ArcBrain is a local memory server that connects VS Code Copilot, Claude Desktop, and Cursor simultaneously via MCP. Every 5 minutes, it extracts structured facts from your AI sessions — not raw logs, but knowledge like "Auth uses JWT with 15-min expiry." Facts age through Working → Operational → Canonical layers. Fix a bug in one tool, the others know in minutes. All data stays on your machine. Supports OpenAI, Anthropic, Gemini, Grok, or local Ollama.