GPT-5.6 Sol, Terra and Luna are three tiered models launched by OpenAI. They are not "shrinked versions" of the same model, but independent product lines for different task scenarios, the core difference lies inreasoning ability, speed and pricing:
Sol (Sun):Flagship strongest model, mainly focuses on highest-level reasoning, complex software engineering, deep research, and multi-step tool orchestration.
Terra (Earth):Balanced main model, performance close to Sol, but cost reduced by half. It is the default first choice for daily production, technical development, and content creation.
Luna (Moon):High cost-performance model, focuses on ultra-fast response and massive batch processing, the cheapest price, suitable for tasks with less strict logical requirements.