Paid tiers use GPT-6 Sol; Free/Go use Luna. Enterprise access depends on admin settings. GPT-6 can start answering while reasoning. In OpenAI's internal tests, GPT-6 Instant began answering web-search questions 44% sooner on average, not a 44% cut in total time for all tasks. This affects the Chat tab only; Work and Codex models are unchanged. Rollout is staged.