Is gpt-oss-20b available on FastMetal?

Not at the moment. GPT-5.6 Sol, from the same lab, is available on the FastMetal API today.

What is the context window of gpt-oss-20b?

131,072 tokens, shared between the prompt and the response.

How does gpt-oss-20b rank?

#175 on the public arena's Japanese board (ELO 1,257). Ranks move as the leaderboard is updated.

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openai/gpt-oss-20b

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gpt-oss-20b

gpt-oss-20b is an open-weight 21B parameter model released by OpenAI under the Apache 2.0 license. It uses a Mixture-of-Experts (MoE) architecture with 3.6B active parameters per forward pass, optimized for lower-latency inference and deployability on consumer or single-GPU hardware. The model is trained in OpenAI’s Harmony response format and supports reasoning level configuration, fine-tuning, and agentic capabilities including function calling, tool use, and structured outputs.

8/5/2025

131,072 tokens

#175 Text (Japanese)

Specifications

Modalities

Input

text

Output

text

Supported Parameters

frequency_penalty

include_reasoning

logit_bias

max_tokens

min_p

presence_penalty

reasoning

reasoning_effort

repetition_penalty

response_format

seed

stop

structured_outputs

temperature

tool_choice

tools

top_k

top_p

Reasoning Configuration

Default: Thinking on (effort: medium)
Selectable effort levels: high
medium
low
Turning thinking off: Not possible (always thinks)

How to control thinking, and what it costs

Frequently asked questions

Is gpt-oss-20b available on FastMetal?: Not at the moment. GPT-5.6 Sol, from the same lab, is available on the FastMetal API today.
What is the context window of gpt-oss-20b?: 131,072 tokens, shared between the prompt and the response.
How does gpt-oss-20b rank?: #175 on the public arena's Japanese board (ELO 1,257). Ranks move as the leaderboard is updated.