> ## 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.

# ChatGPT desktop app

> Connect the ChatGPT desktop app to Fireworks with the Nexus CLI so open models and Nexus Auto appear next to your OpenAI models.

The ChatGPT desktop app and the [Codex CLI](https://fireworks.ai/docs/nexus/harnesses/codex.md) both read `~/.codex/config.toml`, so connecting one connects the other.

**Quit the ChatGPT desktop app and close open Codex sessions before connecting or running `off`.** The app loads its model list only at startup. Nexus CLI waits for both to close. `--force` writes anyway, which isn't recommended.

Generally availableOpenAI ResponsesNexus AutoNative web search

## Quick start

**1. Install and sign in**

```bash wrap theme={null}
curl -fsSL https://nexus.fireworks.ai/install.sh | bash
```

You need Node.js 22 or later, `git`, and `bash`. On Windows, run the installer from Git Bash. PowerShell breaks the script's line endings.

```bash wrap theme={null}
nexus login
```

Sign in with your browser, or paste a Fireworks API key (`fw_...`).

Already set up? Skip to step 2.

**2. Connect the ChatGPT desktop app**

```bash wrap theme={null}
nexus chatgpt
nexus chatgpt status
```

`nexus chatgpt` is the same command as `nexus codex`.

**3. Reopen the app**

Reopen the app. Its model list starts on Nexus Auto (`auto`) and adds the Fireworks models next to the OpenAI models.

> [!TIP]
>
> The model list starts on Nexus Auto (`auto`) and shows the Fireworks models.

## Use Nexus Auto

The app keeps its own ChatGPT sign-in, which pays for OpenAI model turns. Your Fireworks key pays for Fireworks models. See [Who pays for OpenAI model turns](https://fireworks.ai/docs/nexus/harnesses/codex.md#who-pays-for-openai-model-turns).

## MCP and tools

**MCP servers and plugins** keep working through Codex's tool search.

Native web search is supported while connected through Nexus CLI. Fireworks runs the search server-side and returns the results. You don't need an MCP server or a search service.

## Troubleshooting

Upgrading from an earlier version? See [Upgrading from earlier versions](https://fireworks.ai/docs/nexus/cli.md#upgrading-from-earlier-versions).

> [!NOTE]
>
> **Threads keep the provider they started on.** A thread started on an
> OpenAI model before you connected stays on OpenAI, even after you pick
> Nexus Auto or a Fireworks model. ChatGPT then shows an error such as
> `The 'auto' model is not supported when using Codex with a ChatGPT account.`
> The error names whichever Fireworks model you picked.
>
> * Start a new thread to use Nexus Auto and Fireworks models.
> * To keep working in the old thread, switch back to an OpenAI model, or run
>   `nexus chatgpt off` and turn it back on when you start a new thread.
> * After `off`, threads started on Fireworks models don't open until you run `nexus chatgpt` again.

## Manual setup (advanced)

Quit the app, follow the [Codex manual setup](https://fireworks.ai/docs/nexus/harnesses/codex.md#manual-setup-advanced), then reopen the app and pick the model you set.

## What the Nexus CLI writes

Nexus CLI writes the same `config.toml` and model catalog as for Codex. See [What the Nexus CLI writes](https://fireworks.ai/docs/nexus/harnesses/codex.md#what-the-nexus-cli-writes).


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