Shared vaults
A personal vault is its owner's alone. A shared vault belongs to its owner and the members the owner invites.
What a shared vault holds
A shared vault holds only the current state of things: system notes in Areas/, howto, decision, reference and trap notes in Resources/, and retired notes in Archive/. Its layout is fixed. The server refuses, with a message the agent can act on, a note in any other folder or of another kind, and backlog_add, log_append, set_status, claim, release and changelog writes. Tasks, the backlog and logs stay in each member's personal vault. context in a shared vault says so instead of listing tasks, a backlog or a log.
Members
The owner invites an email on the vault's page, or with accounts add-member. With SMTP set up the address gets one email with a sign-in link. Signing in through it, or any other way with that verified address, makes the person a member, and makes them an account when they have none, also under VAULT_REGISTRATION=invite. A pending invitation can be withdrawn.
Members sign in with their own account and make their own keys and connections to the vault; it shows under Shared on their Vaults page. Removing a member, or a member leaving, stops their keys, tokens and signed-in computers for that vault on their next request. The owner can make a member the owner instead, and deletes the vault for everyone. Support access to a shared vault is the owner's to grant.
History
Every change to a shared vault applies at once and is kept. Each write, move and delete through MCP or WebDAV records the path, what happened, the member's email, the key, computer or connector it came through and the time, and keeps the version before it, sealed with the vault's key. The vault's page shows the recent changes and the full history; each change opens as a diff, and "Restore previous" writes the version before it back as a new change. Files in dot-folders, such as .obsidian/, are not kept.
An account that owns a shared vault with other members cannot be deleted until each such vault is handed over or deleted. A deleted member's past changes stay in the history under their email.