update CHANGELOG.md and add comment to BoundedAttributes __deepcopy__ implementation

Author: herin049

CHANGELOG.md

@@ -22,7 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#4935](https://github.com/open-telemetry/opentelemetry-python/pull/4935))
 - `opentelemetry-sdk`: upgrade vendored OTel configuration schema from v1.0.0-rc.3 to v1.0.0
   ([#4965](https://github.com/open-telemetry/opentelemetry-python/pull/4965))
-- `opentelemetry-api`, `opentelemetry-sdk`: Add deepcopy support for `BoundedAttributes`
+- `opentelemetry-api`, `opentelemetry-sdk`: Add deepcopy support for `BoundedAttributes` and `BoundedList`
   ([#4934](https://github.com/open-telemetry/opentelemetry-python/pull/4934))
 
 ## Version 1.40.0/0.61b0 (2026-03-04)

opentelemetry-api/src/opentelemetry/attributes/__init__.py

@@ -328,6 +328,8 @@ def __deepcopy__(self, memo: dict) -> "BoundedAttributes":
         )
         memo[id(self)] = copy_
         with self._lock:
+            # Assign _dict directly to avoid re-cleaning already clean values
+            # and to bypass the immutability guard in __setitem__
             copy_._dict = copy.deepcopy(self._dict, memo)
             copy_.dropped = self.dropped
         return copy_