Learn MYOS
The vault
The vault is a folder on your computer full of plain text files. It is your system's memory, and it is yours in the ordinary sense: you can open it, copy it, back it up, or walk away with it.
Why markdown
Markdown is text with a few punctuation marks for headings and links. It opens in Notepad, in Obsidian, in any editor written in the last forty years.
That matters for two reasons. Nothing you write is trapped in a format that needs someone's app to read, and an AI assistant can work with it directly with no integration, no export, and no plugin standing in between.
The trade is that markdown will not do spreadsheets or drawings. Those live in the area's Documents/ folder as ordinary files, and your notes point at them by name.
Obsidian is the window, not the vault
Obsidian is a free app that reads a folder of markdown and makes it pleasant to browse: links become clickable, headings become structure, search works. Your assistant writes, you read.
If Obsidian vanished tomorrow, your vault would be unaffected. It is a viewer over files that already exist.
History and undo
Your vault can keep its own version history using git, which is a local record of every change over time. It is not switched on by default. Your assistant offers it during setup and can set it up any time you ask.
Turn it on. It costs nothing, it stays on your machine, and it turns "that file got mangled" into a two minute fix rather than a bad afternoon.
Privacy, said accurately
Your files sit on your disk. There is no MYOS account, no MYOS server, and nobody receives a copy of your vault because you installed it.
What does leave your machine is the conversation. When you talk to your assistant, the parts of your files it reads are sent to Anthropic as part of that conversation, exactly as they would be in any Claude chat. That is the honest boundary, and it is worth knowing before you write something sensitive into a file and then ask about it.
Two practical consequences. Your profile files are as personal as your phone notes, so treat a screenshot of your vault the way you would treat a screenshot of those. And if a folder holds something that must never go to a model, keep it out of the vault rather than trusting yourself to remember.
It is portable
Copy the folder to a drive and it is backed up. Copy it to another Windows machine, point Claude Code at it, and your system is running there too.
Next: Trust and permissions. Or see what ships in the kit.