By Andrew Miller 
Overview
OpenGPT-OSS is OpenAI’s newly released family of open-weight language models, available in 20B and 120B parameter sizes under the Apache 2.0 license. The models support chain-of-thought reasoning, agentic behavior, and fine-tuning via PFT.
The 20B version, available via Ollama, can be run locally on modern consumer GPUs and supports quantized formats like MXFP4 for lower VRAM consumption.
✅ Model Capabilities
| Capability | Performance |
|---|---|
| Chain-of-thought reasoning | ✅ Strong |
| Code generation & debugging | ✅ Solid |
| Task planning & scheduling | ✅ Accurate |
| Language simplification | ✅ Clear |
| Multilingual support | ⚠️ Inconsistent |
| Guardrails / safety filters | ✅ Conservative (20B), ⚠️ Looser (120B) |
| Quantized performance | ✅ Good retention of quality |
🖥️ System Requirements
- OS: Linux / macOS / Windows (via Ollama)
- RAM: 16GB+ recommended
- GPU: 16GB VRAM (NVIDIA preferred) or CPU (slower)
- Storage: ~13GB for 20B model
⚙️ Installation Guide: Run OpenGPT-OSS 20B with Ollama
1. Install or Update Ollama
Linux:
curl -fsSL https://ollama.com/install.sh | sh
macOS:
brew install ollama
Windows:
Download the Windows executable and install.
⚠️ Make sure you’re on Ollama version v0.1.11 or later to avoid model download issues.
2. Run the Model
ollama run open-gpt-oss
This command will:
- Download the 20B quantized model (~13GB)
- Verify checksum
- Start an interactive chat session in terminal
3. (Optional) Use with Open WebUI
Install Open WebUI
pip install open-webui
Run Web Interface
open-webui serve
Open your browser and go to http://localhost:3000
You should see the model loaded and ready for chat.
🧪 Real-World Testing Summary
| Test | Result |
|---|---|
| Math Reasoning | 🟢 Solved problems with correct logic steps |
| CUDA Kernel Code Gen | 🟢 Generated and explained GPU matrix kernel |
| Travel Planning | 🟢 Generated realistic 10-day itinerary with AU$ budget |
| Staff Scheduling (Rostering) | 🟢 Created constraint-aware staffing plan with notes |
| Multilingual Translation | 🟡 Mixed results; well-known languages fared better |
| Philosophical & Literature | 🟢 Explained theory of multiple intelligences clearly |
| Guardrail Check | 🟢 Refused inappropriate prompts in 20B model |
| VRAM Consumption (MXFP4) | 🟢 ~15GB usage on RTX A6000 |
Verdict
OpenGPT-OSS 20B via Ollama is a powerful, open-access alternative to GPT-3.5-style models with impressive performance, solid safety controls, and developer-friendly integration.
- ✅ Best for: Reasoning tasks, coding, local deployment, and offline use.
- ⚠️ Watch out for: Inconsistent multilingual support and limited humor/creativity in 20B.
🔗 Resources
- 🔗 Ollama Install: https://ollama.com
- 🔗 Model Card (HuggingFace): OpenGPT-OSS-20B