Codex

High-reasoning capabilities for complex tasks and critical reviews

Overview

Codex is powered by OpenAI’s models and offers high-reasoning capabilities for complex tasks and critical reviews.

Latest Model

• GPT 5.2 - OpenAI’s latest model with advanced reasoning capabilities

Authentication

Codex supports two authentication methods:

OpenAI API Key

Pay-as-you-go API access

1. Get an API key at OpenAI Platform
2. In Blocks Dashboard, go to Dashboard → Agents
3. Select Codex and choose “API Key”
4. Paste your API key (starts with sk-)

OpenAI Subscription

Connect your ChatGPT Plus/Team subscription

1. Go to Blocks Dashboard → Dashboard → Agents
2. Select Codex and choose “Connect Subscription”
3. Authorize Blocks to use your OpenAI subscription

This uses your subscription credits instead of pay-as-you-go billing.

Setting as Default

To use Codex automatically for all requests:

1. Go to Dashboard → Agents
2. Select “Set as default agent” from Codex’s dropdown menu

Learn more: Setting Your Default Agent

Using Codex

Once configured, Codex is used automatically if it’s your default agent:

@blocks can you implement this feature?

Or use the /codex slash command to use it specifically:

@blocks /codex implement this API endpoint

Best For

• Complex reasoning tasks
• Critical code reviews
• Advanced problem solving
• Detailed analysis
• Architecture decisions
• In-depth explanations

Cost

Codex uses your OpenAI API key or subscription:

• Check pricing at OpenAI Pricing
• Monitor usage in OpenAI Dashboard
• API usage is billed by OpenAI based on tokens

Next Steps

Agents Overview

Compare all available agents

Set Default Agent

Configure your default agent

Claude Code

Learn about Claude Code

Gemini CLI

Explore Gemini CLI (experimental)