Messages and removal records

Send messages between systems and observe component removals.

Registering a message

An unmanaged [Message] value is registered through an included system parameter, IncludeMessage<T>, or WorldBuilder.AddMessage<T>().

Writers and readers

• scoped MessageWriter<T> sends values with Send(in value).
• scoped MessageReader<T> enumerates unread retained values and exposes MissedCount.

Readers own independent cursors. Writers conflict with readers and with other writers of the same message type. An explicitly ordered reader sees a writer’s messages in the same schedule execution.

Retention

world.SendMessage(in value) sends while the world is idle. world.AdvanceMessages() rotates retention while idle. The current and previous rotations remain available, so a message expires on the second rotation after it was sent.

A reader that falls behind sees skipped records in MissedCount.

Removal records

scoped RemovedComponents<T> enumerates Removal records with Entity and Tick. It has the same retention and missed-count behavior as messages. Recording for a component begins when its removal reader is bound.