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Sweep 06 Nov 2026 · 01:32Z Build v2.1.319 537 read Stable v2.1.311 Latest v2.1.319 Next v2.1.319 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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compaction-background changedbuild-with-claude/compaction-background

Nearest release: v2.1.280, published 15 hours after 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 edits14to this page, all time

## Compatibility

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22title: Compaction in the background
33url: https://platform.claude.com/docs/en/build-with-claude/compaction-background
44description: Request an on-demand compaction summary while the conversation continues on its full history, then swap the block in when it arrives.
5featureMetadata:
6 status: beta
7 betaHeader: compact-2026-09-04
8 supportedModels:
9 - claude-fable-5-1
10 - claude-mythos-5-1
11 - claude-fable-5
12 - claude-mythos-5
13 - claude-mythos-preview
14 - claude-opus-5
15 - claude-opus-4-8
16 - claude-opus-4-7
17 - claude-opus-4-6
18 - claude-sonnet-5
19 - claude-sonnet-4-6
20 supportedPlatforms:
21 Claude API: beta
22 Claude Platform on AWS: beta
23 Amazon Bedrock: not available
24 Google Cloud: beta
25 Microsoft Foundry: beta
526---
6 
7## Compatibility
8- Status: Beta
9- [Beta header](https://platform.claude.com/docs/en/api/beta-headers): `compact-2026-09-04`
10- Supported models: `claude-fable-5-1`, `claude-mythos-5-1`, `claude-fable-5`, `claude-mythos-5`, `claude-mythos-preview`, `claude-opus-5`, `claude-opus-4-8`, `claude-opus-4-7`, `claude-opus-4-6`, `claude-sonnet-5`, `claude-sonnet-4-6`
11- Platforms: Claude API (beta), Claude Platform on AWS (beta), Microsoft Foundry (beta); not available on Amazon Bedrock, Google Cloud
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1328Background compaction, often called async compaction, changes two things in the [compaction loop](https://platform.claude.com/docs/en/build-with-claude/compaction-on-demand#compact-in-a-loop): the compaction request runs while the conversation continues on its full history, and the swap waits until the block arrives. [Continue from the summary](https://platform.claude.com/docs/en/build-with-claude/compaction-on-demand#continue-from-the-summary) and [Handle a missing summary or an error](https://platform.claude.com/docs/en/build-with-claude/compaction-on-demand#when-no-summary-comes-back) apply unchanged.
1429 
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