diff --git a/tests-js/bugreport-proxy-worker.test.mjs b/tests-js/bugreport-proxy-worker.test.mjs
index 5739e2be0..cfcd1c310 100644
--- a/tests-js/bugreport-proxy-worker.test.mjs
+++ b/tests-js/bugreport-proxy-worker.test.mjs
@@ -118,3 +118,53 @@ test("non-error routing is untouched", async () => {
     new Request("https://proxy.example/update", { method: "GET" }), SECRET_ENV);
   assert.equal(unauth.status, 401, "a wrong/absent secret still 401s first");
 });
+
+const FIXTURE = join(dirname(fileURLToPath(import.meta.url)),
+  "..", "tests", "fixtures", "bugreport_contract", "automatic_report.md");
+const REPORT_ENV = { GITHUB_TOKEN: "g", TARGET_REPO: "a/b" };
+
+// POST a report to the Worker with GitHub stubbed; returns the response, its JSON
+// body, and every request the Worker sent upstream.
+async function postReport(worker, payload) {
+  const realFetch = globalThis.fetch;
+  const upstream = [];
+  globalThis.fetch = async (u, init) => {
+    upstream.push({ url: String(u), body: init && init.body ? JSON.parse(init.body) : null });
+    return new Response(JSON.stringify({ html_url: "https://github.com/a/b/issues/1", number: 1 }),
+      { status: 201, headers: { "Content-Type": "application/json" } });
+  };
+  try {
+    const res = await worker.fetch(new Request("https://proxy.example/", {
+      method: "POST", headers: { "Content-Type": "application/json" },
+      body: JSON.stringify(payload) }), REPORT_ENV);
+    return { res, body: await res.json(), upstream };
+  } finally {
+    globalThis.fetch = realFetch;
+  }
+}
+
+test("a body without the report's sections is still filed, flagged in the note", async () => {
+  const worker = await loadWorker();
+  for (const payload of [{ title: "%n", body: "%s%s%s" }, { title: "A".repeat(128), body: "name" }]) {
+    const { res, upstream } = await postReport(worker, payload);
+    assert.equal(res.status, 201, "a report is never refused for its shape");
+    assert.equal(upstream.length, 1);
+    const filed = upstream[0].body.body;
+    assert.ok(filed.startsWith("> Filed through the localm bug reporter on behalf of a user."), filed.slice(0, 120));
+    assert.match(filed, /does not have the sections a report built by localm contains/);
+    assert.ok(filed.endsWith(payload.body));
+  }
+});
+
+test("a report built by localm is filed, prefixed with the reporter note", async () => {
+  const worker = await loadWorker();
+  const report = readFileSync(FIXTURE, "utf8");
+  const { res, body, upstream } = await postReport(worker, { title: "localm bug report", body: report });
+  assert.equal(res.status, 201);
+  assert.equal(body.number, 1);
+  assert.equal(upstream.length, 1);
+  const filed = upstream[0].body.body;
+  assert.ok(filed.startsWith("> Filed through the localm bug reporter on behalf of a user."), filed.slice(0, 120));
+  assert.ok(filed.endsWith(report), "the report follows the note unchanged");
+  assert.doesNotMatch(filed, /does not have the sections/, "a real report is not flagged");
+});
\ No newline at end of file
diff --git a/tools/bugreport-proxy/worker.js b/tools/bugreport-proxy/worker.js
index 33ff69125..7e2c84d47 100644
--- a/tools/bugreport-proxy/worker.js
+++ b/tools/bugreport-proxy/worker.js
@@ -101,9 +101,10 @@ async function fileReport(request, env) {
   let payload;
   try { payload = await request.json(); } catch { return json({ error: "invalid JSON" }, 400); }
   const title = (String(payload.title || "").slice(0, 200).trim()) || "localm bug report";
-  const body = String(payload.body || "").slice(0, 60000);
-  if (!body.trim()) return json({ error: "empty report body" }, 400);
-  const issue = { title, body };
+  const report = String(payload.body || "").slice(0, 60000);
+  if (!report.trim()) return json({ error: "empty report body" }, 400);
+  const note = looksLikeLocalmReport(report) ? REPORTER_NOTE : REPORTER_NOTE_UNSHAPED;
+  const issue = { title, body: note + report };
   if (env.ISSUE_LABELS) {
     const labels = env.ISSUE_LABELS.split(",").map((s) => s.trim()).filter(Boolean);
     if (labels.length) issue.labels = labels;
@@ -119,6 +120,26 @@ async function fileReport(request, env) {
   return json({ ok: true, url: data.html_url, number: data.number }, 201);
 }
 
+// Prepended to the body of every issue this proxy files.
+const REPORTER_NOTE =
+  "> Filed through the localm bug reporter on behalf of a user. " +
+  "This text was not written by the repository owner.\n\n";
+
+// Prepended instead of REPORTER_NOTE when the body lacks the REPORT_SECTIONS headings.
+const REPORTER_NOTE_UNSHAPED =
+  "> Filed through the localm bug reporter on behalf of a user. " +
+  "This text was not written by the repository owner.\n" +
+  "> It does not have the sections a report built by localm contains.\n\n";
+
+// Section headings every report built by localm's reporter contains.
+const REPORT_SECTIONS = ["## What happened", "## Environment"];
+
+// True when *text* has every heading in REPORT_SECTIONS on a line of its own.
+function looksLikeLocalmReport(text) {
+  const lines = text.split(/\r?\n/).map((line) => line.trim());
+  return REPORT_SECTIONS.every((h) => lines.includes(h));
+}
+
 // ---------------------------- issues ------------------------------------
 
 async function listIssues(request, env, url) {