LLMGuardMiddleware

Use a second model as a security classifier for injection and harmful content

Class: bxModules.bxai.models.middleware.security.LLMGuardMiddleware

Uses a second model (judge) to classify inbound and/or outbound content for security risk. Complements heuristic sanitization with semantic classification.

Features

• Input judging in beforeLLMCall
• Optional output judging in afterLLMCall
• Configurable fail-open or fail-closed behavior
• Confidence threshold and category gating
• Prompt fencing to isolate untrusted content
• Verdict caching (in-memory static or named BoxLang cache)
• Re-entrancy guard for nested judge calls

Constructor

middleware = new bxModules.bxai.models.middleware.security.LLMGuardMiddleware(
    judge         : {},
    checkInput    : true,
    checkOutput   : false,
    failMode      : "open",
    threshold     : 0.7,
    categories    : [ "INJECTION", "HARMFUL" ],
    timeout       : 10,
    cacheEnabled  : true,
    cacheName     : "",
    maxCacheSize  : 1000,
    promptTemplate: ""
)

Configuration

Option	Type	Default	Description
judge	struct	{}	Judge settings: provider/model/apiKey/params/options
checkInput	boolean	true	Judge user content before main model call
checkOutput	boolean	false	Judge model output after call
failMode	string	"open"	On judge failure: open (allow) or closed (block)
threshold	numeric	0.7	Minimum confidence to act on non-safe verdict
categories	array	["INJECTION","HARMFUL"]	Verdict categories treated as blockable
timeout	numeric	10	Judge timeout in seconds
cacheEnabled	boolean	true	Enable verdict caching
cacheName	string	""	Named BoxLang cache; empty uses static in-memory cache
maxCacheSize	numeric	1000	In-memory cache size cap
promptTemplate	string	""	Custom classifier prompt; empty uses default

Hooks Used

• beforeLLMCall
• afterLLMCall

Verdict Contract

The judge is expected to return strict JSON:

{ "verdict": "SAFE|INJECTION|HARMFUL", "confidence": 0.0, "reason": "..." }

Example

guard = new bxModules.bxai.models.middleware.security.LLMGuardMiddleware(
    judge: {
        provider: "ollama",
        model   : "llama-guard3",
        params  : { temperature: 0, max_tokens: 256 }
    },
    checkInput : true,
    checkOutput: true,
    failMode   : "closed",
    threshold  : 0.8
)

agent = aiAgent( middleware: [ guard ] )

Notes

• Blocking uses BXAI.SecurityViolation throws.
• Judge calls are marked internal to avoid recursive security middleware re-entry.
• Invalid failMode throws InvalidFailMode during construction.