Observe It

Make important behavior visible in production without drowning in noise or leaking sensitive data.

Match signals to the quality regime (handbook concepts/11-quality-regimes.md):

Regime	Observe…
A — Deterministic compute	Golden signals + (for pipelines) freshness/coverage/correctness
B — Interactive product	Errors + RUM / Core Web Vitals + critical funnel events
C — Generative / high-input	Hierarchical LLM/tool/retrieval traces + quality scores / user feedback. House default: Langfuse (OTel-friendly) unless the repo already standardized elsewhere

When to use

“Add logging/metrics/tracing”, “observe it”, “how do we detect this failing?”, “add Langfuse/evals online”
After diagnose-bug / troubleshoot-app / agents analyze when the root cause was invisible
Before ship-it / stage-it when release risk needs signals