All five client CLIs now share one credential contract for `authenticate-user`:
flags `--password` / `--password-env` (Go: `-password` / `-password-env`) with
default env `MXGATEWAY_VERIFY_PASSWORD`, resolution flag-then-env, and a resolved
credential that is missing *or empty* is a usage error naming the flag and the
variable. The value is never echoed and never reaches the wire.
Go and Java previously sent an empty credential when the variable was unset,
turning a misconfigured environment into a real MXAccess authentication attempt.
Go now returns the guard error before dialing; Java throws a picocli
ParameterException instead of falling back to "". Python's `--password-env`
gained the canonical default and its UsageError names the resolved variable.
Rust treats an empty flag or env value as missing, with the resolution extracted
into a testable `resolve_verify_user_password`. .NET adopts the canonical flags
and keeps `--verify-user-password`, `--verify-user-password-env`, and
MXGATEWAY_VERIFY_USER_PASSWORD as deprecated aliases for one release.
Docs same commit: CrossLanguageSmokeMatrix.md gains the credential contract and
the per-CLI subcommand-coverage table (the documented-not-fixed half of the
finding); all five READMEs name the canonical variable and the fail-fast rule,
and the .NET README carries the deprecation note. Tracking flipped to Done in
both remediation registers with a change-log row.
No .proto changed; no generated code regenerated.
Joseph Doherty
37cb3b0df8