# Optimize Voice Agent Latency with Eager End of Turn Eager end of turn processing is the practice of starting LLM processing on **medium-confidence transcripts** (`EagerEndOfTurn` events) before waiting for a high-confidence `EndOfTurn`. By overlapping LLM generation with user speech, you can cut **hundreds of milliseconds** from your agent's response time. > **Important Note** > > `EagerEndOfTurn` and `TurnResumed` events are ONLY triggered if you have configured the `eager_eot_threshold` in your connection string. ## How Eager End of Turn Processing Works 1. **Receive `EagerEndOfTurn`** - Flux is moderately confident the user has finished speaking. - Send the transcript downstream to your LLM and begin preparing a reply. 2. **If `TurnResumed` occurs** - The user wasn't finished after all. - Cancel the in-progress response and wait for the next `EagerEndOfTurn` or `EndOfTurn`. 3. **If `EndOfTurn` occurs** - The user is done speaking with high confidence. - Finalize and deliver the response you've already started preparing. - `EndOfTurn` transcript will exactly match the `EagerEndOfTurn` transcript, ensuring consistent transcription throughout the turn lifecycle. ## Implementation Strategies ### 1. Simple (Recommended Starting Point) - Use **only `EndOfTurn`** events. - Simplest implementation and minimal LLM calls - Ideal for majority of developers ### 2. Optimized (With Eager End of Turn Processing) - Use **both `EagerEndOfTurn` and `EndOfTurn`** events. - Reduce latency by preparing replies early with speculative response generation. - Expect more LLM calls and slightly more complexity. - Recommended once you’re confident in your pipeline and want production-grade performance. ## Tips & Tricks for Eager End of Turn Processing ### Tune Confidence Thresholds - `eager_eot_threshold`: Lower values → earlier triggers, but more false starts. - `eot_threshold`: Higher values → more reliable `EndOfTurn`, but may increase latency. - Experiment with values to balance **speed vs. stability**. ### Handle `TurnResumed` Gracefully - Treat `TurnResumed` as a cancellation signal. - Be ready to discard or revise any LLM replies in progress. - Consider a retry strategy if this happens often in your use case. ### Keep Responses Flexible - Avoid committing to a reply until `EndOfTurn`. - Use `EagerEndOfTurn` outputs to **draft**, not finalize. - Build resilience for handling `TurnResumed` events when the user continues speaking. ### Optimize LLM Cost - Eager end of turn processing means **more LLM requests**. - To reduce spend: - Use smaller/faster models for EagerEndOfTurn drafts. - Only call the full LLM on `EndOfTurn`. - Cache prepared responses and reuse on `EndOfTurn` (transcript guaranteed to match). ### Monitor and Log Events - Track how often `EagerEndOfTurn` → `TurnResumed` vs. `EagerEndOfTurn` → `EndOfTurn`. - Use this data to refine thresholds and tune your pipeline. ### Optimize Audio Input - Echo and background noise can cause false `StartOfTurn` events, which disrupt the turn lifecycle. For guidance on echo cancellation, noise suppression, and barge-in strategies, see [Audio Preprocessing & Barge-In](/guides/guides-deep-dives-audio-preprocessing-barge-in). ## Example Code This code demonstrates how to handle Flux message events to implement eager end-of-turn processing. The examples show message parsing and event handling for the three critical events: - - `EagerEndOfTurn` (start preparing response) - `TurnResumed` (cancel draft response) - `EndOfTurn` (finalize and deliver response) ```javascript ws.onmessage = (event) => { const data = JSON.parse(event.data); if (data.type !== 'TurnInfo') return; switch (data.event) { case 'EagerEndOfTurn': console.log('EagerEndOfTurn:', data.transcript); prepareDraftResponse(data.transcript); break; case 'TurnResumed': console.log('User kept speaking, cancel draft'); cancelDraftResponse(); break; case 'EndOfTurn': console.log('Final:', data.transcript); finalizeResponse(data.transcript); break; } }; ``` ```Python def on_message(message): # Parse incoming Flux message if not hasattr(message, 'type') or message.type != 'TurnInfo': return event = getattr(message, 'event', None) transcript = getattr(message, 'transcript', '') if event == 'EagerEndOfTurn': print(f'EagerEndOfTurn: {transcript}') prepare_draft_response(transcript) elif event == 'TurnResumed': print('User kept speaking, cancel draft') cancel_draft_response() elif event == 'EndOfTurn': print(f'Final: {transcript}') finalize_response(transcript) def prepare_draft_response(transcript): # Start preparing LLM response with moderate confidence transcript pass def cancel_draft_response(): # Cancel any in-progress response preparation pass def finalize_response(transcript): # Use the final transcript to deliver the response pass ``` **`C#`** ```csharp C# public void OnMessage(FluxMessage message) { // Parse incoming Flux message if (message.Type != "TurnInfo") return; switch (message.Event) { case "EagerEndOfTurn": Console.WriteLine($"EagerEndOfTurn: {message.Transcript}"); PrepareDraftResponse(message.Transcript); break; case "TurnResumed": Console.WriteLine("User kept speaking, cancel draft"); CancelDraftResponse(); break; case "EndOfTurn": Console.WriteLine($"Final: {message.Transcript}"); FinalizeResponse(message.Transcript); break; } } private void PrepareDraftResponse(string transcript) { // Start preparing LLM response with moderate confidence transcript } private void CancelDraftResponse() { // Cancel any in-progress response preparation } private void FinalizeResponse(string transcript) { // Use the final transcript to deliver the response } ``` ```Go func onMessage(message *FluxMessage) { // Parse incoming Flux message if message.Type != "TurnInfo" { return } switch message.Event { case "EagerEndOfTurn": fmt.Printf("EagerEndOfTurn: %s\n", message.Transcript) prepareDraftResponse(message.Transcript) case "TurnResumed": fmt.Println("User kept speaking, cancel draft") cancelDraftResponse() case "EndOfTurn": fmt.Printf("Final: %s\n", message.Transcript) finalizeResponse(message.Transcript) } } func prepareDraftResponse(transcript string) { // Start preparing LLM response with moderate confidence transcript } func cancelDraftResponse() { // Cancel any in-progress response preparation } func finalizeResponse(transcript string) { // Use the final transcript to deliver the response } ``` ## Summary ### When to Use Eager End of Turn - High-interruption environments (e.g., call centers, IVRs). - Conversational agents where natural back-and-forth timing matters. - Latency-sensitive apps where response speed is critical to user experience. - If your LLM configuration is complex and has high latency issues. e.g., Good for trimming that last 100-200ms of end-to-end latency at the cost of 50-70% more LLM calls. - If Your LLM configuration has complex RAG (Retrieval-Augmented Generation) or Function Calling involved. ### When to use End of Turn only - Most developers will find `EndOfTurn` detection sufficiently fast enough to support natural conversation, but not all voice AI workflows are the same. - For more complex and expensive voice AI workflows, it might be worthwhile to use `EagerEndOfTurn`to call LLMs speculatively, i.e., in preparation for an upcoming turn end, in order to minimize response latency. ## Related pages - [Bring Your Own Turn Detection](./streaming-audio-flux-own-turn-detection.md) # Agent Instructions Cite this page’s canonical URL and keep its documentation version. 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