diff --git a/reporting/reporting-api-orders-reports-buffered.https.html b/reporting/reporting-api-orders-reports-buffered.https.html
new file mode 100644
index 00000000000000..14fb60698f50a6
--- /dev/null
+++ b/reporting/reporting-api-orders-reports-buffered.https.html
@@ -0,0 +1,84 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>
+    Reporting API: buffered observer preserves ordering across report types
+  </title>
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/testdriver.js"></script>
+  <script src="/resources/testdriver-vendor.js"></script>
+</head>
+
+<body>
+<script>
+promise_test(async t => {
+  assert_true("ReportingObserver" in self);
+
+  function generateTest(i) {
+    test_driver.generate_test_report(`Test report ${i}`);
+  }
+
+  function generateDeprecation(i) {
+    let img = document.createElement("img");
+
+    img.src = `/some/bunk/file${i}.png`;
+    document.body.appendChild(img);
+  }
+
+  let nonBufferedReports = [];
+  const observeTwoReports = async () => {
+    let { promise, resolve } = Promise.withResolvers();
+    let count = 0;
+    let reportingObserver = new ReportingObserver(reports => {
+      count += reports.length;
+      nonBufferedReports.push(...reports);
+      if (count >= 2) {
+        resolve();
+      }
+    });
+
+    reportingObserver.observe();
+    return promise.finally(() => reportingObserver.disconnect());
+  }
+
+  // Generate interleaved reports
+  for (let i = 0; i < 25; i++) {
+    generateTest(i);
+    generateDeprecation(i);
+    await observeTwoReports();
+  }
+
+  const collected = [];
+  const { promise: collectedAll, resolve } = Promise.withResolvers();
+
+  const observer = new ReportingObserver(
+    reports => {
+      collected.push(...reports);
+      if (collected.length == nonBufferedReports.length) {
+        resolve();
+      }
+    },
+    { buffered: true }
+  );
+
+  observer.observe();
+
+  await collectedAll;
+  observer.disconnect();
+
+  assert_greater_than(
+    collected.length,
+    0,
+    "Some reports must be delivered"
+  );
+
+  // Verify relative ordering by type
+  const observedTypes = collected.map(r => r.type);
+
+  assert_array_equals(observedTypes, nonBufferedReports.map(r => r.type));
+}, "Buffered ReportingObserver preserves report generation order");
+</script>
+</body>
+</html>
diff --git a/reporting/reporting-api-orders-reports-buffered.https.html.sub.headers b/reporting/reporting-api-orders-reports-buffered.https.html.sub.headers
new file mode 100644
index 00000000000000..e6e488d4aa6b92
--- /dev/null
+++ b/reporting/reporting-api-orders-reports-buffered.https.html.sub.headers
@@ -0,0 +1,7 @@
+Expires: Mon, 26 Jul 1997 05:00:00 GMT
+Cache-Control: no-store, no-cache, must-revalidate
+Cache-Control: post-check=0, pre-check=0, false
+Pragma: no-cache
+Set-Cookie: reporting-api-sends-reports-on-violation={{$id:uuid()}}; Path=/content-security-policy/reporting-api
+Reporting-Endpoints: csp-group="https://{{host}}:{{ports[https][0]}}/reporting/resources/report.py?op=put&reportID={{$id}}"
+Content-Security-Policy: script-src 'self' 'unsafe-inline'; img-src 'none'; report-to csp-group
