Skills
Claude Code now tells you why the prompt cache missed instead of just charging you for it
Release 2.1.260 adds a likely cause for prompt-cache misses, naming things like changed tool definitions, a changed system prompt, or idling past the TTL, to both /cost and the status line's prompt_cache field. The same release fixes prompt caching on Claude Fable 5.1 not covering the context attached after tool results, which meant that context was re-sent as uncached input on every tool-call turn, and makes /effort changes mid-session no longer invalidate the cache on Fable 5.1. For long agent sessions the Fable fix is the material one: tool-heavy turns were silently paying full input price for the attached context.
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