Marginalia

A desktop ebook reader with a built-in AI companion.

Marginalia (n.) — notes, comments, and annotations made in the margins of a book; from Latin marginalis, "of the margin."

What it does

I built this to aid in reading technical books, where I find I constantly wish to stop and ask questions about the material. Inspired by Andrej Karpathy's reader3. Select a passage, ask a question, and have an ongoing conversation about it without leaving the page.

Marginalia combines a slimmed-down fork of Readest (an open-source ebook reader) with Pi (an AI agent framework) into a single desktop app. Read on the left, chat on the right. The AI knows what book you're reading, what chapter you're in, and has the full chapter text as context.

Features

Reading:

• EPUB, PDF, MOBI, AZW/AZW3, FB2, CBZ, TXT, Markdown
• Page and scroll mode
• Highlights, bookmarks, annotations
• Export annotations as Markdown
• Full-text search
• Dark/light/auto theme
• Customizable fonts, margins, layout

AI chat:

• Collapsible sidebar panel
• Select text, click "Ask AI" to discuss it
• Full chapter text included as context
• Multiple conversations per book, persisted across sessions
• Web search for real-world context beyond the book
• Claude Opus 4.6, Claude Sonnet 4.6 (via Claude Code Max)
• GPT-5.4 (via Codex CLI)
• Auto-loads auth tokens from Claude Code and Codex CLI

How it works

The app piggybacks on your existing Claude Code and Codex CLI credentials — no separate API keys needed. Open a book, open the chat panel, and start asking questions.

Credentials are loaded from:

• Claude Code — macOS Keychain (service Claude Code-credentials)
• Codex CLI — ~/.codex/auth.json

If you get a 401, make sure you've authenticated first (claude auth login / codex auth).

Installation

Homebrew (Recommended)

brew install eddmann/tap/marginalia

Manual Download

Download the latest release from GitHub Releases:

• macOS: .dmg (Apple Silicon and Intel)
• Linux: .AppImage or .deb

Development

Requires Rust, Node.js 20+, and pnpm.

make install   # Install all dependencies
make dev       # Start development server
make build     # Build production app
make lint      # Run all linting
make fmt       # Format all code
make clean     # Remove all build artifacts

Built with

• Readest — ebook reader
• Pi — AI agent framework
• Tauri v2 — native desktop runtime

License

AGPL-3.0 — same as Readest, from which this project is forked.