Perplexity Policy Guardrails

Overview

Policy enforcement for Perplexity Sonar API. Since Perplexity performs live web searches, guardrails must address: query content moderation (what users can search for), citation reliability (filtering low-quality sources), cost control (model selection + token limits), and responsible AI usage.

Policy Pipeline

User Query
    │
    ▼
Query Moderation (block harmful queries)
    │
    ▼
PII Sanitization (strip personal data)
    │
    ▼
Quota Check (daily limit by user tier)
    │
    ▼
Model Selection (enforce tier-appropriate model)
    │
    ▼
Perplexity API Call
    │
    ▼
Citation Quality Scoring (filter low-trust sources)
    │
    ▼
Response to User

Prerequisites

• Perplexity API configured
• Content moderation policy defined
• User tier system in place
• Redis for quota tracking (optional: in-memory for simple apps)

Instructions

Step 1: Query Content Moderation

const BLOCKED_PATTERNS = [
  /\b(write|generate|create)\s+(malware|virus|exploit|ransomware)\b/i,
  /\b(personal|private)\s+(address|phone|ssn)\s+of\s+\w+/i,
  /\b(bypass|circumvent|hack)\s+(security|firewall|authentication)\b/i,
  /\b(how to|tutorial)\s+(stalk|dox|harass)\b/i,
];

const MAX_QUERY_LENGTH = 2000;

class PolicyError extends Error {
  constructor(public code: string, message: string) {
    super(message);
    this.name = "PolicyError";
  }
}

function moderateQuery(query: string): string {
  if (query.length > MAX_QUERY_LENGTH) {
    throw new PolicyError("QUERY_TOO_LONG", `Query exceeds ${MAX_QUERY_LENGTH} characters`);
  }

  for (const pattern of BLOCKED_PATTERNS) {
    if (pattern.test(query)) {
      throw new PolicyError("CONTENT_BLOCKED", "Query blocked by content policy");
    }
  }

  return query;
}

Step 2: Model Selection Policy

interface ModelPolicy {
  model: string;
  maxTokens: number;
  costPerRequest: number;
}

const MODEL_POLICIES: Record<string, ModelPolicy> = {
  free:       { model: "sonar",     maxTokens: 256,  costPerRequest: 0.005 },
  basic:      { model: "sonar",     maxTokens: 1024, costPerRequest: 0.005 },
  pro:        { model: "sonar-pro", maxTokens: 2048, costPerRequest: 0.02 },
  enterprise: { model: "sonar-pro", maxTokens: 4096, costPerRequest: 0.02 },
};

function enforceModelPolicy(
  userTier: string,
  requestedModel?: string
): ModelPolicy {
  const policy = MODEL_POLICIES[userTier] || MODEL_POLICIES.free;

  // Prevent free users from using expensive models
  if (requestedModel === "sonar-pro" && !["pro", "enterprise"].includes(userTier)) {
    console.warn(`User tier ${userTier} not allowed sonar-pro, using sonar`);
    return MODEL_POLICIES.free;
  }

  return requestedModel ? { ...policy, model: requestedModel } : policy;
}

Step 3: Per-User Usage Quotas

class UsageQuota {
  private usage: Map<string, { count: number; resetAt: number }> = new Map();

  private readonly limits: Record<string, number> = {
    free: 50,
    basic: 200,
    pro: 1000,
    enterprise: 5000,
  };

  check(userId: string, tier: string = "free"): void {
    const key = `${userId}:${new Date().toISOString().slice(0, 10)}`;
    const entry = this.usage.get(key) || { count: 0, resetAt: this.endOfDay() };

    // Reset if past end of day
    if (Date.now() > entry.resetAt) {
      entry.count = 0;
      entry.resetAt = this.endOfDay();
    }

    const limit = this.limits[tier] || this.limits.free;
    if (entry.count >= limit) {
      throw new PolicyError(
        "QUOTA_EXCEEDED",
        `Daily quota exceeded (${entry.count}/${limit}). Resets at midnight UTC.`
      );
    }

    entry.count++;
    this.usage.set(key, entry);
  }

  getUsage(userId: string): { used: number; limit: number; remaining: number } {
    const key = `${userId}:${new Date().toISOString().slice(0, 10)}`;
    const entry = this.usage.get(key);
    const used = entry?.count || 0;
    return { used, limit: 50, remaining: Math.max(0, 50 - used) };
  }

  private endOfDay(): number {
    const d = new Date();
    d.setUTCHours(23, 59, 59, 999);
    return d.getTime();
  }
}

Step 4: Citation Quality Scoring

const TRUSTED_TLDS = new Set(["gov", "edu", "org"]);
const HIGH_QUALITY_DOMAINS = new Set([
  "nature.com", "science.org", "arxiv.org", "wikipedia.org",
  "nih.gov", "cdc.gov", "who.int",
]);
const LOW_QUALITY_DOMAINS = new Set([
  "reddit.com", "quora.com", "medium.com", "yahoo.com",
]);

interface CitationQuality {
  url: string;
  trust: "high" | "medium" | "low";
  domain: string;
}

function scoreCitations(citations: string[]): {
  scored: CitationQuality[];
  highTrustPercent: number;
} {
  const scored = citations.map((url) => {
    const domain = new URL(url).hostname;
    const tld = domain.split(".").pop() || "";

    let trust: "high" | "medium" | "low" = "medium";
    if (TRUSTED_TLDS.has(tld) || HIGH_QUALITY_DOMAINS.has(domain)) {
      trust = "high";
    } else if (LOW_QUALITY_DOMAINS.has(domain)) {
      trust = "low";
    }

    return { url, trust, domain };
  });

  const highTrust = scored.filter((s) => s.trust === "high").length;
  return {
    scored,
    highTrustPercent: citations.length > 0 ? highTrust / citations.length : 0,
  };
}

Step 5: Full Policy Pipeline

const quota = new UsageQuota();

async function policiedSearch(
  query: string,
  userId: string,
  userTier: string = "free",
  requestedModel?: string
) {
  // 1. Content moderation
  const moderated = moderateQuery(query);

  // 2. PII sanitization
  const { clean } = sanitizeQuery(moderated);

  // 3. Quota check
  quota.check(userId, userTier);

  // 4. Model policy
  const policy = enforceModelPolicy(userTier, requestedModel);

  // 5. API call
  const response = await perplexity.chat.completions.create({
    model: policy.model,
    messages: [{ role: "user", content: clean }],
    max_tokens: policy.maxTokens,
  });

  // 6. Citation quality
  const citations = (response as any).citations || [];
  const quality = scoreCitations(citations);

  return {
    answer: response.choices[0].message.content,
    citations: quality.scored,
    citationQuality: quality.highTrustPercent,
    model: response.model,
    tokens: response.usage?.total_tokens,
  };
}

Error Handling

Issue	Cause	Solution
Query blocked	Content moderation triggered	Review patterns, adjust if false positive
Quota exceeded	User hit daily limit	Upgrade tier or wait for reset
Model downgraded	User tier restricts access	Inform user of tier limitations
Low citation quality	All sources from forums	Add search_domain_filter for trusted sources

Output

• Query content moderation with blocked patterns
• Model selection enforced by user tier
• Per-user daily quotas
• Citation quality scoring and filtering
• Full policy pipeline combining all layers

Resources

• Perplexity API Documentation
• Perplexity Responsible Use

Next Steps

For architecture patterns, see perplexity-architecture-variants.