Overview
Compaction attempts to preserve meaning in fewer tokens.
A simple sentence such as "Hello, how are you doing?" can be compressed into "Hi, how are you?" The meaning remains similar while the representation becomes shorter.
The same idea is applied across a much larger conversation. Repetition is removed, detailed sequences are summarized, and information is rewritten more densely.
This increases information density, but it also changes the context. A summary cannot preserve every detail of the original. A complex tool result or technical decision may be reduced to a general statement.
For this reason, critical project information should not depend entirely on a long conversation history. Important requirements, decisions, and state should be stored in deliberate files or structured records that can be re-read when needed.