TL;DR

Prometheus compatibility is significantly improved with stabilized configurations and transformations, ensuring more reliable data export from OpenTelemetry to Prometheus (observability backend).

Breaking

• Prometheus Metric Exporter configuration property names have changed (without_scope_info to scope_info_enabled, etc.).
• OTel SDKs should no longer use unofficial Prometheus clients.

New

• Semantic Convention Schema v2 introduces support for multiple convention registries and a resolved schema format (data standardization).
• A new Bind API is available for synchronous instruments (metric creation).

Fixes Worth Knowing

• Stabilized Prometheus and OpenMetrics compatibility, including label and instrumentation scope translation.
• Stabilized OpenTelemetry Gauge and Sum to Prometheus transformations.

Before You Upgrade

• Update your Prometheus Metric Exporter configurations to use the new property names (scope_info_enabled, target_info_enabled, resource_constant_labels).
• Ensure your OTel SDKs are using official Prometheus clients.

TL;DR

The OpenTelemetry specification has been significantly updated, freezing the Trace API and introducing extensive semantic conventions and API refinements across tracing, metrics, and baggage management to improve data richness and interoperability.

Breaking

• Span Context Parent: Only a full Context can now be used to specify a parent Span; SpanContext is no longer accepted.
• Lazy Span APIs Removed: Implementations should remove any existing lazy Event and Link APIs to avoid future conflicts.
• HTTP Status Text: The http.status_text attribute has been removed from semantic conventions.
• Null Values: null is now explicitly invalid for attributes, leading to undefined behavior if attempted.
• Sampler Decisions: Sampler Decision values have been renamed to DROP, RECORD_ONLY, and RECORD_AND_SAMPLE.
• Metric Aggregation: "Additive" and "Non-Additive" terms in the Metrics API are now "Adding" and "Grouping" respectively.
• Baggage Header: The custom header name for baggage has been removed; use the official header instead.

New

• Exception Events: Added API and