claude-code-with-codex

Use Claude Code with your Claude subscription and your ChatGPT (Codex) subscription at the same time, and switch between them mid-conversation.

It runs as a tiny local proxy. Claude Code already speaks the Anthropic API, so the proxy sits in front of it and sends each request to the right place based on the model name:

• Ask for a Claude model and it uses your Claude subscription (the login Claude Code already has). Nothing is translated and no API key is needed.
• Ask for a gpt-5.6-* model and it uses your ChatGPT subscription through the Codex login.

So you can keep Opus on your Claude plan for hard work and run the fast slot on your ChatGPT plan, in the same session, and flip between them whenever you want.

Quickstart · Switching models · How it works · Configuration · Other backends · Limitations

What you need

• Claude Code installed and signed in with a Claude Pro or Max plan.
• A ChatGPT Plus, Pro, or Team plan and the Codex CLI signed in.
• Rust only if you install from crates.io or source. The prebuilt binary needs nothing.

Quickstart

Three steps, each block is copy-paste ready.

1. Install claude-codex (pick one).

Prebuilt binary, no Rust needed (macOS and Linux):

curl -fsSL https://raw.githubusercontent.com/fcakyon/claude-code-with-codex/main/scripts/install.sh | bash

Or from crates.io, if you have Rust (rustup.rs):

cargo install claude-codex --locked

2. Sign in to your ChatGPT plan through the Codex CLI:

codex login

Confirm it worked (prints your account and expiry):

claude-codex codex auth status

3. Start the proxy and leave it running (listens on 127.0.0.1:18765):

claude-codex serve

To build from a specific commit instead: cargo install --git https://github.com/fcakyon/claude-code-with-codex --locked.

Then, in a second terminal, point Claude Code at the proxy and launch it:

export ANTHROPIC_BASE_URL="http://localhost:18765"

# Leave these unset. Claude Code forwards your Claude subscription login for
# Claude models only when no token is set here. Setting one breaks that route.
unset ANTHROPIC_AUTH_TOKEN ANTHROPIC_API_KEY

# The opus slot runs on your Claude plan, the sonnet slot on your ChatGPT plan.
export ANTHROPIC_DEFAULT_OPUS_MODEL="claude-opus-4-8"
export ANTHROPIC_DEFAULT_SONNET_MODEL="gpt-5.6-terra"
export CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC=1

claude

That is it. Inside Claude Code, pick Opus to run on your Claude plan and Sonnet to run on your ChatGPT plan.

To make it permanent, put the export lines in your ~/.zshrc or ~/.bashrc.

Switching models

• The /model picker. Choosing Opus uses ANTHROPIC_DEFAULT_OPUS_MODEL (your Claude plan) and choosing Sonnet uses ANTHROPIC_DEFAULT_SONNET_MODEL (your ChatGPT plan). Switch as often as you like, even mid-conversation.
• A specific model for one run. claude --model gpt-5.6-terra or claude --model claude-opus-4-8.
• List what is available. claude-codex models.

Reasoning is carried across a switch. When you move a conversation from one plan to the other, the earlier turn's thinking is kept and shown to the next model as plain tagged text, so context is not lost.

How it works

Claude Code sends normal Anthropic API requests to the proxy. The proxy reads the model name and routes:

• Claude models are relayed straight to api.anthropic.com, untouched, reusing the subscription token Claude Code already sends. The request body is forwarded as-is so Anthropic's prompt caching keeps working. The proxy stores no Claude credentials.
• Codex models are translated to the OpenAI Responses API and sent with the ChatGPT login from the Codex CLI's ~/.codex/auth.json. The proxy refreshes that token when needed and writes it back so the Codex CLI keeps working.

An unknown model name returns a clear 400 that lists the ids you can use.

Configuration

Set through environment variables when launching Claude Code.

Variable	What it does
ANTHROPIC_BASE_URL	Point Claude Code at the proxy, e.g. http://localhost:18765.
ANTHROPIC_DEFAULT_OPUS_MODEL	Model id for the Opus slot in the picker. Use a claude-* id for your Claude plan.
ANTHROPIC_DEFAULT_SONNET_MODEL	Model id for the Sonnet slot. Use gpt-5.6-terra for your ChatGPT plan.
ANTHROPIC_MODEL	Force a single model for the whole session instead of using the picker.
CLAUDE_CODE_DISABLE_NONESSENTIAL_TRAFFIC	Set to 1 to skip Claude Code's non-essential background calls.

Do not set ANTHROPIC_AUTH_TOKEN or ANTHROPIC_API_KEY. Either one overrides the Claude subscription login and the Claude route returns 401.

The proxy listens on 127.0.0.1:18765 by default. Change it with PORT=11435 claude-codex serve, and match ANTHROPIC_BASE_URL.

Background requests Claude Code makes for its small, fast model use a Claude id by default, so they run on your Claude plan. Set ANTHROPIC_DEFAULT_HAIKU_MODEL to a gpt-5.6-* id if you would rather run them on your ChatGPT plan.

Other backends

The same proxy can also route to Kimi, Grok, and Cursor models, each with its own login. Run claude-codex models to see every id, and claude-codex <backend> auth status to check a login. These backends keep the behavior of the upstream project this is based on.

Limitations

• Switching plans in the middle of an active tool call (for example pressing Esc during a tool use, then switching and continuing) can fail, because the next model cannot verify reasoning that came from the other plan. Starting the next step fresh avoids it.

Credits

Built on raine/claude-code-proxy, which provides the Codex, Kimi, Grok, and Cursor backends. This fork adds using your Claude subscription as a backend alongside Codex, reasoning that survives a mid-conversation switch, and reading the Codex login from the Codex CLI.