KatanA Desktop
A fast, lightweight Markdown workspace for macOS, Windows, and Linux — built with Rust and egui.
🌐 Official Website | 📚 Documentation
English | 日本語
What is KatanA
The name KatanA comes from the Japanese word "刀" (katana) — a razor-sharp blade forged with precision and purpose.
Just as a katana cuts cleanly through its target, this tool is designed to slice through the complexity of documentation workflows with speed and clarity. The name reflects the creator's desire to build something that helps developers cut through challenges decisively, one problem at a time.
KatanA Desktop is a fast, lightweight Markdown workspace for macOS, Windows, and Linux, purpose-built for developers who work with specification documents and technical writing.
The trailing uppercase A stands for "AI"and"Agent"— KatanA is designed for the era of AI agent-assisted development, where Markdown specifications serve as the bridge between humans and AI.Katana × AI Agent = KatanA.
Background
As of 2026, software development is rapidly evolving with the rise of AI agents assisting engineers in writing, reviewing, and maintaining code.
Alongside this shift, Spec-Driven Development (SDD) is gaining attention as a development methodology where specifications, architecture descriptions, and tasks are defined before implementation. These specifications are typically written in Markdown documents and serve as the central source of truth for both developers and AI agents.
This repository is operated with an AI-agent-first workflow in mind.
Repository-local skills are maintained canonically under .agents/skills/.
If another AI agent expects a different skill directory layout, copy the same skill content from .agents/skills/ into that agent's expected path instead of maintaining a separate variant.
KatanA itself is also developed through a Codex-centered AI-agent workflow.
We primarily use Codex and combine it with other AI agents where they fit best, such as implementation, review, investigation, documentation, and release preparation.
This keeps the project aligned with the same human-and-agent collaboration model that KatanA is built to support.
Mandatory Tools for AI-Agent Workflow
To minimize token consumption and manage context window bloat, the use of rtk is mandatory for all AI agents working in this repository.
AI agents MUST wrap noisy commands (tests, linters, builds) with rtk to ensure outputs are filtered and summarized before being ingested into the context.
However, existing Markdown tools are often either:
- general-purpose editors not optimized for technical documentation workflows, or
- heavy knowledge-management tools with unnecessary complexity.
KatanA Desktop was created to solve this problem
The goal of KatanA is to provide a simple, fast, and workspace-oriented Markdown environment where developers can easily browse and edit documentation used in SDD workflows.
Features
- Live split-view preview — Edit on the left, rendered HTML on the right, scroll-synced
- Native document viewing — Open interactive HTML, PDF, DOCX, XLSX, and PPTX files or direct document URLs inside the workspace
- Diagram rendering — First-class support for Mermaid, PlantUML, and Draw.io fenced code blocks
- GitHub Flavored Markdown — Tables, strikethrough, task lists, footnotes, autolinks
- Workspace-aware — Open a folder and navigate files from the integrated file tree
- Tab bar — Multiple documents open simultaneously with VSCode-style tabs
- i18n — UI strings fully localised (English / Japanese bundled)
- Fast native performance — Built with Rust and egui, no Electron, no Node.js — just a single native binary
Installation
> Available on macOS (Apple Silicon & Intel), Windows, and Linux.
macOS
Homebrew (Recommended for macOS)
brew tap HiroyukiFuruno/KatanA && brew install --cask katana-desktop
No additional steps required — the app is ready to use immediately.
Manual Download (macOS)
- Go to the Releases page
- Download the latest
KatanA-Desktop-x.y.z.dmg
- Open the DMG and drag KatanA Desktop.app into your Applications folder
- Run the following command once to allow the app to launch:
xattr -cr /Applications/KatanA\ Desktop.app
> Note: On macOS Sequoia (15.x), Gatekeeper requires this command for apps not notarized with Apple.
> Alternatively, go to System Settings → Privacy & Security → "Open Anyway" after the first launch attempt.
Windows
Winget (Recommended)
On Windows 10 / 11, you can easily install KatanA Desktop using the official winget package manager:
winget install HiroyukiFuruno.katana-desktop
Manual Download (Windows)
You can also download the files manually from the Releases page.
- Portable ZIP: Extract the archive to your preferred location and run
KatanA.exe.
- MSI Installer: Automatically creates Start Menu and Desktop shortcuts. (Note: Since the MSI is not code-signed, Windows SmartScreen may display a warning. Select "More info" -> "Run anyway" to proceed).
Linux
Homebrew (Recommended)
brew tap HiroyukiFuruno/KatanA && brew install katana-desktop
Manual Download (Linux)
- Go to the Releases page
- Download the
KatanA-linux-x86_64.tar.gz
- Extract the archive and run
./KatanA
Updating KatanA
KatanA features a built-in auto-updater. Once installed (whether via Homebrew or manually), KatanA will notify you when a new release is available.
- macOS / Windows / Linux: You can update the app directly from within the UI by clicking the "Install and Restart" button.
- macOS Homebrew installs: The first in-app update automatically untaps KatanA from Homebrew to prevent double-management issues.
Current Status
KatanA Desktop is under active development. See the Releases page for the latest version and changelog.
Core features available today:
- Workspace-based Markdown browsing
- Diagram support (Mermaid / PlantUML / draw.io)
- Split preview with synchronized scrolling
- Fast native desktop performance (Rust-based)
The project is evolving rapidly — new features and improvements are released frequently.
Diagram Rendering Setup
KatanA supports Mermaid, PlantUML, and Draw.io diagrams in Markdown fenced code blocks. Diagram rendering is handled by the bundled KDV / KRR integration, so no Java runtime or renderer download step is required.
Project Goals
KatanA aims to become a tool that helps developers:
- Read and navigate Markdown documentation efficiently
- Work with specification-driven workflows
- Integrate documentation with modern AI-assisted development
The long-term vision is to build a lightweight documentation workspace that complements modern development tools.
We Want Your Ideas
This project is still in its early stages. We welcome features ideas, usability suggestions, and bug reports.
If you have thoughts on how KatanA can improve the documentation workflow for developers, please open an issue or discussion.
For Contributors
If you would like to help shape the future of KatanA, please read our:
- 🤝 Contributing Guide — How to join discussions, provide design feedback, and collaborate via AI-agent-assisted workflows.
Open Source Commitment
KatanA Desktop is an open source project.
We are committed to keeping the core functionality available for free, especially features that do not incur ongoing operational costs.
These include:
- Markdown viewing
- Workspace navigation
- Documentation browsing
- Diagram rendering
Future Plans
Some advanced features may require external services or operational costs.
For sustainability, the project may introduce:
- optional paid features (e.g., AI-assisted tools)
- small advertisements within the application
However, the core documentation functionality will remain free.
For Developers
If you want to build from source, contribute, or understand the architecture:
Common development tasks use just:
brew install just
just init
just run
just check
Support the Project
If you find KatanA useful and would like to support its development, you can do so through sponsorship.
Support helps cover:
- development time
- infrastructure
- tooling costs
👉 Become a Sponsor
- ⭐ Star this repository — it helps others discover KatanA
- Share KatanA with people who might find it useful
License
KatanA Desktop is released under the MIT License.