FS Code

A native macOS code editor for working with AI, without losing sight of your code.

FS Code is an early, MIT-licensed editor built with Swift and AppKit. No Electron, no Monaco, and no VS Code dependency. Created by Daniel Lares with Codex.

0.1.8 Alpha · macOS 15+ · English interface

This is a working prototype, not a finished IDE. Expect rough edges and keep your projects backed up. Performance is a design priority; we do not yet claim benchmark superiority over other editors.

Why this exists

I like VS Code, Cursor, and Zed. FS Code starts from what I want to do differently in my own daily work:

1. Stay native and lightweight. Opening several projects should not require several heavyweight application runtimes. I prefer native macOS components wherever they fit.
2. Keep a real editor beside the agent. AI-assisted development still involves reading code, checking decisions, and making manual edits. I want a focused editor, not an entire IDE that gets in the way.
3. Make instructions visible. System prompts and project guardrails should be inspectable and editable. I want to understand which rules apply to a file and what context a request receives.
4. Make efficient tools part of the workflow. RTK (Rust Token Killer) belongs in the workflow I want to build. Compatible agent commands now use RTK when it is available locally.
5. Show what the agent changed. File and block changes should be visible in the editor and associated with the conversation, without requiring a trip through Git just to discover them.
6. Make undoing AI changes straightforward. Review the previous content and restore changes, with safeguards for subsequent edits.
7. Keep AI accounts scoped to projects. Different projects can use different accounts from the same service.
8. No product telemetry. I do not want an editor that collects analytics about how I work.

In this alpha

• Project library: choose a folder, give it a name, search and reopen it.
• Independent project windows: File → New Window (⌘⇧N), with a native Window menu.
• File tree including hidden files; tabs, unsaved indicators, line numbers, current-line highlighting, and native Find/Undo.
• Language detection and lexical syntax highlighting with Dracula/Alucard colors. This is not semantic highlighting or an LSP implementation.
• Integrated local terminal powered by SwiftTerm.
• Image previews; SVG and Markdown Preview/Code views; native Quick Look for supported documents and media. Unsupported binaries show an inline read-only state.
• Project TODOs and a local, deterministic instruction/context inspector.
• Editable Shared / Build / Plan / Ask system prompts. Plans open in preview and can be edited, approved, and executed.
• Agent conversations with model/reasoning selection, queued messages, steering, file references, and activity display.
• A native Swift agent runtime using AgentRunKit. ChatGPT browser sign-in and OpenAI API-key connections are available; API-key access has not yet received the same live-account validation as ChatGPT.
• Audited AI file edits, modified-file indicators, block review/revert, and restore points with conflict checks.

The native agent currently exposes bounded project tools. It is not a full autonomous shell/subagent environment. The integrated terminal remains available for manual commands.

Download and run

Download FS Code 0.1.8 Alpha for Apple Silicon, extract FS Code.app, and move it to Applications. This macOS 15+ build is Developer ID signed and notarized by Apple. See the release notes and checksum.

AI features require your own supported account or API key. Opening a project and using the editor do not require an FS Code account.

Build from source

Requirements: macOS 15+, Xcode/Command Line Tools with Swift 6.1 or later, and network access to fetch pinned Swift packages. RTK is not required to build the application.

bash scripts/build-app.sh
open "dist/FS Code.app"

The default local build is ad-hoc signed. Developer ID distribution is documented in Releasing.

swift test --build-system native

The native SwiftPM backend avoids requiring the Metal shader compiler for SwiftTerm's unused Metal path; the terminal uses Core Graphics. This backend is deprecated in newer toolchains. Building through Xcode's normal path may require the Metal Toolchain component.

Privacy and local data

FS Code contains no product analytics or crash-reporting service. Activity records are local conversation history, not analytics uploads.

AI requests are not offline: prompts, selected project context, and tool results are sent to the provider you connect. That provider's data policies apply. Terminal commands and external tools can also access the network.

• The project library lives under ~/Library/Application Support/FS Code/.
• Project instructions and plans use .fs/; conversation and other local project state may use .fscode/.
• Connection credentials are stored through macOS Keychain. Do not commit local project state or credential exports to a public repository.
• Sparkle uses a public signed-update feed. Use FS Code → Check for Updates…; automatic checks and installation remain disabled by default. Version 0.1.0 requires one manual upgrade because it shipped without a feed.

See Privacy for the scope of these statements.

What is next

• Broader RTK command coverage and measured token savings.
• Project-scoped MCP connections.
• Additional model providers, with supported authentication paths.
• Native Git status, history, and graph.
• Broader agent tool coverage and subagents with explicit controls.
• A lightweight extension model, language services, and larger-file performance work.
• End-to-end upgrade validation across published versions.

These are planned capabilities, not features promised by this release.

Architecture

AppKit UI → editor/project/context services → AgentEngine boundary → native AgentRunKit runtime.

EditorCore, ProjectLibrary, AgentContextCore, and AgentConnectionCore separate persistence and domain behavior from the application UI. We reuse dependencies where they support the product rather than minimizing lines of code at the expense of maintainability.

Contributing

Small, focused contributions are welcome. See Contributing. Please open an issue before proposing a large dependency or a change to the native macOS direction.

License and acknowledgments

FS Code's original code is licensed under MIT. Third-party components keep their own licenses and attribution requirements; MIT is not a replacement for those licenses.

FS Code builds on the work of these open-source projects:

Project	Contribution to FS Code
AgentRunKit	Native Swift agent runtime behind our AgentEngine interface.
SwiftTerm	Terminal emulation for the integrated local terminal.
Sparkle	macOS update framework with a public signed-update feed.
Dracula / Alucard	Dark and light color palettes.

We appreciate their maintainers and contributors. As the editor matures, we hope to contribute generally useful fixes and improvements upstream while keeping FS Code-specific behavior in the editor.

Full notices ship in ThirdPartyNotices.txt. Our vendored AgentRunKit version and local changes are documented in UPSTREAM.md.

RTK — Rust Token Killer is used for compatible agent commands when installed locally.