I Got Burned by This Last Week

Last Wednesday afternoon, I asked my AI to draft a follow-up email to a client. It had always worked smooth ly — but this time the tone came out stiff and rob otic, like a form letter. I assumed I'd written my prompt badly, so I tweaked it four or five times and burned half an hour troubleshooting. Turns out it wasn't me at all: the AI tool had quietly pushed an update, and the default behavior instructions running behind the scenes had changed. Have you ever had that feeling — same tool, same workflow, and then one day it just... doesn't get you anymore?

What's Actually Changing Behind the Scenes: What a System Prompt Is

Every time you open an AI tool and start a conversation, the AI isn't starting from a blank slate. The platform writes a hidden backst age briefing that you never see — it tells the AI who it is, how it should respond, and what it can't do. This invisible brief ing is called a system prompt (think of it as the AI's factory default settings).

Recently someone in the tech community did a side -by-side comparison and found that Anthropic — the company behind Claude — had quietly changed this factory setting between two adjacent versions. The result : the AI's response style and judgment on edge cases both shifted . That comparison post got 163 upvotes, which tells me plenty of people are running into the same confusion.

Xiaoting, a freelance writer based in Guangzhou who manages social media content for three brand clients, told me about this exact headache. Each client wants a different voice from her AI assistant. She used to re-explain the same thing at the start of every new conversation — "write in a Little Red Book style, no formal language" — and sometimes the AI would drift back anyway. She eventually learned one move: now the very first thing she pastes into any new conversation is a fixed personal briefing she wrote herself. It locks the style in place. She hasn't had to re -train the AI since.

The Move You Can Copy Today

Cost: $0 — works with whatever AI tool you already have
Time: 15– 20 minutes to write it the first time; 10 seconds to paste it every time after
Technical barrier: If you can type, you can do this — no settings to configure
First step: Open your usual AI chat window and type a short brief ing at the very top: who you are + what style you want + what to avoid

Here's an example of how to open:
"You are my copywriting assistant. I'm a solo founder in children's education, and I post content mainly on WeChat and Little Red Book. Write in a casual, warm tone — like chatting with a friend. Avoid words like 'empower' or 'value proposition.' Before you start any task I give you, ask me one question to confirm you understood correctly."

Once you've written yours, save it in your notes app or a Notion doc. Paste it at the top of every new conversation. Whatever the platform changes in its factory settings, your personal briefing takes priority and overrides it.

( This isn't something everyone needs right now. If your AI workflow is running smoothly and you haven't noticed any style drift, there's zero urgency — skip it for now.)

Which Stage Are You At?

If you're just starting out with AI and still figuring things out: I'd say don't rush to lock in a system prompt yet. Try different ways of prompting first and get a feel for what the AI can and can't do. The signal that you're ready for this move is when you catch yourself explaining the same thing over and over at the start of every conversation.

If you already have one or two steady clients and you're using AI to help deliver work: This move is worth doing properly . Write a separate style briefing for each client and save them somewhere easy to grab . Since I started doing this, I've cut my revision rounds by at least half.

If you're managing a small team or serving multiple brand clients at once: Consider turning these style briefings into a shared doc so everyone on the team opens conversations with the same template. That way the AI output stays consistent regardless of who's operating it that day — and clients don't feel a different experience depending on who handled their account.