Coding Harnesses

Pick your harness for its quick start, Nexus Auto setup, and troubleshooting. Most harnesses also have manual setup. Claude Desktop is Nexus CLI only. Harnesses marked Preview work, but they may change and some features are limited. Each harness page lists its limits.

Connections

Code

Claude Code

Messages API

Claude Agent SDK

Messages API

Codex

Responses API

OpenCode

Chat Completions

Pi

Chat Completions

DeepSeek Harness

Chat Completions

Cursor IDE

Chat Completions

VS Code

Chat Completions

Copilot App

Chat Completions

Copilot CLI

Chat Completions

Cowork

ChatGPT desktop app

Responses API

Claude Desktop

macOS and Linux

What works where

Nexus CLI starts each harness’s main model on auto. A Provider Key on your account works in every harness.

Harness	Status	API	Nexus Auto	How Anthropic and OpenAI keys arrive	MCP	Manual setup
Code
Claude Code	Generally available	Messages	Supports `auto`	Your Claude login or `ANTHROPIC_API_KEY` for Anthropic models. OpenAI models use a key saved with `nexus auto` or an OpenAI Provider Key	Servers stay in `~/.claude.json`. Nexus CLI sets `ENABLE_TOOL_SEARCH`	Yes
Claude Agent SDK	Preview	Messages	Supported when the SDK reads the user settings written by Nexus CLI	Same as Claude Code	Not touched. Follows the setting sources your application loads	Through Claude Code settings
Codex	Generally available	Responses	Supports `auto`	Codex sign-in for OpenAI models. Anthropic models use a key saved with `nexus auto` or an Anthropic Provider Key	Servers stay in `[mcp_servers]`. Tools load through Codex’s tool search	Yes
OpenCode	Generally available	Chat Completions	Supports `auto`. Closed models need a key saved with `nexus auto`, Provider Keys, or manual setup	A key saved with `nexus auto`, or headers in manual setup	Servers stay in the `mcp` block of `opencode.json`	Yes
Pi	Generally available	Chat Completions	Supports `auto`. Closed models need a key saved with `nexus auto`, Provider Keys, or manual setup	A key saved with `nexus auto`, or headers in manual setup	Not touched	Yes
DeepSeek Harness	Generally available	Chat Completions	Supports `auto`. Closed models need a key saved with `nexus auto`, Provider Keys, or manual setup	A key saved with `nexus auto`, or headers in manual setup	Not touched	Yes
Cursor IDE	Preview	Chat Completions	Supports `auto`. Closed models need Provider Keys. `nexus auto --providers` has no effect	Provider Keys only	Not touched	Yes
VS Code	Preview	Chat Completions	Supports `auto`. Closed models need a key saved with `nexus auto`, Provider Keys, or manual setup	A key saved with `nexus auto`, or headers in manual setup	Not touched	Yes
Copilot App	Preview	Chat Completions	Supports `auto`. Closed models need Provider Keys	Provider Keys only	Not touched	Yes
Copilot CLI	Preview	Chat Completions	Supports `auto`. Closed models need a key saved with `nexus auto`, Provider Keys, or manual setup	A key saved with `nexus auto`, or headers in manual setup	Not touched	Yes
Cowork
ChatGPT desktop app	Generally available	Responses	Supports `auto`	Same as Codex	Same as Codex	Yes
Claude Desktop	Preview	Messages	Supports `auto`. Closed models need a key saved with `nexus auto` or Provider Keys	A key saved with `nexus auto`, added to `auto` turns by the local proxy	`on` imports your connectors. It includes your claude.ai organization’s when the Claude Code CLI is installed and signed in. `nexus claude-desktop mcp sync` imports ones you add later	No

Nexus Auto is not available on Microsoft Foundry, and Foundry support differs by harness. See the compatibility matrix in Nexus for Microsoft Foundry, including Claude Code through a gateway.

Claude Code

Moved to Claude Code.

Claude Agent SDK

Moved to Claude Agent SDK.

Codex

Moved to Codex.

OpenCode

Moved to OpenCode.

Pi

Moved to Pi.

DeepSeek Harness

Moved to DeepSeek Harness.

Cursor IDE

Moved to Cursor IDE.

VS Code

Moved to VS Code.

Copilot App

Moved to Copilot App.

Copilot CLI

Moved to Copilot CLI.

ChatGPT desktop app

Moved to ChatGPT desktop app.

Claude Desktop

Moved to Claude Desktop.

Get started

Nexus CLI

Model Orchestration

Harness Support

Nexus settings

More

Connections

Code

Claude Code

Claude Agent SDK

Codex

OpenCode

Pi

DeepSeek Harness

Cursor IDE

VS Code

Copilot App

Copilot CLI

Cowork

ChatGPT desktop app

Claude Desktop

What works where

Claude Code

Claude Agent SDK

Codex

OpenCode

Pi

DeepSeek Harness

Cursor IDE

VS Code

Copilot App

Copilot CLI

ChatGPT desktop app

Claude Desktop

​Connections

​Code

Claude Code

Claude Agent SDK

Codex

OpenCode

Pi

DeepSeek Harness

Cursor IDE

VS Code

Copilot App

Copilot CLI

​Cowork

ChatGPT desktop app

Claude Desktop

​What works where

​Claude Code

​Claude Agent SDK

​Codex

​OpenCode

​Pi

​DeepSeek Harness

​Cursor IDE

​VS Code

​Copilot App

​Copilot CLI

​ChatGPT desktop app

​Claude Desktop

Connections

Code

Cowork

What works where

Claude Code

Claude Agent SDK

Codex

OpenCode

Pi

DeepSeek Harness

Cursor IDE

VS Code

Copilot App

Copilot CLI

ChatGPT desktop app

Claude Desktop