### Added

- Add experimental observability metrics to `BatchProcessor` in
`go.opentelemetry.io/otel/sdk/log`. (#7124)
- Add the experimental `WithUnsafeAttributes` no-copy attribute option
to `go.opentelemetry.io/otel/metric/x` for future performance
improvements. This API is a work in progress. (#8251)
- Add `Map` and `MapValue` functions for the new `MAP` attribute type in
`go.opentelemetry.io/otel/attribute`. (#8445)
- Support `MAP` attributes in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace`. (#8453)
- Support `MAP` attributes in
`go.opentelemetry.io/otel/exporters/otlp/otlplog`. (#8453)
- Support `MAP` attributes in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric`. (#8453)
- Support `MAP` attributes in
`go.opentelemetry.io/otel/exporters/zipkin`. (#8453)
- Apply `AttributeValueLengthLimit` recursively to values contained in
`attribute.MAP` attributes in `go.opentelemetry.io/otel/sdk/trace`.
(#8454)
- Remove duplicate keys from `attribute.MAP` values in
`go.opentelemetry.io/otel/sdk/resource` using last-value-wins semantics.
(#8471)
- Remove duplicate keys by default from `attribute.MAP` values in
instrumentation scope attributes in `go.opentelemetry.io/otel/sdk/log`
using last-value-wins semantics. (#8471)
- Remove duplicate keys by default from `attribute.MAP` values in span,
event, link, and instrumentation scope attributes in
`go.opentelemetry.io/otel/sdk/trace` using last-value-wins semantics.
(#8471)
- Remove duplicate keys by default from `attribute.MAP` values in
measurement and instrumentation scope attributes in
`go.opentelemetry.io/otel/sdk/metric` using last-value-wins semantics.
(#8471)
- Extend `WithAllowKeyDuplication` in `go.opentelemetry.io/otel/sdk/log`
to disable duplicate-key removal in `attribute.MAP` values for
instrumentation scope attributes. (#8471)
- Add the `go.opentelemetry.io/otel/semconv/v1.42.0` package.
The package contains semantic conventions from the `v1.42.0` version of
the OpenTelemetry Semantic Conventions.
See the [migration documentation](./semconv/v1.42.0/MIGRATION.md) for
information on how to upgrade from
`go.opentelemetry.io/otel/semconv/v1.41.0`. (#8484)
- Add `WithoutPanicRecording` as a `TracerProviderOption` in
`go.opentelemetry.io/otel/sdk/trace` to disable exception event
recording for panics. (#8532)
- Add the `go.opentelemetry.io/otel/semconv/v1.43.0` package.
The package contains semantic conventions from the `v1.43.0` version of
the OpenTelemetry Semantic Conventions.
See the [migration documentation](./semconv/v1.43.0/MIGRATION.md) for
information on how to upgrade from
`go.opentelemetry.io/otel/semconv/v1.42.0`. (#8628)

### Changed

- `HistogramReservoir` in `go.opentelemetry.io/otel/sdk/metric/exemplar`
now uses a time-unbiased sampling algorithm for exemplars. (#8306)
- ⚠️ **Breaking Change:** Use `go.opentelemetry.io/otel/attribute.Value`
and `go.opentelemetry.io/otel/attribute.KeyValue` for log bodies and
attributes in `go.opentelemetry.io/otel/log`,
`go.opentelemetry.io/otel/log/logtest`,
`go.opentelemetry.io/otel/sdk/log`, and
`go.opentelemetry.io/otel/sdk/log/logtest`. (#8490)
- Encode log bodies and attributes as
`go.opentelemetry.io/otel/attribute.Value` JSON in
`go.opentelemetry.io/otel/exporters/stdout/stdoutlog`. (#8490)
- Improve the performance of hashing `BOOLSLICE`, `INT64SLICE`,
`FLOAT64SLICE`, and `STRINGSLICE` attribute values by avoiding
reflection for short slices in `go.opentelemetry.io/otel/attribute`.
(#8511)
- ⚠️ **Breaking Change:** `WithEndpointURL` in
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp` no
longer appends the default signal path when an endpoint URL has no path,
making the behavior consistent with
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp` and with
setting the endpoint through `OTEL_EXPORTER_OTLP_METRICS_ENDPOINT`. If
the URL has no path component, the root path (`/`) is used. Use
`WithEndpointURL(url.JoinPath(endpoint, "/v1/metrics"))` to preserve the
previous behavior. (#8538)
- ⚠️ **Breaking Change:** `WithEndpointURL` in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp` no
longer appends the default signal path when an endpoint URL has no path,
making the behavior consistent with
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp` and with
setting the endpoint through `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT`. If
the URL has no path component, the root path (`/`) is used. Use
`WithEndpointURL(url.JoinPath(endpoint, "/v1/traces"))` to preserve the
previous behavior. (#8538)

### Deprecated

- Deprecate `WithExportBufferSize` in
`go.opentelemetry.io/otel/sdk/log`. The option remains available for
source compatibility but no longer affects behavior; `BatchProcessor` no
longer maintains a separate export-request buffer. (#8620)

### Removed

- ⚠️ **Breaking Change:** Remove `Kind`, `Value`, `KeyValue`, their
constructors, and attribute conversion helpers from
`go.opentelemetry.io/otel/log`. (#8490)
- ⚠️ **Breaking Change:** Remove the `AttributeValueLengthLimit` and
`AttributeCountLimit` fields from `RecordFactory` in
`go.opentelemetry.io/otel/sdk/log/logtest`; records produced by the
factory now keep attribute limits disabled so test code can append exact
attributes. (#8556)

### Fixed

- Fix an off-by-one error in `FixedSizeReservoir` in
`go.opentelemetry.io/otel/sdk/metric/exemplar` that prevented the first
exemplar from being sampled after the reservoir was filled. (#8309)
- Interpret HTTP `Retry-After` header values as seconds instead of
nanoseconds when retrying OTLP HTTP exports in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`,
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`, and
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#8383)
- Fix a memory leak in the `Reservoir` implementation in
`go.opentelemetry.io/otel/sdk/metric/exemplar`, where storing the full
`context.Context` pinned large objects such as gRPC transport buffers.
(#8389)
- Prevent a non-empty attribute set whose computed hash is zero from
collapsing to an empty set in `go.opentelemetry.io/otel/attribute`.
(#8402)
- Fix histogram data point reuse in
`go.opentelemetry.io/otel/sdk/metric` aggregation to avoid leaking stale
sum, minimum, and maximum values when they are disabled in subsequent
collections. (#8403)
- Avoid preallocating scope attributes when they are disabled in
`go.opentelemetry.io/otel/exporters/prometheus`. (#8404)
- Support HTTP-date values in the HTTP `Retry-After` header when
retrying OTLP HTTP exports in
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`,
`go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp`, and
`go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp`. (#8417)
- Reduce histogram heap allocations by reusing `BucketCounts` and
`Exemplars` slices across `Collect` cycles in the cumulative histogram
aggregation in `go.opentelemetry.io/otel/sdk/metric`. (#8428)
- Fix `go.opentelemetry.io/otel/exporters/stdout/stdouttrace`
self-observability to record `error.type` on the operation-duration
histogram when the `exportedSpans` metric is disabled. (#8432)
- Stop including trace exporter endpoint configuration in internal logs
from `go.opentelemetry.io/otel/sdk/trace`,
`go.opentelemetry.io/otel/exporters/otlp/otlptrace`,
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc`,
`go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp`, and
`go.opentelemetry.io/otel/exporters/zipkin`. (#8438)
- Fix invalid error formatting for out-of-range JSON code values in
`go.opentelemetry.io/otel/codes`. (#8497)
- Clarify in `go.opentelemetry.io/otel/log` that `Logger.Enabled` should
be checked for every log emission because its result may change over
time. (#8565)
- Preserve user-provided exception attributes while independently
deriving missing exception message and type attributes in
`go.opentelemetry.io/otel/sdk/log`. (#8566)
- Make `WithAttributeCountLimit(0)` and
`OTEL_LOGRECORD_ATTRIBUTE_COUNT_LIMIT=0` discard all log record
attributes in `go.opentelemetry.io/otel/sdk/log`. (#8570)
- Clarify that the `Record` methods of `Float64Histogram` and
`Int64Histogram` in `go.opentelemetry.io/otel/metric` expect
non-negative values. (#8574)
- Clarify in `go.opentelemetry.io/otel/log` that `LoggerProvider`
implementations should retain an empty `Logger` name instead of
replacing it with a default. (#8587)
- Ensure that the built-in processors in
`go.opentelemetry.io/otel/sdk/log` call exporter `ForceFlush` during
`Shutdown`. (#8599)
- Prevent panics in `go.opentelemetry.io/otel/bridge/opentracing` when
OpenTracing baggage is propagated concurrently with
`Span.SetBaggageItem`.
([GHSA-42cj-99w8-cp2p](GHSA-42cj-99w8-cp2p))
- Prevent processor operations in `go.opentelemetry.io/otel/sdk/log`
from overlapping with processor shutdown or running after
`LoggerProvider` shutdown. (#8608)
- Prevent `BatchProcessor` in `go.opentelemetry.io/otel/sdk/log` from
busy-spinning under exporter backpressure and serialize dequeue, export,
force-flush, and shutdown work in one worker. (#8620)
- Make `BatchProcessor` in `go.opentelemetry.io/otel/sdk/log` return
errors encountered while draining records during `ForceFlush` and
`Shutdown`, while continuing to attempt later batches as long as the
request context remains valid. (#8620)
- Keep the default `BatchProcessor` maximum export batch size in
`go.opentelemetry.io/otel/sdk/log` at or below the configured maximum
queue size. (#8620)