# Cobalt (Kobo) **Cobalt adds apps to Kobo e-readers and leaves the reader you already have alone.** It's an [[Open Source|open-source]] ([[Affero General Public License (AGPL)|AGPL-3.0]]) platform by BandarLabs, made of four pieces: a Launcher, a signed app Store, a Rust SDK and a runtime. It is not affiliated with Rakuten Kobo. What caught my attention first is the safety model. Most e-reader hacks ask you to trust them with the whole device. Cobalt only adds files to user storage and never touches the boot chain. Your books, library and settings stay where they are, and a restart always brings you back to the stock reader. Each app runs in its own unprivileged process, packages are verified before they open, and an interrupted install keeps the working version. Platform updates ship separately from app updates, so the Store can't replace the platform itself. That's how I'd want ANY extension system to be designed: reversible by default, and boring when something fails. ## What you get The app catalog is where it gets fun (and a bit wild for an e-reader): - **Reading**: Preprints ([[arXiv]]), [[Really Simple Syndication (RSS)|RSS]] Feeds and Digest, Read Later (Wallabag), Stacks ([[Zotero]]), Gutenbird (OPDS catalogs), Library (calibre-web), Panels for comics, and a [[Hacker News]] client. - **AI and dev**: an AI Command Center, Sidekick (answers coding-agent permission prompts from the e-reader), Paperterm (mirrors a terminal session), Deck (a remote for your computer) and a Terminal. - **Productivity**: Vault (notes), Todo, Habits, Flashcards, Daily Brief, Sync ([[Syncthing]]) and Kitchen Card (Mealie recipes). - **Games**: Sudoku, Crossword, Nonograms, Lichess and a few more. - **System**: Home Panel (Home Assistant), Frame and others. The UI is designed for e-ink: large touch targets, readable type, and full screen refreshes only when they're needed. ## Why I find it interesting Two angles. The first is research reading. Pulling arXiv preprints, Zotero collections and RSS feeds onto a screen that can't show you notifications beats reading papers in a browser tab next to your chat app. The second is agent supervision. When [[Claude Code]] or other [[AI Agents]] run for long stretches, your job is mostly approving permission prompts and checking progress. Sidekick and Paperterm move that to a calm, single-purpose device. You glance, you approve, you put it down. There's no inbox one click away... which is really the point. ## Install and build Setup happens once over USB, either through the browser installer (Chrome, Edge or Opera) or from macOS/Linux with: ```sh curl -fsSL https://bandarlabs.github.io/Cobalt/install.sh | sh ``` Restart the Kobo, then open Cobalt from the Kobo menu. From then on, apps install, update and uninstall over Wi-Fi. Developers write apps in [[Rust]] with the SDK, test them in the simulator, and submit them to the Store. Apps ship on their own schedule, independent of platform releases. ## Before you install - Tested on the Kobo Clara BW, Clara Colour, Clara HD, Elipsa 2E, Libra 2, Libra Colour and Libra H2O. Other models are untested and get a warning before Cobalt starts. Kobo firmware 5.x isn't supported. - It's young. The repository was created at the end of July 2026; it then hit #1 on Hacker News with 662 points in August 2026 and was featured on Product Hunt. - There's no warranty. The reversible design limits the damage, but you're still modifying your device. - If you'd rather replace the stock reading software entirely, look at [[KOReader]] instead. Cobalt keeps the stock reader and adds apps around it. ## References - Website: https://bandarlabs.github.io/Cobalt/ - Source code: https://github.com/BandarLabs/Cobalt - Hacker News discussion ("Kobo can run apps now", 662 points): https://news.ycombinator.com/item?id=49390427 - Show HN: https://news.ycombinator.com/item?id=49141871 - Community: https://www.reddit.com/r/CobaltForKobo/ ## Related - [[KOReader]] - [[Open Source]] - [[Affero General Public License (AGPL)]] - [[Calibre OPDS (COPS)]] - [[BookOrbit]] - [[reMarkable]] - [[Reading (MoC)]]