One long AI chat per ad account, or a fresh one with a brief each time?

I've been going back and forth on how to set up the chat itself when you run paid search through an AI assistant. Some people keep one long thread per account so the model remembers past changes, naming conventions and what got tested. Others start fresh each session and paste in a short brief. My hunch is the long thread works well for analysis and badly for changes. After a few weeks the context is full of old decisions that no longer apply, and the model can treat a paused test as current. A fresh chat with a one-page brief (goals, target CPA, what's off limits, last major change) feels safer for anything that writes to the account. Does anyone have a rule for when to reset, or is telling it to ignore old context good enough?

Agreed on the fresh chat for anything that writes. Telling the model to ignore old context doesn't really work, because those messages are still in what it reads, and it will often treat a paused test as live. Say a plumbing company ran a call-only ad test in spring and paused it when cost per lead climbed. Six weeks later the old thread still says "test running," and a suggestion built on that is easy to get.

I'd add dates and status to the brief, not just the goal. Something like "Call-only test paused 14 March, cost per lead over $60, don't restart without fresh data." Then have the model pull the current campaign status before it proposes any change, and treat that live state as the source of truth over both the brief and the old thread.