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.