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The test in one paragraph

50 real files from my working vault, set up twice. Once as well-named folders, once as a wiki that Claude built itself with the claude-obsidian plugin. Then the same 10 questions to both, using Claude Code in the terminal: simple facts, questions spanning two files, and why questions.

	Folders	Second brain (wiki)
Correct answers	10 of 10	10 of 10
Upfront work	none	38 minutes to build the wiki
Tokens per answer (mean)	about 399,000	about 639,000

The wiki used roughly 1.6 times as many tokens per answer. In money the gap is smaller, because a large share of those are cached tokens. The real cost is the build: 38 minutes and about 21 million tokens before the first question was asked. With 50 files and my questions, it wasn't worth it. With thousands of files that may change. I haven't tested that.

Step 1: Understand the structure

This is the top level of my vault:

vault/
├── CLAUDE.md        ← the router: who I am, what lives where, rules
├── 00_inbox/        ← everything new lands here first
├── 01_brands/       ← one subfolder per brand, each with a BRAND.md
├── 02_projects/     ← one folder or file per project
├── 04_areas/        ← ongoing topics: backlog, infrastructure, strategy
├── 06_routines/     ← daily notes and briefings
├── 99_archive/      ← finished work, never deleted
└── wiki/            ← knowledge about tools and concepts, plain Markdown files

Three things make this readable for Claude:

• Numbers in front of the names. The order is fixed, and Claude sees what matters on the first ls.
• Descriptive file names in kebab-case. Claude finds agentic-os-pipeline.md by search. It won't find notes-v3.md.
• A CLAUDE.md at the root. Claude Code reads it on every start. It says in a few lines which folder is for what. That is all the navigation you need.

In the test, this is exactly how Claude found the answers: read the router, jump into the right folder, find the file by search.

Step 2: Start with three folders

My structure grew over months. You don't need to copy it. This is enough to start:

vault/
├── CLAUDE.md
├── 00_inbox/
├── 01_projects/
└── 02_notes/

Inbox for everything new, projects for ongoing work, notes for knowledge that stays. Add a fourth folder only when one of the three gets messy. That's how brands and routines showed up in mine, one at a time.

Step 3: The four prompts

All four run in Claude Code, opened in the vault folder.

Prompt 1: Create the structure and CLAUDE.md

Create this structure in this folder: 00_inbox, 01_projects, 02_notes.
Also write a CLAUDE.md at the root, 40 lines max:
1. Who I am and what I work on (ask me if you don't know)
2. What goes into which folder, one sentence each
3. Rules: file names in kebab-case, no dates in file names,
   every note starts with one line saying what it's about
Show me the CLAUDE.md before you save it.

Prompt 2: Sort the inbox

Go through 00_inbox. For each file, suggest:
target folder, new file name in kebab-case, a one-line summary.
Show me the list as a table. Only move files after I say "ok".

Prompt 3: Ask questions

This is the prompt from my test (I ran it in German):

<Your question> Answer from the files in this folder.
Keep it short (2 sentences max) and name the source file.

The source file is the important part. It lets you check in seconds whether the answer is right.

Prompt 4: Clean up once a month

Check the vault for:
1. Files with unclear names
2. Duplicate or contradicting information (quote both places)
3. Projects that haven't changed in over 60 days
Suggest one action per finding (rename, merge, move to 99_archive).
Don't change anything without my ok.

In my vault a check like this found 13 contradictions, for example a price that differed between two files. Spots like these make answers wrong, whether you use folders or a wiki.

Common mistakes

• Starting with twenty folders. On day one you don't know which categories you need. Empty folders confuse you and Claude.
• No CLAUDE.md. Without a router Claude searches the whole tree every time. That costs tokens and time.
• Letting Claude move files without approval. The ok in prompts 2 and 4 is there on purpose. You want to see what happens.
• Second brain first. A wiki generator turns a messy folder into a messy wiki, just more expensive.

Next steps

1. Create an empty folder and open it in Claude Code
2. Run prompt 1, read the CLAUDE.md and adjust it
3. Put ten files into the inbox, run prompt 2
4. Ask a question you can answer yourself and check the source