TranscriptionStreamReceiver class

Converts LiveKit transcription text streams into ReceivedMessages.

This receiver is intended for agent-powered transcription streams produced by the LiveKit Agents framework (text streams require livekit-agents >= 1.0.0).

The receiver listens on a text stream topic (default: 'lk.transcription') and aggregates chunked updates into a single ReceivedMessage per transcript segment.

Text stream semantics

• Agent transcripts: the agent emits a new text stream for each message. The stream yields chunks that should be appended until the transcript is finalized.
• User transcripts: the agent may resend the full transcription text for a segment on each update (until finalized).

Message identity / diffing

The segment id (lk.segment_id) is stable across the lifetime of a transcript segment. This receiver uses it as ReceivedMessage.id, which makes it safe to use for UI diffing (e.g. ListView keys). If lk.segment_id is missing, the text stream id is used as a fallback.

When a new segment for the same participant arrives, older partial segments are removed to keep memory usage bounded.

Example (agent transcript chunks)

Incoming chunks (same segment id):

{ segment_id: "1", content: "Hello" }
{ segment_id: "1", content: " world" }
{ segment_id: "1", content: "!" }

Output messages:

ReceivedMessage(id: "1", content: AgentTranscript("Hello"))
ReceivedMessage(id: "1", content: AgentTranscript("Hello world"))
ReceivedMessage(id: "1", content: AgentTranscript("Hello world!"))

• SeeAlso: https://docs.livekit.io/agents/