fix: Guard isinstance AsyncHttpTransport with ASYNC_TRANSPORT_ENABLED

When httpcore[asyncio] is not installed, AsyncHttpTransport is aliased
to HttpTransport. isinstance(transport, AsyncHttpTransport) would then
be True for ALL transports, causing close()/flush() to skip the sync
flush path. Guard with ASYNC_TRANSPORT_ENABLED flag.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: BYK

sentry_sdk/client.py

@@ -31,7 +31,12 @@
 from sentry_sdk.serializer import serialize
 from sentry_sdk.tracing import trace
 from sentry_sdk.tracing_utils import has_span_streaming_enabled
-from sentry_sdk.transport import HttpTransportCore, make_transport, AsyncHttpTransport
+from sentry_sdk.transport import (
+    ASYNC_TRANSPORT_ENABLED,
+    HttpTransportCore,
+    make_transport,
+    AsyncHttpTransport,
+)
 from sentry_sdk.consts import (
     SPANDATA,
     DEFAULT_MAX_VALUE_LENGTH,
@@ -1037,7 +1042,9 @@ def close(
         semantics as :py:meth:`Client.flush`.
         """
         if self.transport is not None:
-            if isinstance(self.transport, AsyncHttpTransport):
+            if ASYNC_TRANSPORT_ENABLED and isinstance(
+                self.transport, AsyncHttpTransport
+            ):
                 logger.warning(
                     "close() used with AsyncHttpTransport. "
                     "Prefer close_async() for graceful async shutdown. "
@@ -1060,7 +1067,10 @@ async def close_async(
         semantics as :py:meth:`Client.flush_async`.
         """
         if self.transport is not None:
-            if not isinstance(self.transport, AsyncHttpTransport):
+            if not (
+                ASYNC_TRANSPORT_ENABLED
+                and isinstance(self.transport, AsyncHttpTransport)
+            ):
                 logger.debug(
                     "close_async() used with non-async transport, aborting. Please use close() instead."
                 )
@@ -1085,7 +1095,9 @@ def flush(
         :param callback: Is invoked with the number of pending events and the configured timeout.
         """
         if self.transport is not None:
-            if isinstance(self.transport, AsyncHttpTransport):
+            if ASYNC_TRANSPORT_ENABLED and isinstance(
+                self.transport, AsyncHttpTransport
+            ):
                 logger.warning(
                     "flush() used with AsyncHttpTransport. Please use flush_async() instead."
                 )
@@ -1109,7 +1121,10 @@ async def flush_async(
         :param callback: Is invoked with the number of pending events and the configured timeout.
         """
         if self.transport is not None:
-            if not isinstance(self.transport, AsyncHttpTransport):
+            if not (
+                ASYNC_TRANSPORT_ENABLED
+                and isinstance(self.transport, AsyncHttpTransport)
+            ):
                 logger.debug(
                     "flush_async() used with non-async transport, aborting. Please use flush() instead."
                 )

sentry_sdk/integrations/asyncio.py

@@ -11,7 +11,7 @@
     reraise,
     is_internal_task,
 )
-from sentry_sdk.transport import AsyncHttpTransport
+from sentry_sdk.transport import ASYNC_TRANSPORT_ENABLED, AsyncHttpTransport
 
 try:
     import asyncio
@@ -68,7 +68,10 @@ async def _flush() -> None:
             return
 
         try:
-            if not isinstance(client.transport, AsyncHttpTransport):
+            if not (
+                ASYNC_TRANSPORT_ENABLED
+                and isinstance(client.transport, AsyncHttpTransport)
+            ):
                 return
 
             await client.close_async()