From 6bea0f26398cfe72726497500db31a8d11793f23 Mon Sep 17 00:00:00 2001
From: Andrew Ferrazzutti <andrewf@element.io>
Date: Tue, 1 Oct 2024 12:26:28 -0400
Subject: [PATCH 1/3] Don't say MSC4140 is supported when it's disabled

---
 synapse/rest/client/versions.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index 1cfac876064..8028cf8ad2c 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -172,7 +172,7 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
                         )
                     ),
                     # MSC4140: Delayed events
-                    "org.matrix.msc4140": True,
+                    "org.matrix.msc4140": bool(self.config.server.max_event_delay_ms),
                     # MSC4151: Report room API (Client-Server API)
                     "org.matrix.msc4151": self.config.experimental.msc4151_enabled,
                     # Simplified sliding sync

From 1ec244b42f516c59007cc7e42258739867a92147 Mon Sep 17 00:00:00 2001
From: Andrew Ferrazzutti <andrewf@element.io>
Date: Wed, 2 Oct 2024 19:29:51 -0400
Subject: [PATCH 2/3] Add test coverage

---
 tests/rest/client/test_delayed_events.py | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/tests/rest/client/test_delayed_events.py b/tests/rest/client/test_delayed_events.py
index 34d9fe79587..cb77c73da24 100644
--- a/tests/rest/client/test_delayed_events.py
+++ b/tests/rest/client/test_delayed_events.py
@@ -8,11 +8,12 @@
 from twisted.test.proto_helpers import MemoryReactor
 
 from synapse.api.errors import Codes
-from synapse.rest.client import delayed_events, room
+from synapse.rest.client import delayed_events, room, versions
 from synapse.server import HomeServer
 from synapse.types import JsonDict
 from synapse.util import Clock
 
+from tests import unittest
 from tests.unittest import HomeserverTestCase
 
 PATH_PREFIX = "/_matrix/client/unstable/org.matrix.msc4140/delayed_events"
@@ -21,6 +22,21 @@
 _EVENT_TYPE = "com.example.test"
 
 
+class DelayedEventsUnstableSupportTestCase(HomeserverTestCase):
+    servlets = [versions.register_servlets]
+
+    def test_false_by_default(self) -> None:
+        channel = self.make_request("GET", "/_matrix/client/versions")
+        self.assertEqual(channel.code, 200, channel.result)
+        self.assertFalse(channel.json_body["unstable_features"]["org.matrix.msc4140"])
+
+    @unittest.override_config({"max_event_delay_duration": "24h"})
+    def test_true_if_enabled(self) -> None:
+        channel = self.make_request("GET", "/_matrix/client/versions")
+        self.assertEqual(channel.code, 200, channel.result)
+        self.assertTrue(channel.json_body["unstable_features"]["org.matrix.msc4140"])
+
+
 class DelayedEventsTestCase(HomeserverTestCase):
     """Tests getting and managing delayed events."""
 

From 59ca2ee3233b3a9ecf6e1d176660a4644d4e099e Mon Sep 17 00:00:00 2001
From: Andrew Ferrazzutti <andrewf@element.io>
Date: Thu, 3 Oct 2024 00:07:03 -0400
Subject: [PATCH 3/3] Add changelog

---
 changelog.d/17780.bugfix | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/17780.bugfix

diff --git a/changelog.d/17780.bugfix b/changelog.d/17780.bugfix
new file mode 100644
index 00000000000..9d918ae745e
--- /dev/null
+++ b/changelog.d/17780.bugfix
@@ -0,0 +1 @@
+In the response to `GET /_matrix/client/versions`, set the `unstable_features` flag for MSC4140 to `false` when server configuration disables support for delayed events.