diff --git a/README.rst b/README.rst
index 190b9a1..1c982c2 100644
--- a/README.rst
+++ b/README.rst
@@ -64,7 +64,6 @@ which can seen by running ``sphinx-autobuild --help``:
      --ignore IGNORE       glob expression for files to ignore, when watching for changes
      --no-initial          skip the initial build
      --open-browser        open the browser after building documentation
-     --delay DELAY         how long to wait before opening the browser
      --watch DIR           additional directories to watch
      --pre-build COMMAND   additional command(s) to run prior to building the documentation
      --post-build COMMAND  additional command(s) to run after building the documentation
diff --git a/sphinx_autobuild/__main__.py b/sphinx_autobuild/__main__.py
index b1f058f..88ce9a3 100644
--- a/sphinx_autobuild/__main__.py
+++ b/sphinx_autobuild/__main__.py
@@ -5,6 +5,8 @@
 import argparse
 import shlex
 import sys
+import webbrowser
+from contextlib import asynccontextmanager
 from pathlib import Path
 
 import colorama
@@ -22,7 +24,7 @@
 from sphinx_autobuild.filter import IgnoreFilter
 from sphinx_autobuild.middleware import JavascriptInjectorMiddleware
 from sphinx_autobuild.server import RebuildServer
-from sphinx_autobuild.utils import find_free_port, open_browser, show_message
+from sphinx_autobuild.utils import find_free_port, show_message
 
 
 def main(argv=()):
@@ -80,15 +82,15 @@ def main(argv=()):
     ]
     ignore_dirs = list(filter(None, ignore_dirs))
     ignore_handler = IgnoreFilter(ignore_dirs, args.re_ignore)
-    app = _create_app(watch_dirs, ignore_handler, builder, serve_dir, url_host)
+
+    app = _create_app(
+        watch_dirs, ignore_handler, builder, serve_dir, url_host, args.open_browser
+    )
 
     if not args.no_initial_build:
         show_message("Starting initial build")
         builder(changed_paths=())
 
-    if args.open_browser:
-        open_browser(url_host, args.delay)
-
     show_message("Waiting to detect changes...")
     try:
         uvicorn.run(app, host=host_name, port=port_num, log_level="warning")
@@ -96,16 +98,25 @@ def main(argv=()):
         show_message("Server ceasing operations. Cheerio!")
 
 
-def _create_app(watch_dirs, ignore_handler, builder, out_dir, url_host):
+def _create_app(
+    watch_dirs, ignore_handler, builder, out_dir, url_host, open_browser=False
+):
     watcher = RebuildServer(watch_dirs, ignore_handler, change_callback=builder)
 
+    @asynccontextmanager
+    async def lifespan(app):
+        async with watcher.lifespan(app):
+            if open_browser:
+                webbrowser.open(f"http://{url_host}")
+            yield
+
     return Starlette(
         routes=[
             WebSocketRoute("/websocket-reload", watcher, name="reload"),
             Mount("/", app=StaticFiles(directory=out_dir, html=True), name="static"),
         ],
         middleware=[Middleware(JavascriptInjectorMiddleware, ws_url=url_host)],
-        lifespan=watcher.lifespan,
+        lifespan=lifespan,
     )
 
 
@@ -216,13 +227,7 @@ def _add_autobuild_arguments(parser):
         default=False,
         help="open the browser after building documentation",
     )
-    group.add_argument(
-        "--delay",
-        dest="delay",
-        type=float,
-        default=5,
-        help="how long to wait before opening the browser",
-    )
+
     group.add_argument(
         "--watch",
         action="append",
diff --git a/sphinx_autobuild/server.py b/sphinx_autobuild/server.py
index c32b3f2..55ad079 100644
--- a/sphinx_autobuild/server.py
+++ b/sphinx_autobuild/server.py
@@ -2,7 +2,7 @@
 
 import asyncio
 from concurrent.futures import ProcessPoolExecutor
-from contextlib import AbstractAsyncContextManager, asynccontextmanager
+from contextlib import asynccontextmanager
 from pathlib import Path
 from typing import TYPE_CHECKING
 
@@ -10,20 +10,24 @@
 from starlette.websockets import WebSocket
 
 if TYPE_CHECKING:
-    import os
-    from collections.abc import Callable, Sequence
+    from collections.abc import AsyncGenerator, Sequence
+    from os import PathLike
+    from typing import Protocol
 
     from starlette.types import Receive, Scope, Send
 
     from sphinx_autobuild.filter import IgnoreFilter
 
+    class ChangeCallback(Protocol):
+        def __call__(self, *, changed_paths: Sequence[Path]) -> None: ...
+
 
 class RebuildServer:
     def __init__(
         self,
-        paths: list[os.PathLike[str]],
+        paths: list[PathLike[str]],
         ignore_filter: IgnoreFilter,
-        change_callback: Callable[[Sequence[Path]], None],
+        change_callback: ChangeCallback,
     ) -> None:
         self.paths = [Path(path).resolve(strict=True) for path in paths]
         self.ignore = ignore_filter
@@ -32,7 +36,7 @@ def __init__(
         self.should_exit = asyncio.Event()
 
     @asynccontextmanager
-    async def lifespan(self, _app) -> AbstractAsyncContextManager[None]:
+    async def lifespan(self, _app) -> AsyncGenerator[None]:
         task = asyncio.create_task(self.main())
         yield
         self.should_exit.set()
diff --git a/sphinx_autobuild/utils.py b/sphinx_autobuild/utils.py
index 16e19fb..e3fc9ed 100644
--- a/sphinx_autobuild/utils.py
+++ b/sphinx_autobuild/utils.py
@@ -4,9 +4,6 @@
 
 import shlex
 import socket
-import threading
-import time
-import webbrowser
 
 from colorama import Fore, Style
 
@@ -22,16 +19,6 @@ def find_free_port():
         return s.getsockname()[1]
 
 
-def open_browser(url_host: str, delay: float) -> None:
-    def _opener():
-        time.sleep(delay)
-        webbrowser.open(f"http://{url_host}")
-
-    t = threading.Thread(target=_opener)
-    t.start()
-    t.join()
-
-
 def _log(text, *, colour):
     print(f"{Fore.GREEN}[sphinx-autobuild] {colour}{text}{Style.RESET_ALL}")