Using Deepgram Conversational STT (Rust SDK)

Use this skill for Deepgram Flux, the crate's supported turn-based conversational streaming path.

When to use this product

• Building turn-based STT for voice-agent pipelines.
• Handling TurnEvent::{StartOfTurn, EndOfTurn, EagerEndOfTurn, TurnResumed, Update}.
• Tuning end-of-turn behavior with eotthreshold, eagereotthreshold, and eottimeout_ms.

Authentication

Flux is under the listen feature.

[dependencies]
deepgram = { version = "0.10.0", default-features = false, features = ["listen"] }
tokio = { version = "1", features = ["full"] }
futures = "0.3"

let dg = deepgram::Deepgram::new(std::env::var("DEEPGRAM_API_KEY")?)?;

Quick start

use std::{io::Write, time::Duration};

use deepgram::{
    common::{
        flux_response::{FluxResponse, TurnEvent},
        options::{Encoding, Model, Options},
    },
    Deepgram,
};
use futures::stream::StreamExt;

static PATH_TO_FILE: &str = "examples/audio/sample-mono.wav";
static AUDIO_CHUNK_SIZE: usize = 18_063;
static FRAME_DELAY: Duration = Duration::from_millis(100);

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let api_key = std::env::var("DEEPGRAM_API_KEY")?;
    let dg = Deepgram::new(&api_key)?;

    let options = Options::builder()
        .model(Model::FluxGeneralEn)
        .eot_threshold(0.75)
        .eot_timeout_ms(5000)
        .keyterms(["activate", "cancel"])
        .build();

    let mut results = dg
        .transcription()
        .flux_request_with_options(options)
        .encoding(Encoding::Linear32)
        .sample_rate(44100)
        .file(PATH_TO_FILE, AUDIO_CHUNK_SIZE, FRAME_DELAY)
        .await?;

    println!("Flux Request ID: {}", results.request_id());
    while let Some(result) = results.next().await {
        match result? {
            FluxResponse::Connected { request_id, sequence_id } => {
                println!("Connected: {request_id} (seq: {sequence_id})");
            }
            FluxResponse::TurnInfo { event, turn_index, transcript, end_of_turn_confidence, .. } => {
                match event {
                    TurnEvent::StartOfTurn => println!("▶ [Turn {turn_index}] START"),
                    TurnEvent::EndOfTurn => println!("✓ [Turn {turn_index}] END ({end_of_turn_confidence:.2}): {transcript}"),
                    TurnEvent::Update => {
                        if !transcript.is_empty() {
                            print!("\r[Turn {turn_index}] UPDATE: {transcript}");
                            std::io::stdout().flush().unwrap();
                        }
                    }
                    _ => {}
                }
            }
            FluxResponse::FatalError { code, description, .. } => {
                eprintln!("{code}: {description}");
                break;
            }
            FluxResponse::Unknown(value) => println!("unknown: {value}"),
        }
    }

    Ok(())
}

Key parameters

• Entrypoints: fluxrequest(), fluxrequestwithoptions(options).
• Flux transport builder fields: encoding, sample_rate, then .file(...), .stream(...), or .handle().await?.
• Flux-specific tuning in shared OptionsBuilder: model(Model::FluxGeneralEn), eotthreshold, eagereotthreshold, eottimeout_ms, keyterms.
• Main response type: common::flux_response::FluxResponse.

API reference (layered)

1. In-repo

- src/listen/flux.rs - src/common/fluxresponse.rs - src/common/options.rs - examples/transcription/flux/simpleflux.rs - tests/fluxunknownmessages.rs - tests/flux_e2e.rs

1. OpenAPI

- Raw spec: https://developers.deepgram.com/openapi.yaml - Endpoint reference: https://developers.deepgram.com/reference/speech-to-text/listen-flux

1. AsyncAPI

- Raw spec: https://developers.deepgram.com/asyncapi.yaml - Flux channel docs are surfaced from the same product reference page above

1. Context7

- /llmstxt/developersdeepgramllms_txt

1. Product docs

- https://developers.deepgram.com/docs/stt/getting-started

Gotchas

1. Flux is English-only in this crate's model surface. The default supported model is Model::FluxGeneralEn.
2. Real-time pacing matters even more than standard streaming. The example warns that bad chunk size / delay values can break turn detection.
3. Unknown events are intentional. FluxResponse::Unknown and TurnEvent::Unknown are there for forward compatibility; handle them instead of assuming exhaustiveness.
4. Use Flux for turn-taking, not full agent control. If you need TTS replies, prompts, or tool calls, that is Voice Agent territory and not a typed Rust SDK surface yet.

Example files in this repo

• examples/transcription/flux/simple_flux.rs
• examples/transcription/flux/simplefluxtoken.rs
• examples/transcription/flux/microphone_flux.rs
• tests/fluxunknownmessages.rs
• tests/flux_e2e.rs

Central product skills

For cross-language Deepgram product knowledge — the consolidated API reference, documentation finder, focused runnable recipes, third-party integration examples, and MCP setup — install the central skills:

npx skills add deepgram/skills

This SDK ships language-idiomatic code skills; deepgram/skills ships cross-language product knowledge (see api, docs, recipes, examples, starters, setup-mcp).