claudecodex — Run Claude Code with GPT-5.6 using your ChatGPT subscription

claudecodex lets you use Claude Code with OpenAI models — GPT-5.6 (Sol / Terra / Luna) as the engine — billed to your ChatGPT Plus/Pro subscription through a local Codex proxy, without an Anthropic API key or an OpenAI API key.

You keep the Claude Code agent workflow you like (file edits, terminal flow, approvals, MCP servers, skills) but the model answering is GPT-5.6, running on the ChatGPT subscription you already pay for instead of your Anthropic usage.

One-line install. Plain claude stays completely stock.

How it works

claudecodex launches the real Claude Code UI, points it at a local Anthropic-compatible proxy on 127.0.0.1:18765, and the proxy forwards requests to GPT-5.6 via Codex auth on your ChatGPT subscription:

claudecodex
   → claude (real Claude Code UI)
   → local Anthropic-compatible proxy (127.0.0.1:18765)
   → Codex auth via your ChatGPT Plus/Pro subscription
   → GPT-5.6-sol
   → streamed back into Claude Code

Jump to: Install · Usage & model switching · Configuration · vs alternatives · Troubleshooting · FAQ: Claude Code without an Anthropic API key

Demo

(8× speed — watch the full demo video)

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Why run Claude Code with OpenAI models?

• Claude Code UI + GPT models — the best agentic coding interface, driving OpenAI's strongest coding model (GPT-5.6 Sol at max reasoning effort).
• Uses the ChatGPT subscription you already have — no pay-per-token API bills; requests go through Codex auth on your Plus/Pro plan.
• Zero interference — a thin launcher that execs claude with process-local environment variables. Your normal claude command, login, settings, and Anthropic models are untouched.
• Full 372K context window — configured to GPT-5.6 Sol's real Codex context limit, so the context gauge and auto-compaction are accurate.
• Model switching built in — flip between Sol (best), Terra (mid), and Luna (fast/cheap) per launch or mid-session.

claudecodex is a thin launcher: it starts the proxy if needed, exports the right environment only for that process, then execs claude.

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Requirements

1. Claude Code — the claude CLI. Install: https://claude.com/claude-code
2. claude-code-proxy — the local Anthropic⇄Codex proxy by @raine. Needs a build that knows the GPT-5.6 models (v0.1.8+; v0.1.17 or newer recommended).
3. A ChatGPT Plus/Pro account, authenticated through the proxy's Codex login. The proxy keeps its own login (it does not reuse the standalone Codex CLI's credentials), so you authenticate it once with claude-code-proxy codex auth login.

This is for personal, local use with your own subscription. Don't expose it as a public API or resell access — routing a ChatGPT subscription through non-official clients is a gray area under OpenAI's terms.

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Install

1 — install the launcher (one-liner):

curl -fsSL https://raw.githubusercontent.com/karem505/claudecodex/main/install.sh | bash

2 — install the proxy (skip if you already have v0.1.8+):

curl -fsSL https://raw.githubusercontent.com/raine/claude-code-proxy/main/scripts/install.sh | bash

3 — log the proxy in to your ChatGPT/Codex account:

claude-code-proxy codex auth login      # browser OAuth
# or, on a headless box:
claude-code-proxy codex auth device     # device-code flow

That's it — the installer checks steps 2 and 3 for you and prints these exact commands if anything's missing.

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Usage

claudecodex                 # start Claude Code on gpt-5.6-sol (max effort)
claudecodex --mini          # start on gpt-5.6-luna (fast/cheap)   (alias: --luna)
claudecodex --terra         # start on gpt-5.6-terra (mid tier)
claudecodex --big           # start on gpt-5.6-sol explicitly      (alias: --sol)
claudecodex "fix the bug"   # any normal claude args pass straight through

Switch models mid-session: type /model, pick gpt-5.6-sol or gpt-5.6-luna, then press s (session-only). Both models are always listed. Use s, not Enter — Enter saves it as a default in the shared settings and would change plain claude too.

By default claudecodex starts in --dangerously-skip-permissions (bypass) mode so tool calls run without prompting. Toggle it off with the env var below, or cycle modes live with shift+tab.

Thinking level

gpt-5.6-sol launches at max effort — the highest reasoning level reachable through claude-code-proxy today (forwarded to Codex as reasoning.effort=max). luna/terra keep Claude Code's own effort setting. Change it live with /effort, or per-launch with CLAUDECODEX_EFFORT.

About "ultra": GPT-5.6 Sol's ultra mode (parallel subagents) exists in the official Codex app, but it is not yet exposed by claude-code-proxy — the proxy caps at max, and Claude Code's effort scale has no ultra (it would clamp to xhigh). claudecodex therefore uses max, the real ceiling. If you set CLAUDECODEX_EFFORT=ultra it is auto-downgraded to max with a notice; once a proxy build ships ultra, that env value will pass straight through.

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Configuration

All optional — set as environment variables:

| Variable | Default | Meaning | |---|---|---| | CLAUDECODEX_MODEL | gpt-5.6-sol | The "big" model | | CLAUDECODEX_SMALL_MODEL | gpt-5.6-luna | The fast/cheap model | | CLAUDECODEX_EFFORT | max (on sol) | Thinking level: low/medium/high/xhigh/max | | CLAUDECODEX_CONTEXT | 372000 | Context window (see note) | | CLAUDECODEX_SKIP_PERMISSIONS | 1 | 1 = bypass permissions, 0 = normal prompts | | CLAUDECODEX_PORT | 18765 | Proxy port | | CLAUDECODEX_AGENT_VIEW | 0 | 1 = show the background-jobs dashboard on start | | CLAUDECODEX_PROXY_BIN | claude-code-proxy | Proxy binary name/path |

Example:

CLAUDECODEX_EFFORT=high CLAUDECODEX_MODEL=gpt-5.6-terra claudecodex

Context window note

gpt-5.6-sol's Codex context window is 372K tokens (~353K effective after the 95% multiplier). The API model is 1.05M, but the Codex subscription path caps at 372K — advertising more triggers "exceeds the context window" errors. The 272K figure often quoted is just the pricing knee (input past 272K bills at ~2×), not the hard cap. Claude Code otherwise assumes 200K for unknown model names, so claudecodex sets the real 372K; its autocompact buffer keeps a margin below that. Tune with CLAUDECODEX_CONTEXT.

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What it sets (and why plain claude is safe)

Everything below is exported inside the launcher process and dies with it — nothing is written to ~/.claude/settings.json or your shell:

ANTHROPIC_BASE_URL=http://localhost:18765
ANTHROPIC_AUTH_TOKEN=clau…[redacted]
ANTHROPIC_MODEL=gpt-5.6-sol
ANTHROPIC_SMALL_FAST_MODEL=gpt-5.6-luna
CLAUDE_CODE_MAX_CONTEXT_TOKENS=372000
CLAUDE_CODE_AUTO_COMPACT_WINDOW=372000
CLAUDE_CODE_DISABLE_AGENT_VIEW=1
# plus, session-scoped via flags: --model / --effort / --dangerously-skip-permissions

Your plugins, skills, and MCP servers are shared (the launcher does not change CLAUDE_CONFIG_DIR), so they work in claudecodex too. Note that claude.ai-hosted connectors are disabled while a token auth source is set — that's expected for any custom endpoint.

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FAQ

How do I use Claude Code with my ChatGPT Plus or Pro subscription?

Install the claudecodex launcher, install claude-code-proxy (v0.1.8+), and run claude-code-proxy codex auth login once. Then run claudecodex — Claude Code starts with GPT-5.6 Sol as the model, billed to your ChatGPT subscription. See Install.

Can I use Claude Code with GPT or other OpenAI models?

Yes — that is exactly what claudecodex does. Claude Code talks to any Anthropic-compatible endpoint via ANTHROPIC_BASE_URL; claude-code-proxy translates those requests to OpenAI's Codex backend, so Claude Code runs GPT-5.6 (Sol, Terra, or Luna) as its model.

Can I use Claude Code without an Anthropic subscription or API key?

Yes. In a claudecodex session, no Anthropic account is used at all — auth and billing go through your ChatGPT Plus/Pro subscription via Codex. (You still install the Claude Code CLI itself, which is free to download.)

Does this cost anything beyond my ChatGPT subscription?

No. Requests are billed against the ChatGPT Plus/Pro plan you already have — there are no per-token API charges, because it uses Codex subscription auth, not an OpenAI API key.

Will this break or change my normal claude setup?

No. The launcher exports everything process-locally and passes session-scoped flags only. Plain claude keeps its own login, model, settings, and history. See What it sets.

Which GPT-5.6 model should I pick?

• Sol (claudecodex) — strongest coding model, launches at max effort. Default.
• Terra (claudecodex --terra) — mid tier, faster.
• Luna (claudecodex --mini) — fastest/cheapest, good for quick edits.

Is it against OpenAI's terms to use a ChatGPT subscription with Claude Code?

It's for personal, local use with your own subscription. Routing a ChatGPT subscription through non-official clients is a gray area under OpenAI's terms — don't expose it as a public API or resell access. Use at your own discretion.

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claudecodex vs other ways to use Claude Code with OpenAI models

| | claudecodex | claude-code-router / LiteLLM | OpenRouter bridges | |---|---|---|---| | Billing | ChatGPT Plus/Pro subscription — no per-token cost | OpenAI API key, pay per token | OpenRouter credits, pay per token | | Anthropic API key needed | No | No | No | | Setup | One-liner + one proxy login | Router/proxy config files | API key + config | | Touches plain claude | No — process-local env only | Often global config/env | Varies | | GPT-5.6 Sol at max effort | Yes, default | Depends on provider support | Depends on provider support |

If you want pay-per-token API access with many providers, a router is the better fit. If you want the strongest OpenAI coding model inside Claude Code on the flat-rate ChatGPT subscription you already pay for, that's claudecodex.

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Related projects

• raine/claude-code-proxy — the local Anthropic⇄Codex proxy that makes this possible.
• Claude Code — Anthropic's agentic coding CLI.
• OpenAI Codex — the subscription backend serving GPT-5.6.

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Troubleshooting

"exceeds the context window" error

The Codex subscription path caps GPT-5.6 Sol at 372K tokens (the API model's 1.05M does not apply). claudecodex sets 372K by default; if you overrode CLAUDECODEX_CONTEXT, lower it back to 372000.

Claude Code can't connect / proxy not running

Check that claude-code-proxy is installed (v0.1.8+) and authenticated:

claude-code-proxy --version
claude-code-proxy codex auth login

If the proxy fails to start, check the log at `~/.local/st