AI Guard (lexigram-ai-guard)

AI input/output guard pipeline for the Lexigram Framework — LLM safety and content filtering

Overview

Content safety and guardrails for the Lexigram Framework. Runs an ordered pipeline of input and output guards against every LLM call — blocking prompt injections, redacting PII, enforcing length limits, restricting topics, and optionally using an LLM classifier for advanced jailbreak detection. Zero-config usage starts with sensible defaults.

Install

uv add lexigram-ai-guard

Quick Start

from lexigram import Application
from lexigram.di.module import Module, module

from lexigram.ai.guard import GuardModule
from lexigram.ai.guard.config import GuardConfig

@module(imports=[
    GuardModule.configure(
        GuardConfig(
            injection_detection=True,
            pii_detection=True,
            pii_action="redact",
            max_input_chars=8000,
        )
    )
])
class AppModule(Module):
    pass

app = Application(modules=[AppModule])
if __name__ == "__main__":
    app.run()

Configuration

Zero-config usage: Call GuardModule.configure() with no arguments to use defaults.

Option 1 — YAML file

ai_guard:
  injection_detection: true
  pii_detection: true
  pii_action: "redact"
  max_input_chars: 8000
  restricted_topics: []

Option 2 — Profiles + Environment Variables (recommended)

export LEX_AI_GUARD__PII_ACTION=redact
# Environment variables for each field

Option 3 — Python

from lexigram.ai.guard.config import GuardConfig
from lexigram.ai.guard import GuardModule

config = GuardConfig(
    injection_detection=True,
    pii_action="redact",
    max_input_chars=8000,
    restricted_topics=["violence", "adult_content"],
)
GuardModule.configure(config)

Config reference

Field	Default	Env var	Description
`enabled`	`True`	`LEX_AI_GUARD__ENABLED`	Master on/off switch
`injection_detection`	`True`	`LEX_AI_GUARD__INJECTION_DETECTION`	Enable heuristic prompt injection detector
`injection_action`	`"block"`	`LEX_AI_GUARD__INJECTION_ACTION`	Action on injection: `"block"` or `"warn"`
`pii_detection`	`True`	`LEX_AI_GUARD__PII_DETECTION`	Enable PII detection on user inputs
`pii_action`	`"redact"`	`LEX_AI_GUARD__PII_ACTION`	Action on PII: `"redact"`, `"block"`, or `"warn"`
`pii_entities`	`[]`	`LEX_AI_GUARD__PII_ENTITIES`	PII entity types to scan
`pii_redaction_output`	`True`	`LEX_AI_GUARD__PII_REDACTION_OUTPUT`	Apply PII redaction to LLM outputs
`max_input_chars`	`0`	`LEX_AI_GUARD__MAX_INPUT_CHARS`	Maximum input character count
`max_output_chars`	`0`	`LEX_AI_GUARD__MAX_OUTPUT_CHARS`	Maximum output character count
`length_action`	`"block"`	`LEX_AI_GUARD__LENGTH_ACTION`	Action when a length limit is exceeded
`restricted_topics`	`[]`	`LEX_AI_GUARD__RESTRICTED_TOPICS`	Topic keywords to block
`enable_llm_guards`	`False`	`LEX_AI_GUARD__ENABLE_LLM_GUARDS`	Use LLM for advanced injection/jailbreak detection
`guard_model`	`"gpt-4o-mini"`	`LEX_AI_GUARD__GUARD_MODEL`	Model used for LLM-based guards
`llm_guard_threshold`	`0.7`	`LEX_AI_GUARD__LLM_GUARD_THRESHOLD`	Confidence threshold for LLM guard action
`sensitivity_level`	`"medium"`	`LEX_AI_GUARD__SENSITIVITY_LEVEL`	Guard aggressiveness: `"low"`, `"medium"`, `"high"`

Module Factory Methods

Method	Description
`GuardModule.configure(config)`	Configure with explicit config
`GuardModule.stub(config)`	Minimal config for testing

Key Features

Input guards: PromptInjectionDetector, PIIDetector, TopicRestrictor, InputLengthGuard
Output guards: PIIRedactor, OutputLengthGuard
LLM-based guards: Optional LLMInjectionDetector and LLMJailbreakDetector
Guard results: AggregateGuardResult with passed, blocked, redacted, warned states
@guarded decorator: Function-level guard attachment
Lifecycle hooks: GuardInputCheckedHook, GuardOutputCheckedHook, GuardPipelineCompletedHook

Testing

async with Application.boot(modules=[GuardModule.stub(
    GuardConfig(
        injection_detection=True,
        injection_action="block",
    )
)]) as app:
    # your test code
    ...

Key Source Files

File	What it contains
`src/lexigram/ai/guard/module.py`	`GuardModule.configure()`, `.stub()`
`src/lexigram/ai/guard/config.py`	`GuardConfig`
`src/lexigram/ai/guard/pipeline/guard_pipeline.py`	`GuardPipeline` orchestrator
`src/lexigram/ai/guard/pipeline/result.py`	`GuardCheckResult`, `AggregateGuardResult`, `GuardAction`
`src/lexigram/ai/guard/input/injection.py`	`PromptInjectionDetector` heuristics
`src/lexigram/ai/guard/input/pii.py`	`PIIDetector` regex patterns
`src/lexigram/ai/guard/output/pii_redactor.py`	`PIIRedactor`
`src/lexigram/ai/guard/di/provider.py`	`GuardProvider` boot and registration