CodeMantis — The Mac app Claude Code and Codex deserve
CodeMantis is a free, open-source native macOS application that wraps the Claude Code and OpenAI Codex CLIs in a three-panel graphical interface — pick which agent each session uses, or route different tasks to different agents. Built with Tauri v2 and Rust on a pluggable agent architecture, it launches in under 3 seconds, uses under 120MB of memory, and includes AI-powered spec writing, 10+ project templates, integrated terminals, and a live preview browser. Under 50MB download, MIT licensed.
Native macOS · Apple Silicon & IntelBuilt with Tauri v2 + RustSee it in action
CodeMantis in under 3 minutes
Two Coding Agents. One Mac App.
CodeMantis is the first native macOS app that treats Claude Code and OpenAI Codex as equals. Pick your agent when you open a project. Switch mid-flight. Or route different task categories to different agents — write specs with Claude, run hot main chat on Codex, keep the in-app Help assistant on whichever you're logged in to. The agent you bring is yours; the interface is the same.
- Agent Picker in the Project Picker when both CLIs are installed
- Per-session agent selection — sessions carry an agent_id
- Per-task routing for main chat, SpecWriter, Help, and the Assistant panel (v1.5.0)
- 7-day usage-split card shows tokens and cost per agent
- Codex Policy Pill (sandbox × approval-policy) replaces the Mode Selector for Codex sessions
- Works with your existing Claude Pro/Max or ChatGPT Plus/Pro/Business subscription — no extra API key required
- Pluggable AgentAdapter — additional CLIs ship as a config, not a rewrite
Write the Spec, Not the Code
Your coding agent implements what you describe — but the quality of the description determines the quality of the result. SpecWriter is an AI conversation partner that draws out the details you'd forget to mention: loading states, error handling, validation rules, edge cases. It produces professional specification documents, verification checklists, and multi-session implementation plans. Then Self-Drive implements everything automatically through Claude Code or Codex — from idea to finished feature.
- Interactive multi-turn conversation
- Attach mockups, screenshots, and PDFs
- Reads your existing codebase and references real file paths
- Confidence tagging — the AI tells you when it's guessing
- Generates companion verification checklists
- Implementation Guide breaks specs into multi-session plans
- Self-Drive automates the entire implementation — build, verify, fix, advance
- Two modes: spec a new app from scratch, or add a feature to an existing project
See Everything at Once
A coding agent's power comes from its ability to read, write, and execute across your entire project. CodeMantis makes that visible. Chat conversations flow on the left. Every file read, write, edit, and bash command appears in the Activity Feed on the right — color-coded, expandable, with one-click approval. For Claude Code sessions, pick Normal mode (approve each action), Auto-Accept (work freely), or Plan (reasoning only). For Codex sessions, the Codex Policy Pill lets you dial sandbox × approval-policy independently.
Start Projects in Seconds
Your agent is at its best when it understands your project from the first message. CodeMantis gives it that head start. Pick from 10+ curated templates — Next.js, Vite+React, FastAPI, Astro, Expo, and more. One click scaffolds the project, installs dependencies, and generates a CLAUDE.md (or AGENTS.md) file that teaches the agent the project's structure, conventions, and commands. From empty folder to productive conversation in under a minute.
Preview Your App Live
A native macOS preview window shows your running application right alongside your coding conversation. Auto-detects your dev server, supports responsive viewport presets — phone, tablet, desktop — and captures console logs so you can spot errors without switching to Chrome DevTools. It's the workflow you always wanted: describe a change, watch your agent implement it, see it live.
More Than One Brain
Sometimes you want a second opinion before committing to an approach. Open parallel AI assistants — the latest models from OpenAI, Google, or Anthropic — in tabs alongside your main coding session. Brainstorm architecture. Review code. Draft documentation. Compare suggestions. Each assistant has per-session cost tracking. The Assistant panel is agent-agnostic: it works the same whether your main session runs Claude Code or Codex. Your coding agent stays in control of your files; the assistants are your advisory board.
Everything in One Window
CodeMantis is a native Mac app built with Tauri v2 and Rust — not an Electron wrapper, not a web page in a frame. It launches instantly, uses minimal memory, and respects macOS conventions: native menus, keyboard shortcuts, proper window management. Inside that native shell: a Monaco code editor, xterm.js terminals, MCP server management for 15+ services, AI-powered changelogs, slash commands, and six carefully designed themes. Everything a Mac developer expects, nothing a Mac developer would compromise on.
What the Community Says
Early feedback from developers using CodeMantis with Claude Code.
I went from a terminal-only Claude Code workflow to CodeMantis and immediately felt the difference. Seeing the activity feed separate from the chat is a game-changer — I actually know what Claude is doing to my files now.
Early Beta Tester
Full-Stack Developer · Discord community
SpecWriter alone is worth the download. I used to spend 20 minutes writing prompts for Claude Code. Now I have a conversation with SpecWriter and get a proper spec in 5 minutes that Claude follows precisely.
Community Member
Product Engineer · Discord community
Finally a Claude Code interface that respects macOS conventions. It launches fast, uses minimal memory, and the three-panel layout makes so much more sense than a single scrolling terminal.
Community Member
macOS Developer · GitHub discussion
Frequently Asked Questions
Common questions about CodeMantis and how it works with Claude Code and Codex.
CodeMantis is a free, open-source native macOS application that wraps Anthropic's Claude Code CLI and OpenAI's Codex CLI in a graphical interface. You pick which coding agent each session uses — or route different task categories (main chat, SpecWriter, Help, Assistant) to different agents from Settings > Agents. Three-panel layout with a file tree, chat, and activity feed, plus integrated terminals, a Monaco editor, AI-powered spec writing, and a live preview browser. Built with Tauri v2 and Rust, it launches in under 3 seconds and uses under 120MB of memory.
Yes, completely. CodeMantis is MIT licensed with no subscription fees, no API keys required, and no telemetry. You do need an existing subscription for at least one of the two supported agents — Claude Pro ($20/mo) or Max ($100-200/mo) for Claude Code, or ChatGPT Plus/Pro/Business for OpenAI Codex. CodeMantis itself costs nothing and brings nothing of its own to bill against.
Both CLIs run in a single scrolling pane where chat messages and tool operations are interleaved. CodeMantis separates them into dedicated panels: chat on the left, activity feed on the right. You also get a built-in file editor (Monaco), integrated terminals, a live preview browser, project templates, AI-powered spec writing (SpecWriter), MCP server management, and per-task agent routing — all in one native Mac window. The same panel separation makes sense for Claude Code or Codex; the agent you pick is just a setting.
Cursor and VS Code extensions add AI to an existing code editor. CodeMantis takes the opposite approach: it builds a purpose-designed interface around a coding agent as the primary workflow — and it isn't locked to one. You get a dedicated activity feed showing every file operation, SpecWriter for creating implementation-ready specifications, session modes (Normal, Auto-Accept, Plan) for Claude or the Codex Policy Pill (sandbox × approval-policy) for Codex, and a native macOS app that uses 40-120MB of memory versus 300-500MB for Electron-based editors.
CodeMantis requires macOS 12 (Monterey) or later, on Apple Silicon or Intel. You also need at least one of the supported agent CLIs installed: Claude Code (npm install -g @anthropic-ai/claude-code) with a Claude Pro/Max subscription, or OpenAI Codex (npm install -g @openai/codex, or brew install codex) with a ChatGPT Plus/Pro/Business subscription. You can install both — CodeMantis will let you pick per session or route per task. The app itself is under 50MB to download.
SpecWriter is an AI-powered specification assistant built into CodeMantis. Instead of giving your coding agent a vague prompt, SpecWriter guides you through an interactive conversation to extract every detail — loading states, error handling, validation rules, edge cases. It produces a structured specification document with a verification checklist, then hands off to whichever agent you've chosen for spec_writer in Settings > Agents. Two modes: New Application (from scratch) and Feature Mode (for existing projects, with codebase context).
Yes. CodeMantis includes Multi-AI Assistant tabs where you can run OpenAI, Google Gemini, or Anthropic API models alongside your active session. These assistants are chat-only (they cannot edit files or run commands) — perfect for brainstorming, code review, or getting a second opinion. The Assistant panel is agent-agnostic: it works the same whether your main session is Claude Code or Codex. Each assistant tracks per-session token usage and cost.
Yes. CodeMantis is released under the MIT License. The full source code is available on GitHub at github.com/codemantis-dev/codemantis. You can inspect the code, contribute features, report issues, or fork it.
On June 15, 2026, Anthropic restructured Claude subscription billing — Agent SDK and `claude -p` (programmatic) usage moved to a separate, metered credit pool, while interactive use of Claude Code stays on the original subscription. CodeMantis runs the user's own claude binary, which keeps us in the explicitly-permitted lane, but the change made the case for vendor optionality clear. We had already shipped an AgentAdapter abstraction internally, so adding Codex took a single release. Per-task routing in v1.5.0 lets you split workloads across both agents — write specs with Claude, run hot main chat on Codex, or whatever balance fits your subscription pool. Read the full reasoning in our blog post: 'Why CodeMantis Now Supports Two Coding Agents (and Soon More).'
Built by a creator.
Powered by Claude Code and Codex.
Made for creators.
AI coding enables a new dawn of creators. Ideas that were impossible due to budget, time, or team constraints are suddenly within reach. CodeMantis was built entirely by a non-developer using Claude Code itself — from the Rust backend to the React frontend — as proof that the path from idea to product is now open to everyone.
When Anthropic restructured Claude subscription billing on June 15, 2026, we learned a hard lesson: the agent you build on can change the rules underneath you. So we added OpenAI Codexas a first-class second agent — and the architecture to add more whenever they show up. The app you choose shouldn't lock you into one vendor's billing decisions.
CodeMantis exists to support the creator's journey. Not for the engineers who already know how to code, but for the innovators who finally can — on whichever coding agent makes sense for them today.
Free. Open source. Built for Mac.
CodeMantis is MIT licensed. No API keys, no subscription fees, no telemetry. Just download, connect your Claude Pro/Max or ChatGPT Plus/Pro/Business subscription, and start building. The two best coding agents, in the interface they've been missing.