Lightning v3.1

A new Lightning v3.1 Pro checkpoint is in preview until 2026-11-28 as lightning_v3.1_pro_10_26. It covers three languages:

• English (en)
• Spanish with English code-switching (es)
• Hindi with English code-switching (hi)

Try it by passing "model": "lightning_v3.1_pro_10_26" with one of those language values on POST /waves/v1/tts, POST /waves/v1/tts/live (SSE) or wss://api.smallest.ai/waves/v1/tts/live (WebSocket). Endpoints, regions, sample rates, pricing, concurrency and features are the same as lightning_v3.1_pro. For any other language, use lightning_v3.1_pro. The checkpoint may receive updates during the preview; this changelog lists them.

curl -X POST "https://api.smallest.ai/waves/v1/tts" \
  -H "Authorization: Bearer $SMALLEST_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Accept: audio/wav" \
  -d '{
    "text": "Hi, thanks for calling. How can I help you today?",
    "voice_id": "kelsey",
    "language": "en",
    "model": "lightning_v3.1_pro_10_26"
  }' --output speech.wav

Voices. Every Pro voice works on the preview checkpoint. For the best results, start with kelsey or spencer (English, US), bethany or henry (English, UK), sofia or rafael (Spanish) and rhea or ahan (Hindi). See Recommended voices for the full list.

See Checkpoints for how the preview compares with lightning_v3.1_pro, and the benchmarks against other providers.

What changes on 2026-11-28. For English, Spanish and Hindi only, the preview becomes the stable lightning_v3.1_pro, including requests that omit language (they default to en + hi). From then on, use "model": "lightning_v3.1_pro" for these languages. lightning_v3.1_pro_10_26 remains available for 30 more days, until 2026-12-28. The other 28 languages and auto stay on their current checkpoints and do not change.

Migration. No action required today. If you use lightning_v3.1_pro in English, Spanish or Hindi, or without setting language, test lightning_v3.1_pro_10_26 before 2026-11-28. If you call lightning_v3.1_pro_10_26 directly, switch to lightning_v3.1_pro by 2026-12-28. No action is needed for other languages or auto. Enterprise customers who need more time can contact their account team to pin their current checkpoint.