GPT-5.6 Terra
The middle tier of the GPT-5.6 generation, released 9 July 2026: pitched at launch as the balanced everyday model, with GPT-5.5-competitive performance at half the price ($2.50/$15 per million tokens). 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, the early safety writeups, ChatGPT Work) is fullest on Sol’s page — Sol was the only tier public during the preview window; this page holds what is Terra-specific and will grow as a distinct record accumulates — if one does. Corpus pass pending.
Sources
Official
- 2026-07-09 GPT-5.6 launch post — Terra 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 Terra’s public release; only Sol was live).
Tweets
tk — corpus pass pending; the local dbs end before launch.
Official record
- Mid tier of the GPT-5.6 generation: “balanced model for everyday work,” GPT-5.5-competitive performance at 2× lower cost, as published.
- Pricing $2.50 / $15 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, which ChatGPT surfaces default to Terra.
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 Luna (fast tier).
- tk — whether Terra develops a distinct record from its siblings; reception specific to Terra.
Impressions
tk — too fresh; no attributed Terra-specific reads yet.