No cache breakpoint marker found
PrefixAudit rule no-breakpoint · v0.1.0
Why it breaks your cache
On Anthropic nothing is cached unless cache_control is attached to the block. Setting the parameter is not automatic: a custom system prompt passed as a plain string bypasses the tagging code path entirely, so you pay a 1.25x write on every call and collect zero reads.
How to fix it
Attach cache_control: {"type":"ephemeral"} to the system block and/or the last tool definition. A breakpoint on the last tool also caches every tool before it. Then verify with cache_read_input_tokens > 0 on call 2.
How common is it?
This rule needs request or runtime context that an extracted prompt cannot supply, so it is excluded from the corpus study. It still runs in the auditor when you supply that context.
Estimated impact
Modelled as invalidating 0% of the cached prefix.
Is your prompt affected?
Paste it and find out. Static analysis, in-browser, nothing leaves the page.
Run the audit →