Codex

Codex speaks the OpenAI Responses API. Add Deference as a provider in ~/.codex/config.toml. The base URL ends in /v1, and Codex adds /responses itself.

Set up

1. Create a key in API keys and export it as DEFERENCE_API_KEY in the shell that starts Codex.
2. Add the provider to ~/.codex/config.toml (on Windows, %USERPROFILE%\.codex\config.toml). Keep the top-level keys above the first table.

model = "openai/gpt-5.3-codex"
model_provider = "deference"
web_search = "disabled"

[model_providers.deference]
name = "Deference"
base_url = "https://deference.si/v1"
wire_api = "responses"
env_key = "DEFERENCE_API_KEY"

3. Restart Codex.

Codex's built-in web search is a tool hosted by OpenAI, so this guide turns it off.

Rules from Codex itself:

• Provider settings are read from the user-level file only. A model_provider or model_providers entry in a project .codex/config.toml is ignored, with a warning at startup.
• The ids openai, ollama and lmstudio are reserved. Name the provider anything else.
• wire_api = "responses" is the only accepted value.
• model must be an exact id from Models.
• The key must be in the environment of the process that starts Codex. An app launched from the Dock or Start menu does not see variables you export in a terminal.

Verify

1. Run codex doctor. It checks the installation, the config and the authentication.
2. Start codex and run /status. It shows the active model and provider.
3. Send Reply with exactly: gateway-ok.
4. Open Activity. The request is the top row, with the endpoint Responses, and its client reads Codex. The reply alone does not prove the route, so check this row.

Pick a model

• Any catalog model can serve POST /v1/responses, but each model handles Codex's message layout differently. Start with a model made for coding, such as openai/gpt-5.3-codex, and switch if a run fails.
• Choose a model per run with codex -m <id>, or in a session with /model.
• Codex has no catalog entry for ids it does not know, so it uses default limits. To set them, add model_context_window and model_auto_compact_token_limit at the top level of the file.

Let the agent manage keys

Connect the MCP server and Codex creates, rotates and revokes its own capped keys and checks your credit. You sign in once.

Troubleshooting