How Claude Code uses prompt caching changedprompt-caching
Nearest release: v2.1.260, published 4 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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2929The prefix-match rule explains most of the behaviors on this page. [Plan mode](/docs/en/permission-modes#analyze-before-you-edit-with-plan-mode) and [skill loading](/docs/en/skills), for example, append their instructions as conversation messages, so the cached prefix stays intact.
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31Two settings aren't part of the prompt text at all, so they don't appear in the layer table, but both are part of the cache key:
31Two settings don't appear in the layer table but still affect what stays cached:
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3333* **Model**: each model has its own cache. Switching models recomputes the entire request even when the content is identical. See [Switching models](#switching-models) below.
34* **Effort level**: each effort level has its own cache for the same model. Changing effort mid-session recomputes the entire request. See [Changing effort level](#changing-effort-level) below.
34* **Effort level**: on most models, each effort level has its own cache, so changing effort mid-session recomputes the entire request. On Fable 5.1 with an API key or a Claude subscription, the cache stays intact by default. See [Changing effort level](#changing-effort-level) below.
3535
3636<Tip>
3737 Pick your model and effort level at the top of a session, then save `/compact` for natural breaks between tasks. The fewer changes you make mid-task, the higher your cache hit rate.
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8989### Changing effort level
9090
91The cache is keyed by [effort level](/docs/en/model-config#adjust-effort-level) as well as model, so switching with `/effort` means the next request reads the entire conversation history with no cache hits. Changing effort follows the same confirmation as [switching models](#switching-models). When a change resolves to the same level already in effect, such as setting the model's default explicitly, Claude Code keeps the cache and applies the change without asking.
91On most models, changing the [effort level](/docs/en/model-config#adjust-effort-level) mid-session means the next request reads the entire conversation history with no cache hits. While the cache is still warm, Claude Code asks you to confirm the change first.
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93On Fable 5.1 with an API key or a Claude subscription, changing effort keeps the cache, and Claude Code applies the new level without asking. This doesn't apply on Amazon Bedrock, Google Cloud's Agent Platform, or a [Claude apps gateway](/docs/en/claude-apps-gateway), or when you set [`CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS`](/docs/en/llm-gateway-protocol#disable-pre-release-capabilities) or your organization has a HIPAA configuration.
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95Before v2.1.260, changing effort on Fable 5.1 with an API key or a Claude subscription also invalidated the cache.
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9397### Turning on fast mode
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