Changes from previous version
First Luna-tier release under the new durable naming system. Brings GPT 5.6-generation cyber and agentic improvements to OpenAI's lowest-priced API tier, below GPT Terra 5.6 on cost.
Release Summary
OpenAI's fast, affordable GPT 5.6 tier: strong capability at the lowest cost in the family ($1/M input, $6/M output). Completes the durable Sol/Terra/Luna lineup alongside GPT Sol 5.6 (flagship) and GPT Terra 5.6 (balanced). All three GPT 5.6 tiers show strong ExploitGym cyber improvements as reasoning scales. Positioned as OpenAI's volume tier, comparable in role to Claude Haiku 4.5 for low-latency, cost-sensitive workloads, while GPT 5.5 remains the prior-generation unified flagship on the legacy GPT product line. Limited preview via API and Codex.
Timeline
GPT-5.6 Luna preview begins
OpenAI previews GPT-5.6 Luna as the affordable volume tier in the Sol/Terra/Luna family at $1/$6 per million tokens.