Cobalt: Open-Source App Platform for Kobo E-Readers Launches
Original: Kobo can run apps now
Why This Matters
Cobalt opens Kobo's largely closed e-reader ecosystem to third-party app development via an open-source, safety-focused platform.
Bandar Labs has released Cobalt, an open-source application platform for Kobo e-readers. It includes a launcher, a signed App Store, a Rust SDK, and a process-isolated runtime. Installed once via USB, all subsequent apps install, update, and remove over Wi-Fi directly on the device.
Bandar Labs has launched Cobalt, an open-source platform that enables Kobo e-readers to run third-party applications. The system comprises four main components: a launcher, a signed App Store, a Rust-based SDK, and a runtime that isolates each app in its own unprivileged process on stock hardware. Installation is performed once over USB; after that, apps are managed wirelessly on the device itself. A reboot returns the reader to the standard Kobo experience, requiring no permanent firmware modification. Apps are distributed as signed static ARMv7 binaries, and signatures are verified before launch. The platform ships with a range of built-in apps including an arXiv preprint reader (supporting HTML-rendered papers published since December 2023), Hacker News, RSS feeds, an OPDS library reader (Gutenbird), an audiobook creator, a Sudoku game, a terminal, and Sidekick—a tool for approving or denying coding agent requests remotely. The Rust SDK allows developers to build an app from a single source file by implementing the KoboApp trait and describing screens declaratively. The runtime manages e-ink refresh planning, layout, back navigation, and lifecycle. Access to device resources such as network, storage, audio, and Wi-Fi is capability-gated. The project is not affiliated with Rakuten Kobo.