fix(usage): Cursor account history loads about 4x faster

apps/server/src/usage/cursorUsageReader.test.ts

@@ -19,4 +19,75 @@ describe("readCursorAccountUsage", () => {
       error: "Allow Keychain access on the Mac running T3 Code, then refresh.",
     });
   });
+
+  it("reads the pages behind the first together and keeps them in page order", async () => {
+    const accessToken = `header.${Buffer.from(JSON.stringify({ sub: "auth|demo" })).toString("base64url")}.signature`;
+    let inFlight = 0;
+    let mostInFlight = 0;
+    const result = await readCursorAccountUsage(
+      { kind: "keychain" },
+      0,
+      1781000000000,
+      async (_url, init) => {
+        const page: number = JSON.parse(String(init.body)).page;
+        inFlight++;
+        mostInFlight = Math.max(mostInFlight, inFlight);
+        // Later pages answer first, so record order cannot come from arrival order.
+        for (let turn = page; turn < 9; turn++) await Promise.resolve();
+        inFlight--;
+        return Response.json({
+          totalUsageEventsCount: 8001,
+          usageEventsDisplay: Array.from({ length: page === 9 ? 1 : 1000 }, (_, index) => ({
+            timestamp: String(1780000000000 + (page - 1) * 1000 + index),
+            model: "gpt-5",
+            tokenUsage: { inputTokens: 1 },
+          })),
+        });
+      },
+      async () => accessToken,
+    );
+    assert.isNull(result.error);
+    assert.strictEqual(mostInFlight, 6);
+    assert.deepStrictEqual(
+      result.records.map((record) => record.timestampMs),
+      Array.from({ length: 8001 }, (_, index) => 1780000000000 + index),
+    );
+  });
+
+  it("ends like a page-by-page read when a page fails, leaving no request open", async () => {
+    const accessToken = `header.${Buffer.from(JSON.stringify({ sub: "auth|demo" })).toString("base64url")}.signature`;
+    const fullPage = {
+      totalUsageEventsCount: 8001,
+      usageEventsDisplay: Array.from({ length: 1000 }, () => ({ tokenUsage: null })),
+    };
+    // Page 3 fails while the pages after it are still waiting on Cursor.
+    for (const [secondPage, error] of [
+      [() => Response.json(fullPage), "Cursor account usage could not be read."],
+      [() => new Response(null, { status: 401 }), "Sign in to Cursor again to read account usage."],
+    ] as const) {
+      let open = 0;
+      const result = await readCursorAccountUsage(
+        { kind: "keychain" },
+        0,
+        1781000000000,
+        (_url, init) => {
+          const page: number = JSON.parse(String(init.body)).page;
+          if (page === 1) return Promise.resolve(Response.json(fullPage));
+          if (page === 2) return Promise.resolve(secondPage());
+          if (page === 3) return Promise.reject(new Error("connection reset"));
+          open++;
+          return new Promise((_resolve, reject) => {
+            init.signal?.addEventListener("abort", () => {
+              open--;
+              reject(init.signal?.reason);
+            });
+          });
+        },
+        async () => accessToken,
+      );
+      assert.strictEqual(result.error, error);
+      assert.deepStrictEqual(result.records, []);
+      assert.strictEqual(open, 0);
+    }
+  });
 });

apps/server/src/usage/cursorUsageReader.ts

@@ -106,6 +106,7 @@ export async function readCursorAccountUsage(
     };
   }
   let accountKey: string | null = null;
+  const cancel = new AbortController();
   try {
     const payload = accessToken.split(".")[1];
     const subject = object(
@@ -117,14 +118,14 @@ export async function readCursorAccountUsage(
     accountKey = accountHash(subject);
     if (!Number.isFinite(sinceMs) || !Number.isFinite(endDate) || sinceMs < 0 || sinceMs > endDate)
       throw new Error("Invalid date window");
-    const deadline = AbortSignal.timeout(60_000);
+    const deadline = AbortSignal.any([cancel.signal, AbortSignal.timeout(60_000)]);
     const records: UsageRecord[] = [];
     const occurrences = new Map<string, number>();
     const pages: unknown[][] = [];
     let completed = false;
     const pageSize = 1000;
     let total: number | undefined;
-    for (let page = 1; ; page++) {
+    const readPage = async (page: number) => {
       // A count can include overlapping page boundaries. Allow room to
       // reconcile them without imposing a fixed account-size limit.
       if (page > (total === undefined ? 1000 : Math.ceil(total / pageSize) * 2 + 1)) {
@@ -181,6 +182,21 @@ export async function readCursorAccountUsage(
         throw new Error("Inconsistent account usage page");
       }
       if (typeof count === "number") total = count;
+      return events;
+    };
+    // Cursor caps a page at 1,000 events and takes about a second to answer one, so the pages
+    // the first one's count implies are requested up to six ahead and consumed in page order.
+    const ahead: ReturnType<typeof readPage>[] = [];
+    for (let page = 1; ; page++) {
+      while (ahead.length < Math.min(6, Math.ceil((total ?? 0) / pageSize) - page + 1)) {
+        const pending = readPage(page + ahead.length);
+        // Handled when its turn comes, or cancelled if the read ends first.
+        pending.catch(() => undefined);
+        ahead.push(pending);
+      }
+      const events = await (ahead.shift() ?? readPage(page));
+      // A rejected login comes back as the finished result instead of a page.
+      if (!Array.isArray(events)) return events;
       pages.push(events);
       if (events.length < pageSize) {
         completed = true;
@@ -268,5 +284,8 @@ export async function readCursorAccountUsage(
       missing: false,
       error: "Cursor account usage could not be read.",
     };
+  } finally {
+    // An early exit leaves the pages requested ahead of it in flight.
+    cancel.abort();
   }
 }