> ## Documentation Index
> Fetch the complete documentation index at: https://fireworks.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Coding Harnesses

> Connect Claude Code, Claude Agent SDK, Claude Desktop, Codex CLI, ChatGPT, OpenCode, Pi, Cursor IDE, VS Code, Copilot, or DeepSeek Harness to Fireworks.

Every harness except Claude Desktop also supports [manual setup](https://fireworks.ai/docs/nexus/manual-setup.md).

Nexus CLI sets each harness's main model to `auto`, and a [Provider Key](https://fireworks.ai/docs/nexus/provider-keys.md) on your account works in every harness.

## Code

> [card] [Claude Code](https://fireworks.ai/docs/nexus/harnesses/claude-code.md)
>
> Messages API

> [card] [Claude Agent SDK](https://fireworks.ai/docs/nexus/harnesses/claude-code.md#claude-agent-sdk)
>
> Messages API

> [card] [Codex](https://fireworks.ai/docs/nexus/harnesses/codex.md)
>
> Responses API

> [card] [OpenCode](https://fireworks.ai/docs/nexus/harnesses/opencode.md)
>
> Chat Completions

> [card] [Pi](https://fireworks.ai/docs/nexus/harnesses/pi.md)
>
> Chat Completions

> [card] [DeepSeek Harness](https://fireworks.ai/docs/nexus/harnesses/deepseek.md)
>
> Chat Completions

> [card] [Cursor IDE](https://fireworks.ai/docs/nexus/harnesses/cursor.md)
>
> Chat Completions

> [card] [VS Code](https://fireworks.ai/docs/nexus/harnesses/vscode.md)
>
> Chat Completions

> [card] [Copilot App](https://fireworks.ai/docs/nexus/harnesses/copilot-app.md)
>
> Chat Completions

> [card] [Copilot CLI](https://fireworks.ai/docs/nexus/harnesses/copilot-cli.md)
>
> Chat Completions

## Cowork

> [card] [ChatGPT desktop app](https://fireworks.ai/docs/nexus/harnesses/chatgpt.md)
>
> Responses API

> [card] [Claude Desktop](https://fireworks.ai/docs/nexus/harnesses/claude-desktop.md)
>
> Limited support on macOS. Linux is coming soon

## What works where

| Harness | API | Nexus Auto | How Anthropic and OpenAI keys arrive | MCP | Manual setup |
| - | - | - | - | - | - |
| **Code** | | | | | |
| [Claude Code](https://fireworks.ai/docs/nexus/harnesses/claude-code.md) | 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](https://fireworks.ai/docs/nexus/harnesses/claude-code.md#claude-agent-sdk) | 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](https://fireworks.ai/docs/nexus/harnesses/codex.md) | 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](https://fireworks.ai/docs/nexus/harnesses/opencode.md) | 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](https://fireworks.ai/docs/nexus/harnesses/pi.md) | 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](https://fireworks.ai/docs/nexus/harnesses/deepseek.md) | 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](https://fireworks.ai/docs/nexus/harnesses/cursor.md) | Chat Completions | Supports `auto`. Closed models need Provider Keys. `nexus auto --providers` has no effect | Provider Keys only | Not touched | Yes |
| [VS Code](https://fireworks.ai/docs/nexus/harnesses/vscode.md) | 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](https://fireworks.ai/docs/nexus/harnesses/copilot-app.md) | Chat Completions | Supports `auto`. Closed models need Provider Keys | Provider Keys only | Not touched | Yes |
| [Copilot CLI](https://fireworks.ai/docs/nexus/harnesses/copilot-cli.md) | 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](https://fireworks.ai/docs/nexus/harnesses/chatgpt.md) | Responses | Supports `auto` | Same as Codex | Same as Codex | Yes |
| [Claude Desktop](https://fireworks.ai/docs/nexus/harnesses/claude-desktop.md) (Limited) | 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 |


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