> ## Documentation Index
> Fetch the complete documentation index at: https://docs.snapgen.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Codex CLI

> Configure Codex CLI with SnapGen's OpenAI Responses-compatible endpoint.

Codex CLI supports custom model providers in `~/.codex/config.toml`. SnapGen's `/v1/responses` route was verified with the current Codex CLI and GPT text models.

## Prerequisites

* Install or update Codex CLI and confirm `codex --version` works.
* Create a SnapGen API key and add prepaid balance.
* Use a current text model. `gpt-5.4-mini` is the lowest-cost starting point.

## Set the API key

```bash theme={null}
export SNAPGEN_API_KEY="sk-xxxx"
```

Add that export to your shell profile or load it from a secret manager. Do not put the key directly in `config.toml`.

## Add the provider

Edit `~/.codex/config.toml`:

```toml theme={null}
model = "gpt-5.4-mini"
model_provider = "snapgen"

[model_providers.snapgen]
name = "SnapGen"
base_url = "https://api.snapgen.org/v1"
wire_api = "responses"
env_key = "SNAPGEN_API_KEY"
```

`wire_api` must be `responses`. Current Codex versions do not use Chat Completions for custom agent sessions.

## Verify

```bash theme={null}
codex exec "Reply with OK only."
```

The startup summary should show `provider: snapgen` and your selected model. Use `codex` for an interactive session.

## Switch models

Change the top-level `model` value, or override it for one run:

```bash theme={null}
codex --model gpt-5.5
```

Current model IDs include `gpt-5.4`, `gpt-5.4-mini`, `gpt-5.5`, `gpt-5.6`, `gpt-5.6-luna`, `gpt-5.6-sol`, and `gpt-5.6-terra`.

## Troubleshooting

<AccordionGroup>
  <Accordion title="Codex opens a ChatGPT sign-in flow">
    Confirm `model_provider = "snapgen"` is at the top level and the provider
    block has the same `snapgen` identifier.
  </Accordion>

  <Accordion title="Codex reports a missing API key">
    Export `SNAPGEN_API_KEY` in the shell that launches Codex. The `env_key`
    field names the variable; it does not contain the secret itself.
  </Accordion>

  <Accordion title="The provider rejects wire_api">
    Set `wire_api = "responses"` and update Codex CLI. Do not use `chat` with a
    current version.
  </Accordion>

  <Accordion title="Plugin or hosted OpenAI features return 401">
    Custom inference routes do not authenticate hosted ChatGPT services. Core
    Codex agent requests can work while optional OpenAI-hosted features remain
    unavailable.
  </Accordion>
</AccordionGroup>