diff --git a/src/openai/_send_queue.py b/src/openai/_send_queue.py
index b35d0fbcba..998b14850a 100644
--- a/src/openai/_send_queue.py
+++ b/src/openai/_send_queue.py
@@ -11,31 +11,32 @@
 class SendQueue:
     """Bounded byte-size queue for outgoing WebSocket messages.
 
-    Messages are stored as pre-serialized strings. The queue enforces a
-    maximum byte budget so that unbounded buffering cannot occur during
-    reconnection windows.
+    Messages are stored as either ``str`` (text frames) or ``bytes`` (binary
+    frames), preserving the original frame type so that binary payloads are
+    not corrupted on replay. The queue enforces a maximum byte budget so that
+    unbounded buffering cannot occur during reconnection windows.
     """
 
     def __init__(self, max_bytes: int = 1_048_576) -> None:
-        self._queue: list[tuple[str, int]] = []  # (data, byte_length)
+        self._queue: list[tuple[bytes | str, int]] = []  # (data, byte_length)
         self._bytes: int = 0
         self._max_bytes = max_bytes
         self._lock = threading.Lock()
 
-    def enqueue(self, data: str) -> None:
+    def enqueue(self, data: bytes | str) -> None:
         """Append *data* to the queue.
 
         Raises :class:`WebSocketQueueFullError` if the message would
         exceed the byte-size limit.
         """
-        byte_length = len(data.encode("utf-8"))
+        byte_length = len(data) if isinstance(data, bytes) else len(data.encode("utf-8"))
         with self._lock:
             if self._bytes + byte_length > self._max_bytes:
                 raise WebSocketQueueFullError("send queue is full, message discarded")
             self._queue.append((data, byte_length))
             self._bytes += byte_length
 
-    def flush_sync(self, send: typing.Callable[[str], object]) -> None:
+    def flush_sync(self, send: typing.Callable[[bytes | str], object]) -> None:
         """Send every queued message via *send*.
 
         If *send* raises, the failing message and all subsequent messages
@@ -56,7 +57,7 @@ def flush_sync(self, send: typing.Callable[[str], object]) -> None:
                     self._bytes = sum(bl for _, bl in self._queue)
                 raise
 
-    async def flush_async(self, send: typing.Callable[[str], typing.Awaitable[object]]) -> None:
+    async def flush_async(self, send: typing.Callable[[bytes | str], typing.Awaitable[object]]) -> None:
         """Async variant of :meth:`flush_sync`."""
         with self._lock:
             pending = list(self._queue)
@@ -73,7 +74,7 @@ async def flush_async(self, send: typing.Callable[[str], typing.Awaitable[object
                     self._bytes = sum(bl for _, bl in self._queue)
                 raise
 
-    def drain(self) -> list[str]:
+    def drain(self) -> list[bytes | str]:
         """Remove and return all queued messages."""
         with self._lock:
             items = [data for data, _ in self._queue]
diff --git a/src/openai/resources/realtime/realtime.py b/src/openai/resources/realtime/realtime.py
index e4c5bd8163..a29248e3c8 100644
--- a/src/openai/resources/realtime/realtime.py
+++ b/src/openai/resources/realtime/realtime.py
@@ -359,10 +359,13 @@ async def send(self, event: RealtimeClientEvent | RealtimeClientEventParam) -> N
 
     async def send_raw(self, data: bytes | str) -> None:
         if self._is_reconnecting:
-            raw = data if isinstance(data, str) else data.decode("utf-8")
-            self._send_queue.enqueue(raw)
+            self._send_queue.enqueue(data)
             return
-        await self._connection.send(data)
+        try:
+            await self._connection.send(data)
+        except Exception:
+            self._send_queue.enqueue(data)
+            raise
 
     async def close(self, *, code: int = 1000, reason: str = "") -> None:
         self._intentionally_closed = True
@@ -839,10 +842,13 @@ def send(self, event: RealtimeClientEvent | RealtimeClientEventParam) -> None:
 
     def send_raw(self, data: bytes | str) -> None:
         if self._is_reconnecting:
-            raw = data if isinstance(data, str) else data.decode("utf-8")
-            self._send_queue.enqueue(raw)
+            self._send_queue.enqueue(data)
             return
-        self._connection.send(data)
+        try:
+            self._connection.send(data)
+        except Exception:
+            self._send_queue.enqueue(data)
+            raise
 
     def close(self, *, code: int = 1000, reason: str = "") -> None:
         self._intentionally_closed = True
diff --git a/src/openai/resources/responses/responses.py b/src/openai/resources/responses/responses.py
index 5019d7e831..06f3d8e28a 100644
--- a/src/openai/resources/responses/responses.py
+++ b/src/openai/resources/responses/responses.py
@@ -3852,10 +3852,13 @@ async def send(self, event: ResponsesClientEvent | ResponsesClientEventParam) ->
 
     async def send_raw(self, data: bytes | str) -> None:
         if self._is_reconnecting:
-            raw = data if isinstance(data, str) else data.decode("utf-8")
-            self._send_queue.enqueue(raw)
+            self._send_queue.enqueue(data)
             return
-        await self._connection.send(data)
+        try:
+            await self._connection.send(data)
+        except Exception:
+            self._send_queue.enqueue(data)
+            raise
 
     async def close(self, *, code: int = 1000, reason: str = "") -> None:
         self._intentionally_closed = True
@@ -4309,10 +4312,13 @@ def send(self, event: ResponsesClientEvent | ResponsesClientEventParam) -> None:
 
     def send_raw(self, data: bytes | str) -> None:
         if self._is_reconnecting:
-            raw = data if isinstance(data, str) else data.decode("utf-8")
-            self._send_queue.enqueue(raw)
+            self._send_queue.enqueue(data)
             return
-        self._connection.send(data)
+        try:
+            self._connection.send(data)
+        except Exception:
+            self._send_queue.enqueue(data)
+            raise
 
     def close(self, *, code: int = 1000, reason: str = "") -> None:
         self._intentionally_closed = True
diff --git a/tests/test_realtime_reconnect.py b/tests/test_realtime_reconnect.py
new file mode 100644
index 0000000000..27b14744bc
--- /dev/null
+++ b/tests/test_realtime_reconnect.py
@@ -0,0 +1,89 @@
+from __future__ import annotations
+
+from typing import Any
+
+import pytest
+
+from openai.resources.realtime.realtime import AsyncRealtimeConnection
+
+
+def _connection_closed_error(code: int = 1011) -> Exception:
+    from websockets.frames import Close
+    from websockets.exceptions import ConnectionClosedError
+
+    return ConnectionClosedError(Close(code=code, reason=""), None)
+
+
+class _DeadConnection:
+    """A connection whose send() always fails, simulating a dropped socket."""
+
+    async def send(self, _data: bytes | str) -> None:
+        raise _connection_closed_error()
+
+    async def close(self, *, code: int = 1000, reason: str = "") -> None:
+        pass
+
+
+class _RecordingConnection:
+    """The connection returned after a successful reconnect."""
+
+    def __init__(self) -> None:
+        self.sent: list[bytes | str] = []
+
+    async def send(self, data: bytes | str) -> None:
+        self.sent.append(data)
+
+
+def _make_connection(new_conn: _RecordingConnection) -> AsyncRealtimeConnection:
+    async def make_ws(_extra_query: Any, _extra_headers: Any) -> Any:
+        return new_conn
+
+    return AsyncRealtimeConnection(
+        _DeadConnection(),  # type: ignore[arg-type]
+        make_ws=make_ws,
+        on_reconnecting=lambda _event: None,
+        max_retries=1,
+        initial_delay=0.0,
+        max_delay=0.0,
+    )
+
+
+@pytest.mark.asyncio
+async def test_reconnect_resends_binary_payload_unchanged() -> None:
+    """End-to-end: a binary send_raw() that fails mid-send is queued and
+    replayed byte-for-byte after reconnect, without UTF-8 corruption."""
+    from websockets.exceptions import ConnectionClosedError
+
+    new_conn = _RecordingConnection()
+    conn = _make_connection(new_conn)
+
+    binary = b"\xff\xfe\x00audio"  # not valid UTF-8 (would crash on decode)
+
+    # send fails on the dead socket -> the original connection error must
+    # surface (NOT a UnicodeDecodeError from decoding the binary payload),
+    # and the payload must be queued for replay.
+    with pytest.raises(ConnectionClosedError):
+        await conn.send_raw(binary)
+
+    # Drive the real reconnect path, which flushes the queue to the new socket.
+    reconnected = await conn._reconnect(_connection_closed_error())
+    assert reconnected is True
+
+    assert new_conn.sent == [binary]
+    assert isinstance(new_conn.sent[0], bytes)
+
+
+@pytest.mark.asyncio
+async def test_reconnect_resends_text_payload() -> None:
+    """A str send_raw() is replayed as text after reconnect."""
+    from websockets.exceptions import ConnectionClosedError
+
+    new_conn = _RecordingConnection()
+    conn = _make_connection(new_conn)
+
+    with pytest.raises(ConnectionClosedError):
+        await conn.send_raw('{"type": "input_audio_buffer.append"}')
+
+    assert await conn._reconnect(_connection_closed_error()) is True
+    assert new_conn.sent == ['{"type": "input_audio_buffer.append"}']
+    assert isinstance(new_conn.sent[0], str)
diff --git a/tests/test_send_queue.py b/tests/test_send_queue.py
index 61db916bc4..6d0676337f 100644
--- a/tests/test_send_queue.py
+++ b/tests/test_send_queue.py
@@ -19,6 +19,39 @@ def test_enqueue_and_drain(self) -> None:
         assert items == ['{"type": "session.update"}', '{"type": "response.create"}']
         assert len(q) == 0
 
+    def test_enqueue_preserves_binary_frames(self) -> None:
+        """Binary payloads must be stored as-is, not decoded to text.
+
+        Decoding to UTF-8 would corrupt binary frames and raise
+        ``UnicodeDecodeError`` for arbitrary bytes (e.g. audio chunks).
+        """
+        q = SendQueue()
+        binary = b"\xff\xfe\x00audio"  # not valid UTF-8
+        q.enqueue(binary)
+        q.enqueue("text")
+
+        items = q.drain()
+        assert items == [binary, "text"]
+        assert isinstance(items[0], bytes)
+        assert isinstance(items[1], str)
+
+    def test_enqueue_counts_binary_byte_length(self) -> None:
+        q = SendQueue(max_bytes=4)
+        q.enqueue(b"\xff\xfe\xfd\xfc")  # 4 bytes, fits exactly
+        with pytest.raises(WebSocketQueueFullError):
+            q.enqueue(b"\x00")  # would exceed
+        assert len(q) == 1
+
+    def test_flush_sync_preserves_binary(self) -> None:
+        q = SendQueue()
+        binary = b"\xff\xfe"
+        q.enqueue(binary)
+        q.enqueue("text")
+
+        sent: list[bytes | str] = []
+        q.flush_sync(sent.append)
+        assert sent == [binary, "text"]
+
     def test_enqueue_respects_byte_limit(self) -> None:
         q = SendQueue(max_bytes=10)
         q.enqueue("12345")  # 5 bytes, fits