# How PromptMason keeps your libraries safe *What PromptMason protects when your libraries sync or back up, and what it doesn't, in plain words.* Online version: https://promptmason.ai/docs/security-overview If you only use PromptMason on one PC, your library stays on that PC. This page is about what changes when a library leaves the PC: when it syncs to your other PCs or your team, or when you turn on backups. For how libraries work day to day, see [Personal and team libraries](https://promptmason.ai/docs/libraries). For everything else that can leave your PC, such as AI features, see [Privacy in PromptMason](https://promptmason.ai/docs/privacy-overview). ## How it works A library that syncs uses a folder in cloud storage you already have, such as OneDrive, Google Drive or Dropbox. No PromptMason server holds your libraries, and there's no PromptMason account. We never see your libraries. Every PC keeps its own full copy of the library and works from it, even offline. Changes travel through the folder, locked before they leave the PC. ## What PromptMason protects - **Only your library's members can read it.** What's in the library is locked with a key that only the library's approved PCs hold. Your cloud storage company, someone the folder was shared with by mistake, or anyone who copies the folder sees files they can't read. - **Every edit is signed and checked.** Each PC signs what it writes, and every other PC checks it before using it. A change that was altered, or that comes from a PC that isn't in the library, is ignored, and the rest of the library keeps working. - **You approve every PC.** Nobody joins a team library, and no PC is added, unless the primary owner approves it. For someone new, the primary owner first compares an approval code with them. See [Approve a PC](https://promptmason.ai/docs/approve-device). Nobody can join as an existing member without one of that member's own PCs, their recovery kit, or the primary owner's check. - **Removed people are locked out of new work.** When someone is removed, the library switches to a new key. People you remove can't read edits made after every PC has picked up the change. See [Remove a person or a PC](https://promptmason.ai/docs/remove-someone). - **History shows who made each version.** Names come from the library's own member list, never from the change itself. A ✓ means the edit came from a PC proven to be that person's; "via AI app" means an AI app made it. - **Backups are locked too.** Only you can open them ([Backups](https://promptmason.ai/docs/backups)). ## Where your keys are Your PCs hold your keys, protected by Windows the same way as your other saved sign-ins. Your [recovery kit](https://promptmason.ai/docs/recovery-kit) is a spare copy, one file and a code, for when you've lost every PC. Your keys are never in the folder in a form anyone else can use. Your settings, your AI assist key and your AI activity log never sync at all. ## What it doesn't protect against - **Someone at your unlocked PC.** Whoever is at your unlocked, signed-in PC is you, as with your email. Lock your PC when you step away, and turn on App Lock if others use it (**Settings → Privacy & security → Enable App Lock**). If a PC is lost or stolen, remove it straight away ([Lost or stolen PC or kit](https://promptmason.ai/docs/lost-device)). - **Harmful software on an approved PC.** It can do anything that PC's user can do. - **What someone already has.** Removing a person stops new changes reaching them; it doesn't take back what they could already read, copy or export. - **Seeing the shape of the library.** Anyone with access to the folder can see that the library exists and how it's made up: how many files, PCs and members there are, each member's role, which PCs belong to the same person, when PCs joined or were removed, when each PC is busy, and roughly how big each change is. They can't see what's in it, members' names or its settings. The library's name is locked inside the files, but the folder PromptMason makes is called "PromptMason - [library name]", so anyone who can see the folder sees that name. - **Holding files back.** Someone who controls the folder can delete files or stop them syncing. PromptMason notices missing changes and puts back what it can, but it can't force your cloud storage to deliver. - **Checking who a person really is.** The approval-code call proves the PC you approve is the one in front of the person you're talking to. Call them on a number you already know is theirs. - **The primary owner being unexpectedly away.** Only the primary owner approves PCs, removes people and changes settings. If they're away without handing the role over, those things wait until they're back; editing carries on ([The primary owner](https://promptmason.ai/docs/primary-owner)). - **Losing everything.** If you lose every PC *and* your recovery kit, your personal library can't be recovered. Nobody else can open it, PromptMason included. In a team library, the primary owner can put you back after a quick call. If you're the primary owner, nobody can put you back: another owner exports the library and starts a new one ([The primary owner](https://promptmason.ai/docs/primary-owner#if-the-primary-owner-is-unexpectedly-away)). ## AI apps and team libraries An AI app you connect to PromptMason (a connected app) reads and changes your libraries through PromptMason. In a team library, the primary owner decides for everyone what AI apps can do: **Read only (recommended)**, **Read and change**, or **Nothing: AI apps can’t see it**, and how many changes an AI app can make per hour. Each person's own Connected apps setting still applies, and the stricter of the two wins. This setting limits AI agents and Chat. It doesn't limit a member's own AI assist or Evaluate. Each member chooses their provider there, so text from the library can still go to the provider a member picks. Changes an AI app makes show "via AI app" in History. See [Team libraries](https://promptmason.ai/docs/team-libraries#working-together) and [Control what connected apps can do](https://promptmason.ai/docs/agent-access). ## Something in the library folder was ignored You may see this in Notifications. It means PromptMason found a file in the library's folder that it doesn't trust, so it ignored it, or put the real one back. The library is fine. See [Sync problems](https://promptmason.ai/docs/sync-problems#something-in-the-library-folder-was-ignored) for each message. If it keeps happening, check who the folder is shared with in your cloud storage. ## Questions Email [support@promptmason.ai](mailto:support@promptmason.ai). ## Want a hand? Paste this prompt into Claude, ChatGPT or another AI assistant, together with this guide, to be walked through it step by step: > Explain in plain words how PromptMason protects a team library that syncs through our OneDrive, what it doesn't protect against, and what our team should do to stay safe.