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

# Codex compatibility

> Understand why Codex cannot currently connect to Prem API.

Codex is not compatible with Prem API today.

<Warning>
  Codex custom providers use the OpenAI Responses API. Prem API does not expose
  `/v1/responses`, so changing `base_url` is not enough.
</Warning>

## Use a supported coding harness

* Use [OpenCode](/guides/opencode) for an OpenAI-compatible coding agent.
* Use [Claude Code](/guides/claude-code) through Prem's Anthropic-compatible launcher.

Codex support requires a verified Responses API adapter. See the [Codex configuration reference](https://developers.openai.com/codex/config-reference#configtoml) for its current provider protocol.