From ca10f366249e1bfcbe686bbdb4d602c55e842b24 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Sat, 3 Oct 2026 04:57:38 +0000
Subject: [PATCH] Landing stats band takes the versioned stats file from the
 browser cache again; the build log names the baked file

Since e537a4b the backend writes a new versioned file per publish, so its
immutable header holds again. The browser revalidates only the manifest
(no-cache) and serves the file it names from its cache (default mode),
instead of revalidating both, the workaround in 762fef4 for the per-day name.

The build log names the baked file ("Platform stats baked into the landing
page from platform-stats.<date>T<time>Z.json (as of ...)"), so every web
deploy shows which publish it carries.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N4ddfosgdeCwXo7NvB9xd2
---
 .../lib/__tests__/platformStats.test.ts       | 12 +++---
 .../lib/platformStats.ts                      | 38 +++++++++++++------
 2 files changed, 32 insertions(+), 18 deletions(-)

diff --git a/src/Web/autopilot-monitor-web/lib/__tests__/platformStats.test.ts b/src/Web/autopilot-monitor-web/lib/__tests__/platformStats.test.ts
index 54f98598..40047dc4 100644
--- a/src/Web/autopilot-monitor-web/lib/__tests__/platformStats.test.ts
+++ b/src/Web/autopilot-monitor-web/lib/__tests__/platformStats.test.ts
@@ -8,10 +8,10 @@ import {
 
 const CONTAINER = "https://stats.example.test/publicstats";
 const MANIFEST_URL = `${CONTAINER}/platform-stats.json`;
-const PAYLOAD_URL = `${CONTAINER}/platform-stats.2026-10-02.json`;
+const PAYLOAD_URL = `${CONTAINER}/platform-stats.2026-10-02T140005Z.json`;
 
 /** What the backend publishes (MaintenanceService.TryPublishPlatformStatsJsonAsync). */
-const MANIFEST = { latest: "platform-stats.2026-10-02.json", generatedAtUtc: "2026-10-02T14:00:05.1234567Z" };
+const MANIFEST = { latest: "platform-stats.2026-10-02T140005Z.json", generatedAtUtc: "2026-10-02T14:00:05.1234567Z" };
 const PAYLOAD = {
   totalEnrollments: 12481,
   totalUsers: 310,
@@ -91,13 +91,13 @@ describe("toStatItems", () => {
 });
 
 describe("fetchLivePlatformStats", () => {
-  it("reads the manifest, then the file it names, revalidating both with the blob", async () => {
+  it("revalidates the manifest and takes the immutable file it names from the browser cache", async () => {
     const fetchMock = serve(BOTH_FILES);
 
     expect(await fetchLivePlatformStats(MANIFEST_URL)).toEqual(PAYLOAD);
     expect(fetchMock.mock.calls).toEqual([
       [MANIFEST_URL, { cache: "no-cache" }],
-      [PAYLOAD_URL, { cache: "no-cache" }],
+      [PAYLOAD_URL, { cache: "default" }],
     ]);
   });
 
@@ -106,7 +106,7 @@ describe("fetchLivePlatformStats", () => {
     Object.defineProperty(redirected, "url", { value: "https://stats.example.test/v2/platform-stats.json" });
     const fetchMock = serve({
       [MANIFEST_URL]: () => redirected,
-      "https://stats.example.test/v2/platform-stats.2026-10-02.json": () => json(PAYLOAD),
+      "https://stats.example.test/v2/platform-stats.2026-10-02T140005Z.json": () => json(PAYLOAD),
     });
 
     expect(await fetchLivePlatformStats(MANIFEST_URL)).toEqual(PAYLOAD);
@@ -161,7 +161,7 @@ describe("loadPlatformStatsSnapshot", () => {
       expect(init?.signal).toBeInstanceOf(AbortSignal);
     }
     expect(inits[0]?.signal).toBe(inits[1]?.signal);
-    expect(log).toHaveBeenCalledWith(expect.stringContaining(PAYLOAD.lastUpdated));
+    expect(log).toHaveBeenCalledWith(expect.stringContaining(`from ${MANIFEST.latest} (as of ${PAYLOAD.lastUpdated})`));
   });
 
   it("fails soft with the reason in the build log when the blob does not answer", async () => {
diff --git a/src/Web/autopilot-monitor-web/lib/platformStats.ts b/src/Web/autopilot-monitor-web/lib/platformStats.ts
index 23b698c3..b0f5652d 100644
--- a/src/Web/autopilot-monitor-web/lib/platformStats.ts
+++ b/src/Web/autopilot-monitor-web/lib/platformStats.ts
@@ -95,9 +95,23 @@ export function toStatItems(payload: PlatformStatsPayload): StatItem[] {
   });
 }
 
-/** Manifest, then the file it names. Throws with the reason; the callers decide what to report. */
-async function readPlatformStats(manifestUrl: string, init: RequestInit): Promise<PlatformStatsPayload> {
-  const manifestResponse = await fetch(manifestUrl, init);
+/** One read: the numbers and the versioned file they came from (named in the build log). */
+interface PlatformStatsRead {
+  payload: PlatformStatsPayload;
+  file: string;
+}
+
+/**
+ * Manifest, then the file it names. Throws with the reason; the callers decide what to report.
+ * Each hop takes its own request options: the manifest changes with every publish, a versioned
+ * file never does.
+ */
+async function readPlatformStats(
+  manifestUrl: string,
+  manifestInit: RequestInit,
+  payloadInit: RequestInit = manifestInit,
+): Promise<PlatformStatsRead> {
+  const manifestResponse = await fetch(manifestUrl, manifestInit);
   if (!manifestResponse.ok) throw new Error(`${manifestUrl} answered HTTP ${manifestResponse.status}`);
   const manifest = (await manifestResponse.json()) as Partial<PlatformStatsManifest> | null;
   if (typeof manifest?.latest !== "string" || !manifest.latest) {
@@ -111,23 +125,23 @@ async function readPlatformStats(manifestUrl: string, init: RequestInit): Promis
     throw new Error(`${manifestUrl} names a file on another origin`);
   }
 
-  const payloadResponse = await fetch(payloadUrl.toString(), init);
+  const payloadResponse = await fetch(payloadUrl.toString(), payloadInit);
   if (!payloadResponse.ok) throw new Error(`${payloadUrl} answered HTTP ${payloadResponse.status}`);
   const payload: unknown = await payloadResponse.json();
   if (typeof payload !== "object" || payload === null) throw new Error(`${payloadUrl} holds no stats object`);
-  return payload as PlatformStatsPayload;
+  return { payload: payload as PlatformStatsPayload, file: manifest.latest };
 }
 
 /**
- * The browser's read. `no-cache` revalidates both files with the blob: the versioned file is
- * named per day but rewritten every 2 hours under `Cache-Control: immutable`, so a copy cached
- * earlier that day would replace the newer baked numbers with older ones.
+ * The browser's read. The manifest is revalidated on every load; the versioned file it names
+ * comes from the browser cache once fetched: the backend writes a new name per publish and serves
+ * it immutable (MaintenanceService.PlatformStatsVersionedFileName).
  */
 export async function fetchLivePlatformStats(
   manifestUrl: string = PLATFORM_STATS_MANIFEST_URL,
 ): Promise<PlatformStatsPayload | null> {
   try {
-    return await readPlatformStats(manifestUrl, { cache: "no-cache" });
+    return (await readPlatformStats(manifestUrl, { cache: "no-cache" }, { cache: "default" })).payload;
   } catch {
     // The band is decorative: a failed read only means no live numbers.
     return null;
@@ -147,14 +161,14 @@ export async function loadPlatformStatsSnapshot(
 ): Promise<PlatformStatsSnapshot | null> {
   if (!/^https?:\/\//i.test(manifestUrl)) return null;
   try {
-    const payload = await readPlatformStats(manifestUrl, {
+    const { payload, file } = await readPlatformStats(manifestUrl, {
       cache: "no-store",
       signal: AbortSignal.timeout(BUILD_FETCH_TIMEOUT_MS),
     });
     const items = toStatItems(payload);
-    if (items.length === 0) throw new Error("the stats file holds no positive figure");
+    if (items.length === 0) throw new Error(`${file} holds no positive figure`);
     const asOf = typeof payload.lastUpdated === "string" ? payload.lastUpdated : null;
-    console.log(`Platform stats baked into the landing page (as of ${asOf ?? "unknown"}).`);
+    console.log(`Platform stats baked into the landing page from ${file} (as of ${asOf ?? "unknown"}).`);
     return { items, asOf };
   } catch (err) {
     // Node's fetch reports every network failure as "fetch failed" and keeps the reason in `cause`.