How to Build a Multi-Model AI Router in 50 Lines of Python

Every AI-powered app I've seen makes the same mistake: sending every request to the same expensive model. A simple "format this JSON" doesn't need GPT-5.4 or Opus 4.6. A complex architecture review does. Here's a multi-model router in 50 lines of Python that cut my API costs by 60%+ while maintaining quality where it matters. The Core Idea Simple task → cheap/fast model ($0.15/1M tokens) Medium task → mid-tier model ($1.00/1M tokens) Complex task → frontier model ($15.00/1M tokens) The router classifies each request and sends it to the right model automatically. The Full Router (50 Lines) import os import hashlib import json from openai import OpenAI # Model tiers with pricing (input $/1M tokens) TIERS = { "fast": {"model": "gpt-4o-mini", "cost": 0.15, "max_tokens": 1024}, "mid": {"model": "gpt-4o", "cost": 2.50, "max_tokens": 4096}, "power": {"model": "gpt-5.4", "cost": 15.00, "max_tokens": 8192}, } # Classification rules (runs locally, no API call) COMPLEXITY_SIGNALS = { "power": ["a