From ad5ff87c869e8a34e9b04fcd5ca38d65c526893c Mon Sep 17 00:00:00 2001
From: Eugene Toder <eltoder@users.noreply.github.com>
Date: Thu, 30 Apr 2026 14:26:13 -0400
Subject: [PATCH] Treat `fd=0` as a valid file descriptor with reload/workers
 (#2927)

Co-authored-by: Marcelo Trylesinski <marcelotryle@gmail.com>
---
 tests/test_config.py | 31 +++++++++++++++++++++++++++++++
 tests/test_server.py | 18 +++++++-----------
 uvicorn/config.py    |  4 ++--
 3 files changed, 40 insertions(+), 13 deletions(-)

diff --git a/tests/test_config.py b/tests/test_config.py
index db758662..f330dea3 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -553,6 +553,37 @@ def test_bind_fd_works_with_reload_or_workers(reload: bool, workers: int):  # pr
     fdsock.close()
 
 
+@pytest.fixture
+def stdin_socket() -> Iterator[socket.socket]:  # pragma: py-win32
+    with closing(socket.socket(socket.AF_INET)) as sock:
+        sock.bind(("127.0.0.1", 0))
+        saved_stdin = os.dup(0)
+        os.dup2(sock.fileno(), 0)
+        try:
+            yield sock
+        finally:
+            os.dup2(saved_stdin, 0)
+            os.close(saved_stdin)
+
+
+@pytest.mark.parametrize(
+    "reload, workers",
+    [
+        (True, 1),
+        (False, 2),
+    ],
+    ids=["--reload=True --workers=1", "--reload=False --workers=2"],
+)
+@pytest.mark.skipif(sys.platform == "win32", reason="require unix-like system")
+def test_bind_stdin_works_with_reload_or_workers(
+    reload: bool, workers: int, stdin_socket: socket.socket
+):  # pragma: py-win32
+    config = Config(app=asgi_app, fd=0, reload=reload, workers=workers)
+    config.load()
+    with closing(config.bind_socket()) as sock:
+        assert sock.getsockname() == stdin_socket.getsockname()
+
+
 @pytest.mark.parametrize(
     "reload, workers, expected",
     [
diff --git a/tests/test_server.py b/tests/test_server.py
index f57c1f23..b6f56084 100644
--- a/tests/test_server.py
+++ b/tests/test_server.py
@@ -142,17 +142,13 @@ async def test_limit_max_requests_jitter(
     config = Config(
         app=app, limit_max_requests=1, limit_max_requests_jitter=2, port=unused_tcp_port, http=http_protocol_cls
     )
-    server = Server(config=config)
-    limit = server.limit_max_requests
-    assert limit is not None
-    assert 1 <= limit <= 3
-    task = asyncio.create_task(server.serve())
-    while not server.started:
-        await asyncio.sleep(0.01)
-    async with httpx.AsyncClient() as client:
-        for _ in range(limit + 1):
-            await client.get(f"http://127.0.0.1:{unused_tcp_port}")
-    await task
+    async with run_server(config) as server:
+        limit = server.limit_max_requests
+        assert limit is not None
+        assert 1 <= limit <= 3
+        async with httpx.AsyncClient() as client:
+            tasks = [client.get(f"http://127.0.0.1:{unused_tcp_port}") for _ in range(limit + 1)]
+            await asyncio.gather(*tasks)
     assert f"Maximum request limit of {limit} exceeded. Terminating process." in caplog.text
 
 
diff --git a/uvicorn/config.py b/uvicorn/config.py
index 84bf9a20..34d04e47 100644
--- a/uvicorn/config.py
+++ b/uvicorn/config.py
@@ -537,7 +537,7 @@ class Config:
 
     def bind_socket(self) -> socket.socket:
         logger_args: list[str | int]
-        if self.uds:  # pragma: py-win32
+        if self.uds is not None:  # pragma: py-win32
             path = self.uds
             sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
             try:
@@ -552,7 +552,7 @@ class Config:
             sock_name_format = "%s"
             color_message = "Uvicorn running on " + click.style(sock_name_format, bold=True) + " (Press CTRL+C to quit)"
             logger_args = [self.uds]
-        elif self.fd:  # pragma: py-win32
+        elif self.fd is not None:  # pragma: py-win32
             sock = socket.fromfd(self.fd, socket.AF_UNIX, socket.SOCK_STREAM)
             message = "Uvicorn running on socket %s (Press CTRL+C to quit)"
             fd_name_format = "%s"