Skip to main content

OpenAI Codex

Adapter for OpenAI's Codex CLI.

Install​

amux install codex

Minimum CLI version: 1.0.0. Supported on macOS, Linux and Windows.

Auth​

  • API key only — set OPENAI_API_KEY in your environment.

Config file: ~/.codex/config.json.

Minimal run​

amux run codex --prompt "Write a unit test for utils.ts"

Notable flags​

  • --model <id> — default o4-mini; codex-mini-latest also available.
  • --full-auto — emitted when approvalMode: 'yolo'.
  • --quiet <prompt> — used by the adapter to stream prompt output.

Session files​

  • Location: ~/.codex/sessions/*.jsonl
  • Parsed via the standard JSONL session reader.
  • Resume/fork supported by the adapter layer.

Plugins​

Plugin support: yes. Codex has a plugin directory with @plugin-creator skill.

Plugin Management​

amux plugin install codex <plugin>
amux plugin list codex

MCP Servers​

amux mcp install codex <mcp-server>
amux mcp list codex

Registry: https://modelcontextprotocol.io for MCP servers.

Capabilities​

Thinking models (o4-mini) with low/medium/high effort levels, tool calling with parallel calls, JSON / structured output, text streaming.

Known limitations​

  • No image input/output, no file attachments.
  • No MCP or plugin ecosystem — bring-your-own tooling only.
  • Only two bundled models; other Codex variants must be specified explicitly via --model.
  • Project-level config is not supported (supportsProjectConfig: false); configuration is global.