Datadog dashboards for prompt regression: the panels we actually keep

We wired our LLM eval suite into Datadog over about four months. Most of the panels we built got deleted. These are the five that stayed, and the metrics that feed them. TL;DR: We run an LLM-as-judge eval suite on every PR that touches a prompt, and we ship the results to Datadog as custom metrics. The dashboard started with fourteen panels. We kept five. The one that catches the most real regressions is per-criterion pass-rate split out by judge criterion, not the single rolled-up pass-rate number, because an aggregate of 91 percent hid the fact that one criterion had dropped from 0.95 to 0.62. Below are the metrics we emit, the Python that submits them, the monitor config we alert on, and the panels we tried and dropped. Some context on the setup so the rest makes sense. We are a Series-C dev-tool startup. We have a handful of prompts in production that do real work (classification, extraction, a summarization step in an agent loop). Each one has an eval set of tagged examples, somewhere between 80 and 400 per prompt. The judge is a separate model call that scores each output against a rubric. We run the suite in GitHub Actions. The eval job emits metrics to Datadog at the end of every run. Backend service health was already in Datadog, so putting eval data next to it meant one place to look during an incident instead of two. 1. Emit per-criterion pass-rate, not just the rolled-up number This is the one that earns its place. Our judge scores each output against multiple criteria. For the extraction prompt it is four: correct fields, no hallucinated fields, format valid, no refusal. Early on we only emitted one number, prompt_eval.pass_rate, the fraction of examples that passed every criterion. That number is fine for a smoke test and useless for debugging. The problem showed up on a prompt change that looked clean. Overall pass-rate went from 0.93 to 0.91. Two points. Nobody would block a PR on two points. But underneath, the "no hallucinated fields" criterion had