perf(server): count active tasks in SQL before create

apps/server/src/db.ts

@@ -30,6 +30,14 @@ export class Store {
     );
     return result.rows.map((row) => row.data as T);
   }
+  async countActiveTasks(owner: string, terminalStatuses: string[]): Promise<number> {
+    const result = await this.db.query(
+      "SELECT count(*)::int AS n FROM records WHERE owner=$1 AND kind='tasks' AND NOT (COALESCE(data->>'status','') = ANY($2::text[]))",
+      [owner, terminalStatuses],
+    );
+    const row = result.rows[0] as unknown as { n: number } | undefined;
+    return row?.n ?? 0;
+  }
   async put<T extends { id: string }>(owner: string, kind: string, value: T): Promise<T> {
     await this.db.query(
       "INSERT INTO records(owner,kind,id,data) VALUES($1,$2,$3,$4::jsonb) ON CONFLICT(owner,kind,id) DO UPDATE SET data=excluded.data,updated_at=now()",

apps/server/src/engine/service.ts

@@ -184,10 +184,7 @@ export class AgentService {
     const id = idempotencyKey ? hash(`task:${idempotencyKey}`) : randomUUID();
     const existing = await this.db.get<AgentTask>(owner, "tasks", id);
     if (existing) return existing;
-    if (
-      (await this.db.list<AgentTask>(owner, "tasks")).filter((t) => !terminal.has(t.status))
-        .length >= 100
-    )
+    if ((await this.db.countActiveTasks(owner, [...terminal])) >= 100)
       throw new AppError("Finish or cancel some tasks before adding more", 409);
     const titles =
       input.kind === "document"

tests/persistence.test.ts

@@ -31,3 +31,37 @@ test("idle Postgres client errors are logged instead of crashing the process", a
     await pool.end();
   }
 });
+
+test("countActiveTasks matches the createTask cap semantics", async () => {
+  const store = await createStore();
+  try {
+    const terminal = ["succeeded", "failed", "cancelled"];
+    const statuses = [
+      "queued",
+      "running",
+      "scheduled",
+      "waiting_input",
+      "waiting_approval",
+      "paused",
+      "succeeded",
+      "failed",
+      "cancelled",
+    ];
+    for (let i = 0; i < statuses.length; i++)
+      await store.put("owner", "tasks", { id: `t${i}`, status: statuses[i] });
+    await store.put("owner", "tasks", { id: "t-none" });
+
+    const expected = (await store.list<{ id: string; status?: string }>("owner", "tasks")).filter(
+      (item) => !terminal.includes(item.status ?? ""),
+    ).length;
+    assert.equal(await store.countActiveTasks("owner", terminal), expected);
+    assert.equal(expected, 7);
+
+    await store.put("other", "tasks", { id: "x", status: "queued" });
+    await store.put("owner", "goals", { id: "g", status: "queued" });
+    assert.equal(await store.countActiveTasks("owner", terminal), 7);
+    assert.equal(await store.countActiveTasks("nobody", terminal), 0);
+  } finally {
+    await store.close();
+  }
+});