Finding a bug in GNU Tar, and tracking down the problem: https://utcc.utoronto.ca/~cks/space/blog/sysadmin/TarFindingTruncateBug
(Old tools are often robust, but by no means bug free!)
Related Posts
Chekhov's repro: If a line of code is included in a bug report, it should contribute to the debugging somewhere.
"After I linked difftastic, one of my friends immediately used difftastic to find a stealthy bug, five stars!"
https://www.scannedinavian.com/tools-built-on-tree-sitters-concrete-syntax-trees.html
I've added syntax highlighting to the prompt of my programming language!
It's not strictly necessary, but it's nice to have. It caught a bug with lexing incomplete string literals too.