Logs volume stopped showing log level after switching to native OTLP ingestion endpoint

[jmichalek132]

Describe the bug A clear and concise description of what the bug is.

To Reproduce Steps to reproduce the behavior:

1. Started Loki (SHA or version) 3.1
2. Started Java app with the otel java agent (1.25.1) (sending logs to otel collector via OTLP) and otel collector contrib 0.98.0
3. Switching from using the loki exporter to using the native OTLP ingest endpoint
4. Query: {service_name="<service_name>"}

Expected behavior I expected the log volume to keep showing the log severity but now it's just showing unknown.

After reading https://grafana.com/docs/loki/latest/send-data/otel/native_otlp_vs_loki_exporter/#formatting-of-logs I assume it's due to with the previous configuration severity would be an indexed label. I wonder if there is a way to restore the behavior with native OTLP log ingestion. To be clear the log level is still present it's just under different name (detected_level) and in the structured metatada instead of the index as far I can tell.

Environment:

• Infrastructure: AKS Kubernetes
• Deployment tool: helm 6.7.3

Screenshots, Promtail config, or terminal output If applicable, add any output to help explain your problem.

[jmichalek132]

Maybe related to https://github.com/grafana/loki/issues/13688