This issue track work left to stabilize PROM-39 feature.

• flag and OM, prom (text+proto) parsing, PromQL engine support (feature: type-and-unit-labels (PROM-39 implementation) #16228)
• When performing rate() or increase() over series without the correct __type__ label, surface warnings to the user (PROM-39: Provide PromQL info annotations when rate()/increase() over series without __type__="counter" label #16632)
• PromQL Annotation/warning when type or unit mismatch across series (Return info annotation when query returns metrics with same name but different type or unit label #16641)
  • Idea: Middleware storage.Storage with storage.SeriesSet.Next that saves first seen type and unit and produce annotation when we see another.
• metric family switch bug for text formats
  - Detection like this: https://github.com/prometheus/prometheus/blob/main/scrape/scrape.go#L1920
  - Fix todos
• PROM-39: Add tests for relabeling of type and unit labels #16738
• OTLP receive support (PROM-39: Add type and unit labels to OTLP endpoint #16630)
• PRW send support
• PRW recv support

cc @ArthurSens @dashpole