GPT-5.6 Luna — Pantheon
  
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    # 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](../gpt-5-6-sol/); 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](../claude-3-haiku/), [4o mini](../gpt-4o-mini/)). Corpus pass pending.

    
## Sources

    
### Official

    

      
- 2026-07-09 [GPT-5.6 launch post](https://openai.com/index/gpt-5-6/) — Luna introduced with the family.
      
- 2026-07 [Help center](https://help.openai.com/en/articles/20001325-a-preview-of-gpt-56-sol-terra-and-luna) — shared specs: 1M context, 128K max output, cutoff 16 Feb 2026.
    
    
### Writing & commentary

    

      
- 2026-07-09 [Simon Willison](https://simonwillison.net/2026/Jul/9/gpt-5-6/) — day-of family read.
      
- 2026-07 Zvi Mowshowitz, [Better Call Sol The Workhorse](../mirror/posts/zvi-better-call-sol.md) (mirrored) — covers the cheaper tiers alongside Sol.
      
- 2026-06-28 Zvi Mowshowitz, [GPT-5.6: The System Card](../mirror/posts/zvi-gpt-56-system-card.md) (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](../gpt-5-6-sol/) (flagship) and [Terra](../gpt-5-6-terra/) (mid tier).
      
- tk — whether Luna develops a distinct record; reception specific to Luna.
    

    
## Impressions

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

    
    
    
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