When concatenating literal values with a newline separator in group_concat, always escape existing backslashes and replace CR/LF sequences in the individual values first: replace(replace(?val, \"\\\\\\\\\", \"\\\\\\\\\\\\\\\\\"), \"[\\r\\n]+\", \"\\\\\\\\n\"). First escape existing backslashes (\\\\ → \\\\\\\\), then replace any sequence of CR/LF characters with the two-character escape \\\\n. This ensures values containing these characters can be safely split on newlines later.