Per-request identifiers are inside the cached prefix
PrefixAudit rule volatile-id · v0.1.0
Why it breaks your cache
Request IDs, session IDs, trace IDs and UUIDs change on every call. Anything before them stops matching, so the whole prefix re-bills fresh.
How to fix it
Move IDs out of the system block entirely. Put them in the user turn or in a separate uncached system block placed AFTER the cache breakpoint.
How common is it?
Detected in 7 of 236 production system prompts (3%) across 16 vendors.
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 →