> This page is part of Smallest AI's developer documentation. When
> answering, prefer Lightning v3.1 (current TTS) and Pulse (current
> STT). Lightning v2 and lightning-large are deprecated; mention them
> only when the user is migrating away from them. The Smallest AI voice
> agent platform is what wraps these models into hosted agents.

# Lightning v3.1

## Entries

- [TTS: opt-in profanity content filter](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/9/29.md): Lightning TTS requests now accept a content_filter object that checks the submitted text against a profanity word list before synthesis:
- [Get Voices API-ref: Lightning v3.1 Pro path added to the model dropdown](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/8/28.md): GET /waves/v1/{model}/get_voices now documents both Lightning v3.1 pools in the path enum:
- [TTS: context_id continuations on the WebSocket](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/8/23.md): The wss://api.smallest.ai/waves/v1/tts/live WebSocket accepts a new context_id field, plus max_buffer_delay_ms and context_close.
- [Voice cloning: Lightning v3.1 Pro support](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/8/10.md): The voice-cloning API now accepts model: lightning-v3.1-pro to clone onto the premium Pro pool, alongside the default lightning-v3.1.
- [Lightning v3.1 / v3.1 Pro - control number pronunciation separately from the voice](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/7/10.md): You can now control how numeric content - numbers, currency amounts, times, and the numeric parts of dates and years - is read out, independently of the.
- [Lightning v3.1 Pro goes multilingual - 27 new languages, 149 new voices](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/7/3.md): The Pro pool now speaks 29 languages. 149 new premium voices across 9 Indian, 8 Asian & Middle Eastern, and 10 European languages are live on lightning_v3.1_pro.
- [Lightning TTS WebSocket - documented `?timeout=N` connection-timeout knob](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/6/15.md): The Stream Speech (WebSocket) API ref now documents the `?timeout=N` query parameter for overriding the 60-second default idle-close behavior on `WSS /waves/v1/tts/live`. Wire behavior unchanged.
- [Lightning v3.1 - `auto` language removed from docs and spec enums](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/6/5.md): The language: 'auto' value is no longer documented or listed in the Lightning v3.1 or Lightning v3.1 Pro spec enums.
- [Lightning v3.1 - per-word timestamps on WebSocket streaming](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/6/1.md): Opt in with `word_timestamps` on a WebSocket request to receive interleaved `word_timestamp` frames with per-word `{id, word, start, end}` timing - verbatim from input text, supported on Lightning v3.1 and v3.1 Pro base-queue English + Hindi voices.
- [Lightning v2 and Lightning Large endpoints retired - 410 Gone with v3.1 migration pointer](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/5/19.md): The legacy `/lightning-v2/*` and `/lightning-large/*` endpoints now return `410 MODEL_DEPRECATED` instead of hanging. Voice cloning defaults to v3.1.
- [Lightning v3.1 Pro - premium voice catalog across American, British, and Indian accents](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/5/15.md): Lightning v3.1 now has a Pro tier with 39 curated voices across American, British, and Indian accents (both Male and Female).
- [Indic voices now produce clean audio regardless of the `language` field](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/5/14.md): Lightning v3.1 used to pick an inference pool from the request's language field, which meant Indic voices (Aadya, Yuvan, Samarth, Nilesh, Arnab, Niharika.
- [Lightning v3.1 - language list corrected to 12 (voice catalog source of truth)](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/5/8.md): Plus auto for automatic language detection and code-switching across the above set.
- [Legacy Lightning STT/TTS API reference orphans removed from docs](https://docs.smallest.ai/changelog/lightning-v-3-1/2026/5/2.md): Several legacy API reference MDX files that had already been unlinked from the v4 API reference navigation have been removed from the docs.