python-zeroconf · bluetoothbot · May 18, 2026 · May 18, 2026 · May 18, 2026
diff --git a/src/zeroconf/_core.py b/src/zeroconf/_core.py
@@ -104,6 +104,10 @@
 
 _REGISTER_BROADCASTS = 3
 
+# Random delay before probing (RFC 6762 §8.1) to avoid a thundering
+# herd when multiple services start at once.
+_REGISTER_RANDOM_INTERVAL = (150, 250)  # ms
+
 
 def async_send_with_transport(
     log_debug: bool,
@@ -561,7 +565,7 @@ async def async_check_service(
 
         # Wait a random amount of time up avoid collisions and avoid
         # a thundering herd when multiple services are started on the network
-        await self.async_wait(random.randint(150, 250))  # noqa: S311
+        await self.async_wait(random.randint(*_REGISTER_RANDOM_INTERVAL))  # noqa: S311
 
         next_instance_number = 2
         next_time = now = current_time_millis()

diff --git a/tests/conftest.py b/tests/conftest.py
@@ -49,15 +49,17 @@ def quick_timing() -> Generator[None]:
     """Shorten the probe/announce/goodbye intervals for tests on loopback.
 
     The production values (_CHECK_TIME=500ms, _REGISTER_TIME=225ms,
-    _UNREGISTER_TIME=125ms) exist for RFC 6762 interop on real
-    networks. Tests on 127.0.0.1 do not need them and pay 1-2s per
-    register/unregister cycle without this fixture. Opt in by adding
-    `quick_timing` to a test's argument list.
+    _UNREGISTER_TIME=125ms, _REGISTER_RANDOM_INTERVAL=(150, 250)ms)
+    exist for RFC 6762 interop on real networks. Tests on 127.0.0.1
+    do not need them and pay 1-2s per register/unregister cycle
+    without this fixture. Opt in by adding `quick_timing` to a
+    test's argument list.
     """
     with (
         patch.object(_core, "_CHECK_TIME", 10),
         patch.object(_core, "_REGISTER_TIME", 10),
         patch.object(_core, "_UNREGISTER_TIME", 10),
+        patch.object(_core, "_REGISTER_RANDOM_INTERVAL", (1, 5)),
     ):
         yield
 

diff --git a/tests/test_asyncio.py b/tests/test_asyncio.py
@@ -1060,6 +1060,12 @@ def send(out, addr=const._MDNS_ADDR, port=const._MDNS_PORT, v6_flow_scope=()):
             "ash-2.local.",
             addresses=[socket.inet_aton("10.0.1.2")],
         )
+        # Wait for the browser's first startup query to land (with an empty
+        # cache) before registering — otherwise on fast loopback the register
+        # may finish before the first query fires, and answers[0] picks up
+        # the known PTR via §7.1 suppression.
+        await asyncio.wait_for(got_query.wait(), 1)
+        got_query.clear()
         task = await aio_zeroconf_registrar.async_register_service(info)
         await task
         loop = asyncio.get_running_loop()

diff --git a/tests/utils/test_asyncio.py b/tests/utils/test_asyncio.py
@@ -65,6 +65,7 @@ async def _async_wait_or_timeout():
         await task
 
 
+@patch.object(aioutils, "_TASK_AWAIT_TIMEOUT", 0.1)
 def test_shutdown_loop() -> None:
     """Test shutting down an event loop."""
     loop = None
@@ -89,7 +90,7 @@ def _run_coro() -> None:
         runcoro_thread_ready.set()
         assert loop is not None
         with contextlib.suppress(concurrent.futures.TimeoutError):
-            asyncio.run_coroutine_threadsafe(_still_running(), loop).result(1)
+            asyncio.run_coroutine_threadsafe(_still_running(), loop).result(0.1)
 
     runcoro_thread = threading.Thread(target=_run_coro, daemon=True)
     runcoro_thread.start()