GPT-5.6 Luna

OpenAI · released 9 Jul 2026 · current fast tier

The small tier of the GPT-5.6 generation, released 9 July 2026: the fastest and cheapest member ($1/$6 per million tokens), carrying the generation’s shared 1M-token context. In OpenAI’s new naming system the number marks the generation and Sol / Terra / Luna are durable tiers that can advance on their own cadence.

Fresh page (19 Jul 2026) — visibly incomplete by design. The generation-level launch record (the government-preview arc, early safety writeups, ChatGPT Work) is fullest on Sol’s page; this page holds what is Luna-specific and will grow as a distinct record accumulates — small tiers sometimes grow the most distinct characters (see Haiku, 4o mini). Corpus pass pending.

Sources

Official

• 2026-07-09 GPT-5.6 launch post — Luna introduced with the family.
• 2026-07 Help center — shared specs: 1M context, 128K max output, cutoff 16 Feb 2026.

Writing & commentary

• 2026-07-09 Simon Willison — day-of family read.
• 2026-07 Zvi Mowshowitz, Better Call Sol The Workhorse (mirrored) — covers the cheaper tiers alongside Sol.
• 2026-06-28 Zvi Mowshowitz, GPT-5.6: The System Card (mirrored) — the generation’s system-card read; preview-era (predates Luna’s public release; only Sol was live).

Tweets

tk — corpus pass pending; the local dbs end before launch.

Official record

• Small tier of the GPT-5.6 generation: “fast and affordable,” as published.
• Pricing $1 / $6 per Mtok; shared generation specs: 1M context, 128K max output, cutoff 2026-02-16.
• Generation naming: the number marks the generation; Sol / Terra / Luna are durable capability tiers advancing on their own cadence, per OpenAI.
• tk — checkpoint strings, published benchmarks, batch/latency positioning.

History

• 2026-07-09 Released with the generation (public launch followed a government-approved limited preview of Sol from 26 Jun; shipped alongside the ChatGPT Work product). Siblings: Sol (flagship) and Terra (mid tier).
• tk — whether Luna develops a distinct record; reception specific to Luna.

Impressions

tk — too fresh; no attributed Luna-specific reads yet.

← back to the Pantheon