Merge branch 'main' into old_short_name

CHANGELOG.md

@@ -21,6 +21,9 @@ release.
 
 ### Logs
 
+- Add environment variables for configuring the `BatchLogRecordProcessor`.
+  ([#2785](https://github.com/open-telemetry/opentelemetry-specification/pull/2785))
+
 ### Resource
 
 - Add `browser.mobile` and `browser.language` resource attributes
@@ -38,6 +41,8 @@ release.
 
 - Add user agent to OTLP exporter specification
   ([#2684](https://github.com/open-telemetry/opentelemetry-specification/pull/2684))
+- Clarify that unknown fields must be ignored when receiving OTLP/JSON
+  ([#2816](https://github.com/open-telemetry/opentelemetry-specification/pull/2816))
 
 ### SDK Configuration
 
@@ -93,8 +98,6 @@ release.
   ([#2768](https://github.com/open-telemetry/opentelemetry-specification/pull/2768)).
 - Add the signal-specific OTEL_EXPORTER_OTLP_LOGS_* environment variables
   ([#2782](https://github.com/open-telemetry/opentelemetry-specification/pull/2782)).
-- Add environment variables for configuring the `BatchLogRecordProcessor`.
-  ([#2785](https://github.com/open-telemetry/opentelemetry-specification/pull/2785))
 
 ### Resource
 

specification/protocol/otlp.md

@@ -419,6 +419,11 @@ for mapping between Protobuf and JSON, with the following deviations from that m
   represented like this:
   { "kind": 2, ... }
 
+- OTLP/JSON receivers MUST ignore message fields with unknown names and MUST unmarshal the
+  message as if the unknown field was not present in the payload.
+  This aligns with the behavior of the Binary Protobuf unmarshaler and ensures that adding
+  new fields to OTLP messages does not break existing receivers.
+
 Note that according to [Protobuf specs](
 https://developers.google.com/protocol-buffers/docs/proto3#json) 64-bit integer
 numbers in JSON-encoded payloads are encoded as decimal strings, and either