Prompt-Safe AI Assistants: Guardrails, Memory Boundaries, and Fallbacks

Advanced Problem

Small AI assistants often look good in demos but become risky in production when memory, prompt construction, and fallback behavior are loosely coupled.

Step 1: Separate instruction layers

type PromptLayers = {
  systemRules: string;
  taskContext: string;
  userInput: string;
};

Step 2: Add response quality gates

function passesQuality(output: string): boolean {
  if (output.length < 180) return false;
  if (/\b(I am just an AI|cannot provide)\b/i.test(output)) return false;
  return true;
}

Step 3: Use fallback paths with explicit reason codes

async function generate(primary: () => Promise, fallback: () => Promise) {
  try {
    const out = await primary();
    if (!passesQuality(out)) throw new Error('quality_gate_failed');
    return { output: out, source: 'primary' };
  } catch (e) {
    const out = await fallback();
    return { output: out, source: 'fallback', reason: String(e) };
  }
}