How to use Codex CLI with a custom OpenAI-compatible endpoint

model = "gpt-5.5"
model_provider = "ccsub"

[model_providers.ccsub]
name = "CCSub"
base_url = "https://www.ccsub.net/api/v1"
wire_api = "responses"
env_key = "OPENAI_API_KEY"

Codex CLI is OpenAI's coding agent for the terminal. It talks to the OpenAI Responses API (POST /responses), so it uses CCSub's OpenAI-compatible base URL, https://www.ccsub.net/api/v1 — not the bare https://www.ccsub.net that Claude Code uses. Mixing the two up is the most common setup mistake.

Check your version first

Codex changed how custom endpoints are configured in 2026. Run codex --version:

If you are unsure, use the config.toml method below — it works on both.

Recommended: a custom provider in config.toml

First, export your key as OPENAI_API_KEY:

echo 'export OPENAI_API_KEY="sk-your-key"' >> ~/.zshrc
source ~/.zshrc

On Windows, in PowerShell:

[System.Environment]::SetEnvironmentVariable('OPENAI_API_KEY', 'sk-your-key', 'User')

Then edit ~/.codex/config.toml (%USERPROFILE%\.codex\config.toml on Windows; create it if it does not exist):

model = "gpt-5.5"
model_provider = "ccsub"

[model_providers.ccsub]
name = "CCSub"
base_url = "https://www.ccsub.net/api/v1"
wire_api = "responses"
env_key = "OPENAI_API_KEY"

What each line does: base_url is the endpoint root, and Codex appends /responses. wire_api only accepts responses now — the chat value from older tutorials is a hard error. env_key names the environment variable that holds the key. Custom providers do not require an OpenAI account login by default, so the ChatGPT sign-in screen goes away.

Older versions: environment variables only

On Codex 0.118 and earlier you can skip the config file and use the two variables from the CCSub install docs:

echo 'export OPENAI_BASE_URL="https://www.ccsub.net/api/v1"' >> ~/.zshrc
echo 'export OPENAI_API_KEY="sk-your-key"' >> ~/.zshrc
source ~/.zshrc

After upgrading to 0.119, OPENAI_BASE_URL is silently ignored and requests go back to OpenAI, which shows up as a login prompt or a 401. Switch to the config.toml method when that happens.

There is a third option: a top-level openai_base_url = "https://www.ccsub.net/api/v1" line, which re-points Codex's built-in openai provider. The built-in provider requires a login, so you would also run printenv OPENAI_API_KEY | codex login --with-api-key. It is more steps than a custom provider, so we do not recommend it.

Start Codex and choose a model

cd ~/your-project
codex

The model field takes IDs such as gpt-5.5; every available ID is on the models page. Change model in config.toml or use /model inside Codex. Once you have sent a message, the request should appear on the Usage page of your CCSub dashboard.

Gotchas

• Project config does not count. A project-level .codex/config.toml ignores model_provider, model_providers and openai_base_url. Keep these in ~/.codex/config.toml.
• Desktop launches miss shell variables. If you start a Codex desktop app or editor integration from the Dock or Start menu, it may not see the OPENAI_API_KEY you exported in your shell. Test from a terminal first.
• Two tools, two URLs, one key. Claude Code uses https://www.ccsub.net; Codex uses https://www.ccsub.net/api/v1. The same CCSub key works for both.

If you switch providers often, CC Switch has a CCSub preset and writes the Codex config for you. For Anthropic's terminal agent, see the Claude Code guide.