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Sweep 22 Oct 2026 · 21:04Z Build v2.1.309 528 read Stable v2.1.308 Latest v2.1.309 Next v2.1.309 Feeds RSS JSON llms.txt llms-full.txt Unofficial
HomeDocsClaude Developer Platform 23 Oct 2026
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compaction-background changedbuild-with-claude/compaction-background

Nearest release: v2.1.309, published 3 hours before this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.

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First seen 21 Sep 2026 this site's first read of the page
Recorded edits12to this page, all time

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2323 supportedPlatforms:
2424 Claude API: beta
2525 Claude Platform on AWS: beta
26 Google Cloud: beta
26 Claude Models on Google Cloud (Google managed): beta
2727 Microsoft Foundry: beta
2828---
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4141For example, if the compaction request held messages 1 to 5 and the conversation gained messages 6 to 8 while it ran, after the swap your history is the block followed by messages 6 to 8.
4242 
4343<Frame>
44 ![Background compaction: while a compaction request for messages 1 to 5 runs, 6 to 8 arrive; then the block replaces 1 to 5](https://platform.claude.com/docs/images/compaction-background-timeline.svg)
44 ![Messages 6 to 8 join the full history while messages 1 to 5 are summarized; the arriving block then replaces messages 1 to 5](https://platform.claude.com/docs/images/compaction-background-timeline.svg)
4545</Frame>
4646 
4747If the response has any other `stop_reason`, no summary was produced, which counts as a failure in step 2. Keep the full history; [Handle a missing summary or an error](https://platform.claude.com/docs/en/build-with-claude/compaction-on-demand#when-no-summary-comes-back) lists the causes and what to do for each.
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