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Sweep 09 Oct 2026 · 17:27Z Build v2.1.296 517 read Stable v2.1.287 Latest v2.1.296 Next v2.1.296 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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compaction-on-demand changedbuild-with-claude/compaction-on-demand

Nearest release: v2.1.296, published an hour 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 edits9to this page, all time

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2323 supportedPlatforms:
2424 Claude API: beta
2525 Claude Platform on AWS: beta
26 Amazon Bedrock: not available
2726 Google Cloud: beta
2827 Microsoft Foundry: beta
2928---
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834833* **Threshold compaction and context editing.** You can't send `compaction` and `context_management` on the same request. Threshold compaction (`compact_20260112`) can't run on a request that carries a signed block.
835834* **Prompt caching.** `cache_control` on the block places a breakpoint after the summary.
836* **Mid-conversation system messages and tool changes.** `role: "system"` messages inside the summarized range are summarized too, so their text instructions stop applying once the block replaces them. If an instruction still matters, state it again in a `role: "system"` message. Send that message right after your next new `user` turn, and leave it in your history from then on. For [tool changes](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages#mid-conversation-tool-changes), and for where that message goes when you keep turns after the block, see [Change the system prompt or tools](https://platform.claude.com/docs/en/build-with-claude/compaction-thinking-blocks#change-the-system-prompt-or-tools).
835* **Mid-conversation system messages and tool changes.** `role: "system"` messages inside the summarized range are summarized too, so their text instructions stop applying once the block replaces them. A [per-message effort](https://platform.claude.com/docs/en/build-with-claude/effort#change-effort-mid-conversation-beta) level they set isn't carried over either: until a later message sets a level, turns run at the request's top-level `output_config.effort`, or the model's default if you don't set one. If an instruction or effort level still matters, state it again in a `role: "system"` message. Send that message right after your next new `user` turn, and leave it in your history from then on. For [tool changes](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages#mid-conversation-tool-changes), and for where that message goes when you keep turns after the block, see [Change the system prompt or tools](https://platform.claude.com/docs/en/build-with-claude/compaction-thinking-blocks#change-the-system-prompt-or-tools).
837836* **Task budgets.** Don't send the `remaining` value of a [task budget](https://platform.claude.com/docs/en/build-with-claude/task-budgets) (`output_config.task_budget.remaining`) with `compaction` or on requests that carry the block. Doing so returns a 400 error.
838837* **Token counting.** The [token counting](https://platform.claude.com/docs/en/build-with-claude/token-counting) endpoint ignores the `compaction` parameter.
839838* **Content the summary can't carry.** Images, documents, `container_upload` blocks, and fetched URLs inside the summarized messages are gone once the block replaces them. Restate or re-upload anything a later turn still needs.
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