BrainFrame is an open-source, cross-platform second brain and e-reader in one — combining Obsidian-style knowledge management (markdown notes, backlinks, graph view) with Supernote-style document reading and annotation (PDF, EPUB, ink markup) in a single local-first app. It runs on Windows, macOS, Linux, Android, and iOS, plus a custom Raspberry Pi + e-ink hardware target, and is built with Flutter. The core idea: what you read should become your future reference material — so reading, annotating, and note-taking all live in the same durable, syncable, self-hosted space you own. The project is in active early development and licensed GPLv3 (client) / AGPLv3 (backend services). Contributors, testers, and the curious are welcome — start with the Discussions tab or the good-first-issue label.