⏺ The remaining ~79 defer.* usages are all in code that depends on the Twisted reactor to schedule and resolve Deferreds. They'll be eliminated when the entry point switches from reactor.run() to asyncio.run(). At that point:

- defer.Deferred() → asyncio.Future() or asyncio.Event()
  - defer.gatherResults() → asyncio.gather()
  - defer.succeed/fail → direct returns / asyncio.Future.set_result/set_exception
  - defer.TimeoutError → asyncio.TimeoutError
  - defer.ensureDeferred → asyncio.ensure_future or direct await
  - Linearizer, ReadWriteLock, etc. → NativeLinearizer, NativeReadWriteLock

synapse/handlers/auth.py

@@ -43,7 +43,7 @@ import unpaddedbase64
 from prometheus_client import Counter
 
 try:
-    from twisted.internet.defer import CancelledError
+    from asyncio import CancelledError
     from twisted.web.server import Request
 except ImportError:
     pass

synapse/logging/_remote.py

@@ -36,7 +36,7 @@ except ImportError:
 
 try:
     from twisted.application.internet import ClientService
-    from twisted.internet.defer import CancelledError
+    from asyncio import CancelledError
     from twisted.internet.defer import Deferred
     from twisted.internet.endpoints import (
         HostnameEndpoint,

synapse/types/__init__.py

@@ -59,7 +59,7 @@ except ImportError:
     pass
 
 try:
-    from twisted.internet.defer import CancelledError
+    from asyncio import CancelledError
     from twisted.internet.interfaces import (
         IReactorCore,
         IReactorPluggableNameResolver,

synapse/util/async_helpers.py

@@ -1146,7 +1146,8 @@ class NativeLinearizer:
             # do work
     """
 
-    def __init__(self, name: str, max_count: int = 1) -> None:
+    def __init__(self, name: str, max_count: int = 1, clock: Any = None) -> None:
+        # clock parameter accepted for backward compatibility with Linearizer(clock=...)
         self.name = name
         self.max_count = max_count
         self._key_to_entry: dict[Hashable, _NativeLinearizerEntry] = {}
@@ -1350,7 +1351,8 @@ class NativeAwakenableSleeper:
     Allows explicit waking of sleeping coroutines by name.
     """
 
-    def __init__(self) -> None:
+    def __init__(self, clock: Any = None) -> None:
+        # clock parameter accepted for backward compatibility
         self._streams: dict[str, set[asyncio.Event]] = {}
 
     def wake(self, name: str) -> None:
@@ -1383,7 +1385,8 @@ class NativeEvent:
     Like threading.Event but for asyncio code.
     """
 
-    def __init__(self) -> None:
+    def __init__(self, clock: Any = None) -> None:
+        # clock parameter accepted for backward compatibility
         self._event = asyncio.Event()
 
     def set(self) -> None:
@@ -1490,3 +1493,12 @@ class DeferredEvent:
             pass
 
         return self.is_set()
+
+
+# ===========================================================================
+# The native asyncio versions (NativeLinearizer, NativeReadWriteLock,
+# NativeAwakenableSleeper, NativeEvent) are available above and will replace
+# the Deferred-based versions once the entry point switches from reactor.run()
+# to asyncio.run(). Until then, the old classes remain as they need the
+# Twisted reactor to drive their Deferred-based internals.
+# ===========================================================================