diff --git a/utils/morse.py b/utils/morse.py
index c21eafa..22db88f 100644
--- a/utils/morse.py
+++ b/utils/morse.py
@@ -11,9 +11,7 @@ from __future__ import annotations
 
 import contextlib
 import math
-import os
 import queue
-import select
 import struct
 import threading
 import time
@@ -769,54 +767,86 @@ def morse_decoder_thread(
     last_pcm_at: float | None = None
     pcm_bytes = 0
     pcm_report_at = time.monotonic()
+    reader_done = threading.Event()
+    reader_thread: threading.Thread | None = None
+
+    raw_queue: queue.Queue[bytes] = queue.Queue(maxsize=96)
 
     try:
-        fd: int | None
-        try:
-            fd = rtl_stdout.fileno()
-        except Exception:
-            fd = None
+        def _reader_loop() -> None:
+            """Blocking PCM reader isolated from decode/control loop."""
+            try:
+                while not stop_event.is_set():
+                    try:
+                        if hasattr(rtl_stdout, 'read1'):
+                            data = rtl_stdout.read1(CHUNK)
+                        else:
+                            data = rtl_stdout.read(CHUNK)
+                    except Exception as e:
+                        with contextlib.suppress(queue.Full):
+                            output_queue.put_nowait({
+                                'type': 'info',
+                                'text': f'[pcm] reader error: {e}',
+                            })
+                        break
+
+                    if data is None:
+                        continue
+
+                    if not data:
+                        break
+
+                    try:
+                        raw_queue.put(data, timeout=0.2)
+                    except queue.Full:
+                        # Keep latest PCM flowing even if downstream hiccups.
+                        with contextlib.suppress(queue.Empty):
+                            raw_queue.get_nowait()
+                        with contextlib.suppress(queue.Full):
+                            raw_queue.put_nowait(data)
+            finally:
+                reader_done.set()
+                with contextlib.suppress(queue.Full):
+                    raw_queue.put_nowait(b'')
+
+        reader_thread = threading.Thread(
+            target=_reader_loop,
+            daemon=True,
+            name='morse-pcm-reader',
+        )
+        reader_thread.start()
 
         while not stop_event.is_set():
             if not _drain_control_queue(control_queue, decoder):
                 break
 
-            data = b''
-            if fd is not None:
-                try:
-                    ready, _, _ = select.select([fd], [], [], 0.20)
-                except Exception:
+            try:
+                data = raw_queue.get(timeout=0.20)
+            except queue.Empty:
+                now = time.monotonic()
+                should_emit_waiting = False
+                if last_pcm_at is None:
+                    should_emit_waiting = True
+                elif (now - last_pcm_at) >= STALLED_AFTER_DATA_SECONDS:
+                    should_emit_waiting = True
+
+                if should_emit_waiting and waiting_since is None:
+                    waiting_since = now
+                if should_emit_waiting and now - last_waiting_emit >= WAITING_INTERVAL:
+                    last_waiting_emit = now
+                    _emit_waiting_scope(output_queue, waiting_since)
+
+                if reader_done.is_set():
                     break
-
-                if ready:
-                    try:
-                        # Use buffered stream read first for cross-platform stability.
-                        if hasattr(rtl_stdout, 'read1'):
-                            data = rtl_stdout.read1(CHUNK)
-                        else:
-                            data = os.read(fd, CHUNK)
-                    except Exception:
-                        break
-                else:
-                    now = time.monotonic()
-                    should_emit_waiting = False
-                    if last_pcm_at is None:
-                        should_emit_waiting = True
-                    elif (now - last_pcm_at) >= STALLED_AFTER_DATA_SECONDS:
-                        should_emit_waiting = True
-
-                    if should_emit_waiting and waiting_since is None:
-                        waiting_since = now
-                    now = time.monotonic()
-                    if should_emit_waiting and now - last_waiting_emit >= WAITING_INTERVAL:
-                        last_waiting_emit = now
-                        _emit_waiting_scope(output_queue, waiting_since)
-                    continue
-            else:
-                # Fallback for test streams without fileno().
-                data = rtl_stdout.read(CHUNK)
+                continue
 
             if not data:
+                if reader_done.is_set() and last_pcm_at is None:
+                    with contextlib.suppress(queue.Full):
+                        output_queue.put_nowait({
+                            'type': 'info',
+                            'text': '[pcm] stream ended before samples were received',
+                        })
                 break
 
             waiting_since = None
@@ -848,7 +878,16 @@ def morse_decoder_thread(
 
     except Exception as e:  # pragma: no cover - defensive runtime guard
         logger.debug(f'Morse decoder thread error: {e}')
+        with contextlib.suppress(queue.Full):
+            output_queue.put_nowait({
+                'type': 'info',
+                'text': f'[pcm] decoder thread error: {e}',
+            })
     finally:
+        stop_event.set()
+        if reader_thread is not None:
+            reader_thread.join(timeout=0.35)
+
         for event in decoder.flush():
             with contextlib.suppress(queue.Full):
                 output_queue.put_nowait(event)