> ## Documentation Index
> Fetch the complete documentation index at: https://documentation.deepmask.io/llms.txt
> Use this file to discover all available pages before exploring further.

# GPT-OSS 120B

> OpenAI's open-source 120B model, EU-hosted via StackIT and Infercom. GPQA 80.9%, transparent chain-of-thought, adaptive reasoning effort levels.

GPT-OSS 120B is OpenAI's 2026 open-source contribution to the frontier model ecosystem, available in DeepMask through two EU-hosted infrastructure providers: StackIT and Infercom. It delivers GPT-4-tier intelligence under an Apache 2.0 license, with full chain-of-thought transparency and adjustable reasoning effort — making it the model of choice for organizations that need frontier-class AI without black-box opacity or data leaving European infrastructure.

## About GPT-OSS 120B

Built on a Mixture-of-Experts (MoE) architecture, GPT-OSS 120B uses sparse activation to stay fast and efficient — activating only a fraction of its parameters per request. The Infercom variant is optimized for high-throughput deployments, reaching up to 544 tokens/sec. The StackIT variant is tuned for sovereign enterprise deployments with a focus on transparent reasoning and strict schema enforcement. Neither variant supports image inputs.

<Note>
  Both the StackIT and Infercom variants of GPT-OSS 120B are hosted entirely within the European Union, making them suitable for use cases governed by GDPR and sector-specific data residency requirements.
</Note>

## Key Capabilities

<CardGroup cols={2}>
  <Card title="Transparent Chain-of-Thought" icon="list-tree">
    Full visibility into internal reasoning steps — critical for legal, medical, and compliance use cases where "black box" AI is unacceptable.
  </Card>

  <Card title="Adjustable Reasoning Effort" icon="sliders">
    Switch between Low (fast), Medium (balanced), and High (deep analytical thinking) per request to control cost and latency.
  </Card>

  <Card title="JSON Mode Precision" icon="brackets-curly">
    Native strict schema enforcement ensures near-perfect reliability for API-driven agents and structured output pipelines.
  </Card>

  <Card title="High-Speed Throughput" icon="gauge-high">
    The Infercom variant exceeds 500 tokens/sec on optimized stacks — one of the fastest models in its weight class.
  </Card>
</CardGroup>

## Best For

GPT-OSS 120B is ideal when you need frontier-level reasoning on-premises or within EU-hosted infrastructure. It is the right choice for legal and clinical workflows where reasoning transparency is mandatory, for privacy-sensitive production environments in finance and healthcare, and for high-volume agentic pipelines that need both speed and analytical depth. It does not support image inputs or tool use in the DeepMask interface — for those capabilities, see GPT-4o or the GPT-5 series.

<Tip>
  For legal and compliance workflows, use High reasoning effort to maximize analytical depth. For high-volume document classification or extraction pipelines, Medium effort typically provides the best cost-per-quality tradeoff.
</Tip>

## Use Cases

* **Clinical summarization** — Processing patient histories locally under HIPAA- or GDPR-equivalent data residency requirements.
* **Legal research** — Analyzing sensitive litigation documents without any cloud exposure outside the EU.
* **Local coding assistants** — Running a high-intelligence coding model entirely on private, EU-resident infrastructure.
* **STEM and technical research** — Graduate-level science and mathematics reasoning with verifiable reasoning steps.

## Specifications

| Specification  | StackIT                            | Infercom                                     |
| -------------- | ---------------------------------- | -------------------------------------------- |
| Provider       | OpenAI (open-source)               | OpenAI (open-source)                         |
| Hosting        | EU (StackIT)                       | EU (Infercom)                                |
| Context Window | 131K tokens                        | 131K tokens                                  |
| Reasoning      | High                               | Adaptive (Low, Medium, High)                 |
| GPQA Diamond   | 80.9%                              | 80.9%                                        |
| Latency (TTFT) | 0.27s                              | 0.37s                                        |
| Throughput     | 262 tokens/sec                     | 313–544 tokens/sec                           |
| Image support  | No                                 | No                                           |
| Key use cases  | Agentic security, sovereign DevOps | High-speed agents, API orchestration, coding |

[Try GPT-OSS 120B in DeepMask →](https://chat.deepmask.io/)