diff --git a/supervisor/api/proxy.py b/supervisor/api/proxy.py
index 8f03e8af4..74a9346a8 100644
--- a/supervisor/api/proxy.py
+++ b/supervisor/api/proxy.py
@@ -6,7 +6,10 @@ import logging
 import aiohttp
 from aiohttp import web
 from aiohttp.client_exceptions import ClientConnectorError
+from aiohttp.client_ws import ClientWebSocketResponse
 from aiohttp.hdrs import AUTHORIZATION, CONTENT_TYPE
+from aiohttp.http import WSMessage
+from aiohttp.http_websocket import WSMsgType
 from aiohttp.web_exceptions import HTTPBadGateway, HTTPUnauthorized
 
 from ..coresys import CoreSysAttributes
@@ -114,7 +117,7 @@ class APIProxy(CoreSysAttributes):
                 body=data, status=client.status, content_type=client.content_type
             )
 
-    async def _websocket_client(self):
+    async def _websocket_client(self) -> ClientWebSocketResponse:
         """Initialize a WebSocket API connection."""
         url = f"{self.sys_homeassistant.api_url}/api/websocket"
 
@@ -167,6 +170,25 @@ class APIProxy(CoreSysAttributes):
 
         raise APIError()
 
+    async def _proxy_message(
+        self,
+        read_task: asyncio.Task,
+        target: web.WebSocketResponse | ClientWebSocketResponse,
+    ) -> None:
+        """Proxy a message from client to server or vice versa."""
+        if read_task.exception():
+            raise read_task.exception()
+
+        msg: WSMessage = read_task.result()
+        if msg.type == WSMsgType.TEXT:
+            return await target.send_str(msg.data)
+        if msg.type == WSMsgType.BINARY:
+            return await target.send_bytes(msg.data)
+
+        raise TypeError(
+            f"Cannot proxy websocket message of unsupported type: {msg.type}"
+        )
+
     async def websocket(self, request: web.Request):
         """Initialize a WebSocket API connection."""
         if not await self.sys_homeassistant.api.check_api_state():
@@ -214,13 +236,13 @@ class APIProxy(CoreSysAttributes):
 
         _LOGGER.info("Home Assistant WebSocket API request running")
         try:
-            client_read = None
-            server_read = None
+            client_read: asyncio.Task | None = None
+            server_read: asyncio.Task | None = None
             while not server.closed and not client.closed:
                 if not client_read:
-                    client_read = self.sys_create_task(client.receive_str())
+                    client_read = self.sys_create_task(client.receive())
                 if not server_read:
-                    server_read = self.sys_create_task(server.receive_str())
+                    server_read = self.sys_create_task(server.receive())
 
                 # wait until data need to be processed
                 await asyncio.wait(
@@ -229,14 +251,12 @@ class APIProxy(CoreSysAttributes):
 
                 # server
                 if server_read.done() and not client.closed:
-                    server_read.exception()
-                    await client.send_str(server_read.result())
+                    await self._proxy_message(server_read, client)
                     server_read = None
 
                 # client
                 if client_read.done() and not server.closed:
-                    client_read.exception()
-                    await server.send_str(client_read.result())
+                    await self._proxy_message(client_read, server)
                     client_read = None
 
         except asyncio.CancelledError:
@@ -246,9 +266,9 @@ class APIProxy(CoreSysAttributes):
             _LOGGER.info("Home Assistant WebSocket API error: %s", err)
 
         finally:
-            if client_read:
+            if client_read and not client_read.done():
                 client_read.cancel()
-            if server_read:
+            if server_read and not server_read.done():
                 server_read.cancel()
 
             # close connections
diff --git a/tests/api/test_proxy.py b/tests/api/test_proxy.py
new file mode 100644
index 000000000..0da8675cc
--- /dev/null
+++ b/tests/api/test_proxy.py
@@ -0,0 +1,177 @@
+"""Test Home Assistant proxy."""
+
+from __future__ import annotations
+
+import asyncio
+from collections.abc import Awaitable, Callable, Coroutine, Generator
+from json import dumps
+from typing import Any, cast
+from unittest.mock import patch
+
+from aiohttp import ClientWebSocketResponse
+from aiohttp.http_websocket import WSMessage, WSMsgType
+from aiohttp.test_utils import TestClient
+import pytest
+
+from supervisor.addons.addon import Addon
+from supervisor.api.proxy import APIProxy
+from supervisor.const import ATTR_ACCESS_TOKEN
+
+
+def id_generator() -> Generator[int, None, None]:
+    """Generate IDs for WS messages."""
+    i = 0
+    while True:
+        yield (i := i + 1)
+
+
+class MockHAClientWebSocket(ClientWebSocketResponse):
+    """Protocol for a wrapped ClientWebSocketResponse."""
+
+    client: TestClient
+    send_json_auto_id: Callable[[dict[str, Any]], Coroutine[Any, Any, None]]
+
+
+class MockHAServerWebSocket:
+    """Mock of HA Websocket server."""
+
+    closed: bool = False
+
+    def __init__(self) -> None:
+        """Initialize object."""
+        self.outgoing: asyncio.Queue[WSMessage] = asyncio.Queue()
+        self.incoming: asyncio.Queue[WSMessage] = asyncio.Queue()
+        self._id_generator = id_generator()
+
+    def receive(self) -> Awaitable[WSMessage]:
+        """Receive next message."""
+        return self.outgoing.get()
+
+    def send_str(self, data: str) -> Awaitable[None]:
+        """Incoming string message."""
+        return self.incoming.put(WSMessage(WSMsgType.TEXT, data, None))
+
+    def send_bytes(self, data: bytes) -> Awaitable[None]:
+        """Incoming string message."""
+        return self.incoming.put(WSMessage(WSMsgType.BINARY, data, None))
+
+    def respond_json(self, data: dict[str, Any]) -> Awaitable[None]:
+        """Respond with JSON."""
+        return self.outgoing.put(
+            WSMessage(
+                WSMsgType.TEXT, dumps(data | {"id": next(self._id_generator)}), None
+            )
+        )
+
+    def respond_bytes(self, data: bytes) -> Awaitable[None]:
+        """Respond with binary."""
+        return self.outgoing.put(WSMessage(WSMsgType.BINARY, data, None))
+
+    async def close(self) -> None:
+        """Close connection."""
+        self.closed = True
+
+
+WebSocketGenerator = Callable[..., Coroutine[Any, Any, MockHAClientWebSocket]]
+
+
+@pytest.fixture(name="ha_ws_server")
+async def fixture_ha_ws_server() -> MockHAServerWebSocket:
+    """Mock HA WS server for testing."""
+    with patch.object(
+        APIProxy,
+        "_websocket_client",
+        return_value=(mock_server := MockHAServerWebSocket()),
+    ):
+        yield mock_server
+
+
+@pytest.fixture(name="proxy_ws_client")
+def fixture_proxy_ws_client(
+    api_client: TestClient, ha_ws_server: MockHAServerWebSocket
+) -> WebSocketGenerator:
+    """Websocket client fixture connected to websocket server."""
+
+    async def create_client(auth_token: str) -> MockHAClientWebSocket:
+        """Create a websocket client."""
+        websocket = await api_client.ws_connect("/core/websocket")
+        auth_resp = await websocket.receive_json()
+        assert auth_resp["type"] == "auth_required"
+        await websocket.send_json({"type": "auth", "access_token": auth_token})
+
+        auth_ok = await websocket.receive_json()
+        assert auth_ok["type"] == "auth_ok"
+
+        _id_generator = id_generator()
+
+        def _send_json_auto_id(data: dict[str, Any]) -> Coroutine[Any, Any, None]:
+            data["id"] = next(_id_generator)
+            return websocket.send_json(data)
+
+        # wrap in client
+        wrapped_websocket = cast(MockHAClientWebSocket, websocket)
+        wrapped_websocket.client = api_client
+        wrapped_websocket.send_json_auto_id = _send_json_auto_id
+        return wrapped_websocket
+
+    return create_client
+
+
+async def test_proxy_message(
+    proxy_ws_client: WebSocketGenerator,
+    ha_ws_server: MockHAServerWebSocket,
+    install_addon_ssh: Addon,
+):
+    """Test proxy a message to and from Home Assistant."""
+    install_addon_ssh.persist[ATTR_ACCESS_TOKEN] = "abc123"
+    client: MockHAClientWebSocket = await proxy_ws_client(
+        install_addon_ssh.supervisor_token
+    )
+
+    await client.send_json_auto_id({"hello": "world"})
+    proxied_msg = await ha_ws_server.incoming.get()
+    assert proxied_msg.type == WSMsgType.TEXT
+    assert proxied_msg.data == '{"hello": "world", "id": 1}'
+
+    await ha_ws_server.respond_json({"world": "received"})
+    assert await client.receive_json() == {"world": "received", "id": 1}
+
+    assert await client.close()
+
+
+async def test_proxy_binary_message(
+    proxy_ws_client: WebSocketGenerator,
+    ha_ws_server: MockHAServerWebSocket,
+    install_addon_ssh: Addon,
+):
+    """Test proxy a binary message to and from Home Assistant."""
+    install_addon_ssh.persist[ATTR_ACCESS_TOKEN] = "abc123"
+    client: MockHAClientWebSocket = await proxy_ws_client(
+        install_addon_ssh.supervisor_token
+    )
+
+    await client.send_bytes(b"hello world")
+    proxied_msg = await ha_ws_server.incoming.get()
+    assert proxied_msg.type == WSMsgType.BINARY
+    assert proxied_msg.data == b"hello world"
+
+    await ha_ws_server.respond_bytes(b"world received")
+    assert await client.receive_bytes() == b"world received"
+
+    assert await client.close()
+
+
+@pytest.mark.parametrize("auth_token", ["abc123", "bad"])
+async def test_proxy_invalid_auth(
+    api_client: TestClient, install_addon_example: Addon, auth_token: str
+):
+    """Test invalid access token or addon with no access."""
+    install_addon_example.persist[ATTR_ACCESS_TOKEN] = "abc123"
+    websocket = await api_client.ws_connect("/core/websocket")
+    auth_resp = await websocket.receive_json()
+    assert auth_resp["type"] == "auth_required"
+    await websocket.send_json({"type": "auth", "access_token": auth_token})
+
+    auth_not_ok = await websocket.receive_json()
+    assert auth_not_ok["type"] == "auth_invalid"
+    assert auth_not_ok["message"] == "Invalid access"
diff --git a/tests/fixtures/addons/local/ssh/config.yaml b/tests/fixtures/addons/local/ssh/config.yaml
index 3e67c70d5..38dac441c 100644
--- a/tests/fixtures/addons/local/ssh/config.yaml
+++ b/tests/fixtures/addons/local/ssh/config.yaml
@@ -17,6 +17,7 @@ panel_icon: "mdi:console"
 panel_title: Terminal
 hassio_api: true
 hassio_role: manager
+homeassistant_api: true
 audio: true
 uart: true
 ports: