gpt-oss-20b — Pantheon
  
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    # gpt-oss-20b

    
OpenAI · open weights released 5 Aug 2025 · Apache 2.0
    
The smaller of the two open-weight models OpenAI released on 5 August 2025 — its first open weights since [GPT-2](../gpt-2/). A ~21B-parameter mixture-of-experts reasoner (~3.6B active) sized to run in 16GB of memory: the laptop-and-phone tier of the release, alongside [gpt-oss-120b](../gpt-oss-120b/).
    
Thin page — launch facts here; corpus/dossier pass pending (the dbs cover Aug 2025). Sibling: [gpt-oss-120b](../gpt-oss-120b/). Small tiers sometimes grow the most distinct characters (see [Haiku](../claude-3-haiku/), [4o mini](../gpt-4o-mini/)) — whether this one did is exactly what the pending pass should find out.

    
## Sources

    
### Official

    

      
- 2025-08-05 [Introducing gpt-oss](https://openai.com/index/introducing-gpt-oss/) — the announcement: both sizes, Apache 2.0.
      
- 2025-08-05 [openai/gpt-oss-20b](https://huggingface.co/openai/gpt-oss-20b) (Hugging Face) — the weights.
      
- tk — model card / paper link; mirror the announcement + card.
    
    
### Writing & commentary

    
tk — Zvi and day-of coverage to collect at the dossier pass.
    
### Tweets

    
tk — corpus pass pending. Records will populate when cited.

    
## Official record

    

      
- Released 5 August 2025, open weights, Apache 2.0, with gpt-oss-120b.
      
- As published: ~21B-parameter MoE, ~3.6B active per token; positioned as o3-mini-class; runs in 16GB of memory (consumer laptops, on-device use); adjustable reasoning effort; the “harmony” response format.
      
- tk — benchmark table as published, exact context window.
    

    
## History

    

      
- 2025-08-05 Released two days before [GPT-5](../gpt-5/), into an open-weights field led from China — shared launch context documented on both siblings’ pages by design.
      
- tk — the local-llama reception (a 16GB OpenAI reasoner was that community’s event of the season), on-device deployment arcs, distinct-character question.
    

    
## Impressions

    
tk — corpus pass pending; no attributed reads collected yet.

    
    
    
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