diff --git a/test/conformance.mjs b/test/conformance.mjs
new file mode 100644
index 0000000..0d8517c
--- /dev/null
+++ b/test/conformance.mjs
@@ -0,0 +1,54 @@
+// The TypeScript implementation, held to the shared fixtures (novox/hq ADR 0074, design 19).
+//
+// Run against a NATS server, because the question is what actually reaches the wire:
+//
+//   docker run -d --rm --name c -p 14222:4222 nats:2.10-alpine -js
+//   node test/conformance.mjs
+//
+// **The runner lives with the implementation it exercises; the fixture does not.** It is read
+// from the sdk's conformance directory by sibling path — the same file the Go suite reads. A
+// fixture copied into each implementation is two fixtures, and two fixtures drift, which is the
+// failure the suite exists to prevent.
+import { readFileSync } from "node:fs";
+import { connect } from "nats";
+
+const clientPath = process.argv[2] ?? "../dist/broker-nats.js";
+const { connectNats } = await import(clientPath);
+const f = JSON.parse(readFileSync(new URL("../../mesh-sdk/conformance/events/module-event.json", import.meta.url)));
+const URL_ = process.env.MESH_TEST_NATS ?? "nats://127.0.0.1:14222";
+
+let failed = 0;
+const check = (ok, what) => { console.log(`  ${ok ? "ok  " : "FAIL"}  ${what}`); if (!ok) failed++; };
+
+const admin = await connect({ servers: URL_ });
+const jsm = await admin.jetstreamManager();
+await jsm.streams.add({ name: "EVENTS", subjects: ["mesh.mod.*.event.>", "mesh.seat.*.event.>"] });
+
+const shop = await connectNats({ url: URL_, node: f.given.node, module: f.given.module });
+await shop.publish({ key: f.given.key, node: f.given.node, body: f.given.body, headers: f.given.headers });
+
+// What actually landed, read back from the stream rather than from the client that wrote it.
+const msg = await jsm.streams.getMessage("EVENTS", { last_by_subj: f.wire.subject });
+check(!!msg, `it lands on ${f.wire.subject}`);
+
+if (msg) {
+  const got = {};
+  if (msg.header) for (const k of msg.header.keys()) got[k] = msg.header.get(k);
+  for (const h of f.wire.requiredHeaders) {
+    check(got[h] !== undefined && got[h] !== "", `${h} is set`);
+  }
+  check(got["content-type"] === f.wire.headerFormats["content-type"], "content-type is as pinned");
+  check(new RegExp(f.wire.headerFormats["x-event-id"]).test(got["x-event-id"]), "x-event-id is as pinned");
+  check(!Number.isNaN(Date.parse(got["x-time"])), "x-time parses as a date");
+  check(got["x-source"] === f.given.module, "x-source agrees with the subject's module");
+
+  const payload = JSON.parse(new TextDecoder().decode(msg.data));
+  check(payload.envelope === undefined && payload.key === undefined,
+    "the payload is the body alone, not the envelope (the fixture refuses nesting)");
+  check(JSON.stringify(payload) === JSON.stringify(f.given.body),
+    "the body round-trips — semantic, not byte-exact, per the README");
+}
+
+await shop.close(); await admin.close();
+console.log(failed ? `\n${failed} failed` : "\nall passed");
+process.exit(failed ? 1 : 0);