A VS Code agent session contains a long chat history, several attached files, and large tool outputs. As it approaches the model context limit, what is the best description of the constraint?

1. Each attachment has an independent unlimited context window in the same model request.
2. Compaction stores every prior token verbatim in a larger hidden request.
3. These inputs share the context window; older conversation details may be summarized or omitted during compaction.
4. Only the most recent typed user message counts toward the context limit.