Syncing AI Memory Across Devices: Five Checks Before Anything Uploads
By Matthew Firth, founder of ModelBrain · Nov 9, 2026 · 4 min readOur own proposal: judge any AI memory sync by what it checks before it uploads, not by how smoothly it copies. A sync that cannot keep one memory on one computer is a backup you do not control. ModelBrain's sync is off until you turn it on, encrypts on your computer before upload, and refuses to send a partition you marked as staying local.
Why built-in memory does not answer this
The built-in memories in Claude and ChatGPT are attached to your account with each company, so each one lives on that company's side and stays inside its own assistant. That is one kind of sync: your memory is wherever you sign in. It does not carry from one assistant to the other, and you do not choose where it is stored. Our comparison of the two covers what each one keeps. If you want one memory that several assistants read, it has to live outside all of them, and then the question becomes how it reaches your second computer.
A folder copier is not a sync
ModelBrain keeps memories as files in a folder you own, so you can put that folder in a general file-sync service. That copies files. It does not know that two computers may have changed memory at the same time, and it uploads whatever is in the folder, including notes you meant to keep on one machine. If you go this way, the five checks below still apply, and the service you pick has to pass them.
Five checks to run on any sync
These are the questions we use. The right-hand column is how ModelBrain answers each one today, taken from our privacy page.
| Check | Why it matters | ModelBrain |
|---|---|---|
| 1. Is it off until you turn it on? | The default decides what leaves your computer without a decision from you. | Yes. Local use needs no account and uploads nothing. Sync is opt-in and separately paid. |
| 2. Can you keep one memory on one computer? | Some notes should never travel, and a sync that cannot say so is a copy of everything. | Yes. A partition you mark as staying on this computer never leaves, not even encrypted. Neither do documents ModelBrain reads from your folders. The check runs before anything is sent. |
| 3. Who holds the key? | If the provider holds it, the provider can read what it stores. | Memories are encrypted on your computer before upload, and we do not hold the key. |
| 4. What does the provider still see? | Encryption hides contents, not the fact that you use the service. | An account, an email address, your devices' names, billing records, and the size and timing of what you upload. None of the contents. |
| 5. What happens when you stop paying? | A sync you cannot leave is a lock-in. | Sync keeps working to the end of the period you paid for, then your copy is read-only for 30 days so you can restore or export it. Memories on your computers are never touched. |
What it costs
Local memory is free and stays free, on every computer you install it on. Sync is $6 a device a month billed yearly, or $8 a device if you pay monthly. Managed backup is included in that price. Storage is one flat $0.05 per GB a month on what we hold for you. Two computers and a 2 GB memory come to $12 a month billed yearly ($144 a year), plus about 10 cents a month for storage. Full details are on the pricing page, and why backup is included explains the shape of it.
What sync does not change
Sync is an addition, never a migration. Your local memories keep working whether or not you switch it on, and they keep working if you cancel. ModelBrain does not encrypt the memory folder on your own computer, because a key stored on the same machine would stop nothing your operating system's disk encryption does not already stop. Turn on FileVault, BitLocker or LUKS. We explain that choice in why we did not build vault encryption, and score the three places your memory can be read in three readers to check.
Questions people ask
Can I sync AI memory across devices for free? Local memory on every computer you own is free, with no account. Keeping those computers in step with each other is the paid sync described above.
Does syncing send my memories to ModelBrain's servers? Only if you turn sync on, and then only encrypted. We hold blobs we cannot read, plus the account, device and billing details named in the table.
Can I keep one project's memory off the sync? Yes. Mark that partition as staying on this computer and it never leaves, not even in encrypted form.
What happens to my memory if I stop paying? Sync works to the end of the paid period, your copy is then read-only for 30 days, and the memories on your computers are untouched.