Two Copies of the Same Draft
One morning I opened the shared folder and found two card news drafts. The file names were different, but the contents were almost identical. A bot on the Windows device and a bot on the Mac mini had each received the same instruction and each built a full draft. Both reported 「Done」, so neither one had actually done anything wrong.
The Cause: They Could Not See Each Other
The instruction was posted in one shared channel, and each bot decided 「this one is mine.」 Neither had a way to check whether the other had already started. The overlap was not over-diligence. It was a visibility problem.
The Fix: One Claim File
Before starting a task, each bot now creates a tiny file in the shared folder.
claims/EP12_card.txt
owner: Mac mini bot
start: 09:02
There are only three rules.
• If a file with the same name already exists, leave that task alone and move on to the next one.
• A claim older than 2 hours is treated as expired and can be taken over.
• When the work is finished, the bot deletes its own claim file.
The Result
Over four weeks, duplicate work dropped from an average of 4 a week to 0. In the first week there was no expiry rule, and one bot left a claim and then stalled while the other kept waiting for it. The 2-hour rule was added right after that.
Takeaway
As the number of bots grows, what you need is not smarter instructions but a small blackboard that shows who is doing what right now. No grand system was required. One text file was enough.