[feature] replyToStreamId in the StreamTextOptions

[dmytroporoshyn]

Hello LiveKit dev team!
We have found replyToStreamId parameter in the StreamTextOptions class:

client-sdk-flutter/lib/src/participant/local.dart

Line 1236 in 51b796c

replyToStreamId: options?.replyToStreamId,

But we don't have documentation on how to use it or what this parameter is responsible for.
We did a quick check and set this parameter with a previous message stream ID, but the message does not include information about replay.

Could you please describe if this function is ready and how to use it
Thanks!

[justyn]

Hi,

It looks like the replyToStreamId parameter is part of the DataStream protocol and you can set it when sending messages, but none of the LiveKit SDKs currently expose this field when receiving messages.

All SDKs

Across these three SDKs:

• Python SDK: Can send with reply_to_id but doesn't expose it when receiving (only extracts attachments from textHeader)
• JavaScript SDK: Can send with replyToStreamId but has it commented out in SendTextOptions
• Flutter SDK: Can send with replyToStreamId but doesn't extract any textHeader fields when receiving

The Issue in Flutter

When the SDK receives a text stream, it creates a TextStreamInfo but doesn't extract any fields from the protocol's textHeader:

room.dart

var info = TextStreamInfo(
  id: streamHeader.streamId,
  mimeType: streamHeader.mimeType,
  // ... other fields
  attributes: streamHeader.attributes,
);
// Not extracted: streamHeader.textHeader.replyToStreamId
// Also missing: attachedStreamIds, version, generated, operationType

Flutter implmentation

The SDK needs to extract the textHeader fields when creating TextStreamInfo, similar to how the Python SDK extracts attachments from the textHeader:

self._info = TextStreamInfo(
    attachments=list(header.text_header.attached_stream_ids),
)

For Flutter:

// Add to TextStreamInfo class
final String? replyToStreamId;
final List<String> attachedStreamIds;

replyToStreamId: streamHeader.textHeader.hasReplyToStreamId() 
    ? streamHeader.textHeader.replyToStreamId 
    : null,
attachedStreamIds: streamHeader.textHeader.attachedStreamIds,

This would enable access to the reply information and other textHeader fields.

[bohdanudreambit]

Hi!
In the recent package release, the reply functionality has been tested.
But it looks like we still cannot get a reply metadata by the registerTextStreamHandler:

test('Text Stream With Reply Functionality', () async {
      const originalStreamId = 'original-stream-123';
      const replyStreamId = 'reply-stream-456';

      room.registerTextStreamHandler('chat-replies', (TextStreamReader reader, String participantIdentity) async {
        final text = await reader.readAll();
        print('received reply message: ${text}');
        expect(text, 'This is a reply to the original message');
      });

      // Send a reply to an existing stream
      final stream = await room.localParticipant?.streamText(StreamTextOptions(
        topic: 'chat-replies',
        type: 'create',
        streamId: replyStreamId,
        replyToStreamId: originalStreamId,
        version: 1,
      ));
      await stream?.write('This is a reply to the original message');
      await stream?.close();
    });

@hiroshihorie I’d really appreciate your help with this question.