Codex with OpenCheese

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Codex speaks the OpenAI Responses API, which OpenCheese serves at https://api.opencheese.dev/v1. Codex 0.120 or newer is required: older builds use a chat wire protocol that OpenAI has removed, and their configuration will not load.

The Codex CLI, the Codex desktop app and the Codex IDE extension (VS Code, Cursor and other VS Code forks) read the same ~/.codex/config.toml, so one setup serves all three.

The fastest way: the generated file

Sign in, open Configuration, choose the Codex tab, pick an API key and confirm your password, then merge the generated file into your user configuration:

Manual setup

model = "MODEL_ID"
model_provider = "opencheese"
model_reasoning_summary = "auto"

[model_providers.opencheese]
name = "OpenCheese"
base_url = "https://api.opencheese.dev/v1"
wire_api = "responses"
env_key = "OPENCHEESE_API_KEY"
request_max_retries = 4
stream_max_retries = 5
stream_idle_timeout_ms = 300000

Then export the key in the shell that starts Codex, in single quotes (the key contains $ characters that double quotes would expand):

export OPENCHEESE_API_KEY='YOUR_OPENCHEESE_API_KEY'

• base_url must end in /v1: Codex appends /responses itself.
• wire_api must be "responses"; current Codex refuses "chat".
• Every root key (model, model_provider, ...) must come before the first [table] header, or the file will not parse.
• The generated file stores the key as experimental_bearer_token. env_key keeps it out of the file instead. Use one or the other, never both: Codex rejects the combination.
• Keep this in your user configuration. Codex ignores model_provider in a project-local .codex/config.toml and prints a startup warning.

Models and reasoning effort

/model inside Codex lists Codex's built-in OpenAI models, not the OpenCheese catalog; a model from that list works only if your key has a model with the same ID. To use any other model, set model in config.toml, or start Codex with one for this session:

codex -m MODEL_ID

model_reasoning_effort sets the starting reasoning level (for example "high"); the generated file starts at max where the model offers it, otherwise high or medium. A level the model does not offer is refused with a message naming the levels it does. Codex reads config.toml only at startup, so restart it after every edit.

Codex's Fast mode switches to the model's Fast version where one exists: replies come sooner and cost more. Where a model has no Fast version, the normal one answers.

Usage and costs

Every request appears under Transactions in the dashboard, grouped as one session per conversation, with its token usage and cost.

Troubleshooting

• The configuration does not load: update Codex to 0.120 or newer, and check that no root key appears after a [table] header.
• "Invalid or disabled OpenCheese API key": check the key on the API keys page, and that OPENCHEESE_API_KEY is set in the shell that starts Codex.
• The website answers instead of the API: base_url must use api.opencheese.dev.
• /model does not show my OpenCheese models: expected; it lists Codex's built-in catalog. Set model in config.toml or use codex -m MODEL_ID.