Proxilion - Runtime Security SDK for Agentic AI
Author: Clay Good
Description: Proxilion - Runtime Security SDK for LLM-Powered Applications. Deterministic authorization, input validation, and audit logging for agentic AI.
Keywords: proxilion, llm security, ai security sdk, agentic ai, tool authorization, prompt injection, runtime security

## The Problem

LLMs are probabilistic. Security decisions must be deterministic.

####
LLM-Based Authorization

    prompt = f"""
    Should user {user_id} access {file}?
    Respond yes or no.
    """
    response = llm.complete(prompt)

    # Can be jailbroken
    # Different outputs for same inputs
    # 100-500ms latency, $0.01/check

####
Proxilion Authorization

    @auth.authorize("read", resource="file")
    async def read_file(path, user):
        # Policy: user.id == file.owner_id
        return open(path).read()

    # Cannot be bypassed by any input
    # Same input = same output, always
    # <1ms latency, $0/check

## Quickstart

Get Proxilion running in under 5 minutes.

Installation

    pip install proxilion

Define a Policy

    from proxilion import Proxilion, Policy, UserContext

    auth = Proxilion()

    @auth.policy("file_access")
    class FileAccessPolicy(Policy):
        """Users can only access their own files."""

        def evaluate(self, context) -> bool:
            user = context.user
            file_owner = context.tool_call.parameters.get("owner_id")
            return user.user_id == file_owner

Protect a Tool

    @auth.authorize("read", resource="file_access")
    async def read_file(path: str, owner_id: str, user: UserContext = None):
        """Read a file - only accessible to the owner."""
        with open(path) as f:
            return f.read()

Use It

    user = UserContext(user_id="alice", roles=["user"])

    # Allowed - alice accessing her own file
    content = await read_file("/data/alice/notes.txt", owner_id="alice", user=user)

    # Denied - alice trying to access bob's file
    try:
        content = await read_file("/data/bob/secrets.txt", owner_id="bob", user=user)
    except AuthorizationError:
        print("Access denied")

## Core Features

Every security check is deterministic, auditable, and sub-millisecond.

### Policy Engine

Define authorization as Python code. RBAC, ABAC, or custom logic. Testable and auditable.

### Input Guards

Block prompt injection, SQL injection, and command injection with regex patterns.

### Output Guards

Detect and redact API keys, credentials, and PII before they leave your system.

### IDOR Protection

Prevent agents from accessing resources they shouldn't. Runtime ownership validation.

### Rate Limiting

Token bucket and sliding window algorithms. Per-user, per-agent, per-tool limits.

### Audit Logging

Hash-chained, tamper-evident logs. Every decision recorded for compliance.

### Intent Capsules

Cryptographically bind user intent with HMAC signatures that can't be hijacked.

### Kill Switch

Emergency halt for runaway agents. Triggered by cost, error rate, or manual intervention.

### Behavioral Drift

Z-score statistical analysis detects when agent behavior deviates from baseline.

## Architecture

Proxilion runs inside your application, intercepting every tool call.

User Request │ ▼ ┌─────────────────────┐ │ LLM │ │ (Claude, GPT, etc) │ └──────────┬──────────┘ │ Tool Call ▼ ┌────────────────────────────────────────────────────────────┐ │ PROXILION RUNTIME │ │ │ │ ┌──────────────┐ ┌──────────────┐ ┌──────────────┐ │ │ │ Input Guards │ │ Policy │ │ Output Guards│ │ │ │ │ │ Engine │ │ │ │ │ │ • Injection │ │ │ │ • Credential │ │ │ │ • Path trav │ │ • RBAC/ABAC │ │ • PII detect │ │ │ │ • SQLi │ │ • Ownership │ │ • Redaction │ │ │ └──────┬───────┘ └──────┬───────┘ └──────┬───────┘ │ │ │ │ │ │ │ └─────────────────┼─────────────────┘ │ │ │ │ │ ┌────────────────────────┼────────────────────────────┐ │ │ │ Rate Limit │ Circuit Breaker │ Audit Log │ │ │ └────────────────────────┼────────────────────────────┘ │ └────────────────────────────┼────────────────────────────────┘ │ If Allowed ▼ ┌─────────────┐ │ Tool │ │ Execution │ └─────────────┘

## OWASP ASI Top 10 Coverage

Comprehensive protection against Agentic Security Initiative risks.

OWASP Risk | Proxilion Control
--- | ---
ASI01 Goal Hijacking | Intent Capsules with HMAC signatures
ASI02 Tool Misuse | Policy-based authorization engine
ASI03 Privilege Escalation | Role-based policies, IDOR protection
ASI04 Data Exfiltration | Output guards with pattern detection
ASI05 IDOR via LLM | Runtime ownership validation
ASI06 Memory Poisoning | Memory integrity guard with hash chains
ASI07 Insecure Agent Comms | Agent trust manager with HMAC messaging
ASI08 Resource Exhaustion | Rate limiting, circuit breaker
ASI09 Shadow AI | Comprehensive audit logging
ASI10 Rogue Agents | Behavioral drift detection, kill switch

## More Products

Additional security tools for specific use cases.

Gateway

### Proxilion MCP

Security gateway for MCP-compatible AI assistants. Monitors Claude Code, Cursor, and Copilot for insider threats.

Compliance

### Proxilion GRC

Governance, Risk, and Compliance tools for AI systems. Automated policy generation and compliance mapping.

## Secure Your LLM Tools Today

Open source. Zero dependencies. Deploy in minutes.

Get Started on GitHub