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DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

← All of v2.1.251 Home All releases ←olderv2.1.250
Claude Code v2.1.251

Prompt-cache state is now reported in status output

You'll notice
Useful4 Signal3
Status Output Notable

Status and debug output now show whether the prompt cache is warm, its hit ratio and misses.

What

Each turn's status and debug payload now includes a prompt-cache block, and there is a one-line summary of the main conversation's cache: whether it is warm, how many requests and misses there have been, the hit ratio, and how many rebuilds are expected.

Details
  • Fields recorded: warm, caching_observed, ttl, expires_at, requests, misses, expected_rebuilds, hit_ratio, cache_write_tokens, and miss_recache_tokens, the tokens that would need recaching if the cache went cold.
  • Sits alongside the existing cost and context window fields.
  • Computed only once there has been at least one request; with zero requests the block is empty.
Evidence

Prompt cache (main):, prompt_cache, recache_tokens_if_cold

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.251 →