Picture a shared kitchen with one master recipe binder on a stand. Your family and the babysitter all cook from that one binder. The day you improve the lasagna page, you fix it once, and the next person to make lasagna gets the better version without anyone telling them. Now picture the opposite: every cook keeps their own photocopy taped inside a cabinet. To improve the lasagna you would hunt down all thirty copies, and the ones you miss keep cooking the old way. Over months the copies drift, someone scribbles a note on one, and nobody can say which copy is right anymore. The same choice shows up in how you keep the rules for how you want your AI work done.
By now you have prompts, specs, and workflows you have refined, and you keep the canonical versions in formats you own. The next question is where the rules inside them live: the way you want documents summarized, the tone your writing should hold, what counts as finished. The easy habit is to paste those rules into every project that needs them, a copy here, a copy there. The moment a rule lives in thirty places, you have signed up to maintain thirty copies, and they start drifting the day you make them. You tighten the summarizing rule in one project and forget the other twenty-nine still hold the loose version, so your work stops sounding like one person made it.
The fix is the binder on the stand. You keep each rule in one official home, and every project holds a short note that points to that home rather than its own copy of the rule. Improve the rule once in its home, and every project that points to it serves the better version the next time it runs. Nothing drifts, because there are no copies to drift. One rule carries the rest of the idea: how you want long documents summarized, the kind of rule you have probably already pasted into several projects without thinking about it.