Golang Experimental Module Failing to v2 Remote Write Metadata

[steven-freed]

I am attempting to use the golang experimental module to remote write data to a local prometheus instance however the metadata for the gauge is failing to show up in the prometheus ui. I understand that remote_write v1 protocol does not send metadata so I am using a v2 request but still not seeing metadata in the ui. Anyone know if my configuration is incorrect or if this is not possible and I have misinterpreted something?

OS: darwin Tahoe 26.4
Arch: arm64
Prometheus version: 3.11.1

prometheus.yml

global:
  scrape_interval: 7s
  evaluation_interval: 7s

scrape_configs:
  - job_name: "prometheus"
    static_configs:
      - targets: ["localhost:9090"]
        labels:
          app: "prometheus"

remote_write:
- url: "http://localhost:9090/api/v1/write"
  protobuf_message: "io.prometheus.write.v2.Request"
  metadata_config:
    send: true
    send_interval: 5s

Starting prometheus as so...

./prometheus \
  --config.file=prometheus.yml \
  --web.enable-remote-write-receiver

go remote_writer

import (
	"context"
	"crypto/tls"
	"log"
	"net/http"
	"time"

	"github.com/prometheus/client_golang/exp/api/remote"
	writev2 "github.com/prometheus/client_golang/exp/api/remote/genproto/v2"
)

func main() {
	httpClient := &http.Client{
		Transport: &http.Transport{
			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
		},
	}

	apiOpts := []remote.APIOption{remote.WithAPIHTTPClient(httpClient)}
	api, err := remote.NewAPI("http://localhost:9090/", apiOpts...)
	if err != nil {
		log.Fatalf("remote API: %v", err)
	}

	sym := writev2.NewSymbolTable()
	labelsRefs := []string{"__name__", "super_fast_gpu"}
	help := "super_fast_gpu help"
	unit := "_ratio"

	ts := &writev2.TimeSeries{
		LabelsRefs: sym.SymbolizeLabels(labelsRefs, nil),
		Samples: []*writev2.Sample{
			{Value: 100.0, Timestamp: time.Now().UnixMilli()},
		},
		Metadata: &writev2.Metadata{
			Type:    writev2.Metadata_METRIC_TYPE_GAUGE,
			HelpRef: sym.Symbolize(help),
			UnitRef: sym.Symbolize(unit),
		},
	}

	req := &writev2.Request{
		Symbols:    sym.Symbols(),
		Timeseries: []*writev2.TimeSeries{ts},
	}
	req.Symbols = sym.Symbols()

	stats, err := api.Write(context.Background(), remote.WriteV2MessageType, req)
	if err != nil {
		log.Fatalf("remote_write v2 failed: %v", err)
	}
	log.Printf("remote_write v2 ok samples=%d", stats.Samples)
}