## Changes

Addressing feedback received during the last Spec SIG meeting, I'm
splitting my previous
PR(#4533)
into two to ensure we keep the scope of the original one for the
configuration changes.

If I understand correctly, almost all SDKs (if not all) are already
compliant since they are wrappers around Prometheus SDKs, and Prometheus
SDKs already do content negotiation properly. Then the PoCs are already
done :)

* [X] Related issues #4494 
* [ ] Links to the prototypes (when adding or changing features)
* [x]
[`CHANGELOG.md`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/CHANGELOG.md)
file updated for non-trivial changes
* [ ]
[`spec-compliance-matrix.md`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/spec-compliance-matrix.md)
updated if necessary

---------

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>
Co-authored-by: Reiley Yang <reyang@microsoft.com>
Co-authored-by: David Ashpole <dashpole@google.com>

Fixes #7039
Fixes #6704

This uses the common prometheus/otlptranslator library to handle name
conversion. It was a little tricky to work around the fact that the
library only lets us configure whether all suffixes are added or not.
But we want to keep supporting WithoutUnit and WithoutCounterSuffixes
for a while longer. Those will eventually be deprecated and replaced
after
open-telemetry/opentelemetry-specification#4533
is released.

We decided to go ahead with the changes despite it being a small
behavioral change when UTF8 is enabled. See:
prometheus/otlptranslator#44 for the
rationale.

This adds a unit test to verify that it properly handles bracketed
units. The test fails on main with:

```
--- FAIL: TestPrometheusExporter (0.01s)
    --- FAIL: TestPrometheusExporter/counter_with_bracketed_unit (0.00s)
        exporter_test.go:646:
            	Error Trace:	/usr/local/google/home/dashpole/go/src/go.opentelemetry.io/opentelemetry-go/exporters/prometheus/exporter_test.go:646
            	Error:      	Received unexpected error:
            	            	-# HELP "foo_{spans}_total" a simple counter
            	            	-# TYPE "foo_{spans}_total" counter
            	            	-{"foo_{spans}_total",A="B",C="D",E="true",F="42",otel_scope_fizz="buzz",otel_scope_name="testmeter",otel_scope_schema_url="",otel_scope_version="v0.1.0"} 24.3
            	            	-{"foo_{spans}_total",A="D",C="B",E="true",F="42",otel_scope_fizz="buzz",otel_scope_name="testmeter",otel_scope_schema_url="",otel_scope_version="v0.1.0"} 5
            	            	+# HELP foo_total a simple counter
            	            	+# TYPE foo_total counter
            	            	+foo_total{A="B",C="D",E="true",F="42",otel_scope_fizz="buzz",otel_scope_name="testmeter",otel_scope_schema_url="",otel_scope_version="v0.1.0"} 24.3
            	            	+foo_total{A="D",C="B",E="true",F="42",otel_scope_fizz="buzz",otel_scope_name="testmeter",otel_scope_schema_url="",otel_scope_version="v0.1.0"} 5
            	            	 # HELP target_info Target metadata
            	            	 # TYPE target_info gauge
            	            	 target_info{"service.name"="prometheus_test","telemetry.sdk.language"="go","telemetry.sdk.name"="opentelemetry","telemetry.sdk.version"="latest"} 1

            	Test:       	TestPrometheusExporter/counter_with_bracketed_unit
2025/07/18 15:07:47 internal_logging.go:50: "msg"="Using existing type definition." "error"="instrument type conflict" "instrument"="foo_total" "existing"="COUNTER" "dropped"="GAUGE"
2025/07/18 15:07:47 internal_logging.go:50: "msg"="Using existing type definition." "error"="instrument type conflict" "instrument"="foo_bytes" "existing"="GAUGE" "dropped"="HISTOGRAM"
FAIL
FAIL	go.opentelemetry.io/otel/exporters/prometheus	0.054s
FAIL
```

cc @TylerHelmuth @ywwg @ArthurSens

---------

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>
Co-authored-by: Robert Pająk <pellared@hotmail.com>

#### Description
Implements `translation_strategy` as described in
open-telemetry/opentelemetry-specification#4533

#### Link to tracking issue
Fixes #35459

<!--Describe what testing was performed and which tests were added.-->
#### Testing

<!--Describe the documentation added.-->
#### Documentation

<!--Please delete paragraphs that you did not use before submitting.-->

---------

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

…#41530)

#### Description
Implements `translation_strategy` as described in
open-telemetry/opentelemetry-specification#4533

#### Link to tracking issue
Fixes open-telemetry#35459

<!--Describe what testing was performed and which tests were added.-->
#### Testing

<!--Describe the documentation added.-->
#### Documentation

<!--Please delete paragraphs that you did not use before submitting.-->

---------

Signed-off-by: Arthur Silva Sens <arthursens2005@gmail.com>

August 2025 release.

### Logs

- Improve concurrency safety description of `LogRecordProcessor.OnEmit`.

([#4578](#4578))
- Clarify that `SeverityNumber` values are used when comparing
severities.

([#4552](#4552))

### Entities

- Mention entity references in the stability guarantees.

([#4593](#4593))

### OpenTelemetry Protocol

- Clarify protocol defaults on specification.

([#4585](#4585))

### Compatibility

- Flexibilie escaping of characters that are discouraged by Prometheus
Conventions
  in Prometheus exporters.

([#4533](#4533))
- Flexibilize addition of unit/type related suffixes in Prometheus
exporters.

([#4533](#4533))
- Define the configuration option "Translation Strategies" for
Prometheus exporters.

([#4533](#4533))
- Define conversion of Prometheus native histograms to OpenTelemetry
exponential histograms.

([#4561](#4561))
- Clarify what to do when scope attribute conflicts with name, version
and schema URL.

([#4599](#4599))

### SDK Configuration

- Enum values provided via environment variables SHOULD be interpreted
in a case-insensitive manner.

([#4576](#4576))

Co-authored-by: Armin Ruech <7052238+arminru@users.noreply.github.com>