Codex CLI

Configure OpenAI Codex CLI to use the Model Gate Responses endpoint.

Codex CLI through Model Gate

Codex uses the OpenAI Responses protocol. Its provider base_url includes /v1.

npm install -g @openai/codex
codex --version

Check the current official installation instructions at https://developers.openai.com/codex/.

Edit:

- Linux or macOS: ~/.codex/config.toml - Windows: %USERPROFILE%\.codex\config.toml

model = "gpt-5.4"
model_provider = "model_gate"
model_reasoning_effort = "high"

[model_providers.model_gate] name = "Model Gate" base_url = "https://api.model-gate.com/v1" wire_api = "responses" env_key = "MODEL_GATE_API_KEY" ```

wire_api = "responses" sends requests to /v1/responses.

export MODEL_GATE_API_KEY="mg_live_..."

To make it permanent, add the export to your shell profile or secret manager.

[Environment]::SetEnvironmentVariable(
  "MODEL_GATE_API_KEY",
  "mg_live_...",
  "User"
)

Open a new terminal after setting a persistent variable.

codex

model_reasoning_effort = "low"

- low: faster and shorter. - medium: balanced. - high: more thorough for complex work.

The upstream model must support the requested reasoning controls.

Problem	Resolution
Authentication error	Confirm `MODEL_GATE_API_KEY` is visible in the same terminal.
Codex uses OpenAI directly	Confirm `model_provider = "model_gate"` and the provider section name matches.
Unsupported endpoint	Confirm `wire_api = "responses"` and `base_url` ends with `/v1`.
Model not found	Query `/v1/models` and use an enabled canonical ID or alias.

Do not set requires_openai_auth = true for this provider: that option selects OpenAI account authentication instead of the custom env_key.