Function profile 

pub(crate) fn profile() -> &'static str

What this run was built as, which moves the headline figure by 7x.

Same transcript, same command: a debug build reads 1,413 ms where a release one reads 204, and a debug CLIENT reads 2,695 ms of wall where a release one reads 1,250.

This is the MEASURING CLIENT’s build, and it is not the server’s. A row’s charged_cpu_ms is the server’s CPU, which moves with the server’s own build, and the two can differ: a release client measuring a debug server reports client_profile: release about a server built debug. The server’s build is announced by its own serve line and is not recoverable from a row - --pid is an address, and the greeting carries a protocol version rather than a build.

The serve line uses this too, and there the caller IS the server. It says which build is listening; a row’s client_profile says which build is measuring. Two processes, and they can disagree.