diff --git a/src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js b/src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js
index 73cf5ab..7f3e68e 100644
--- a/src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js
+++ b/src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js
@@ -6036,28 +6036,29 @@ function connectDecode() {
   if (window.resetCwHistoryView) window.resetCwHistoryView();
   if (window.resetFt8HistoryView) window.resetFt8HistoryView();
   if (window.resetWsprHistoryView) window.resetWsprHistoryView();
-  const historyBuffer = [];
-  let historyDone = false;
+  // Live messages arrive after the history event; gate on this flag so
+  // onmessage does not dispatch before drainDecodeHistory has started.
+  let historyReceived = false;
   decodeSource = new EventSource("/decode");
   decodeSource.onopen = () => {
     decodeConnected = true;
     updateDecodeStatus("Connected, listening for packets");
   };
-  decodeSource.addEventListener("history_done", () => {
-    historyDone = true;
-    drainDecodeHistory(historyBuffer, 0);
+  // The server sends the entire history as one named "history" event (JSON
+  // array). A single JSON.parse + chunked drain is far cheaper than N
+  // individual EventSource callbacks each blocking the main thread.
+  decodeSource.addEventListener("history", (evt) => {
+    try {
+      const msgs = JSON.parse(evt.data);
+      if (Array.isArray(msgs)) drainDecodeHistory(msgs, 0);
+    } catch (e) { /* ignore parse errors */ }
+    historyReceived = true;
   });
   decodeSource.onmessage = (evt) => {
+    if (!historyReceived) return; // skip anything before history event
     try {
-      const msg = JSON.parse(evt.data);
-      if (!historyDone) {
-        historyBuffer.push(msg);
-      } else {
-        dispatchDecodeMessage(msg);
-      }
-    } catch (e) {
-      // ignore parse errors
-    }
+      dispatchDecodeMessage(JSON.parse(evt.data));
+    } catch (e) { /* ignore parse errors */ }
   };
   decodeSource.onerror = () => {
     // readyState CLOSED (2) = server rejected (404/error), CONNECTING (0) = temporary drop
diff --git a/src/trx-client/trx-frontend/trx-frontend-http/src/api.rs b/src/trx-client/trx-frontend/trx-frontend-http/src/api.rs
index 212bf4e..ffdd63c 100644
--- a/src/trx-client/trx-frontend/trx-frontend-http/src/api.rs
+++ b/src/trx-client/trx-frontend/trx-frontend-http/src/api.rs
@@ -326,14 +326,15 @@ pub async fn decode_events(
         out
     };
 
-    let history_stream = futures_util::stream::iter(history.into_iter().filter_map(|msg| {
-        serde_json::to_string(&msg)
-            .ok()
-            .map(|json| Ok::<Bytes, Error>(Bytes::from(format!("data: {json}\n\n"))))
-    }));
-
-    let history_done =
-        once(async { Ok::<Bytes, Error>(Bytes::from("event: history_done\ndata: {}\n\n")) });
+    // Send the entire history as a single named "history" event (JSON array).
+    // Sending N individual events causes N EventSource callbacks in the browser,
+    // each blocking the main thread — for large histories this interrupts audio
+    // and spectrum rendering for tens of seconds.
+    let history_event = {
+        let json = serde_json::to_string(&history).unwrap_or_else(|_| "[]".to_string());
+        Bytes::from(format!("event: history\ndata: {json}\n\n"))
+    };
+    let history_stream = once(async move { Ok::<Bytes, Error>(history_event) });
 
     let decode_stream = futures_util::stream::unfold(decode_rx, |mut rx| async move {
         loop {
@@ -355,7 +356,7 @@ pub async fn decode_events(
     let pings = IntervalStream::new(time::interval(Duration::from_secs(15)))
         .map(|_| Ok::<Bytes, Error>(Bytes::from(": ping\n\n")));
 
-    let stream = history_stream.chain(history_done).chain(select(pings, decode_stream));
+    let stream = history_stream.chain(select(pings, decode_stream));
 
     Ok(HttpResponse::Ok()
         .insert_header((header::CONTENT_TYPE, "text/event-stream"))