The interop harness prints `[cli] ingest <kind>/<id> via <relay> -> Failure`
for any commit/proposal/app message that quartz can't process. Without
the error string it's impossible to tell `confirmation_tag mismatch` from
`parent_hash invalid` from `commit references unknown proposal` without
reading the Kotlin stack. Append `result.message` for Failure outcomes so
the harness log is self-contained when diagnosing quartz→quartz errors
(the openmls side already has `{e:?}` via the mdk-core patch).
https://claude.ai/code/session_016kAxdp6ubB5CnF9URhCEzP
Claude
94c5e0e833