("2026-09-10T10:59:00Z");
-    const after = at("2026-09-10T11:00:00Z");
-    expect(ratesAt("deepseek-flash", before)).toEqual({ inputHit: 0.007, inputMiss: 0.22, output: 0.66 });
+  test("V4.1 Flash card from 2026-09-10 04:00 UTC; pro unchanged across it", () => {
+    // 03:59 is inside the 01-04 peak window, 04:00 is outside it, so this
+    // also proves the card and the tariff switch independently.
+    const before = at("2026-09-10T03:59:00Z");
+    const after = at("2026-09-10T04:00:00Z");
+    expect(ratesAt("deepseek-flash", before)).toEqual({ inputHit: 0.014, inputMiss: 0.44, output: 1.32 });
+    expect(ratesAt("deepseek-v4-pro", before)).toEqual({ inputHit: 0.044, inputMiss: 1.32, output: 3.96 });
     expect(ratesAt("deepseek-flash", after)).toEqual({ inputHit: 0.003, inputMiss: 0.15, output: 0.6 });
-    expect(ratesAt("deepseek-v4-pro", before)).toEqual(ratesAt("deepseek-v4-pro", after));
     expect(ratesAt("deepseek-v4-pro", after)).toEqual({ inputHit: 0.022, inputMiss: 0.66, output: 1.98 });
   });