GPT-OSS, Simply Explained (The Real Architecture of LLMs)

In August 2025, OpenAI made a surprising announcement: they were going to release open-source and fully open-weight models.

They ended up releasing two new state-of-the-art models under the gpt-oss family, with a larger variant (gpt-oss-120b) and a smaller one (gpt-oss-20b), all available under an Apache 2.0 license.

For a company that had spent years building its reputation on proprietary, API-only models like GPT-4, releasing rivalling open-source models seemed far away.

• This marks OpenAI's first large, fully open-weight release since GPT-2, which may be a signal for what’s to come in terms of collaboration within the AI ecosystem.