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Sweep 22 Sep 2026 · 17:19Z Build v2.1.280 501 read Stable v2.1.267 Latest v2.1.280 Next v2.1.280 Feeds RSS JSON llms.txt Unofficial
Claude Code v2.1.257 ·

Tool-definition prompt cache key gains new bits for query source and prompt trimming

The tool-definition cache key now also reflects the query source and whether prompt trimming was applied.

TierUnder the hoodhow much it should matter to you
Useful2my rating, 1 to 5
Signal3worth watching, 1 to 5
AreaPrompt Cachingwhat it touches
KindInternal Changesin v2.1.257,
Under the hood

The tool-definition cache key now also reflects the query source and whether prompt trimming was applied.

The cache key used to reuse compiled tool definitions across turns now also factors in whether the query came from a particular source, adding a new "K:" prefix, and whether first-line pre-read or bash-first prompt trimming was applied. This joins the existing lean-prompt ("L:") and grep ("G:") bits already in the key.

See this entry in the whole of v2.1.257 →

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