From bed4759b98ba3769d8a722d0abdb59e71d88d79d Mon Sep 17 00:00:00 2001
From: Ryan Gaus <ryan.gaus@livekit.io>
Date: Thu, 23 Jul 2026 13:25:04 -0400
Subject: [PATCH] fix: add useLegacyClientImplementation to ffi to ensure that
 only data streams v1 support is advertised

The node and python sdks today have their own data streams
implementations. If the livekit-ffi upgrade in node-sdks were done today, then it would mean
that the new client_protocol=2 would be advertised, and these
pre-existing implementations would receive data stream v2 messages, not
v1 (ie, single packet data streams, compression, etc).

So for now, add a flag which can be set in livekit-ffi to disable
advertising the new client protocol so this can be merged. Once merged,
node and python can be updated to pass this flag and the livekit-ffi
package can be updated. Then, once data streams v2 is done on both node
+ python and both are updated, this flag can be removed by reverting
this commit.
---
 packages/livekit-rtc/src/index.ts |  9 ++++++++-
 packages/livekit-rtc/src/room.ts  | 10 ++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/packages/livekit-rtc/src/index.ts b/packages/livekit-rtc/src/index.ts
index 7d131a3a..50728c46 100644
--- a/packages/livekit-rtc/src/index.ts
+++ b/packages/livekit-rtc/src/index.ts
@@ -36,7 +36,14 @@ export {
   TrackSource,
 } from '@livekit/rtc-ffi-bindings';
 export { VideoBufferType, VideoCodec, VideoRotation } from '@livekit/rtc-ffi-bindings';
-export { ConnectError, Room, RoomEvent, type RoomOptions, type RtcConfiguration } from './room.js';
+export {
+  ConnectError,
+  Room,
+  RoomEvent,
+  type RoomDataStreamOptions,
+  type RoomOptions,
+  type RtcConfiguration,
+} from './room.js';
 export { RpcError, type PerformRpcParams, type RpcInvocationData } from './rpc.js';
 export {
   LocalAudioTrack,
diff --git a/packages/livekit-rtc/src/room.ts b/packages/livekit-rtc/src/room.ts
index 6ee23de0..b9e4798e 100644
--- a/packages/livekit-rtc/src/room.ts
+++ b/packages/livekit-rtc/src/room.ts
@@ -29,6 +29,7 @@ import {
   type IceServer,
   IceTransportType,
   type ReadyForRoomEventResponse,
+  RoomDataStreamOptions,
   type RoomInfo,
   type SimulateScenarioCallback,
   type SimulateScenarioKind,
@@ -58,6 +59,8 @@ import { RemoteTrackPublication } from './track_publication.js';
 import type { ChatMessage } from './types.js';
 import { bigIntToNumber } from './utils.js';
 
+export { RoomDataStreamOptions };
+
 export interface RtcConfiguration {
   iceTransportType: IceTransportType;
   continualGatheringPolicy: ContinualGatheringPolicy;
@@ -273,6 +276,13 @@ export class Room extends (EventEmitter as new () => TypedEmitter<RoomCallbacks>
    */
   async connect(url: string, token: string, opts?: RoomOptions) {
     const options = { ...defaultRoomOptions, ...opts };
+    // The Node SDK still implements data streams in TypeScript on top of raw FFI
+    // packets, so always advertise only legacy (v1) data stream support to other
+    // clients, preserving any other data stream options provided by the user.
+    options.dataStream = new RoomDataStreamOptions({
+      ...options.dataStream,
+      useLegacyClientImplementation: true,
+    });
     const e2eeEnabled = options.encryption || options.e2ee;
     const e2eeOptions = options.encryption
       ? { ...defaultE2EEOptions, ...options.encryption }