Show HN: Second Brain – AI Visual Board and Knowledge Base

Hi HN, I'm Dom, a solo founder. I built Second Brain to solve a common issue I had with AI chats: the knowledge disappears. There’s no structure, no memory, and no way to reuse or build on them. So I built a tool that combines AI chat with a visual, interconnected knowledge system. Key features: - Save AI responses into editable docs (Notion-style Pages). - AI Visual board with multiple content & chat nodes (like Miro meets ChatGPT). - Add and chat with YouTubes, TikToks, Audio, PDFs, GitHub repos, Looms, websites, etc. - Organize using Projects and Smart Tags — then chat with full contexts. - Chrome extension for saving anything in 1 click. - Built on GPT-4.1, Claude Sonnet 4, Grok 3, and DeepSeek R1. Privacy: user data is never stored on AI providers or used for training. Would love your feedback or ideas. Demo: https://youtu.be/4prRwP2BjxM https://youtu.be/4prRwP2BjxM Happy to answer any questions about the tech or why I built it! — Dom