OpenAI Audio Provider

The OpenAI audio provider contributes audio client families under the openai provider key.

Use it when an agent needs OpenAI speech-to-text, text-to-speech, or realtime audio clients in addition to ordinary chat setup.

Package And Families

Reference the OpenAI audio provider package or project. The provider key is:

openai

Source-confirmed client families:

Family	Config slot
Speech to text	Clients.SpeechToText
Text to speech	Clients.TextToSpeech
Realtime	Clients.Realtime

The OpenAI chat provider package and OpenAI audio provider package can share the same provider key because provider resolution is family-specific.

Secrets

The OpenAI audio provider uses the same common OpenAI aliases:

OPENAI_API_KEY
OPENAI_ENDPOINT
OPENAI_BASE_URL

Configuration keys such as openai:ApiKey can also be resolved by the provider secret system.

Text To Speech

Configure text-to-speech through Clients.TextToSpeech or the audio runtime attachment options used by your application.

In C# apps, the fluent helper configures the same Clients.TextToSpeech family slot:

using HPD.Agent;
using HPD.Agent.Audio;
using HPD.Agent.Providers.Audio.OpenAI;

var agent = await new AgentBuilder()
    .WithOpenAITextToSpeech(
        model: "tts-1",
        voice: "nova",
        outputFormat: "mp3",
        configure: options => options.Speed = 1.0f)
    .WithAudioRuntimeAttachment(audio =>
    {
        audio.AssistantOutputSynthesisMode = AssistantOutputSynthesisMode.FinalText;
    })
    .BuildAsync();

Source defaults include:

Option	Default
Model	tts-1
Voice	nova
Format	mp3

The provider metadata also lists newer TTS model ids such as tts-1-hd and gpt-4o-mini-tts.

Provider-specific TTS options use OpenAITtsConfig through ProviderConfig:

{
  "Clients": {
    "TextToSpeech": {
      "ProviderKey": "openai",
      "ModelName": "tts-1",
      "ProviderConfig": {
        "defaultVoiceId": "nova",
        "outputFormat": "mp3",
        "speed": 1.0
      }
    }
  }
}

Source-confirmed TTS provider configuration:

Option	Use it for
apiKey	Provider-specific API key override.
baseUrl	Provider-specific base URL override.
defaultModelId	Default TTS model when ModelName is not set.
defaultVoiceId	Default voice id.
outputFormat	Default output format.
speed	Speech speed.

Speech To Text

Configure speech-to-text through Clients.SpeechToText.

In C# apps, use the speech-to-text helper when finite audio input should use OpenAI transcription:

using HPD.Agent;
using HPD.Agent.Audio;
using HPD.Agent.Providers.Audio.OpenAI;

var agent = await new AgentBuilder()
    .WithOpenAISpeechToText(
        model: "whisper-1",
        configure: options => options.Prompt = "Technical support call")
    .BuildAsync();

The helper only selects the speech-to-text client family. The audio runtime attachment still decides when finite audio input is transcribed and how committed transcripts are projected into the turn.

Source defaults include:

Option	Default
Model	whisper-1

The provider metadata also lists gpt-4o-transcribe and gpt-4o-mini-transcribe.

Finite audio input uses HPD audio runtime wiring; see Speech To Text Input.

Provider-specific STT options use OpenAISttConfig through ProviderConfig:

{
  "Clients": {
    "SpeechToText": {
      "ProviderKey": "openai",
      "ModelName": "whisper-1",
      "ProviderConfig": {
        "prompt": "Technical support call",
        "responseFormat": "json"
      }
    }
  }
}

Source-confirmed STT provider configuration:

Option	Use it for
apiKey	Provider-specific API key override.
baseUrl	Provider-specific base URL override.
defaultModelId	Default STT model when ModelName is not set.
prompt	Provider transcription prompt.
temperature	Provider transcription temperature.
responseFormat	Provider response format.
timestampGranularities	Timestamp granularities.
includeLogprobs	Include log probabilities when supported.

Realtime

OpenAI realtime support is present in source under Clients.Realtime. Source defaults include:

In C# apps, the realtime helper configures the realtime family; the run path still needs realtime transport:

using HPD.Agent;
using HPD.Agent.Providers.Audio.OpenAI;

var agent = await new AgentBuilder()
    .WithOpenAIRealtime(model: "gpt-realtime")
    .BuildAsync();

Option	Default
Model	gpt-realtime

Use realtime with AgentModelTransportMode.Realtime. The ordinary chat path and finite speech-to-text path are separate from native realtime transport.

Provider-specific realtime options use OpenAIRealtimeConfig through ProviderConfig:

{
  "Clients": {
    "Realtime": {
      "ProviderKey": "openai",
      "ModelName": "gpt-realtime",
      "ProviderConfig": {
        "organizationId": "org_...",
        "projectId": "proj_..."
      }
    }
  }
}

Source-confirmed realtime provider configuration:

Option	Use it for
apiKey	Provider-specific API key override.
baseUrl	Provider-specific base URL override.
defaultModelId	Default realtime model when ModelName is not set.
organizationId	OpenAI organization id.
projectId	OpenAI project id.

C# Construction Options

The fluent helpers are the shortest path. Manual typed config is still useful when you are dynamically composing family configs or loading part of the setup outside normal builder code:

using HPD.Agent;
using HPD.Agent.Providers;
using HPD.Agent.Providers.Audio.OpenAI;

var tts = new TextToSpeechClientConfig
{
    ProviderKey = "openai",
    ModelName = "tts-1"
};

tts.SetProviderConfig(
    new OpenAITtsConfig
    {
        DefaultVoiceId = "nova",
        OutputFormat = "mp3",
        Speed = 1.0f
    },
    ProviderClientFamily.TextToSpeech);

Live Verification

Credentialed text-to-speech can be verified with the live smoke test:

HPD_AUDIO_LIVE_SMOKE=1 OPENAI_API_KEY=... \
dotnet test test/HPD.Agent.Audio.V2.Tests/HPD.Agent.Audio.V2.Tests.csproj \
  --framework net10.0 \
  --filter "FullyQualifiedName~OpenAIAudioProviderTests.LiveTextToSpeech_WithConfiguredApiKey_ReturnsAudio"

Credentialed realtime agent turns can be verified through the public realtime run path:

HPD_REALTIME_LIVE_SMOKE=1 OPENAI_API_KEY=... \
dotnet test test/HPD.Agent.Audio.V2.Tests/HPD.Agent.Audio.V2.Tests.csproj \
  --framework net10.0 \
  --filter "FullyQualifiedName~OpenAIAudioProviderTests.LiveRealtimeAgentTurn_WithConfiguredApiKey_ReturnsText"

Related Reading

• Audio Overview
• Audio Runtime Attachment
• Text To Speech Output
• Speech To Text Input
• Realtime Audio
• Audio Events And Traces
• Provider Families