The action logging in Koha/Config/SysPref.pm does not pass the $original parameter to logaction(), so no structured diff is generated in the action_logs.diff column. Affected calls in Koha/Config/SysPref.pm: - SYSTEMPREFERENCE/MODIFY or ADD (~line 47): C4::Log::logaction( 'SYSTEMPREFERENCE', $action, undef, $self->variable . ' | ' . $self->value ); (concatenates variable name and new value into a string; no before state) - SYSTEMPREFERENCE/DELETE (~line 63): C4::Log::logaction( 'SYSTEMPREFERENCE', 'DELETE', undef, " $variable | $value" ); System preference changes are important for configuration audit trails. This bug covers updating store() in Koha::Config::SysPref to capture the pre-change value and pass it as $original, and to pass a structured hashref (e.g. { variable => ..., value => ... }) as $infos so the diff mechanism can produce a clear before/after comparison.