GPT OSS 120B (IONOS)

GPT OSS 120B is OpenAI's large-scale entry in the gpt-oss family, built as a 117B-parameter Mixture-of-Experts language model that activates only 5.1B parameters per forward pass. That sparse routing, combined with native MXFP4 quantization, lets the model fit onto a single H100 GPU, making it practical for data-center deployments that previously needed multi-GPU clusters. The Apache 2.0 license means organizations can host it themselves, fine-tune it for domain-specific tasks, or run it through hosted APIs, which is why it has rapidly appeared across multiple inference providers shortly after release.

For practical workloads, GPT OSS 120B is positioned as a high-reasoning, agentic model, with configurable reasoning depth and full chain-of-thought access that lets developers tune the trade-off between latency and answer quality. It also ships with native tool use, including function calling, web browsing, and structured output generation, so it can plug directly into agent pipelines rather than being wrapped behind extra orchestration. Combined with a 131,072-token context window, the model is well suited to long-document analysis, multi-step retrieval, code generation, and other complex production tasks where reasoning depth, tool integration, and open deployment flexibility all matter at once.