Brainstorm

Brainstorm is a free, open-source desktop operating system for knowledge management available on macOS, Windows, and Linux. Built as a sandboxed desktop shell, it hosts individual apps—such as Notes, Database, Files, Whiteboard, and Graph—that all read and write to a single vault of plain files stored directly on your disk.

It provides privacy and control over your data and AI interactions. Multi-device synchronization is optional and end-to-end encrypted without requiring an account. An integrated AI broker lets you connect custom API keys or run local models, allowing you to set specific access permissions and cost budgets for each app and agent.