GPT-OSS 120B vs Claude 5 Sonnet
Compare pricing, context windows, and strengths for GPT-OSS 120B by OpenAI and Claude 5 Sonnet by Anthropic - and see how to put either to work in Appaca.
GPT-OSS 120B
OpenAI's most powerful open-weight model (117B params, 5.1B active), fitting on a single H100 GPU - fully customizable, licensed for unrestricted commercial use.
View GPT-OSS 120BClaude 5 Sonnet
Anthropic's most agentic Sonnet yet, closing much of the gap to Opus 4.8 on reasoning, coding, and tool use while staying at Sonnet's speed and price.
View Claude 5 SonnetGPT-OSS 120B vs Claude 5 Sonnet at a glance
Specs and pricing side by side, from the Appaca AI models directory.
| Spec | GPT-OSS 120B | Claude 5 Sonnet |
|---|---|---|
| Provider | OpenAI | Anthropic |
| Model type | Text | Text |
| Context window | 131.1K tokens | 1M tokens |
| Input price | Free (open weight) | $3 / 1M tokens |
| Output price | Free (open weight) | $15 / 1M tokens |
| Status | Current | Current |
How GPT-OSS 120B and Claude 5 Sonnet differ
What the numbers mean in practice when choosing between GPT-OSS 120B and Claude 5 Sonnet.
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GPT-OSS 120B is an open-weight model with no per-token licensing fees, while Claude 5 Sonnet charges $3 per million input tokens.
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Claude 5 Sonnet's 1M tokens context window is roughly 7.6x larger than GPT-OSS 120B's 131.1K tokens, so it can work across bigger codebases, contracts, or archives in one pass.
Strengths side by side
Where each model shines, according to benchmarks and provider positioning.
GPT-OSS 120B
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.
Claude 5 Sonnet
1. Anthropic's most agentic Sonnet yet
- A substantial upgrade over Sonnet 4.6 on reasoning, tool use, coding, and knowledge work - narrows the gap to Opus 4.8 while staying at Sonnet pricing.
- Early partners describe it finishing multi-step jobs end to end where prior Sonnet models used to stall halfway.
2. Clear benchmark gains over Sonnet 4.6
- 63.2% on SWE-bench Pro (vs 58.1%), 80.4% on Terminal-Bench 2.1 (vs 67.0%), 81.2% on OSWorld-Verified (vs 78.5%), and 57.4% on Humanity's Last Exam with tools (vs 46.8%).
- On the GDPval-AA v2 knowledge-work benchmark it edges past Opus 4.8 (1,618 vs 1,615).
3. Near-Opus performance at a fraction of the price
- Priced at $3/M input and $15/M output - 40% cheaper than Opus 4.8's $5/$25 - with introductory pricing of $2/$10 through Aug 31, 2026 during the rollout.
- Supports
low,medium,high, andxhigheffort levels, covering a wider cost-performance range than Sonnet 4.6 and matching Opus 4.8 on some tasks at higher effort.
4. Long-context, long-horizon reliability
- Full 1M token context window with up to 128K output tokens.
- Adaptive thinking automatically decides how long to reason; better self-correction, fewer tool errors, and steadier follow-through across long agent sessions in Claude Code and Cowork.
5. Safer and more honest than its predecessor
- Lower rates of hallucination, sycophancy, and misaligned behavior than Sonnet 4.6 on Anthropic's automated safety audits.
- Deliberately limited cyber capability compared with Opus-class models, shipped with cyber safeguards enabled by default.
6. Updated tokenizer
- Uses a new tokenizer (shared with the Opus 4.7/4.8 line) that can map the same text to up to 1.35x more tokens than Sonnet 4.6 - introductory pricing is set so the switch is roughly cost-neutral.
Use GPT-OSS 120B or Claude 5 Sonnet - or both
Appaca is the AI workspace for operators. Build internal tools and AI co-workers powered by GPT-OSS 120B or Claude 5 Sonnet - connected to your real data and ready for your whole team. No code, no deployment.
Describe it, and it's built
Tell the Appaca agent the internal tool you need and it builds a working app powered by GPT-OSS 120B or Claude 5 Sonnet. No code, no API keys, no deployment.
Switch models without rebuilding
Start on GPT-OSS 120B, test the same tool on Claude 5 Sonnet, and keep whichever performs better - the rest of your app stays exactly as it is.
Automated for the whole team
Schedule tools to run on autopilot - daily digests, weekly reports, real-time triggers - and share them with your whole team from one workspace.
Describe it, and it's built
Tell the Appaca agent what your team needs and it builds a working app powered by GPT-OSS 120B or Claude 5 Sonnet - connected to the tools you already use.
Related comparisons
See how GPT-OSS 120B and Claude 5 Sonnet stack up against other models in the directory.
FAQs
GPT-OSS 120B is open weight and free of per-token licensing fees, while Claude 5 Sonnet costs $3 per million input tokens and $15 per million output tokens.
Claude 5 Sonnet has the larger context window at 1M tokens, compared to 131.1K tokens for GPT-OSS 120B. A larger window means the model can consider more text at once - useful for long contracts, codebases, or months of records.
It depends on the job. Compare the pricing, context window, and strengths above against your workload - and remember the choice isn't permanent. In Appaca you can build a tool on GPT-OSS 120B, test the same tool on Claude 5 Sonnet, and switch at any time without rebuilding anything.
Yes. Appaca is a no-code AI workspace: describe the internal tool your team needs and the Appaca agent builds it as a working app powered by GPT-OSS 120B, Claude 5 Sonnet, or any other model in the directory - with a built-in database, team access, and integrations. No API keys to wire up and nothing to deploy.
Build AI tools with GPT-OSS 120B or Claude 5 Sonnet
Describe the tool your team needs and get a working app powered by the model you choose - with a built-in database, team access, and integrations. No code, no deployment.