Specificationv1.55.0

5 Mar 2026since v1.54.0

9 breaking11 notable13 editorial

From the upstream release notes

Add normative language to the Tracing API/SDK spec concurrency requirements.
Add additional in-development requirements to metric start timestamps.
Stabilize optional Exception parameter to Logger Emit.
Stabilize Prometheus Summary to OTLP Summary transformation.
Declarative configuration: allow language-specific prefixes in environment
Mark significant portions of declarative configuration as stable.

Read the full release notes

Breaking9

Requirements added to, removed from, or restrengthened in a document marked Stable.

new rulerequirementconfiguration/data-model.md#environment-variable-substitutionMUST added: When PREFIX is absent or env, GENERIC-SUBSTITUTION MUST conform to ENV-SUBSTITUTION:
new rulerequirementtrace/api.md#concurrency-requirementsMUST added: TracerProvider - all methods MUST be documented that implementations need to be safe for concurrent use by default.
new rulerequirementtrace/api.md#concurrency-requirementsMUST added: Tracer - all methods MUST be documented that implementations need to be safe for concurrent use by default.
new rulerequirementtrace/api.md#concurrency-requirementsMUST added: Span - all methods MUST be documented that implementations need to be safe for concurrent use by default.
new rulerequirementtrace/api.md#concurrency-requirementsMUST added: Event - Events are immutable and MUST be safe for concurrent use by default.
new rulerequirementtrace/sdk.md#concurrency-requirementsMUST added: Tracer Provider - Tracer creation, ForceFlush and Shutdown MUST be safe to be called concurrently.
new rulerequirementtrace/sdk.md#concurrency-requirementsMUST added: Sampler - ShouldSample and GetDescription MUST be safe to be called concurrently.
new rulerequirementtrace/sdk.md#concurrency-requirementsMUST added: Span processor - all methods MUST be safe to be called concurrently.
new rulerequirementtrace/sdk.md#concurrency-requirementsMUST added: Span Exporter - ForceFlush and Shutdown MUST be safe to be called concurrently.

Notable11

removedsectiontrace/api.md#concurrencySection "Concurrency" removed.
stabilitydocumentconfiguration/api.mdStatus changed from Development to Mixed.
stabilitydocumentconfiguration/data-model.mdStatus changed from Development to Stable.
stabilitydocumentconfiguration/sdk.mdStatus changed from Development to Stable.
new rulerequirementcompatibility/prometheus_and_openmetrics.md#summariesMUST added: In text formats where Prometheus Summaries are represented by multiple samples, samples with same metric family name MUST be merged together into a single OTLP Summary.
new rulerequirementconfiguration/data-model.md#environment-variable-substitutionMAY added: Language implementations MAY support additional prefixes beyond env: to access language-specific configuration sources.
new rulerequirementconfiguration/data-model.md#environment-variable-substitutionSHOULD added: Language implementations SHOULD document any additional prefixes they support.
new rulerequirementmetrics/sdk.md#start-timestampsMUST added: For delta aggregations, the start timestamp MUST equal the previous collection interval's timestamp, or the creation time of the instrument if this is the first collection interval for the instrument.
new rulerequirementmetrics/sdk.md#start-timestampsMUST added: This implies that all data points with delta temporality aggregation for an instrument MUST share the same start timestamp.
new rulerequirementmetrics/sdk.md#start-timestampsMUST added: Cumulative timeseries MUST use a consistent start timestamp for all collection intervals.
new rulerequirementtrace/api.md#concurrency-requirementsSHOULD added: Link - Links are immutable and SHOULD be safe for concurrent use by default.

Editorial13

removedsectionconfiguration/sdk.md#via-otelexperimentalconfig_fileSection "Via OTELEXPERIMENTALCONFIG_FILE" removed.
new rulerequirementmetrics/sdk.md#start-timestampsSHOULD added: For synchronous instruments, the start timestamp SHOULD be the time of the first measurement for the series.
new rulerequirementmetrics/sdk.md#start-timestampsSHOULD added: For asynchronous instrument, the start timestamp SHOULD be:
rewordedrequirementconfiguration/sdk-environment-variables.md#declarative-configurationMUST reworded: When OTELCONFIGFILE is set, all other environment variables besides those referenced in the configuration file for environment variable substitution MUST be ignored.
rewordedrequirementconfiguration/sdk-environment-variables.md#declarative-configurationMAY reworded: Implementations MAY provide a mechanism to customize the configuration model parsed from OTELCONFIGFILE.
rewordedrequirementconfiguration/sdk.md#createMAY reworded: Status: Development SDK implementations MAY provide options to allow programmatic customization of the components initialized by Create.
rewordedrequirementlogs/api.md#emit-a-logrecordMAY reworded: The API MAY accept the following parameter:
rewordedrequirementlogs/sdk.md#emit-a-logrecordMUST reworded: If an Exception is provided, the SDK MUST by default set attributes from the exception on the LogRecord with the conventions outlined in the exception semantic conventions.
addedsectionconfiguration/sdk.md#via-otelconfigfileNew section "Via OTELCONFIGFILE".
addedsectionmetrics/sdk.md#start-timestampsNew section "Start timestamps".
addedsectiontrace/api.md#concurrency-requirementsNew section "Concurrency requirements".
addedsectiontrace/sdk.md#concurrency-requirementsNew section "Concurrency requirements".
rewrittensectioncompatibility/prometheus_and_openmetrics.md#summaries"Summaries" substantially rewritten (802 to 1252 characters).