Cobalt platform enables third-party applications on Kobo e-readers

Introducing Cobalt for Kobo

Cobalt is an open-source application platform designed to bring third-party applications to Kobo e-readers. It comprises a launcher, a signed App Store, a Rust SDK, and a runtime environment. The runtime ensures that each application operates within its own unprivileged process, enhancing system stability and security.

Installation and Management

Initial installation of the Cobalt platform requires a one-time connection via USB. Following this, all subsequent application installations, updates, and removals are managed directly on the Kobo reader over Wi-Fi. Users can revert their device to the stock Kobo reader functionality by simply rebooting it.

Application Architecture and SDK

Applications developed for Cobalt are static ARM binaries that run as unprivileged processes on the standard Kobo hardware. The App Store handles the distribution, verifying signatures before any application is launched. The Rust SDK provides tools for developers to implement KoboApp, declare screens, and manage layout, e-ink refresh, navigation, and application lifecycle. Apps request access to device resources like network, storage, audio, frontlight, and Wi-Fi, with the runtime managing capability gating.

App Store and Updates

The Cobalt App Store reads a signed catalog from a fixed GitHub release, with each package containing an ARM executable and a signed manifest. The runtime verifies these components before an app runs. App releases are independent of platform releases, allowing for continuous updates without requiring a Cobalt version bump or reinstallation. The Cobalt platform itself also updates over Wi-Fi through its settings, on a separate channel from the app catalog.