The setup
A content platform I was updating had a familiar-looking editor: write your post, mark a line as "everything above this is free preview," publish. Readers see the free part; paying customers see the rest. Standard paywall pattern, nothing exotic.
I needed to fix a batch of stale price references across several paid posts — pure text edits, nothing structural. Doing it by hand through the rich-text editor for a dozen posts is slow and error-prone, so I pulled each post's content through the platform's API, did the string replacement in code, and pushed the updated body back through the same API.
Fast, clean, verifiable diff before and after. Or so I thought.
What was actually happening
