diff --git a/tests/integration/admin-drain-cumulative-endpoint.test.ts b/tests/integration/admin-drain-cumulative-endpoint.test.ts
new file mode 100644
index 000000000..eea43554b
--- /dev/null
+++ b/tests/integration/admin-drain-cumulative-endpoint.test.ts
@@ -0,0 +1,188 @@
+/**
+ * v1.4.30 — `POST /api/admin/drain-per-sample-cumulative` real-
+ * Postgres integration. The library-level helper rides
+ * `tests/integration/drain-per-sample-cumulative.test.ts`; this
+ * suite pins the route's admin gate + payload shape + audit log
+ * trail end-to-end.
+ */
+import { NextRequest } from "next/server";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+import { cookieJar } from "./mock-next-headers";
+import { getPrismaClient, truncateAllTables } from "./setup";
+
+const ADMIN_USER_ID = "user-admin-drain";
+const STANDARD_USER_ID = "user-standard-drain";
+
+vi.mock("next/headers", async () => {
+  const { cookieJar, headerJar } = await import("./mock-next-headers");
+  return {
+    headers: vi.fn(async () => ({
+      get: (name: string) => headerJar.get(name.toLowerCase()) ?? null,
+    })),
+    cookies: vi.fn(async () => ({
+      get: (name: string) => {
+        const value = cookieJar.get(name);
+        return value ? { name, value } : undefined;
+      },
+      set: (name: string, value: string) => {
+        cookieJar.set(name, value);
+      },
+      delete: (name: string) => {
+        cookieJar.delete(name);
+      },
+    })),
+  };
+});
+
+vi.mock("@/lib/db-compat", () => ({
+  ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
+}));
+
+beforeEach(async () => {
+  await truncateAllTables(getPrismaClient());
+  cookieJar.clear();
+  await getPrismaClient().user.createMany({
+    data: [
+      {
+        id: ADMIN_USER_ID,
+        username: "admin-drain",
+        email: "admin-drain@example.test",
+        role: "ADMIN",
+        timezone: "Europe/Berlin",
+      },
+      {
+        id: STANDARD_USER_ID,
+        username: "standard-drain",
+        email: "standard-drain@example.test",
+        role: "USER",
+        timezone: "Europe/Berlin",
+      },
+    ],
+  });
+});
+
+async function setSessionFor(userId: string): Promise<void> {
+  const session = await getPrismaClient().session.create({
+    data: {
+      userId,
+      expiresAt: new Date(Date.now() + 60 * 60 * 1000),
+    },
+  });
+  cookieJar.clear();
+  cookieJar.set("healthlog_session", session.id);
+}
+
+function makeRequest(body: unknown): NextRequest {
+  return new NextRequest(
+    "http://localhost/api/admin/drain-per-sample-cumulative",
+    {
+      method: "POST",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify(body),
+    },
+  );
+}
+
+describe("POST /api/admin/drain-per-sample-cumulative (real Postgres)", () => {
+  it("returns 403 when the session belongs to a standard (non-admin) user", async () => {
+    await setSessionFor(STANDARD_USER_ID);
+    const { POST } = await import(
+      "@/app/api/admin/drain-per-sample-cumulative/route"
+    );
+    const res = await POST(makeRequest({ dryRun: true }));
+    expect(res.status).toBe(403);
+  });
+
+  it("dry-runs by default and reports buckets without writing", async () => {
+    const prisma = getPrismaClient();
+    await prisma.measurement.createMany({
+      data: [
+        {
+          userId: STANDARD_USER_ID,
+          type: "ACTIVITY_STEPS",
+          value: 1200,
+          unit: "steps",
+          source: "APPLE_HEALTH",
+          measuredAt: new Date("2026-05-16T08:00:00.000Z"),
+          externalId: "hk-uuid-1",
+        },
+        {
+          userId: STANDARD_USER_ID,
+          type: "ACTIVITY_STEPS",
+          value: 800,
+          unit: "steps",
+          source: "APPLE_HEALTH",
+          measuredAt: new Date("2026-05-16T14:00:00.000Z"),
+          externalId: "hk-uuid-2",
+        },
+      ],
+    });
+
+    await setSessionFor(ADMIN_USER_ID);
+    const { POST } = await import(
+      "@/app/api/admin/drain-per-sample-cumulative/route"
+    );
+    // No body = dryRun defaults to true.
+    const res = await POST(makeRequest({ userId: STANDARD_USER_ID }));
+    expect(res.status).toBe(200);
+    const json = (await res.json()) as {
+      data: {
+        dryRun: boolean;
+        totals: { bucketsCollapsed: number };
+      };
+    };
+    expect(json.data.dryRun).toBe(true);
+    expect(json.data.totals.bucketsCollapsed).toBe(1);
+
+    // DB unchanged.
+    const remaining = await prisma.measurement.findMany({
+      where: { userId: STANDARD_USER_ID, type: "ACTIVITY_STEPS" },
+    });
+    expect(remaining).toHaveLength(2);
+  });
+
+  it("commits when dryRun=false is passed explicitly", async () => {
+    const prisma = getPrismaClient();
+    await prisma.measurement.createMany({
+      data: [
+        {
+          userId: STANDARD_USER_ID,
+          type: "ACTIVITY_STEPS",
+          value: 1200,
+          unit: "steps",
+          source: "APPLE_HEALTH",
+          measuredAt: new Date("2026-05-16T08:00:00.000Z"),
+          externalId: "hk-uuid-1",
+        },
+        {
+          userId: STANDARD_USER_ID,
+          type: "ACTIVITY_STEPS",
+          value: 800,
+          unit: "steps",
+          source: "APPLE_HEALTH",
+          measuredAt: new Date("2026-05-16T14:00:00.000Z"),
+          externalId: "hk-uuid-2",
+        },
+      ],
+    });
+
+    await setSessionFor(ADMIN_USER_ID);
+    const { POST } = await import(
+      "@/app/api/admin/drain-per-sample-cumulative/route"
+    );
+    const res = await POST(
+      makeRequest({ userId: STANDARD_USER_ID, dryRun: false }),
+    );
+    expect(res.status).toBe(200);
+
+    const remaining = await prisma.measurement.findMany({
+      where: { userId: STANDARD_USER_ID, type: "ACTIVITY_STEPS" },
+    });
+    expect(remaining).toHaveLength(1);
+    expect(remaining[0].value).toBe(2000);
+    expect(remaining[0].externalId).toBe(
+      "stats:HKQuantityTypeIdentifierStepCount:2026-05-16",
+    );
+  });
+});