FW-GPT-OSS-20B

Models available for use with Fireworks on Foundry deliver optimized, best-in-class performance on the Fireworks Inference Cloud. Fireworks on Foundry is a Non-Microsoft Product. The following terms apply to a Customer's use of Fireworks on Foundry: When you use Fireworks on Foundry, data is shared between Microsoft and Fireworks AI, Customer Data will be sent outside of Microsoft systems, Customer Data will not be processed pursuant to any Foundry data residency documentation, and different compliance and data handling rules will apply. See Trust Center - Fireworks AI for details. Customers are responsible for evaluating whether data sharing between Microsoft and Fireworks is appropriate for their organization's compliance requirements.

About this model

OpenAI gpt-oss-20b is part of the gpt-oss series of open-weight models designed for powerful reasoning, agentic tasks, and versatile developer use cases. The smaller gpt-oss-20b model is intended for lower-latency, local, or specialized use cases and has 21B total parameters with 3.6B active parameters. The model was trained on OpenAI's harmony response format and should be used with that format.

Key model capabilities

• Configurable reasoning effort across low, medium, and high levels
• Full chain-of-thought access for debugging and trust, not intended for end users
• Agentic capabilities including function calling, web browsing, Python code execution, and Structured Outputs
• Fine-tuning support
• MXFP4 quantization of MoE weights
• Runs within 16GB of memory according to the official model card