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openclaw/docs/providers/gradium.md
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summary read_when title
Use Gradium text-to-speech in OpenClaw
You want Gradium for text-to-speech
You need Gradium API key, voice, or directive token configuration
Gradium

Gradium is a text-to-speech provider for OpenClaw. It renders standard audio replies (WAV), voice-note-compatible Opus output, and 8 kHz u-law audio for telephony surfaces.

Property Value
Provider id gradium
Auth GRADIUM_API_KEY or config apiKey
Base URL https://api.gradium.ai (default)
Default voice Emma (YTpq7expH9539ERJ)

Install plugin

Gradium is an official external plugin. Install it, then restart Gateway:

openclaw plugins install @openclaw/gradium-speech
openclaw gateway restart

Setup

Create a Gradium API key, then expose it with an env var or the config key. Config takes precedence over the env var.

```bash export GRADIUM_API_KEY="gsk_..." ``` ```json5 { messages: { tts: { auto: "always", provider: "gradium", providers: { gradium: { apiKey: "${GRADIUM_API_KEY}", }, }, }, }, } ```

Config

{
  messages: {
    tts: {
      auto: "always",
      provider: "gradium",
      providers: {
        gradium: {
          speakerVoiceId: "YTpq7expH9539ERJ",
          // apiKey: "${GRADIUM_API_KEY}",
          // baseUrl: "https://api.gradium.ai",
        },
      },
    },
  },
}
Key Type Description
messages.tts.providers.gradium.apiKey string Resolved API key. Supports ${ENV} and secret refs.
messages.tts.providers.gradium.baseUrl string API origin override. Trailing slashes stripped. Default https://api.gradium.ai.
messages.tts.providers.gradium.speakerVoiceId string Default voice id used when no directive override is present.

Output format is chosen automatically by target surface (see Output) and is not configurable in openclaw.json.

Voices

Name Voice ID
Arthur 3jUdJyOi9pgbxBTK
Christina 2H4HY2CBNyJHBCrP
Emma (default) YTpq7expH9539ERJ
John KWJiFWu2O9nMPYcR
Kent LFZvm12tW_z0xfGo
Sydney jtEKaLYNn6iif5PR
Tiffany Eu9iL_CYe8N-Gkx_

Per-message voice override

When the active speech policy allows voice overrides, switch voices inline with a directive token (any of these are equivalent, all take a provider-native voice id):

/voice:LFZvm12tW_z0xfGo
/voice_id:LFZvm12tW_z0xfGo
/voiceid:LFZvm12tW_z0xfGo
/gradium_voice:LFZvm12tW_z0xfGo
/gradiumvoice:LFZvm12tW_z0xfGo

If the speech policy disables voice overrides, the directive is consumed but ignored.

Output

Output format is selected by target surface; the provider does not synthesize other formats.

Target Format File ext Sample rate Voice-compatible flag
Standard audio wav .wav provider no
Voice note opus .opus provider yes
Telephony ulaw_8000 n/a 8 kHz n/a

Auto-select order

Among configured TTS providers, Gradium's auto-select order is 30. See Text-to-Speech for how OpenClaw picks the active provider when messages.tts.provider is not pinned.