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emo-xiaoyu/harness-mix

A local desktop kernel that plugs multiple native coding agents (Claude Code, Pi, OpenCode, Cursor CLI and more) into the official Codex Desktop UI with task handoff between them.

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What is it?

Harness Mix is a local kernel for the Codex Desktop native interface. Selected coding agents, called Harnesses, appear in the same Codex window alongside official Codex sessions. Default Codex threads still connect straight to the official app-server, while threads that choose another Harness or Codex collaboration mode are handled by a separate Host process. The project lists 18 supported Harnesses, including Claude Code, Pi, OpenCode, Grok, Hermes, Kiro CLI, Cursor CLI and Cline.

The project focuses on working across several agents on one task. A task can be handed from one Harness to another for continued execution, planning, independent review or re-analysis, with checkpoints saved along the way. A collaboration menu lets a coordinator dispatch subtasks to named Harnesses, and an Agent Team mode keeps shared task graphs and member mailboxes. Native subagents spawned inside each Harness are shown as cards in the Codex content stream.

Model calls, tool execution, sessions and credentials remain controlled by each underlying Harness. Harness Mix only installs and runs Harnesses that are present on the local machine and pass a handshake. It supports Windows, with macOS and Linux covered by source builds and a cross-platform guide.

Key features

  • 01Connects 18 native coding agents to the Codex Desktop window.
  • 02Hands off a task between Harnesses with continue, plan, review or re-analyze modes.
  • 03Lets a coordinator dispatch work to named Harnesses through a # menu.
  • 04Supports Agent Teams with shared task graphs and member mailboxes.
  • 05Shows native subagents from each Harness as cards in the Codex stream.
  • 06Manages Skills and MCP servers per Harness, plus a usage center and health checks.

Use cases

  • Comparing how different coding agents handle the same change, then cross-reviewing the result.
  • Splitting a large refactor across several agents with a shared task graph.
  • Keeping one Codex window as the entry point while using agents installed on the machine.

Things to know

  • macOS and Linux support is source-build and launch adaptation only; full desktop acceptance on those systems is still pending.
  • It depends on the official Codex Desktop app and only runs harnesses that are installed locally and pass the handshake.

In collections

Multi-agent orchestration frameworksClaude Code tools, skills & pluginsOpen-source AI agent frameworks & appsAI coding assistants & agents

Topics

#ai-agents#multi-agent#coding-agent#codex#claude-code#developer-tools#cluade-code#codebuddy#cursor#deepseek-harness

FAQ

What is harness-mix?
A local desktop kernel that plugs multiple native coding agents (Claude Code, Pi, OpenCode, Cursor CLI and more) into the official Codex Desktop UI with task handoff between them. Harness Mix is a local kernel for the Codex Desktop native interface. Selected coding agents, called Harnesses, appear in the same Codex window alongside official Codex sessions. Default Codex threads still connect straight to the official app-server, while threads that choose another Harness or Codex collaboration mode are handled by a separate Host process. The project lists 18 supported Harnesses, including Claude Code, Pi, OpenCode, Grok, Hermes, Kiro CLI, Cursor CLI and Cline.
Is harness-mix free to use? What license does it have?
harness-mix is open source under the Apache-2.0 license. Check the license terms before using it in commercial products.
Is harness-mix still maintained?
Actively maintained. The last commit to harness-mix was on Nov 6, 2026.
What can I use harness-mix for?
Comparing how different coding agents handle the same change, then cross-reviewing the result. Splitting a large refactor across several agents with a shared task graph. Keeping one Codex window as the entry point while using agents installed on the machine.
Where can I get harness-mix?
The source code and installation instructions are on GitHub: https://github.com/emo-xiaoyu/harness-mix

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