Known limitations

Read this before you commit to the Beta. These are constraints, not bugs, and several of them are deliberate.

Platform

• Expo SDK 57 and React Native 0.86, New Architecture only. The Old Architecture is not supported.
• iOS 16.4+ and Android API 24+. Nothing older.
• Development Builds only. Expo Go cannot load ONNX Runtime, and there is no workaround.

Runtime behavior

• One synthesis at a time per client. A second concurrent call throws BUSY. There is no streaming — you get a complete WAV or nothing.
• No runtime model download. The model must be present at build time via @optimalai/model-tools. The app cannot fetch it on first launch.
• WAV playback is the host app's responsibility. The SDK never plays, caches, uploads, or deletes the file it writes.

Text

• English out-of-vocabulary words fail with INVALID_TEXT. eSpeak is not bundled, so there is no phonetic fallback for unknown words. Chinese characters missing from the lexicon fail the same way.
• 2,000 code points per synthesise call, 300 per segment, 510 tokens per model window.
• Chinese prosody and punctuation pauses vary by voice. Only the Recommended voices have passed the Beta corpus.

Distribution

• Private Beta access only. Packages are published as restricted npm packages under the @optimalai scope with a beta dist-tag. There is no latest tag.
• The production model CDN is not yet live. Until OptimalAI injects the production HTTPS URL, you must pass --base-url or set OPTIMALAI_MODELS_BASE_URL for staging.
• The Beta is blocked on an upstream fix. Private Beta release is gated until the official onnxruntime-react-native package ships a release that includes the Gradle compatibility fix and builds without a pnpm patch.

Licensing

The SDK's own code is Apache-2.0. eSpeak and Piper data are deliberately excluded from every model kit to avoid GPL static dependencies.

This is not legal advice

The exclusion of GPL components reflects engineering intent, not a completed commercial license review. Have your own counsel review your distribution before shipping commercially.

What is not here yet

Playback, runtime download, streaming, Flutter, and ExecuTorch are all out of scope for this Beta. If you need one of them, say so — the roadmap is driven by Beta feedback.