I'm Romullo Bernardo, a Senior Full-Stack & Applied AI Engineer based in Tokyo. I build web and mobile products, connecting the interface, backend and AI workflows.

I help SaaS teams turn AI prototypes into usable product features. My work combines product ownership and full-stack delivery with interfaces where users can review, edit and approve agent proposals.

Remote contracts from Japan · Available October 2026 — Connect on LinkedIn

Language Lit is a language-learning SaaS used in 20+ countries. As founder and sole developer, I own product strategy, UX, frontend, backend, subscriptions and cloud infrastructure.

• Built contextual translation, AI-generated stories and mnemonic images, and FSRS spaced-repetition scheduling.
• Moved lesson creation and other selected AI workflows to Mastra within the existing TypeScript application.
• Built with React/Next.js, Firebase, Google Cloud and Stripe.

An independent React implementation of Material 3 Expressive with typed theme/token APIs, precompiled CSS and Vite/Next.js consumer fixtures. The core package has no runtime dependencies; React is a peer dependency.

Separate companion packages in the Language-Lit organization:

• AG-UI: streaming conversations, tool-rendered UI and user approval steps. Editable drafts survive state updates, with proposal revisions available for backend validation.
• A2UI: protocol-driven rendering, streaming placeholders, two-way data binding, validation and action dispatch.
• MCP Apps: host-side and app-side integration, separate-origin sandboxing, configurable tool-authorization hooks and controlled teardown.

Explore the documentation and live demos →

Merged PR #22913: fixed Pino error serialization so error messages and stack traces are preserved when logged under the error key. Included regression tests, documentation and a changeset.

TypeScript · React · Next.js · React Native · Node.js · Go · Mastra · Firebase · Google Cloud · PostgreSQL

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My strongest fit is a product team that needs senior delivery across the interface, backend and AI workflow. I am seeking international remote contracts from October 2026, with Japanese opportunities also of interest.

Let's discuss your product →

Language Lit  ·  M3E documentation  ·  LinkedIn