Tts Updates & Release Notes

OpenAI-compatible speech endpoint

Realtime TTS now serves POST /v1/audio/speech in OpenAI's format, so apps built on OpenAI's text-to-speech can switch to Inworld by pointing the SDK at Inworld and choosing an Inworld model and voice — see OpenAI Compatibility.

• Works with the OpenAI SDKs: The official Python and Node.js SDKs work unchanged, including streaming responses.
• Formats: mp3, opus, flac, wav, and pcm, plus server-sent events with stream_format: "sse".
• One base URL: https://api.inworld.ai/v1 also serves the Inworld Router, so one client configuration covers LLM and TTS.

Realtime TTS-2 Flash

Launched Realtime TTS-2 Flash (inworld-tts-2-flash), the fastest member of the TTS-2 family — see Models:

• Our lowest latency: 20 ms time to first audio (server-side P90 TTFB, excluding network latency) — 5× faster than inworld-tts-2 at 100 ms, making it the best choice for latency-critical real-time agents.
• Our lowest cost: The most cost-efficient model per character, ideal for high-volume workloads.
• Full TTS-2 language coverage: The same 200+ languages and locales as inworld-tts-2, plus instant voice cloning and timestamp alignment.

<Note> [Steering](https://docs.inworld.ai/tts/capabilities/steering.md) instructions and [Professional Voice Cloning](https://docs.inworld.ai/tts/professional-voice-cloning.md) are supported on `inworld-tts-2` only — use it when you need directed, contextually aware delivery. Non-verbal tags like `[laugh]` work on both models. </Note>

Steering instructions now persist

Steering on inworld-tts-2 follows one rule: a [tag] applies from where you write it until you change it. See the Steering guide.

• [reset]: New reserved tag that ends a styled passage and returns the voice to its own character for the rest of the text. [shouting] We need to leave now! [reset] Do you understand me? shouts only the first sentence.
• Instructions survive pauses: A <break/> no longer clears the active instruction. A pause is a pause and never changes delivery.
• Request-level instruction field: Set one instruction for the whole request without putting tags in your text. See instruction. Use either this field or inline tags, not both.

<Warning> **Behavior change.** An inline `[tag]` previously affected only the text immediately after it and delivery could revert on its own partway through longer text. A tag now stays in force until you change it. If you relied on an instruction wearing off — for example `[shout] Hi. Normal text.` expecting the second sentence unstyled — add `[reset]` where normal delivery should resume. Requests that use no inline tags are unaffected, as are `inworld-tts-1.5-max` and `inworld-tts-1.5-mini`. </Warning>