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Overview

Guardrails in Bifrost provide enterprise-grade content safety, security validation, and policy enforcement for LLM requests and responses. The system validates inputs and outputs in real-time against your specified policies, ensuring responsible AI deployment with protection against harmful content, prompt injection, PII leakage, credential leakage, and policy violations.
Guardrails overview showing rules and profiles management

Supported Providers

Secrets Detection

Built-in Gitleaks-backed detection for leaked API keys, tokens, private keys, and credentials.

Custom Regex

In-process regex guardrails, including the built-in PII Detection template.

Microsoft Presidio

Presidio Analyzer based PII detection, blocking, and redaction.

Azure AI Language PII

Azure Language PII entity recognition with configurable categories and redaction.

AWS Bedrock Guardrails

Enterprise content filtering, PII detection, and prompt attack prevention.

Azure Content Safety

Multi-modal content moderation with severity-based filtering.

Google Model Armor

Google Cloud policy enforcement for prompt injection, content safety, malicious URLs, and Sensitive Data Protection.

CrowdStrike AIDR

Inline AI threat detection, policy enforcement, redaction, and AIDR audit visibility.

GraySwan Cygnal

AI safety monitoring with natural language rule definitions.

Patronus AI

LLM security, hallucination detection, and safety evaluation.

Core Concepts

Bifrost Guardrails are built around two core concepts that work together to provide flexible and powerful content protection: How They Work Together:
  • Profiles define how content is evaluated using native Bifrost checks or external provider capabilities
  • Rules define when and what content gets evaluated using CEL expressions
  • A single rule can use multiple profiles for layered protection
  • Profiles can be reused across different rules for consistency

Key Features

Redaction

Supported providers can redact detected text instead of only detecting or blocking it. Bifrost supports three redaction modes:
  • Runtime (runtime) redacts the live request or response and stores redacted values in logs.
  • Logs only (logs_only) leaves runtime content raw but redacts Bifrost logs and trace-export connector content.
  • Runtime + reversible logs (runtime_reversible) redacts runtime content and logs with reversible placeholders.
For the full behavior matrix, reveal permissions, and connector export caveats, see Guardrail Redaction. Access Guardrails from the Bifrost dashboard:

Architecture

The following diagram illustrates how Rules and Profiles work together to validate LLM requests: Flow Description:
  1. Incoming Request - LLM request arrives at Bifrost
  2. Input Validation - Applicable rules evaluate the input using linked profiles
  3. LLM Processing - If input passes, request is forwarded to the LLM provider
  4. Output Validation - Response is evaluated by output rules using linked profiles
  5. Response - Validated response is returned (or blocked/modified based on violations)

Streaming Output Guardrails

When an output guardrail is used with a streaming response, Bifrost accumulates the response until the model is done generating it, then checks the full response. If the response passes, Bifrost sends it to the client. If a guardrail blocks or changes the response, Bifrost applies that result instead. This adds time before the client receives output: Bifrost waits for response generation and guardrail evaluation to finish. The added wait depends on the model’s generation time and the configured guardrail profiles. Input guardrails check the request before Bifrost sends it to the LLM provider.
GraySwan is a tool-call-specific exception. Text-only streams are delivered directly to the client and are not sent to Cygnal. See GraySwan Cygnal for the full behavior.
If the same rule also uses another output guardrail profile, Bifrost waits for that profile to check the completed response. GraySwan’s text-only behavior only skips the GraySwan call; it does not bypass the other profile.

Guardrail Rules

Guardrail Rules are custom policies that define when and how content validation occurs. Rules use CEL (Common Expression Language) expressions to evaluate requests and can be linked to one or more profiles for execution.
Guardrail rules list showing configured rules with status and actions

Rule Properties

Creating Rules

  1. Navigate to Rules
    • Go to Guardrails > Configuration
    • Click Add Rule
Guardrail rules list showing configured rules with status and actions
  1. Configure Rule Settings
Basic Information:
  • Name: Enter a descriptive name (e.g., “Block PII in Prompts”)
  • Description: Explain the rule’s purpose
  • Enabled: Toggle to activate the rule
Evaluation Settings:
  • Apply To: Select when to apply the rule
    • input - Validate incoming prompts only
    • output - Validate LLM responses only
    • both - Validate both inputs and outputs
  • CEL Expression: Define the validation logic
  • Sampling Rate: Set percentage of requests to evaluate (default: 100%)
  • Timeout: Set maximum execution time in seconds (default: 60)
  1. Link Profiles
    • Select one or more profiles to use for evaluation
    • Rules will execute all linked profiles in sequence
  2. Save and Test
    • Click Save Rule
    • Use the Test button to validate with sample content

CEL Expression Examples

CEL (Common Expression Language) provides a powerful way to define rule conditions. Here are common patterns: Always Apply Rule:
Apply to User Messages Only:
Apply to Messages Containing Keywords:
Apply Based on Model:
Apply to Long Prompts:
Combine Multiple Conditions:

Linking Rules to Profiles

Rules can be linked to multiple profiles for comprehensive validation:
Rule configuration showing linked profiles
Best Practices:
  • Link credential-leakage rules to Secrets Detection
  • Link PII detection rules to profiles with PII capabilities (Custom Regex PII template, Presidio, Azure AI Language PII, Bedrock, Patronus)
  • Link content filtering rules to profiles with content safety features (Azure, Bedrock, GraySwan)
  • Use GraySwan for custom natural language rules when you need flexible, readable policies
  • Use multiple profiles for defense-in-depth (e.g., Bedrock + Patronus for PII, Azure + GraySwan for content)
  • Set appropriate timeouts when using multiple profiles

Managing Profiles

Profiles are reusable configurations for guardrail providers. External providers include credentials, endpoints, and detection thresholds. Bifrost-native providers such as Custom Regex and Secrets Detection run locally and do not require external service credentials.
Guardrail profiles list showing configured providers

Profile Properties

Creating Profiles

  1. Navigate to Providers
    • Go to Guardrails > Providers
    • Click Add Profile
Create guardrail profile form
  1. Select Provider Type
    • Choose from: Secrets Detection, Custom Regex, AWS Bedrock, Azure Content Safety, Google Model Armor, CrowdStrike AIDR, GraySwan, or Patronus AI
  2. Configure Provider Settings
    • Enter credentials and endpoint information for external providers, or local settings for native providers
    • Configure detection thresholds and actions
    • See provider-specific setup sections above for detailed configuration
  3. Save Profile
    • Click Save Profile
    • The profile is now available for linking to rules

Provider Capabilities

Third-party guardrail providers offer different capabilities. Bifrost-native providers are documented separately: Secrets Detection covers credential leakage, Custom Regex covers deterministic pattern checks, and Guardrail Redaction covers Bifrost-managed redaction modes.
CrowdStrike AIDR capabilities depend on the AIDR policy and detectors configured in CrowdStrike. Bifrost sends the request to AIDR, then enforces the returned blocked or transformed decision.
Do not configure provider-managed transformations and Bifrost-managed redaction to rewrite the same input or output phase. Bifrost fails closed when a phase produces both provider-managed transformed text and Bifrost-managed redaction findings, because there is no safe unambiguous way to merge two rewritten outputs. Detection-only and blocking guardrails can still run alongside redaction.

Best Practices

Profile Organization:
  • Create separate profiles for different use cases (PII, content filtering, etc.)
  • Use descriptive policy names that indicate the profile’s purpose
  • Keep credentials secure using environment variables
Performance Considerations:
  • Enable only the profiles you need to minimize latency
  • Use sampling rates on rules for high-traffic endpoints
  • Set appropriate timeouts to prevent slow requests
Security:
  • Store API keys and credentials in environment variables or secrets managers
  • Regularly rotate credentials
  • Use least-privilege IAM roles for AWS Bedrock
  • Use least-privilege Google IAM roles for Google Model Armor, such as roles/modelarmor.user or a higher Model Armor role

Using Guardrails in Requests

Attaching Guardrails to API Calls

Once configured, attach guardrails to your LLM requests using custom headers: Single Guardrail:
Multiple Guardrails (Sequential):
Guardrail Configuration in Request:

Guardrail Response Handling

Successful Validation (200):
Validation Failure - Blocked (446):
Validation Warning - Logged (246):