The LLM Monitoring Stack I Run in Production (It's 3 Tools, $50/mo)

I've spent 18 months building and running LLM-powered production systems. Here's exactly what I monitor and what it costs. The Three Tools 1. DriftWatch — £9.90/mo Catches when the model silently changes behaviour. Runs 20 standardized prompts against your model every hour. Alerts you when outputs drift from baseline. This is the one nobody thinks about until they get their first incident from a model update. What I use it for: Detecting GPT-4o or Claude updates before they break my prompts. 2. Helicone — Free tier (or $50/mo) LLM observability. Shows you token usage, latency, failure rates, and what prompts are actually going to your models. What I use it for: Debugging why production is slow or expensive. 3. PagerDuty or Slack — $0-20/mo Alerting. DriftWatch and Helicone both webhook. Point them at Slack or PagerDuty and you're covered. What I use it for: Waking me up at 3am if something goes wrong. The Total Cost Tool Monthly Cost DriftWatch (Starter) £9.90 Helicone (Free tier) $0 S