A guide to building self-checking loops in Claude Projects and Cowork for ecommerce sellers.
A prompt gives you one answer and waits for you to decide what's next. A loop gives Claude a job, a quality standard, and a rule for when to give up. Claude drafts, checks its own work against your criteria, finds the weak spot, fixes it, and repeats until the work actually clears the bar — before you ever see it.
Think of it as the difference between a VA you micromanage (one tiny task, check, next task, check) and one you trust with a brief: "Here's the standard. Don't come back until every box is checked."
Every loop needs three parts:
The check is everything. If you can't explain to a new hire how to tell whether the work is done, you can't explain it to Claude either.
Where this comes from: In June 2026, the head of Claude Code at Anthropic said he no longer writes prompts — he writes loops that prompt Claude for him. Google's Addy Osmani coined the term "loop engineering" the next day. This is the direction the builders of these tools are explicitly moving.
This is the version any seller can use today. No Cowork, no desktop app, nothing to install. You paste a loop protocol into the custom instructions of a Claude Project, and every conversation in that Project follows the loop automatically.