OpenAI Previews GPT-5.6 (Sol, Terra, Luna) — Staggered Release Gated Behind US Government Pre-Deployment Review

Summary

OpenAI began a limited preview of GPT-5.6 on June 26, 2026 — a three-tier model family: **Sol** (flagship, tuned for ambitious agentic work; $5/1M input, $30/1M output), **Terra** (balanced everyday model; $2.50/$15), and **Luna** (fast, high-volume; $1/$6). The release also ships more predictable prompt caching: explicit cache breakpoints, a 30-minute minimum cache life, cache writes billed at 1.25x the uncached input rate, and the existing 90% discount on cache reads. On capability, GPT-5.6 is