← all releases
OpenAI·Jun 26, 2026·v5.6·paid

GPT-5.6 Sol, Terra, and Luna

OpenAI introduces the GPT-5.6 series of large language models (LLMs). The GPT-5.6 series introduces a new tiered naming system designed to give developers and users clearer choices, balancing intelligence, speed, and cost. GPT-5.6 Sol: The flagship model. It is the most capable model yet, featuring advanced agentic capabilities, deep reasoning (with a new max reasoning effort and ultra mode), and top-tier performance in coding, biology, and cybersecurity. GPT-5.6 Terra: The balanced model. It delivers everyday performance competitive with GPT-5.5, but at half the cost. GPT-5.6 Luna: The lightweight model. It is the fastest and most affordable option in the lineup, bringing strong capabilities at the lowest price point.

AI AgentsAgentic AILLMs
overview

OpenAI introduces the GPT-5.6 series of large language models (LLMs). The GPT-5.6 series introduces a new tiered naming system designed to give developers and users clearer choices, balancing intelligence, speed, and cost. GPT-5.6 Sol: The flagship model. It is the most capable model yet, featuring advanced agentic capabilities, deep reasoning (with a new max reasoning effort and ultra mode), and top-tier performance in coding, biology, and cybersecurity. GPT-5.6 Terra: The balanced model. It delivers everyday performance competitive with GPT-5.5, but at half the cost. GPT-5.6 Luna: The lightweight model. It is the fastest and most affordable option in the lineup, bringing strong capabilities at the lowest price point.

key features
  • 01Enhanced reasoning capabilities
  • 02Improved context understanding
  • 03Optimized for AI agent applications
related productsbrowse all →
llmockopen sourcellmock is a deterministic mock LLM server designed for testing purposes. It provides a real HTTP server with authentic SSE streams, allowing developers to simulate interactions with various LLM APIs like OpenAI, Claude, and Gemini without incurring costs or dealing with non-deterministic results.AIBuildAIopen sourceAIBuildAI is an AI agent that autonomously constructs AI models. Given a specific task, it initiates an agent loop to analyze the problem, design models, and execute training processes, all without human intervention.MiroThinkeropen sourceMiroThinker is an open-source search agent model developed by MiroMindAI, designed for tool-augmented reasoning and real-world information seeking. It aims to match the deep research capabilities of leading AI models like OpenAI's Deep Research and Google's Gemini Deep Research.