SentinelGateway is a fast, zero-dependency Go proxy that eliminates LLM downtime, compliance leaks, and token waste. • Drop-In: 1-line OpenAI base_url swap. • Auto-Failover: Routes across Claude, Groq, and Gemini in <25ms on 5xx/429 errors. • In-Flight Privacy: Strips PII with zero data retention. • Smart Caching: Sub-15ms Redis semantic hits. • Telemetry: Real-time cost, error, and latency tracking.