OpenAI launches GPT-5.6 limited preview with Sol, Terra, Luna

OpenAI released three GPT-5.6 variants: Sol (flagship, $5/$30 per 1M tokens), Terra (balanced, $2.50/$15), and Luna (fast/affordable). Sol features enhanced cyber safeguards and matches Anthropic Mythos on ExploitBench with ~1/3 the output tokens. The preview is limited to select companies.