Sayverse

A voice & text translator for live bilingual conversation, built with Expo / React Native. Bring your own OpenAI key — there is no backend.

Conversation mode	Settings

What it does

• Single-shot — type or speak a phrase and get the translation back, with speak-aloud playback.
• Conversation — bilingual turn-taking. Speak in either language; the app auto-detects which one, translates to the other, reads it aloud, and keeps a persisted history of the dialogue.

Translation runs on GPT-4o-mini, speech recognition on Whisper, and text-to-speech on the device. The OpenAI API key is entered on-device and stored locally — calls go straight from the device to OpenAI.

Tech stack

• Expo SDK 55, React Native 0.83, React 19, TypeScript (strict)
• NativeWind v4, react-native-reanimated, @shopify/react-native-skia — a dark "Tron / neon" UI with a signature animated edge-line
• OpenAI GPT-4o-mini + Whisper; expo-audio, expo-speech

See docs/architecture.md for the full picture.

Testing

Three layers, each with a distinct job:

• Unit (Jest) — pure logic: the conversation state machine, helpers.
• Component (Jest + React Native Testing Library) — UI flows driven through the assembled app on the real component tree; runs on every PR.
• Native E2E (Maestro) — the microphone voice path on an emulator.

A separate LLM-evaluation suite scores translation quality against the live model (semantic similarity, an LLM judge, language detection).

Details: docs/test-strategy.md · docs/llm-evaluation.md · docs/tradeoffs.md

Quick start

npm install

# Run on a device — a development build is required (the app uses native
# modules beyond the Expo Go sandbox):
npx expo run:ios       # or: npx expo run:android

On first launch, paste an OpenAI API key (from platform.openai.com). It is stored on the device only.

Scripts

Script	What it does
npm test	Jest unit + component tests
npm run test:watch	Jest unit + component tests, watch mode
npm run test:native	Maestro native E2E (needs an emulator + an e2e build)
npm run eval	LLM-evaluation suite (needs OPENAI_API_KEY)
npm run typecheck	tsc --noEmit
npm run lint	ESLint + NativeWind class validation

License

MIT — see LICENSE.

Status

v1.0 — feature-complete, App Store submission pending.

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Built by Andrii Ozadovskyi.