From e3978d3a465a8d35a1f8578446eefe99ca6b19f9 Mon Sep 17 00:00:00 2001
From: Hiroshi Horie <548776+hiroshihorie@users.noreply.github.com>
Date: Wed, 11 Feb 2026 21:52:59 +0900
Subject: [PATCH 1/3] fix

---
 lib/src/core/room.dart         |  9 ++++-----
 lib/src/types/data_stream.dart | 17 ++++++++++++++---
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/lib/src/core/room.dart b/lib/src/core/room.dart
index 3fbf92a4e..53b8f1125 100644
--- a/lib/src/core/room.dart
+++ b/lib/src/core/room.dart
@@ -1396,9 +1396,7 @@ extension DataStreamRoomMethods on Room {
         );
 
         _byteStreamControllers.remove(chunk.streamId);
-      }
-
-      if (chunk.content.isNotEmpty) {
+      } else if (chunk.content.isNotEmpty) {
         fileBuffer.write(chunk);
       }
     }
@@ -1415,8 +1413,7 @@ extension DataStreamRoomMethods on Room {
 
         logger.warning('encryption type mismatch for text stream ${chunk.streamId}');
         _textStreamControllers.remove(chunk.streamId);
-      }
-      if (chunk.content.isNotEmpty) {
+      } else if (chunk.content.isNotEmpty) {
         textBuffer.write(chunk);
       }
     }
@@ -1484,10 +1481,12 @@ extension DataStreamRoomMethods on Room {
       );
       for (var controller in byteStreamsBeingSentByDisconnectingParticipant) {
         controller.error(abnormalEndError);
+        controller.close();
         _byteStreamControllers.remove(controller.info.id);
       }
       for (var controller in textStreamsBeingSentByDisconnectingParticipant) {
         controller.error(abnormalEndError);
+        controller.close();
         _textStreamControllers.remove(controller.info.id);
       }
     }
diff --git a/lib/src/types/data_stream.dart b/lib/src/types/data_stream.dart
index a5963ff54..4066a2a7e 100644
--- a/lib/src/types/data_stream.dart
+++ b/lib/src/types/data_stream.dart
@@ -159,11 +159,22 @@ class DataStreamController<T extends DataStream_Chunk> {
     this.endTime,
   });
 
-  Future<void> close() => streamController.close();
+  bool get isClosed => streamController.isClosed;
 
-  void write(T chunk) => streamController.add(chunk);
+  Future<void> close() {
+    if (isClosed) return Future.value();
+    return streamController.close();
+  }
+
+  void write(T chunk) {
+    if (isClosed) return;
+    streamController.add(chunk);
+  }
 
-  void error(DataStreamError error) => streamController.addError(error);
+  void error(DataStreamError error) {
+    if (isClosed) return;
+    streamController.addError(error);
+  }
 }
 
 class ByteStreamInfo extends BaseStreamInfo {

From ca1f7e164793bc28ddff43097021c24f73d5414c Mon Sep 17 00:00:00 2001
From: Hiroshi Horie <548776+hiroshihorie@users.noreply.github.com>
Date: Wed, 11 Feb 2026 21:54:07 +0900
Subject: [PATCH 2/3] changes

---
 .changes/fix-data-stream-closed-state | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 .changes/fix-data-stream-closed-state

diff --git a/.changes/fix-data-stream-closed-state b/.changes/fix-data-stream-closed-state
new file mode 100644
index 000000000..9ac8ac382
--- /dev/null
+++ b/.changes/fix-data-stream-closed-state
@@ -0,0 +1 @@
+patch type="fixed" "Fix crash when writing to closed data stream controllers"

From 9d939bc65a5db90f5381f9249fbad5fe5df8d676 Mon Sep 17 00:00:00 2001
From: Hiroshi Horie <548776+hiroshihorie@users.noreply.github.com>
Date: Wed, 11 Feb 2026 22:02:55 +0900
Subject: [PATCH 3/3] fix async

---
 lib/src/core/room.dart | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/src/core/room.dart b/lib/src/core/room.dart
index 53b8f1125..0064713d1 100644
--- a/lib/src/core/room.dart
+++ b/lib/src/core/room.dart
@@ -922,7 +922,7 @@ class Room extends DisposableChangeNotifier with EventsEmittable<RoomEvent> {
     final participant = _remoteParticipants.removeByIdentity(identity);
     if (participant == null) return false;
 
-    validateParticipantHasNoActiveDataStreams(identity);
+    await validateParticipantHasNoActiveDataStreams(identity);
 
     await participant.removeAllPublishedTracks(notify: true);
 
@@ -1464,7 +1464,7 @@ extension DataStreamRoomMethods on Room {
     }
   }
 
-  void validateParticipantHasNoActiveDataStreams(String participantIdentity) {
+  Future<void> validateParticipantHasNoActiveDataStreams(String participantIdentity) async {
     // Terminate any in flight data stream receives from the given participant
     final textStreamsBeingSentByDisconnectingParticipant = _textStreamControllers.values
         .where((controller) => controller.info.sendingParticipantIdentity == participantIdentity)
@@ -1481,12 +1481,12 @@ extension DataStreamRoomMethods on Room {
       );
       for (var controller in byteStreamsBeingSentByDisconnectingParticipant) {
         controller.error(abnormalEndError);
-        controller.close();
+        await controller.close();
         _byteStreamControllers.remove(controller.info.id);
       }
       for (var controller in textStreamsBeingSentByDisconnectingParticipant) {
         controller.error(abnormalEndError);
-        controller.close();
+        await controller.close();
         _textStreamControllers.remove(controller.info.id);
       }
     }