GPT OSS 120B is OpenAI's open-source 20-billion parameter language model, providing a lightweight yet capable open-weights option suitable for cost-efficient deployment.
import { streamText } from 'ai'
const result = streamText({ model: 'openai/gpt-oss-20b', prompt: 'Why is the sky blue?'})GPT OSS 120B became available on August 5, 2025 on AI Gateway alongside gpt-oss-120b as part of OpenAI's open-source model initiative. At 20 billion parameters, it is the more compact of the two releases, designed for scenarios where the full 120B model's resource requirements are impractical.
Despite its smaller size, GPT OSS 120B delivers meaningful language model capability for chat, content generation, summarization, and analysis tasks. Open weights make it inspectable and auditable, which is valuable for organizations with transparency requirements.
The model's compact size makes it a practical option for teams working with deployment patterns that don't scale to 120B+ parameters.