diff --git a/web/chat.html b/web/chat.html
index f368240..a6e9313 100644
--- a/web/chat.html
+++ b/web/chat.html
@@ -334,6 +334,10 @@ const WS_URL = 'ws://127.0.0.1:7777';
 const PBKDF2_SALT = new TextEncoder().encode('zebra-report-v1');
 const PBKDF2_ITER = 600000;
 
+/* dev loopback: bypass PulseAudio, ride BroadcastChannel between tabs.
+ * gated on ?loopback=1. real PA transport stays the production path.   */
+const LOOPBACK = new URLSearchParams(location.search).has('loopback');
+
 /* ============================================================== *
  * tiny utils                                                       *
  * ============================================================== */
@@ -630,6 +634,14 @@ async function txFrame(bytes, baud) {
     while (txQueue.length) {
       const job = txQueue.shift();
       await _txOne(job.bytes, job.baud);
+      if (loopChan) {
+        try {
+          const ab = job.bytes.buffer.slice(
+            job.bytes.byteOffset,
+            job.bytes.byteOffset + job.bytes.byteLength);
+          loopChan.postMessage(ab);
+        } catch (_) {}
+      }
     }
   } finally {
     txBusy = false;
@@ -705,10 +717,19 @@ function recomputeGroupBaud() {
 }
 
 /* ============================================================== *
- * introspector bridge (RX path)                                   *
+ * introspector bridge (RX path) + dev loopback                    *
  * ============================================================== */
 let ws = null;
 let wsReconnectTimer = null;
+let loopChan = null;
+if (LOOPBACK) {
+  loopChan = new BroadcastChannel('zebra-report-loopback');
+  loopChan.onmessage = (ev) => {
+    const buf = ev.data instanceof ArrayBuffer
+      ? new Uint8Array(ev.data) : new Uint8Array(ev.data);
+    onRxFrame(buf);
+  };
+}
 const dotRx = $('dot-rx');
 const rxStatus = $('rx-status');
 
@@ -1053,6 +1074,19 @@ setInterval(updateSendButton, 1000);
 /* try to find the introspector; quiet failure */
 rxConnect(false);
 
+if (LOOPBACK) {
+  const banner = document.createElement('div');
+  banner.style.cssText =
+    'background:#fc0;color:#000;padding:0.6rem 1rem;text-align:center;' +
+    'font-size:0.8rem;font-weight:bold;border:1px solid #000;' +
+    'margin-bottom:1.2rem;letter-spacing:0.03em';
+  banner.textContent =
+    'dev loopback active — frames cross via BroadcastChannel between ' +
+    'same-browser tabs, NOT via PulseAudio. drop ?loopback=1 from the URL for production.';
+  document.body.insertBefore(banner, document.body.firstChild);
+  logLine('sys', 'loopback mode: frames will echo to other tabs of this same browser.');
+}
+
 logLine('sys', 'ready — start the carrier, derive a room key, then send.');
 logLine('sys', 'no chat content ever enters an IP packet. wireshark blind.');