FlyCrys

Fast like a fly, solid like a crystal!

Lightning-fast, Linux-native agentic UI on top of Claude Code CLI.

FlyCrys is not an IDE. It doesn't edit files — agents do. You talk to agents, they write the code. FlyCrys gives you a minimal, focused workspace to orchestrate that workflow without getting in the way.

Why FlyCrys

• Purely agentic. No editor, no keybindings to learn, no plugin ecosystem. You give instructions, agents execute. That's it.
• Native & fast. Built in Rust with GTK4. Starts in under a second. No Electron, no browser, no runtime overhead.
• Minimal by design. One binary. Small footprint. Does one thing well — lets you work with AI agents on your codebase.
• Multi-workspace tabs. One agent per workspace, multiple tabs. Each workspace is a focused session on a project directory.
• Linux-first. Built for Linux desktops. Respects your system theme. Feels at home on GNOME, KDE, Sway, i3.

Quick Start

1. Install system dependencies

Ubuntu / Debian:

sudo apt install libgtk-4-dev libvte-2.91-gtk4-dev

Fedora:

sudo dnf install gtk4-devel vte291-gtk4-devel

Arch:

sudo pacman -S gtk4 vte4

2. Install Claude Code CLI

npm install -g @anthropic-ai/claude-code

3. Build & run

git clone https://github.com/AIsavvyAI/flycrys.git
cd flycrys
cargo build --release
./target/release/flycrys

What It Does

Left panel — agent panel. A streaming chat session with Claude Code CLI. You see tool calls as they happen, watch files get created and modified in real time, and send follow-up instructions. A thinking spinner shows while the agent is working.

Center — file tree. Single-click to browse. Right-click to copy paths, open a terminal, or send files to an agent.

Right panel — read-only text viewer with syntax highlighting (20+ languages via syntect). Terminal below it when you need one (VTE4, spawns your $SHELL).

Drag & drop files from the tree onto the agent panel to reference them. That's the whole interaction model — point agents at code, tell them what to do, watch it happen.

Agent Features

• Real-time streaming responses with markdown rendering
• Tool calls shown inline with spinners while running
• Pause / Resume / Stop agent processes (SIGSTOP / SIGCONT / SIGTERM)
• Multi-turn conversations with session resume
• Agent profiles: Default, Security, Research, and custom
• Tab spinner indicates which workspace's agent is actively working

Workspace Features

• Multiple workspace tabs (one per project directory)
• Session persistence — window state, pane positions, agent configs autosaved
• Light / dark theme toggle (follows system preference)
• 10 MB file size guard on text viewer

Project Structure

src/
tests/

Tech Stack

Crate	Purpose
gtk4 0.10	UI toolkit (GTK4 Rust bindings)
vte4 0.9	Embedded terminal emulator
syntect 5	Syntax highlighting
pulldown-cmark 0.12	Markdown parsing
serde + serde_json	Claude CLI stream-json protocol
uuid	Workspace/session IDs
libc	Process signal handling

Roadmap

• File tree with lazy loading
• Syntax-highlighted text viewer
• Embedded VTE4 terminal
• Agent panel with Claude Code CLI streaming
• Markdown rendering in responses
• Drag-and-drop files to agent chat
• Multi-workspace tabs
• Session persistence
• Agent profiles
• Session resume (continue previous conversations)
• Agent model selector (Haiku / Sonnet / Opus)
• MCP server configuration
• Budget controls & cost display
• Git worktree isolation per agent

Philosophy

FlyCrys is deliberately simple. The goal is a fast, stable, minimal surface for agentic development — not another feature-heavy IDE. FlyCrys handles one thing: giving you a clean window into your codebase and your agent.

Contributions that keep things simple and fast are welcome. Features that add complexity without clear agentic value are not.

License

MIT License — see LICENSE for details.