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Sweep 22 Oct 2026 · 04:32Z Build v2.1.308 527 read Stable v2.1.308 Latest v2.1.308 Next v2.1.308 Feeds RSS JSON llms.txt llms-full.txt Unofficial
A new release is waiting v2.1.309 npm has it, but its platform binary is not downloadable yet
HomeDocsClaude Developer Platform 21 Aug 2026
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Request 2 caches its request content (not the response) changedbuild-with-claude/prompt-caching

Nearest release: v2.1.239, published 2 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 14 Aug 2026 this site's first read of the page
Recorded edits26to this page, all time

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659659| **Non-tool results passed to extended thinking requests** | ✓ | ✓ | Model-specific | On Opus 4.5+ and Sonnet 4.6+, thinking blocks are preserved by default, so the cache remains valid (✓). On earlier Opus/Sonnet models and all Haiku models, all previously-cached thinking blocks are stripped from context, and any messages that follow those thinking blocks are removed from the cache (✘). For more details, see [Caching with thinking blocks](https://platform.claude.com/docs/en/build-with-claude/prompt-caching#caching-with-thinking-blocks). |
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661661<Note>
662 On Claude Fable 5, [Claude Mythos 5](https://anthropic.com/glasswing), Claude Opus 4.8, Claude Opus 5, and Claude Sonnet 5, you can add a new system instruction partway through a conversation without invalidating the system or message caches. Append a `{"role": "system"}` message to `messages` instead of editing the top-level `system` field, so the cached prefix stays unchanged. See [Mid-conversation system messages](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages).
662 On Claude Fable 5, [Claude Mythos 5](https://anthropic.com/glasswing), Claude Opus 4.8, and Claude Opus 5, you can add a new system instruction partway through a conversation without invalidating the system or message caches. Append a `{"role": "system"}` message to `messages` instead of editing the top-level `system` field, so the cached prefix stays unchanged. This feature is not available on Claude Sonnet 5; use the top-level `system` field instead. See [Mid-conversation system messages](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages).
663663</Note>
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665665### Tracking cache performance
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