SJ Cha

Prototyped agentic curricular design system that cut production time from 8 to 2 weeks (75% reduction). Building v2 with MCP servers and knowledge graphs to scale across language pairs and proficiency levels. Established evaluation frameworks using Braintrust, SQL, and Python to measure content performance, and shipped new voice-based lesson experience using OpenAI Realtime API.

Productionized frontier AI with pre-release GPT-4 access, rapidly prototyping conversational AI features (Free Talk, AI Q&A) that set industry design patterns. Updated in-app TTS with more natural delivery via OpenAI RT Audio and Gemini RT Stream. Automated mass lesson content generation via prompt chaining, reducing what took months to three days.

Invented the Speak Method framework for language learning, establishing initial product-market fit. Scaled mobile-first language learning from 3-person pre-product startup to unicorn valuation with $100M+ ARR. Led cross-functional execution across product, growth, marketing, and operations through 0→1→n scaling phases.

0 -> 1 – Invented the "Speak Method" framework of language learning and defined the core UI/UX via content and product that established early PMF, later scaling mobile-first language learning experience from a 3-person pre-product startup to a unicorn