DynamicMessage violates contract of hashCode()

What version of protobuf and what language are you using?
Version: protoc 28.3 / protobuf-java 4.28.3
Language: Java

What operating system (Linux, Windows, ...) and version?
Windows 11

What runtime / compiler are you using (e.g., python version or gcc version)
BellSoft Liberica 21.0.2

What did you do?

syntax = "proto3";
option java_multiple_files = true;

message ExampleMessage {
  uint32 i = 1;
}

ExampleMessage message = ExampleMessage.newBuilder().build();
DynamicMessage dynamicMessage = DynamicMessage.parseFrom(ExampleMessage.getDescriptor(), message.toByteArray());
System.out.println("objects equal:   " + message.equals(dynamicMessage));
System.out.println("hashcodes equal: " + (message.hashCode() == dynamicMessage.hashCode()));

Output:

objects equal:   true
hashcodes equal: false

What did you expect to see
The DynamicMessage's hashcode should be the same as the real message's hashcode since equals() returns true.

What did you see instead?
The hashcodes are not the same. This issue only seems to happen if the message has a field which is not set.

Anything else we should know about your project / environment
n/a

The report identifies Java DynamicMessage and a generated ExampleMessage as the entry points; first reproduce the equality/hashCode mismatch with the provided proto and Java snippet, then inspect their equality and hashCode behavior. Done means equal messages produce identical hash codes, including when fields are unset, with regression coverage for this case.