Mimir's optional local API proxy ("Headroom"-style, our own implementation).
It sits between the agent and api.anthropic.com: forwards every request
verbatim (streaming SSE back untouched) EXCEPT it may rewrite the body of
POST /v1/messages to add prompt-cache breakpoints, dedup repeated blocks,
and (optionally) prune stale tool results. Cache savings are MEASURED from
the response's usage.cache_read_input_tokens; dedup/prune are measured at
the request.
It is OFF by default (you start it with mimir proxy) and it is a
man-in-the-middle on your prompts/completions — see docs/proxy.md. Auth
headers pass through untouched; the proxy never reads your API key.