3.1
The Three Layers
Why this exists
Two weeks in, you'll have noticed something. Every session starts with you explaining yourself again — what this project is, how you like things done, where the files live. And when a project gets big, Claude reads the whole lot to answer a small question, which is slow and makes it vaguer.
Both problems have the same cause and the same fix. It's not a better prompt. It's structure.
The idea
Think of it as an office, not a folder.
A map by the front door. Rooms with their own rules. Tools kept in the rooms that need them. Nobody reads the whole building to answer one question — they check the map, go to the right room, and use what's in it.
| Layer | What it is | When it's read |
|---|---|---|
| The map | CLAUDE.md at the root of your project |
Every single time |
| The rooms | A CONTEXT.md inside each workspace folder |
Only when working in that workspace |
| The tools | Skills | Only when the task calls for one |
The names change between setups. The three layers don't.
The map is the one file Claude reads every time, so it stays small: what this project is in two or three sentences, what's in it, where to go for what. If yours is longer than a screen, you've got room-level detail hiding in it.
The rooms are where the detail lives. Each workspace is a folder for one kind of work, with its own CONTEXT.md describing what happens there, how it's done, and what good output looks like. The rule for deciding what deserves a room: if you shift how you think between two kinds of task, those are two rooms. Drafting and building are different modes. Client A and client B are different rooms. Answering email is probably not a room.
The tools plug into the rooms that need them. Your writing room doesn't need the testing skill. That's Level 7.
The reason this works is the thing you learned in 2.2. Everything Claude reads costs space and dilutes what matters. A flat folder means it reads all of it, every time — your abandoned drafts competing with the thing you asked about. Layers mean it reads the map, then only the room it's in. The context stays clean because most of it never loads.
And the payoff for you is that you stop repeating yourself. Written down once, in the right layer, means never explained again.
Do
Nothing gets built this lesson. This is the sketch that makes the next four straightforward.
- On paper, or in a file called
structure-sketch.md, write down the two or three kinds of work you actually do. Not everything — the two or three you'd notice if they were mixed up. - For each, write one line: what's different about how you think when you're doing it?
- Now write what your map would say. Two or three sentences: what this project is, who it's for.
- List what would live in each room.
- Look at your list of rooms. If you've got more than three, cut it back to three. You can add later; starting wide is the mistake in 3.5.
Step 5 is the one people resist. Everyone's first structure has seven workspaces and four of them are empty a month later. Start narrow — a room proves it needs to exist by getting used.
Done when
Never do
Don't build the whole structure before you use any of it. The version you design on paper is a guess. The version that survives is the one you corrected after two weeks of real work.
Your first structure should take about fifteen minutes to set up. If it's taking an afternoon, you're designing for a project you don't have yet.