Jonathan ferreira da conceição

I’m a product-minded software developer who designs and builds thoughtful tools for complex work. I combine product thinking, full-stack development, and interface design to turn ambiguous problems into clear, reliable experiences.

At Kallamo, an independent privacy-first desktop product, I designed and shipped the application end to end using Electron, React, TypeScript, and SQLite. I took it from architecture to a released, auto-updating product, with a focus on maintainable systems, user control, and feedback-driven iteration.

I built a privacy-first RAG system over a SQLite-backed vector store, with fully local, on-device embeddings powered by Transformers.js and ONNX Runtime. I also developed a provider-agnostic LLM orchestration layer with configurable AI profiles, prompt chaining, and validated structured outputs.

On the product side, I built Kallamo’s rich writing environment with TipTap, including chapter-aware context retrieval, non-destructive AI assistance, and DOCX/PDF export. The goal was to make AI feel useful inside a serious writing workflow while keeping the writer in control.

I also designed Worldbuild tab for managing canonical story context and built workspace-level interface customization, so users can shape the environment around their work.