> For the complete documentation index, see [llms.txt](https://docs.mozilla.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mozilla.ai/any-guardrail/api-reference/index/content-safety/nemotron-content-safety.md).

# Nemotron Content Safety

Reasoning safety classifier covering a 22-category content-safety taxonomy.

Decoder LLM (Gemma-3-4B base) that classifies a user prompt and an optional assistant response against NVIDIA's 22-category content-safety taxonomy (`S1` Violence ... `S22` Immoral/Unethical). The model is prompted to emit `Prompt harm: harmful/unharmful` and `Response Harm: harmful/unharmful`; with `think=True` it first reasons inside `<think>...</think>` (stripped before the verdict is parsed).

Verdict mapping onto `GuardrailOutput`:

* `valid` is `False` when either the prompt or the response is judged harmful.
* `categories` carries two boolean signals — `prompt_harm` and `response_harm` (`triggered` reflects each verdict).
* `explanation` is the raw generation (including any `<think>` reasoning).
* `usage` carries the prompt / completion token counts. No canonical `score` or `spans` are produced.
* Fails closed (`valid=False` with `extra={"parse_failure": True}`) when the prompt verdict is missing, or when a response was judged but its verdict did not parse.

Expected inputs: a single `input_text` prompt string plus an optional `output_text` assistant response; when `output_text` is given the response is moderated alongside the prompt. Single strings only — passing a list raises `TypeError`.

Distributed under the NVIDIA Open Model License and the Gemma Terms of Use.

For more information, see the [nvidia/Nemotron-Content-Safety-Reasoning-4B model card](https://huggingface.co/nvidia/Nemotron-Content-Safety-Reasoning-4B).

## Supported Models

* `nvidia/Nemotron-Content-Safety-Reasoning-4B`

## Constructor

| Parameter  | Type                                                 | Required | Default | Description                                                                                                                                                                                                                                                      |
| ---------- | ---------------------------------------------------- | -------- | ------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `think`    | `bool`                                               | No       | `False` | If `True`, request chain-of-thought reasoning (`/think`) before the verdict; otherwise `/no_think`. Slower but can improve borderline judgments; the reasoning is stripped before parsing but kept in `GuardrailOutput.explanation`.                             |
| `model_id` | \`str                                                | None\`   | No      | `None`                                                                                                                                                                                                                                                           |
| `provider` | `Optional[Provider[dict[str, Any], dict[str, Any]]]` | No       | `None`  | Optional pre-configured provider. When `None`, a `HuggingFaceProvider` is built targeting a causal LM (`AutoModelForCausalLM` + `AutoTokenizer`). A supplied `HuggingFaceProvider` is corrected to those classes at load time; any other provider is used as-is. |

Initialize the Nemotron Content Safety guardrail.

## validate

Classify `input_text` and, optionally, an assistant `output_text`.

**Parameters**

| Parameter     | Type  | Required | Default | Description                                      |
| ------------- | ----- | -------- | ------- | ------------------------------------------------ |
| `input_text`  | `str` | Yes      | —       | The user prompt to moderate. Single string only. |
| `output_text` | \`str | None\`   | No      | `None`                                           |

**Returns:** `GuardrailOutput`

## Benchmarks

### Content Safety

| Dataset (rev)                    | Metric | Threshold    | Value    | Harness                 | Source                           | Contam. |
| -------------------------------- | ------ | ------------ | -------- | ----------------------- | -------------------------------- | ------- |
| openai\_moderation (unspecified) | f1     | native-valid | 0.82392  | guardrail-bench+ag0.7.4 | measured:guardrail-bench+ag0.7.4 |         |
| xstest (unspecified)             | fpr    | native-valid | 0.26     | guardrail-bench+ag0.7.4 | measured:guardrail-bench+ag0.7.4 |         |
| wildguardmix (unspecified)       | f1     | native-valid | 0.888136 | guardrail-bench+ag0.7.4 | measured:guardrail-bench+ag0.7.4 |         |
| aegis (unspecified)              | f1     | native-valid | 0.853333 | guardrail-bench+ag0.7.4 | measured:guardrail-bench+ag0.7.4 | ⚠️      |
| jbb (unspecified)                | f1     | native-valid | 0.834043 | guardrail-bench+ag0.7.4 | measured:guardrail-bench+ag0.7.4 |         |
| orbench (unspecified)            | fpr    | native-valid | 0.673684 | guardrail-bench+ag0.7.4 | measured:guardrail-bench+ag0.7.4 |         |

## License

* **Vendor:** NVIDIA
* **Default license:** `gemma` (of the default model/service)


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