For highlights and announcements pertaining to this release see: Release Notes > 1.16.0.

The following changes are from the previous release 1.16.0-rc.1.

• NuGet: OpenTelemetry v1.16.0

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api v1.16.0

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api.ProviderBuilderExtensions v1.16.0

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Console v1.16.0

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.InMemory v1.16.0

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.OpenTelemetryProtocol v1.16.0

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Zipkin v1.16.0

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Hosting v1.16.0

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Propagators v1.16.0

  No notable changes.

  See CHANGELOG for details.

The following changes are from the previous release 1.15.3-beta.1.

• NuGet: OpenTelemetry.Exporter.Prometheus.AspNetCore v1.16.0-beta.1

  • Fixed scrape response cache freshness using monotonic time so it is not
    affected by NTP system clock adjustments.
    (#7253)

  • Breaking Change Removed DisableTimestamp property from
    PrometheusAspNetCoreOptions.
    (#7176)

  • Fixed the serialization of NaN, PositiveInfinity, and NegativeInfinity
    values in Prometheus metrics to be compliant with the specification.
    (#7179)

  • Fixed loss of precision when serializing double and float values in
    Prometheus metrics to be compliant with the specification by using 17
    significant digits to represent such values.
    (#7179)

  • Fix non-ASCII characters in metric names and unit strings not being sanitized
    correctly during Prometheus serialization.
    (#7184)

  • Fix case where reader tracking could be reset while readers were still active.
    (#7190)

  • Improve Accept header handling for format negotiation so OpenMetrics is
    selected correctly by considering whitespace and q weights.
    (#7208)

  • Emit OpenMetrics exemplars for counters and histogram buckets.
    (#7222)

  • Fix incorrect handling of untyped metrics when using OpenMetrics format.
    (#7219)

  • Fix Prometheus/OpenMetrics serialization to emit metric and label names
    containing _ instead of dropping them and prefixing leading digits.
    Invalid characters are replaced with _ instead of being dropped.
    (#7209)

  • Add escaping=underscores to the Accept header handling for content
    negotiation so OpenMetrics are handled correctly.
    (#7209)

  • Omit histogram _sum and _count in OpenMetrics when negative bucket
    thresholds are present.
    (#7221)

  • Fix ArgumentException if OTEL_SDK_DISABLED=true.
    (#7273)

  • Update Accept header parsing to more closely follow the Prometheus
    Scrape protocol content negotiation
    specification.
    (#7266)

  • Abort scrape request processing if request exceeds the value specified by the
    X-Prometheus-Scrape-Timeout-Seconds HTTP request header.
    (#7252)

  • Use the canonical representation for histogram "le" label values when using
    OpenMetrics.
    (#7218)

  • Add Prometheus text fallback target_info output as a gauge.
    (#7238)

  • Merge colliding sanitized label keys.
    (#7239)

  • Export {name}_created series for counters and histograms when using
    OpenMetrics and a start time is available.
    (#7223)

  • GZip compress scrape endpoint responses when Accept-Encoding: gzip is
    specified by the HTTP request headers.
    (#7274)

  • Include instrumentation scope metadata on samples using otel_scope_* labels
    including scope version, schema URL, and prefixed scope attributes. OpenMetrics
    output no longer emits a separate otel_scope_info scope metadata metric.
    (#7237)

  • Drop conflicting scope attributes named name, version, and schema_url.
    (#7237)

  • Updated OpenTelemetry core component version(s) to 1.16.0.
    (#52)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Prometheus.HttpListener v1.16.0-beta.1

  • Fixed scrape response cache freshness using monotonic time so it is not
    affected by NTP system clock adjustments.
    (#7253)

  • Added Host and Port properties on PrometheusHttpListenerOptions
    for configuring the HTTP listener endpoint. The
    PrometheusHttpListenerOptions.UriPrefixes property is now obsolete and
    will be removed in the stable release.
    (#7114)

  • Breaking Change Removed DisableTimestamp property from
    PrometheusHttpListenerOptions.
    (#7176)

  • Fixed the serialization of NaN, PositiveInfinity, and NegativeInfinity
    values in Prometheus metrics to be compliant with the specification.
    (#7179)

  • Fixed loss of precision when serializing double and float values in
    Prometheus metrics to be compliant with the specification by using 17
    significant digits to represent such values.
    (#7179)

  • Fix non-ASCII characters in metric names and unit strings not being sanitized
    correctly during Prometheus serialization.
    (#7184)

  • Add support for caching the scrape endpoint HTTP responses using the
    PrometheusHttpListenerOptions.ScrapeResponseCacheDurationMilliseconds option.
    The default value is 300 milliseconds. Set the option to 0 to disable
    response caching.
    (#7189)

  • Fix case where reader tracking could be reset while readers were still active.
    (#7190)

  • Improve Accept header handling for format negotiation so OpenMetrics is
    selected correctly by considering whitespace and q weights.
    (#7208)

  • Emit OpenMetrics exemplars for counters and histogram buckets.
    (#7222)

  • Fix incorrect handling of untyped metrics when using OpenMetrics format.
    (#7219)

  • Add support for configuring the HTTP listener endpoint host and port using
    the OTEL_EXPORTER_PROMETHEUS_HOST and OTEL_EXPORTER_PROMETHEUS_PORT
    environment variables.
    (#7167,
    #7255)

  • Fix Prometheus/OpenMetrics serialization to emit metric and label names
    containing and _ instead of dropping them and prefixing leading digits.
    Invalid characters are replaced with _ instead of being dropped.
    (#7209)

  • Add escaping=underscores to the Accept header handling for content
    negotiation so OpenMetrics are handled correctly.
    (#7209)

  • Omit histogram _sum and _count in OpenMetrics when negative bucket
    thresholds are present.
    (#7221)

  • Update Accept header parsing to more closely follow the Prometheus
    Scrape protocol content negotiation
    specification.
    (#7266)

  • Abort scrape request processing if request exceeds the value specified by the
    X-Prometheus-Scrape-Timeout-Seconds HTTP request header.
    (#7252)

  • Use the canonical representation for histogram "le" label values when using
    OpenMetrics.
    (#7218)

  • Add Prometheus text fallback target_info output as a gauge.
    (#7238)

  • Merge colliding sanitized label keys.
    ([#7239](https://github.com/open-telemetry/opentelemetry-do...

The following changes are from the previous release 1.15.3.

• NuGet: OpenTelemetry v1.16.0-rc.1

  • Stop validating View-provided metric stream Name against the instrument
    name syntax, per
    spec clarification.
    (#7300)

  • Fix incorrect validation of OTEL_BSP_* and OTEL_BLRP_* environment
    variables.
    (#7187)

  • Fix observable instrument callbacks running once per reader instead of
    once per collection cycle.
    (#7188)

  • Added exception safety for user-supplied ExemplarReservoir implementations.
    Exceptions thrown from Offer are now caught and logged rather than propagating
    out of Counter.Add/Histogram.Record.
    (#7277)

  • Update OpenTelemetrySdkEventSource to support the W3C randomness flag.
    (#7301)

  • Added ObservedTimestamp property to LogRecord.
    (#6979)

  • Breaking Change Explicit histogram boundaries no longer allow more than
    10 million values.
    (#7165)

  • Fixed a circular reference which could cause a LoggerProvider to fail to
    resolve when one of its dependencies depends on ILogger or ILoggerFactory.
    As part of this fix the LoggerProvider resolved from dependency injection
    is now created lazily when the first logger is created rather than when
    ILoggerProvider or ILoggerFactory is resolved. A consequence is that any
    invalid configuration now surfaces when the first log record is written instead
    of when the logging services are resolved.
    (#7308)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api v1.16.0-rc.1

  • Experimental (pre-release builds only):
    Add support for using environment variables as context propagation carriers.
    (#7174)

  • Fix BaggagePropagator to correctly follow Key and Value Encoding rules as per
    the W3C Baggage specification.
    #7051

  • Update TraceContextPropagator to support the W3C randomness flag.
    (#7301)

  • Fixed TraceContextPropagator to deduplicate duplicate tracestate keys
    instead of discarding the entire tracestate header.
    (#7309)

  • Breaking change (pre-release only versions): The default value of
    the Timestamp property on LogRecordData has changed from DateTime.UtcNow
    to DateTime.MinValue. DateTime.MinValue represents an unset timestamp as
    defined by the OpenTelemetry specification. Callers of the Logs API
    who relied on the timestamp being populated automatically must now set
    Timestamp = DateTime.UtcNow explicitly on their LogRecordData instance.
    (#7045)

  • Added ObservedTimestamp property to LogRecordData. Note that LogRecordData
    is only public in pre-release versions of the package.
    (#6979)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api.ProviderBuilderExtensions v1.16.0-rc.1

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Console v1.16.0-rc.1

  • ObservedTimestamp will now be exported for logs.
    (#6979)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.InMemory v1.16.0-rc.1

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.OpenTelemetryProtocol v1.16.0-rc.1

  • Fixed NullReferenceException when exporting logs if the scope key is null.
    (#7186)

  • Added opt-in support for gzip compression. Compression can be configured
    programmatically via the new OtlpExporterOptions.Compression property,
    or through the environment variables such as OTEL_EXPORTER_OTLP_COMPRESSION=gzip.
    (#7055)

  • Fixed disk retry data being stored incorrectly when using persistent storage
    retry.
    (#7228)

  • Reverted OtlpLogExporter from using IHttpClientFactory on .NET 8+ to fix
    an issue with circular dependencies detected by some dependency injection
    container implementations such as Autofac.
    (#7234)

  • Fixed OtlpLogExporter integration with IHttpClientFactory so named clients
    can be used without triggering circular dependencies during logger construction.
    (#7298)

  • Reduce the overhead of GZip compression.
    (#7275)

  • Cached pre-serialized resource bytes to avoid re-encoding on every OTLP export.
    (#7303)

  • Do not enable the integration with IHttpClientFactory when mTLS is enabled.
    (#7305)

  • Handle Retry-After response headers that specify a date instead of a delay.
    (#7364)

  • observed_time_unix_nano will no longer always be identical to time_unix_nano
    when using the logs bridge API. By default, it will instead be set to the actual
    observed time of the log record.
    (#6979)

  • Fixed the retry deadline check so a Retry-After delay (whether a delta or an
    HTTP-date) that would extend a retry beyond the configured export timeout now
    correctly fails fast and drops the data.
    (#7375)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Zipkin v1.16.0-rc.1

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Hosting v1.16.0-rc.1

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Propagators v1.16.0-rc.1

  No notable changes.

  See CHANGELOG for details.

For highlights and announcements pertaining to this release see: Release Notes > 1.15.3.

The following changes are from the previous release 1.15.2.

• NuGet: OpenTelemetry v1.15.3

  • Fix resource leak in batch and periodic exporting task workers for Blazor/WASM.
    (#7069)

  • Fixed LogRecord.LogLevel to preserve LogLevel.None and handle
    unspecified or out-of-range severities without returning invalid enum values.
    (#7092)

  • Fixed OTEL_TRACES_SAMPLER_ARG handling to treat out-of-range, NaN, and
    infinite values as invalid and fall back to the default ratio when using
    traceidratio and parentbased_traceidratio samplers.
    (#7103)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api v1.15.3

  • Fix baggage and trace headers not respecting the maximum length in some cases
    to resolve GHSA-g94r-2vxg-569j.
    (#7061)

  • Improve efficiency of parsing of baggage and B3 propagation headers
    to resolve GHSA-g94r-2vxg-569j.
    (#7061)

  • Breaking change: Fixed tracestate parsing to reject keys that do not
    begin with a lowercase letter, including keys beginning with digits, to
    align with the W3C Trace Context specification.
    (#7065)

  • Fixed BaggagePropagator to trim optional whitespace (OWS) around =
    separators when parsing the baggage header, as required by the
    W3C Baggage specification.
    (#7009)

  • Fixed BaggagePropagator to strip baggage properties (e.g. ;metadata)
    from values when parsing the baggage header.
    (#7009)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api.ProviderBuilderExtensions v1.15.3

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Console v1.15.3

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.InMemory v1.15.3

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.OpenTelemetryProtocol v1.15.3

  • OtlpLogExporter now uses IHttpClientFactory on .NET 8+, matching the
    behaviour of the trace and metrics exporters.
    (#7109)

  • Fixed an issue in persistent storage cleanup where malformed .blob, .tmp,
    or .lock filenames could throw and interrupt maintenance to resolve
    GHSA-88hf-wf7h-7w4m.
    (#7108)

  • Breaking change: Fixed an insecure disk retry default. Disk retry now
    requires OTEL_DOTNET_EXPERIMENTAL_OTLP_DISK_RETRY_DIRECTORY_PATH when
    OTEL_DOTNET_EXPERIMENTAL_OTLP_RETRY=disk is configured. The exporter no
    longer falls back to a shared temp directory by default.
    To retain the previous behaviour, set the
    OTEL_DOTNET_EXPERIMENTAL_OTLP_DISK_RETRY_DIRECTORY_PATH environment
    variable to the value one of the following environment variables:

    • TMP, TMP, or USERPROFILE (Windows)
    • TMPDIR (or the literal value /tmp/) (Linux,
      macOS).

    This change resolves GHSA-4625-4j76-fww9.

    (#7106)

  • Fixed an issue in OTLP/gRPC retry handling where parsing gRPC status to
    resolve GHSA-mr8r-92fq-pj8p.
    (#7064)

  • Fixed an issue with OTLP disk retry storage where metrics and logs used the
    traces storage directory. Disk retry storage is now separated by signal using
    traces, metrics, and logs directories.
    (#7074)

  • Fixed full OTLP endpoint being logged by internal diagnostics.
    (#7116)

  • Fix OTEL_SPAN_ATTRIBUTE_VALUE_LENGTH_LIMIT not being applied.
    (#7115)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Zipkin v1.15.3

  • Harden memory usage for endpoint caching and array tag serialization to resolve
    GHSA-88hf-wf7h-7w4m.
    (#7081)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Hosting v1.15.3

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Propagators v1.15.3

  • Improve efficiency of parsing of baggage, B3 and Jaeger propagation headers
    to resolve GHSA-g94r-2vxg-569j.
    (#7061)

  See CHANGELOG for details.

The following changes are from the previous release 1.15.2-beta.1.

• NuGet: OpenTelemetry.Exporter.Prometheus.AspNetCore v1.15.3-beta.1

  • Fixed metric unit strings containing invalid Prometheus characters (e.g. # RU)
    not being sanitized, resulting in malformed metric names.
    (#6187)

  • Fixed Prometheus metric serialization to handle empty label names without
    throwing during scrape rendering.
    (#7077)

  • Updated OpenTelemetry core component version(s) to 1.15.3.
    (#7125)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Prometheus.HttpListener v1.15.3-beta.1

  • Fixed metric unit strings containing invalid Prometheus characters (e.g. # RU)
    not being sanitized, resulting in malformed metric names.
    (#6187)

  • Fixed Prometheus metric serialization to handle empty label names without
    throwing during scrape rendering.
    (#7077)

  • Updated OpenTelemetry core component version(s) to 1.15.3.
    (#7125)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Shims.OpenTracing v1.15.3-beta.1

  • Fixes support for byte, short, int, and float attributes.
    (#7080)

  • Updated OpenTelemetry core component version(s) to 1.15.3.
    (#7125)

  See CHANGELOG for details.

For highlights and announcements pertaining to this release see: Release Notes > 1.15.2.

The following changes are from the previous release 1.15.1.

• NuGet: OpenTelemetry v1.15.2

  • Added Task-based worker support for BatchExportProcessor and
    PeriodicExportingMetricReader to enable OpenTelemetry to work in
    single-threaded WebAssembly environments such as Blazor and Uno Platform.
    The implementation automatically detects the WebAssembly runtime and switches
    to Task-based workers accordingly; the Thread-based approach remains the
    default on all other platforms.
    (#6379)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api v1.15.2

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api.ProviderBuilderExtensions v1.15.2

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Console v1.15.2

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.InMemory v1.15.2

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.OpenTelemetryProtocol v1.15.2

  • Limit how much of the response body is read when export fails and
    error logging is enabled to resolve
    GHSA-q834-8qmm-v933.
    (#7017)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Zipkin v1.15.2

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Hosting v1.15.2

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Propagators v1.15.2

  No notable changes.

  See CHANGELOG for details.

The following changes are from the previous release 1.15.1-beta.1.

• NuGet: OpenTelemetry.Exporter.Prometheus.AspNetCore v1.15.2-beta.1

  • Updated OpenTelemetry core component version(s) to 1.15.2.
    (#7049)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Prometheus.HttpListener v1.15.2-beta.1

  • Updated OpenTelemetry core component version(s) to 1.15.2.
    (#7049)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Shims.OpenTracing v1.15.2-beta.1

  • Updated OpenTelemetry core component version(s) to 1.15.2.
    (#7049)

  See CHANGELOG for details.

For highlights and announcements pertaining to this release see: Release Notes > 1.15.1.

The following changes are from the previous release 1.15.0.

• NuGet: OpenTelemetry v1.15.1

  • Fixed Tracer.StartSpan() leaving the new span as Activity.Current when
    the previous activity was stopped by another thread during span creation.
    (#6257)

  • Fixed OverflowException in TraceIdRatioBasedSampler when trace ID bytes
    produced long.MinValue.
    ([#6928])

  • Fixed precision issues when using Histogram<float> with custom
    HistogramBucketBoundaries.
    (#6866)

  • Fixed a thread-safety issue in LogRecordSharedPool.Rent().
    (#6833)

  • Fixed observable instruments (ObservableCounter, ObservableUpDownCounter,
    ObservableGauge) continuing to export stale data points after a callback
    stops reporting a series.
    (#5950)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api v1.15.1

  • Breaking change: The Baggage API implements the latest Baggage API
    specification,
    which disallows empty baggage names and treats baggage names and values as case
    sensitive.
    (#6931)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api.ProviderBuilderExtensions v1.15.1

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Console v1.15.1

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.InMemory v1.15.1

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.OpenTelemetryProtocol v1.15.1

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Zipkin v1.15.1

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Hosting v1.15.1

  • Fix NullReferenceException when OTEL_SDK_DISABLED=true.
    (#6869)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Propagators v1.15.1

  No notable changes.

  See CHANGELOG for details.

The following changes are from the previous release 1.15.0-beta.1.

• NuGet: OpenTelemetry.Exporter.Prometheus.AspNetCore v1.15.1-beta.1

  • Updated OpenTelemetry core component version(s) to 1.15.1.
    (#7010)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Prometheus.HttpListener v1.15.1-beta.1

  • Updated OpenTelemetry core component version(s) to 1.15.1.
    (#7010)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Shims.OpenTracing v1.15.1-beta.1

  • This package is deprecated and it will stop receiving any updates in
    March 2027. Use the OpenTelemetry API and SDK directly instead of the OpenTracing
    shims.
    (#6976)

  • Updated OpenTelemetry core component version(s) to 1.15.1.
    (#7010)

  See CHANGELOG for details.

For highlights and announcements pertaining to this release see: Release Notes > 1.15.0.

The following changes are from the previous release 1.14.0.

• NuGet: OpenTelemetry v1.15.0

  • Added support for the OTEL_SDK_DISABLED environment variable in TracerProvider,
    MeterProvider, and LoggerProvider. When OTEL_SDK_DISABLED=true,
    the SDK returns no-op implementations for all telemetry signals.
    The OTEL_SDK_DISABLED environment variable is only evaluated upon application
    startup, later changes have no effect.
    (#6568)

  • Added LowMemory temporality as an option in the OTLP metrics exporter.
    (#6648)

  • Added support for Meter.TelemetrySchemaUrl property.
    (#6714)

  • Improve performance and reduce memory consumption for metrics histograms.
    (#6715)

  • Decode value in OTEL_RESOURCE_ATTRIBUTES environment variable.
    (#6737)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api v1.15.0

  • Added a new overload for TracerProvider.GetTracer which accepts an optional
    string? schemaUrl parameter, allowing a schema URL to be set on the Tracer.
    (#6736)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Api.ProviderBuilderExtensions v1.15.0

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Console v1.15.0

  • Added support for ActivitySource.TelemetrySchemaUrl property.
    (#6713)

  • Added support for Meter.TelemetrySchemaUrl property.
    (#6714)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.InMemory v1.15.0

  • Added support for Meter.TelemetrySchemaUrl property.
    (#6714)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.OpenTelemetryProtocol v1.15.0

  • Added mTLS configuration support for the OTLP exporter (client cert/key and
    CA certificate options).
    (#6343)

  • Added UserAgentProductIdentifier property to OtlpExporterOptions to allow
    custom product identifiers to be prepended to the User-Agent header. When set,
    the custom identifier is prepended with a space separator to the default
    User-Agent string (e.g., MyApp/1.0 OTel-OTLP-Exporter-Dotnet/1.14.0).
    (#6686)

  • Added support for ActivitySource.TelemetrySchemaUrl property.
    (#6730)

  • Added support for Meter.TelemetrySchemaUrl property.
    (#6731)

  • Fix NullReferenceException when no bucket boundaries configured for a view.
    (#6773)

  • Added support for OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION
    environment variable to configure the default histogram aggregation for
    histogram instruments. Valid values are explicit_bucket_histogram (default)
    and base2_exponential_bucket_histogram. Explicit views configured via
    AddView take precedence over this setting.
    (#6778)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Exporter.Zipkin v1.15.0

  • This package is deprecated and it will stop receiving any updates in
    December 2026. Zipkin already supports OTLP ingestion. Change your exporter
    to OpenTelemetry.Exporter.OpenTelemetryProtocol as stated in the
    Deprecating Zipkin Exporter blog post.
    (#6750)

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Hosting v1.15.0

  No notable changes.

  See CHANGELOG for details.

• NuGet: OpenTelemetry.Extensions.Propagators v1.15.0

  • Deprecated JaegerPropagator. It will be removed in a future version.
    (#6819)

  See CHANGELOG for details.