Smart Router Configuration & Cost Failover: GPT-5.5 (openai/gpt-5.5) to GPT-4.1 Mini (openai/gpt-4.1-mini)

Production LLM API routing configuration, TTFT latency SLA (<400ms), and contribution margin failover benchmark generated by TokenMargin.dev.

1. Pricing & Latency Benchmark Summary

• Primary Model (GPT-5.5 — openai/gpt-5.5): $5.00 / 1M input tokens, $30.00 / 1M output tokens | TTFT: 340ms | Throughput: 85 tok/s
• Fallback Model (GPT-4.1 Mini — openai/gpt-4.1-mini): $0.40 / 1M input tokens, $1.60 / 1M output tokens | TTFT: 340ms | Throughput: 85 tok/s

2. Zero-Dependency TypeScript / Node.js Smart Router Configuration

export const SMART_ROUTER_CONFIG = {
  slaMaxTtftMs: 400,
  primary: { model: "openai/gpt-5.5", inputPer1M: 5.00, outputPer1M: 30.00 },
  fallback: { model: "openai/gpt-4.1-mini", inputPer1M: 0.40, outputPer1M: 1.60 },
  retryOnStatus: [429, 500, 502, 503, 529]
};

3. LiteLLM / OpenRouter YAML Router Configuration (config.yaml)

model_list:
  - model_name: production-primary
    litellm_params:
      model: openrouter/openai/gpt-5.5
      timeout: 15
  - model_name: cost-fallback
    litellm_params:
      model: openrouter/openai/gpt-4.1-mini
router_settings:
  routing_strategy: latency-based-routing
  fallbacks: [{"production-primary": ["cost-fallback"]}]