Context editing, compaction and memory

Three mechanisms, three different jobs. Expect a "which one" question.

4 min read · Lesson 4 of 9 in this domain

Three mechanisms manage long-running context and they are routinely confused, so anchor them by what they physically do. Context editing prunes: stale tool results are removed and not replaced. Compaction summarises: earlier turns are condensed into a summary block so the conversation can continue past the window. Memory persists: files written to a memory directory outlive the session entirely. The first two operate within one session; only memory crosses sessions. A scenario asking about state surviving a restart has exactly one answer.

• Context editing — prunes. Clears stale tool results and thinking blocks. The content is removed, not summarised.
• Compaction — summarises. When a conversation approaches the window limit, earlier context is condensed server-side.
• Memory — persists. State survives across separate sessions via files in a memory directory.
• Critical compaction implementation detail: append the full response.content back to your message history. The compaction blocks must be preserved — extracting only the text silently loses the compaction state.
• Editing and compaction operate within a session; memory is across sessions. Many long-running agents use all three.
• None of these is max_tokens, which is only a per-response output cap.

Source: Claude Docs — Context editing · Independent study aid, not affiliated with or endorsed by Anthropic.