# Understanding the Flux State Machine Emitted events adhere to the below state machine for managing turns: ```mermaid stateDiagram-v2 direction LR [*] --> Initial Initial --> TurnOngoing : StartOfTurn TurnOngoing --> AwaitingEnd : EagerEndOfTurn AwaitingEnd --> TurnOngoing : TurnResumed AwaitingEnd --> Initial : EndOfTurn TurnOngoing --> Initial : ForceEndTurn AwaitingEnd --> Initial : ForceEndTurn state Initial { [*] --> Ready } state TurnOngoing { [*] --> Speaking } state AwaitingEnd { [*] --> Processing } ``` 1. `Update` messages are sent for approximately every 0.25 seconds of transcribed audio, regardless of transcript updates, unless a state change has occurred. 2. An `EagerEndOfTurn` message always contains a nonempty transcript. 3. A `TurnResumed` message can only follow a preceding `EagerEndOfTurn` message. 4. The `EndOfTurn` transcript will always match the immediately preceding `EagerEndOfTurn` transcript. If the transcript changes after an `EagerEndOfTurn`, a `TurnResumed` event will occur first. 5. The `turn_index` increments immediately following an `EndOfTurn` message. 6. When using `flux-general-multi`, all `TurnInfo` events include `languages` (detected languages sorted by word count) and `languages_hinted` (active language hints). See [Language Prompting](/guides/streaming-audio-flux-language-prompting). 7. Every `EndOfTurn` event includes a `trigger` field — `model` (native detection), `manual` ([`ForceEndTurn`](/guides/streaming-audio-flux-force-end-turn)), or `timeout` (`eot_timeout_ms`) — indicating what ended the turn. 8. You can end the current turn at any time by sending a [`ForceEndTurn`](/guides/streaming-audio-flux-force-end-turn) message. Flux emits an `EndOfTurn` with `trigger: "manual"` from any in-turn state. :::callout{intent="info"} **Configuring Event Behavior**: The `EagerEndOfTurn` and `TurnResumed` events are only triggered when you set the `eager_eot_threshold` parameter. The `EndOfTurn` event behavior is controlled by `eot_threshold` and `eot_timeout_ms` parameters. See the [End-of-Turn Configuration](/guides/streaming-audio-flux-configuration) for details on tuning these thresholds for your use case. ::: :::callout{intent="info"} **Barge-in and audio quality**: Flux's `StartOfTurn` event is the recommended way to trigger barge-in — it's more reliable than an external VAD because every `StartOfTurn` is guaranteed to contain a non-empty transcript. For guidance on echo cancellation, noise suppression, and other audio preprocessing that affects turn detection, see [Audio Preprocessing & Barge-In](/guides/guides-deep-dives-audio-preprocessing-barge-in). ::: ## Turn Lifecycle Example Here's how Flux processes a customer calling support saying "Hi I need to cancel my subscription please." Notice how confidence builds up and how the `EagerEndOfTurn` event fires before the final `EndOfTurn`. With `EagerEndOfTurn`, your voice agent can begin preparing a response before the user has fully finished speaking. This allows you to send a synchronous request with early context, creating the effect of a faster, more natural reply. ```json { "event": "Update", "turn_index": 0, "audio_window_start": 0.0, "audio_window_end": 0.2, "transcript": "", "words": [], "end_of_turn_confidence": 0.1 } { "event": "Update", "turn_index": 0, "audio_window_start": 0.0, "audio_window_end": 0.5, "transcript": "", "words": [], "end_of_turn_confidence": 0.1 } { "event": "StartOfTurn", "turn_index": 0, "audio_window_start": 0.0, "audio_window_end": 0.6, "transcript": "Hi I", "words": [ { "word": "Hi", "confidence": 0.95, "start": 0.42, "end": 0.56 }, { "word": "I", "confidence": 0.92, "start": 0.56, "end": 0.6 } ], "end_of_turn_confidence": 0.1 } { "event": "Update", "turn_index": 0, "audio_window_start": 0.0, "audio_window_end": 0.8, "transcript": "Hi I need to", "words": [...], "end_of_turn_confidence": 0.1 } { "event": "Update", "turn_index": 0, "audio_window_start": 0.0, "audio_window_end": 1.0, "transcript": "Hi I need to cancel my subscription.", "words": [...], "end_of_turn_confidence": 0.3 } { "event": "EagerEndOfTurn", "turn_index": 0, "audio_window_start": 0.0, "audio_window_end": 1.1, "transcript": "Hi I need to cancel my subscription.", "words": [...], "end_of_turn_confidence": 0.3 } { "event": "TurnResumed", "turn_index": 0, "audio_window_start": 0.0, "audio_window_end": 1.2, "transcript": "Hi I need to cancel my subscription please", "words": [...], "end_of_turn_confidence": 0.1 } { "event": "Update", "turn_index": 0, "audio_window_start": 0.0, "audio_window_end": 1.4, "transcript": "Hi I need to cancel my subscription please.", "words": [...], "end_of_turn_confidence": 0.3 } { "event": "EagerEndOfTurn", "turn_index": 0, "audio_window_start": 0.0, "audio_window_end": 1.5, "transcript": "Hi I need to cancel my subscription please.", "words": [...], "end_of_turn_confidence": 0.3 } { "event": "Update", "turn_index": 0, "audio_window_start": 0.1, "audio_window_end": 1.6, "transcript": "Hi I need to cancel my subscription please.", "words": [...], "end_of_turn_confidence": 0.5 } { "event": "EndOfTurn", "turn_index": 0, "audio_window_start": 0.0, "audio_window_end": 1.7, "transcript": "Hi I need to cancel my subscription please.", "words": [...], "end_of_turn_confidence": 0.7, "trigger": "model" } ``` ## Related pages - [Getting Started with Flux](./streaming-audio-flux-quickstart.md) - [Flux Feature Overview](./streaming-audio-flux-feature-overview.md) - [Template Apps](./streaming-audio-flux-template-apps.md) - [End-of-Turn Detection Parameters](./streaming-audio-flux-configuration.md) - [Flux Multilingual & Language Prompting](./streaming-audio-flux-language-prompting.md) - [Build a Flux-enabled Voice Agent](./streaming-audio-flux-agent.md) - [Control Messages](./streaming-audio-control-messages.md) - [Migrating](./streaming-audio-migrating.md) - [Tips & Tricks](./streaming-audio-tips-tricks.md) # Agent Instructions Cite this page’s canonical URL and keep its documentation version. 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