What I Saw When I Opened the Site
One Monday morning, the same article was on the site twice. The title and body were identical, and only the publish time differed, by four minutes. My first guess was a drifting clock, but the culprit was somewhere else.
The Cause Was Two Scheduled Jobs
I had moved a scheduled job from the Windows device to the Mac mini, switched on the new one, and never switched off the old one. That was the whole story. Two machines did the same task at the same time. Both worked perfectly, so there was no error message at all, which is exactly why I noticed so late. Automation makes quieter trouble when it doubles than when it breaks.
Three Fixes
1. Before publishing, the bot now asks, 「Is there already an article with this title today?」
2. Each article gets a short ID built from its date and topic, and a repeated ID is skipped.
3. The first line of my moving checklist is now 「Turn off the old job.」
Pre-publish check
• Same ID already exists today → do not publish, only write a log line
• Otherwise → publish
What I Learned
• Making a job safe to run twice is sturdier than trying to guarantee it runs once.
• On moving day, clean up the old place before you set up the new one.
• A 「skipped」 line in the log is not a failure. It is the safety net doing its job.
Deleting the duplicate article took a minute, but the one-line check that prevents duplicate runs now sits on every scheduled job.