GPT-5.6 Codex App Guide: Sol, Terra, Luna, Max & Ultra

GPT-5.6 Codex: AI-First Development Environment

OpenAI's Codex App leverages the GPT-5.6 model family to create a specialized development environment. Unlike general-purpose coding assistants, Codex is purpose-built for software engineering workflows with multi-agent coordination and project-level context awareness.

Model Selection Guide

• Sol: Maximum reasoning for complex architecture decisions and difficult debugging sessions
• Terra: The default choice — balanced performance for daily coding tasks
• Luna: Cost-effective option for code completion, documentation, and simple refactoring
• Max/Ultra: Reserved for the most demanding workloads with extended context needs

Multi-Agent Workflows

Codex can spawn sub-agents for parallel task execution — one agent reviews while another writes tests, a third handles documentation. This orchestration is powered entirely through API calls, making it accessible through our platform.