Agent Client Protocol on a Mac

Pick your
ACP client.

By herval · Published November 1, 2026

The Agent Client Protocol (ACP) lets one app talk to many coding agents, the way the Language Server Protocol lets one editor talk to many languages. Gemini CLI speaks it, and Codex does through an adapter, so the question is which app you want to talk to them from. This guide covers the ones that run on a Mac.

Which Mac apps can I use as an Agent Client Protocol (ACP) client for Gemini CLI or Codex?

Several. If you want the agent inside your code, use an editor: Zed and the JetBrains IDEs install Gemini CLI and Codex from the ACP registry (Codex comes built into IntelliJ IDEA), and both are free to use with outside agents. If you want a chat window outside your editor, littleguys adds them from the same registry as contacts you chat with, approve and schedule, next to your other agents. AionUi runs them inside a big workspace with an agent of its own, and Outmake next to models running on your Mac.

The apps

1. littleguys

   A WhatsApp-style chat app that speaks ACP: pick Codex, Gemini CLI or another agent from the ACP registry, choose a folder, and it's a contact you chat with, approve and schedule.

   Pick it if you want to talk to the agent from a small chat window, outside your editor, with your OpenClaw, Hermes and Claude Code agents next to it.

   macOS 13+, Apple silicon and Intel · Free, MIT · 17 MB · Download it

2. Zed by Zed Industries

   A fast code editor that hosts outside agents over ACP. Gemini CLI, Codex and the rest install from the ACP registry and work in its agent panel, inside your code.

   Pick it if you want the agent next to your code, with its edits in the editor.

   macOS 10.15+, Windows, Linux · Free plan includes outside agents; GPL-3.0 · external agents, pricing

3. JetBrains IDEs by JetBrains

   IntelliJ IDEA and the other JetBrains IDEs run ACP agents in their AI Chat. Codex comes built in, Gemini CLI installs from the ACP registry, and neither needs a JetBrains AI subscription.

   Pick it if you already work in a JetBrains IDE.

   macOS, Windows, Linux · ACP agents need no JetBrains AI subscription · ACP docs, blog

4. AionUi by iOfficeAI

   A full desktop workspace ("Cowork") with an agent of its own that works with any API key, which also runs Claude Code, Codex, OpenClaw, Hermes, Gemini CLI and 20+ more CLI agents over ACP. It starts its own session for each chat.

   Pick it if you want a big workspace with an agent of its own, where Gemini CLI and Codex are two of many. It finds the agents you have installed on its own.

   macOS 10.15+, Windows, Linux, a WebUI · Free, Apache-2.0 · 290 MB; release builds send crash reports and recent logs · site, README, releases

5. Outmake by Ambedo Labs

   A native Mac app for running AI models on the Mac itself, which also runs Claude Code, Codex, OpenCode and Gemini CLI over ACP, on the plans you already pay for.

   Pick it if you also want local models, and have an Apple silicon Mac on macOS 26. It's a free beta, a few weeks old, and sends diagnostics by default outside Europe.

   macOS 26+, Apple silicon only · Free beta; closed source · site, releases, privacy

Checked on November 1, 2026 against each app's own site, docs and releases. The protocol keeps a list of every ACP client: dozens more, including editors such as Athas and plugins for Neovim (CodeCompanion), Emacs (agent-shell), VS Code and Obsidian.

How Gemini CLI and Codex speak ACP

Gemini CLI speaks it on its own: gemini --acp (the older --experimental-acp still works, but is deprecated). Codex goes through an adapter, codex-acp, which OpenAI, JetBrains and Zed maintain under the protocol's own GitHub; the older one under Zed is archived. Both are in the ACP registry, which Zed, the JetBrains IDEs and littleguys install agents from, so you rarely type either command yourself.

Gemini CLI and Codex in littleguys

1. Have the agent signed in on this Mac: run gemini once, or codex login.
2. Install Node.js (brew install node): littleguys starts both with npx, and downloads them the first time.
3. Install littleguys with Homebrew or the .dmg (below), 17 MB.
4. Add a bot → Agents (ACP), pick Gemini CLI or Codex from the registry, choose the folder it works in, and click Add.

Each agent is then a contact with its own threads: replies stream in with its tool calls, permission requests are cards (allow once, always allow, deny), its slash commands are in the composer, and routines run it on a schedule. More on ACP agents in littleguys and on Gemini CLI.

What littleguys doesn't do

• It isn't an editor: no file tree, diff review or terminal. If you want the agent inside your code, use an editor that speaks ACP.
• It doesn't watch a Gemini CLI or Codex session already running in your terminal: it starts its own, over stdio.
• Routines run only while littleguys is open. A run that comes due while it's closed is skipped.

brew install herval/tap/littleguys