AI safety

OpenAI Frontier Models: From GPT-4 to GPT-6 Astra

OpenAI’s frontier line began with GPT-4 in 2023, then added cheaper long-context, multimodal, and reasoning-focused models before GPT-5 combined fast and extended-reasoning modes behind a router. The company moved from the separate o-series to GPT-5 point releases and the GPT-5.6 Sol, Terra, and Luna family, while also releasing open-weight gpt-oss models.