Engine

Engine for guardrail components.

GuardrailEngine

Bases: Protocol

Base engine interface for guardrail engines.

This protocol defines the contract that all guardrail engines must implement. Engines can check content for safety violations using various techniques such as phrase matching, topic classification, or external API calls.

All engines must be asynchronous to support both sync and async guardrail providers.

Attributes:

Name	Type	Description
config	BaseGuardrailEngineConfig	Engine configuration specifying what content types to check

check_input(content, **kwargs) async

Check input content for safety violations.

This method should implement provider-specific safety checks on user input such as query content, context, or prompts before sending to LLM.

Parameters:

Name	Type	Description	Default
content	str	The input text to evaluate for safety	required
**kwargs		Additional engine-specific parameters (optional)	{}

Returns:

Type	Description
GuardrailResult	GuardrailResult indicating if content is safe, with reason if unsafe

Raises:

Type	Description
Exception	If the safety check fails due to engine errors

check_output(content, **kwargs) async

Check output content for safety violations.

This method should implement provider-specific safety checks on system output such as LLM responses, generated text, or static messages before showing to users.

Parameters:

Name	Type	Description	Default
content	str	The output text to evaluate for safety	required
**kwargs		Additional engine-specific parameters (optional)	{}

Returns:

Type	Description
GuardrailResult	GuardrailResult indicating if content is safe, with reason if unsafe

Raises:

Type	Description
Exception	If the safety check fails due to engine errors

NemoGuardrailEngine(config=None)

Bases: GuardrailEngine

Default engine that keeps current NeMo Guardrails behavior.

This engine implements the GuardrailEngine protocol to provide NeMo Guardrails functionality for content safety checking.

Attributes:

Name	Type	Description
config	NemoGuardrailEngineConfig	Engine configuration specifying what content types to check.
rails	LLMRails | None	LLMRails instance.

Initializes a new instance of the NemoGuardrailEngine class.

Parameters:

Name	Type	Description	Default
config	NemoGuardrailEngineConfig | None	NemoGuardrailEngineConfig with both base and NeMo-specific settings. Defaults to None.	None

check_input(content, **kwargs) async

Check input content for safety violations.

This method implements NeMo Guardrails checking for user input such as query content, context, or prompts before sending to LLM.

Parameters:

Name	Type	Description	Default
content	str	The input text to evaluate for safety.	required
**kwargs	Any	Additional engine-specific parameters.	{}

Returns:

Name	Type	Description
GuardrailResult	GuardrailResult	GuardrailResult indicating if content is safe, with reason if unsafe.

Raises:

Type	Description
RuntimeError	If the guardrail engine is not initialized.

check_output(content, **kwargs) async

Check output content for safety violations.

This method implements NeMo Guardrails checking for system output such as LLM responses, generated text, or static messages before showing to users.

Parameters:

Name	Type	Description	Default
content	str	The output text to evaluate for safety.	required
**kwargs	Any	Additional engine-specific parameters.	{}

Returns:

Name	Type	Description
GuardrailResult	GuardrailResult	GuardrailResult indicating if content is safe, with reason if unsafe.

Raises:

Type	Description
RuntimeError	If the guardrail engine is not initialized.

PhraseMatcherEngine(config=None, banned_phrases=None, use_spacy=None, model_name='en_core_web_sm')

Bases: GuardrailEngine

Engine that uses SpaCy PhraseMatcher or Regex for banned phrase detection.

This engine implements the GuardrailEngine protocol to check content for banned phrases using either SpaCy for optimized matching or regex as a fallback.

Attributes:

Name	Type	Description
config		Engine configuration specifying what content types to check
banned_phrases	list[str]	Phrases that are explicitly banned.
use_spacy	bool	Whether to use SpaCy for phrase matching.
model_name	str	SpaCy model name to load.
banned_phrases_regex	Pattern | None	Compiled regex pattern for fallback.
phrase_matcher	PhraseMatcher | None	SpaCy phrase matcher.
nlp	Language | None	SpaCy language model.

Initialize the PhraseMatcherEngine.

Parameters:

Name	Type	Description	Default
config	BaseGuardrailEngineConfig | None	Engine configuration. Defaults to BaseGuardrailEngineConfig with INPUT_ONLY mode.	None
banned_phrases	list[str] | None	List of banned phrases. Defaults to PhraseMatcherEngine.DEFAULT_BANNED_PHRASES.	None
use_spacy	bool | None	Whether to use SpaCy for phrase matching. Defaults to SPACY_AVAILABLE.	None
model_name	str	SpaCy model name to load. Defaults to "en_core_web_sm".	'en_core_web_sm'

check_input(content, **kwargs) async

Check input content for banned phrases.

Parameters:

Name	Type	Description	Default
content	str	The input text to evaluate for safety	required
**kwargs	Any	Additional engine-specific parameters (optional)	{}

Returns:

Type	Description
GuardrailResult	GuardrailResult indicating if content is safe, with reason if unsafe

Raises:

Type	Description
Exception	If the safety check fails due to engine errors

check_output(content, **kwargs) async

Check output content for banned phrases.

Parameters:

Name	Type	Description	Default
content	str	The output text to evaluate for safety	required
**kwargs	Any	Additional engine-specific parameters (optional)	{}

Returns:

Type	Description
GuardrailResult	GuardrailResult indicating if content is safe, with reason if unsafe

Raises:

Type	Description
Exception	If the safety check fails due to engine errors