Every new session opens on an empty context window. The first stretch of it goes to the same catch-up you gave yesterday: what this service does, why the auth layer looks the way it does, which of two approaches you already rejected and why, and what you were halfway through when you stopped.
That briefing is a tax. It is paid in tokens, in time, and in the quiet erosion of trust that comes from explaining yourself to something that felt, an hour ago, like it already understood.
The fix is not a longer system prompt, and it is not a hosted memory service that takes custody of your context. It is a folder. A small set of markdown files with a fixed read order, versioned beside the code, written at the end of every task and read at the start of the next one. The state of the project stops living inside a conversation and starts living in the repository, where it belongs.
A project should outlive the session that made it.