I've built VT Chat, a privacy-first AI chat application that keeps all your conversations local while providing advanced research capabilities and access to 15+ AI models including Claude 4 Sonnet and Claude 4 Opus, O3, Gemini 2.5 Pro and DeepSeek R1.

Live: https://vtchat.io.vn | Source: https://github.com/vinhnx/vtchat

The core difference is true local-first architecture. All chats are stored in IndexedDB with zero server storage. Your API keys never leave your browser, and I can't see them even as the developer. You can switch between OpenAI, Anthropic, Google and other providers to compare responses, with complete data isolation for shared machines.

I've added research features that I actually use daily: Deep Research does multi-step research with source verification, Pro Search integrates real-time web search, and AI Memory creates a personal knowledge base from your conversations. There's also document processing for PDFs, a "thinking mode" to see complete AI reasoning, and structured extraction to turn documents into JSON. AI-powered semantic routing automatically activates tools based on your queries.

Built with Next.js 14, TypeScript, and Turborepo in a monorepo setup. Everything is fully open source for self-hosting with your own API keys. The hosted version keeps most features free, with optional VT+ for premium models and advanced research capabilities.

Happy to discuss the local-first design decisions, research workflow architecture, or any other technical details.