AIccentCoach

AIccentCoach is a full-stack SaaS platform that coaches non-native English speakers on pronunciation using a two-model AI pipeline: OpenAI Whisper transcribes speech with word-level timestamps, then Claude performs deep phonetic analysis against the expected text and generates personalized, session-aware feedback.

AI Pipeline

• Claude Haiku 4.5 — Primary pronunciation analyst. Receives the Whisper transcript alongside the expected passage and a learner profile built from historical sessions. Runs strict phonetic analysis: vowel substitutions, th-sounds, r/l confusion, word stress, consonant cluster reduction. Returns structured coaching with specific sound-level corrections.
• Claude Sonnet 4.6 + web search — Generates contextual reading passages from current news (beginner/intermediate/advanced), so users practice with fresh, relevant text rather than canned sentences.
• OpenAI GPT-4o Mini Transcribe — Converts microphone audio to text with word-level timestamps via the Web Audio API. Rate-limited to 20 requests/60 s per user.
• OpenAI TTS-1 — Plays back AI coaching in natural speech (nova/echo voices) so users can hear correct pronunciation alongside written feedback.

Engineering Highlights

• Word-level diff with LCS — A Longest Common Subsequence algorithm matches expected vs. actual words without cascading mismatches on insertions/deletions, enabling accurate per-word pronunciation scoring.
• Learner profile accumulation — Supabase stores every session. Across sessions, the system aggregates recurring issue frequency/severity and detects likely L1 accent patterns, feeding them back into Claude's system prompt to personalize coaching.
• Three practice modes — Read & Practice (passage-based), Conversation (real-time multi-turn with per-turn analysis), and Presentation (PDF slide extraction via pdfjs-dist with per-slide coaching).
• In-memory sliding-window rate limiter — Serverless-compatible rate limiting without Redis: 20 transcriptions/60 s, 15 analyses/60 s, 5 extractions/day — all enforced in Next.js API routes.
• Stripe subscription — 7-day free trial, tiered session limits on the free tier, full access on Pro. Webhook-driven subscription lifecycle management.

Deployment

Vercel (Next.js 16 + React 19 + TypeScript). Supabase PostgreSQL with Row Level Security for user data isolation. Auth via Supabase Auth (email + Google OAuth).

Platform

Web only — no native mobile or Mac app. Responsive and works on mobile browsers; microphone access required.