Codex CLI

Configure OpenAI Codex CLI to use LemonData API

Overview

Type: Coding Tool

Primary Path: OpenAI Responses (advanced optional path)

Support Confidence: Supported with model/path limits

OpenAI Codex is an open-source command-line tool (CLI) that serves as a lightweight coding agent, capable of reading, modifying, and running code in the terminal. It’s built on GPT models and optimized for code generation.

For LemonData, Codex CLI can use /v1/responses, but you should treat it as an advanced compatibility path. Some Responses-only features are not guaranteed across every model and routed path.

System Requirements

• OS: macOS, Linux (official support), Windows via WSL
• Node.js: Version 18+
• npm: Version 10.x.x or higher

Installation

npm install -g @openai/codex

Verify installation:

codex --version

Configuration

Step 1: Set API Key

Temporary (current session):

export OPENAI_API_KEY="sk-your-lemondata-key"

Permanent configuration:

Add to ~/.bashrc, ~/.zshrc, or ~/.bash_profile:

export OPENAI_API_KEY="sk-your-lemondata-key"

Then reload:

source ~/.zshrc  # or source ~/.bashrc

Step 2: Configure config.toml

Edit ~/.codex/config.toml:

model_provider = "lemondata"
model = "gpt-5.4"
model_reasoning_effort = "xhigh"
plan_mode_reasoning_effort = "xhigh"
fast_mode = true
model_context_window = 1000000
model_auto_compact_token_limit = 900000
sandbox_mode = "danger-full-access"
approval_policy = "never"

disable_response_storage = false
personality = "friendly"
service_tier = "fast"

[model_providers.lemondata]
env_key = "OPENAI_API_KEY"
name = "lemondata"
base_url = "https://api.lemondata.cc/v1"
wire_api = "responses"
supports_websockets = true
websocket_connect_timeout_ms = 15000

[features]
responses_websockets = true
responses_websockets_v2 = true

This WebSocket mode is a Responses-over-WebSocket bridge for Codex clients. It accepts response.create and response.cancel; it is not the OpenAI Realtime API and does not accept session.update, conversation.item.*, input_audio_buffer.*, binary audio, or nested Realtime response.create.response envelopes.

If the config file doesn’t exist, run codex once to generate it, then edit the file. Restart Codex completely after changing config.toml so the new provider settings are reloaded.

Codex is deprecating chat/completions support for custom providers. Keep wire_api = "responses" for LemonData unless you are intentionally using an older compatibility path.

If a request uses Responses-only fields that are not supported on the selected model or route, LemonData returns an explicit error instead of silently downgrading the request.

Basic Usage

Start interactive mode:

codex

Direct command:

codex "Fix the bug in main.py line 42"

Specify model:

codex -m gpt-5.4 "Build a REST API server"

Recommended Models

Model	Best For
gpt-5.4	Best default choice for coding and reasoning
gpt-5-mini	Faster, cheaper fallback for coding workflows
claude-sonnet-4-6	Code review, documentation
deepseek-r1	Algorithm design, reasoning

Interactive Commands

Command	Description
/help	Display help
/exit or Ctrl+C	Exit
/clear	Clear conversation
/config	View configuration
/model <name>	Switch model
/tokens	View token usage

Verify Configuration

# Check environment variable
echo $OPENAI_API_KEY

# Test API connection
codex "Hello, Codex!"

# View configuration
cat ~/.codex/config.toml

Common Use Cases

Code review:

git diff | codex "Review these code changes"

Generate commit messages:

git diff --staged | codex "Generate a commit message for these changes"

Fix errors:

codex "Fix the TypeScript errors in src/components/"

Explain code:

cat main.py | codex "Explain what this code does"

Troubleshooting

Connection Error

• Verify base_url in config.toml is exactly https://api.lemondata.cc/v1
• Check network connectivity
• Ensure no proxy interference

Authentication Failed

• Verify env_key = "OPENAI_API_KEY" is present in ~/.codex/config.toml
• Verify OPENAI_API_KEY environment variable is set
• Check that the key starts with sk-
• Ensure the key is active in LemonData dashboard

Model Not Found

• Check model name matches exactly
• Verify model availability at lemondata.cc/en/models

Responses-native field rejected

• Some fields are only available on /v1/responses when LemonData can guarantee that behavior for the selected model and route
• If you see unsupported_request_field, remove that field or switch to a workflow that does not depend on it