Hadi

Students learning Korean or Japanese need real-time translated subtitles during lectures, with timestamped notes. Most speech-translation apps are one-directional, laggy, or don't save the session.

1. 01

   The phone streams audio straight to Soniox stt-rt-v5 over a raw WebSocket, using a short-lived single-use key minted by a Cloud Function

   Why

   A provider key must never ship inside the client. The temporary key is scoped to transcription and expires after 300 seconds.

   Trade-off

   Soniox is the only provider on the recording path: if it is down, recording and live translation stop, so balance alerts and error monitoring are required.

2. 02

   All AI post-processing runs in Cloud Functions: summaries, retranslation, politeness labels and kanji lookup

3. 03

   Offline-first: sessions are stored in expo-sqlite and synced to Firestore across devices after each lecture

4. 04

   Audio is never stored, only the transcript and its translation; Firestore security rules block any cross-user access

5. 05

   A shared design-token package with a test that fails on hard-coded colours and a numeric WCAG AA contrast check over 56 colour pairs

1. Speech
2. Soniox stt-rt-v5 (WebSocket, temporary key)
3. Live bilingual subtitles
4. expo-sqlite (offline)
5. Firestore sync
6. Cloud Functions: summary and retranslation

Supporting services

Local storage

expo-sqlite

Sync and data

Firestore

Auth

Firebase Auth (Apple, Email)

Server logic

Cloud Functions

Billing

Apple in-app purchase, verified on the server

• Real-time bilingual Korean/Japanese ↔ Vietnamese subtitles on a single socket.
• Offline-first storage with expo-sqlite and multi-device sync via Firestore.
• A marketing website built with Next.js.
• Hadi Live, a Chrome extension that captions a tab's audio (in development).
• Live in production, app version 1.3.2.

More facts

languages

3

version

1.3.2

commits

1,800+

test files

500+