Declarative TTS / STT Providers

The chat-provider and embedding-provider declarative pattern (#979) extends to text-to-speech and speech-to-text. Voice-mode applications no longer need to hard-code provider construction in Go.

Quick Start

spec:
  tts_providers:
    - id: voice
      type: elevenlabs
      model: eleven_turbo_v2
      credential:
        credential_env: ELEVEN_API_KEY
    - id: cart
      type: cartesia
      credential:
        credential_env: CARTESIA_API_KEY
      additional_config:
        ws_url: wss://api.cartesia.ai/tts/websocket

  stt_providers:
    - id: whisper
      type: openai
      model: whisper-1
      credential:
        credential_env: OPENAI_API_KEY

conv, _ := sdk.Open("./pack.json", "chat",
    sdk.WithRuntimeConfig("./runtime.yaml"),
)

The first declared TTS entry becomes the default ttsService unless WithTTS (or WithVADMode) wired one programmatically. Same for STT and sttService.

Supported Types

Block	`type` value	Underlying package
`tts_providers`	`openai`	`runtime/tts` (OpenAI TTS)
`tts_providers`	`elevenlabs`	`runtime/tts` (ElevenLabs)
`tts_providers`	`cartesia`	`runtime/tts` (Cartesia)
`stt_providers`	`openai`	`runtime/stt` (OpenAI Whisper)

additional_config honored extras:

Cartesia — ws_url (string) for the websocket streaming endpoint.

Programmatic Path Still Works

WithTTS(service) and WithVADMode(stt, tts, ...) are unchanged. When set, they win over the YAML default — same precedence rule as chat and embedding providers.

Validation

LoadRuntimeConfig rejects:

Missing type.
A type outside the supported set.
Two entries with the same effective ID (explicit ID, or type when ID is omitted).

Adding a New Provider

The factory pattern is open: a per-provider package can self-register via init():

package mytts

import "github.com/AltairaLabs/PromptKit/runtime/tts"

func init() {
    tts.RegisterFactory("my_tts", func(spec tts.ProviderSpec) (tts.Service, error) {
        return NewMyTTS(spec.Model, tts.APIKeyFromCredential(spec.Credential)), nil
    })
}

Side-effect-import the package from your application and the new type: value works in YAML immediately.