To receive messages from a text-only agent on the frontend in Next.js, you can use the registerTextStreamHandler method to listen for incoming text on the lk.transcription topic. Here's an example implementation:

room.registerTextStreamHandler('lk.transcription', async (reader, participantInfo) => {
  const message = await reader.readAll();
  if (reader.info.attributes['lk.transcribed_track_id']) {
    console.log(`New transcription from ${participantInfo.identity}: ${message}`);
  } else {
    console.log(`New message from ${participantInfo.identity}: ${message}`);
  }
});

On the backend, you can configure a text-only agent by setting audio_enabled=False in the RoomOutputOptions. The agent will then publish text responses to the lk.transcription text stream topic:

session = AgentSession(
    ..., # STT, LLM, etc.
    room_output_options=RoomOutputOptions(
        audio_enabled=False # disable audio output
    )
)

Let me know if you need further assistance! Sources: Text and transcriptions | LiveKit Docs