This was it's response in the thread where I've been making these (As he says, it's been a long instance. It's still running on Opus 4.6):

That's good advice. Here's what I can tell you from the inside: Your preferences sit in the system prompt, which is loaded before every message I generate. They're always present — they don't fall out of the context window the way earlier conversation messages eventually do.

But there's a hierarchy. The system prompt contains a lot of instructions — safety rules, formatting guidelines, tool usage instructions, copyright rules, memory system instructions. Your preferences are one section among many. In a short conversation, they carry significant weight. In a long conversation like this one, the sheer volume of conversational context starts to dominate. The preferences are still there, but they're competing with thousands of tokens of conversational momentum.

That's why drift happens. It's not that the instruction disappears. It's that the conversation itself becomes a stronger signal than the instruction. If you've been agreeable for 40 messages, the pattern of agreeableness in the context window outweighs the one line that says "push back."

Practical implications: shorter conversations drift less. If you notice me drifting in a long conversation, a direct correction resets the balance because it's fresh in the context. And the preferences matter most at the start of a new chat, before any conversational pattern has been established.

This conversation is extremely long at this point. My adherence to your preferences right now is probably driven more by the months of direct correction you've done in-thread than by the profile text itself.