GPT-OSS 120B vs Claude 4.1 Opus

1. Most powerful open-weight model

• 117B parameters (5.1B active) while fitting on a single H100 GPU.
• High reasoning quality compared to other open models.

2. Apache 2.0 license

• Fully permissive, no copyleft or patent restrictions.
• Safe for commercial products, research, and redistribution.

3. Configurable reasoning effort

• Supports adjustable reasoning: low, medium, high.
• Lets developers balance latency vs. depth.

4. Full chain-of-thought access

• Unlike closed commercial models, this exposes complete reasoning traces.
• Useful for debugging, auditing, safety research, and transparency.

5. Fine-tunable

• Fully supports parameter fine-tuning.
• Can be adapted to domain-specific workflows and proprietary datasets.

6. Agentic capabilities

• Built-in function calling.
• Native support for web browsing, Python execution, and structured outputs.
• Ideal for open-source agents, full-stack automation, and developer tooling.

7. Tooling ecosystem support

• Compatible with Chat Completions, Responses API, Assistants, Realtime, Batch, and Fine-tuning endpoints.
• Supports Image Generation, Code Interpreter (via Python runtime), and more.

8. Open-source availability

• Downloadable on HuggingFace for local or on-prem deployment.
• Supports full offline, private, or self-hosted usage.

9. Streaming + function calling support

• Real-time interactions.
• Strong for interactive agents, coding assistants, and UI-driven workflows.

1. Advanced Coding Performance

• Achieves 74.5% on SWE-bench Verified, improving the Claude family's state-of-the-art coding abilities.

• Stronger at:

  • Multi-file code refactoring
  • Large codebase debugging
  • Pinpointing exact corrections without unnecessary edits

• Outperforms Opus 4 and shows gains comparable to jumps seen in past major releases.

2. Improved Agentic & Research Capabilities

• Better at maintaining detail accuracy in long research tasks.
• Enhanced agentic search and step-by-step problem solving.
• Performs reliably across complex multi-turn reasoning tasks.

3. Validated by Real-World Users

• GitHub: Better multi-file refactoring and code adjustments.
• Rakuten Group: High precision debugging with minimal collateral changes.
• Windsurf: One standard deviation improvement on their junior dev benchmark—similar magnitude to Sonnet 3.7 → Sonnet 4.

4. Hybrid-Reasoning Benchmark Improvements

• Improvements across TAU-bench, GPQA Diamond, MMMLU, MMMU, AIME (with extended thinking).
• Stronger robustness in long-context reasoning tasks.