DOCS · SECURITY & PRIVACY
Your data stays yours.
SynthOS is the system that gives every asset its own AI Computer, and it runs on your Mac. Your vault lives there and syncs through a private cloud bound to your account — yours to turn off. Your run log and your credentials never leave the machine at all. This page is the honest account of where your data sits, what that sync does and does not promise, the guardrails that keep an autonomous system in check, how the bring-your-own-key model handles data, and how to reach us if you find a security issue. No marketing — just what is and isn’t true.
WHERE YOUR DATA LIVES
It lives on your Mac.
The original is a folder on your disk — that is the copy that matters, and it stays readable with or without us. It also syncs, through a private cloud bound to your account, so a second Mac picks up where the first left off. Sync is on by default; turning it off per vault is one switch, and the files stay exactly where they are.
Your vault is your files. Everything agents produce is written as ordinary, Obsidian-compatible markdown in a folder you choose, on your disk. You can open it in Obsidian, a text editor, or git — with or without SynthOS running, and without us in the loop. Back it up, sync it, or move it to another machine; it stays readable without us.
Your vault syncs to your account. The cloud copy is private, bound to your SYNTHOS account, and encrypted in transit. Signing in on a second Mac lists your vaults and pulls them down; turning sync off per vault stops it, and deleting your account takes the remotes with it. What we are not telling you: this is not end-to-end encrypted. We hold the keys to the storage, which means we could technically read what is in it. We don’t, and nothing in the product does — but “we can’t” would be a stronger claim than the truth, so we’re not making it.
Your run log stays on your Mac. The audit trail — the record of every tool call an agent made — is written on your machine and deliberately kept out of sync. We don’t need a copy of it to make the app work, so we don’t have one.
Your credentials stay local. Your AI provider key and the credentials SynthOS uses to do its work are stored on your machine, not on our servers. We’re not a middleman holding your secrets.
So, plainly: two things leave your Mac. The request you chose to send to your AI provider — the model runs in their cloud, because that is where the model is. And your vault, to your own private cloud, if you leave sync on. Your keys and your run log leave for neither.
SIGN-IN SCOPE
What sign-in is — and isn’t — for.
You sign in to manage your relationship with us, not to route your work through us. The account and the operating part of SynthOS are deliberately separate.
Sign-in exists to sync across your devices and manage your plan — your subscription, your billing, and your app download. That’s the job of the account: to know which plan you’re on and let you move between machines.
Sign-in is not a pipe your work flows through. We don’t need your vault, your run history, or your provider key to run your subscription — and we don’t collect them as a condition of signing in. The operating part runs locally against your own key.
In short: the account handles billing and the download; the work happens on your Mac.
THE GUARDRAIL STACK
Autonomy with a brake.
An autonomous system without oversight is just risk. SynthOS is built to check in before anything risky, and it writes what ran to a full local audit trail you can read — and both ship in every tier, never a paid add-on.
Before a step that’s hard to undo — deleting files, spending money, sending something out, running a destructive command — the agent is instructed to hold and ask you in plain language. When it does, you answer in the window and nothing moves until you do. Being straight about it: that check-in is behaviour the agent performs, not a gate the app enforces on every tool. You can make it a hard rule for specific tools in your own guardrails file, and the honest default is to watch the work rather than assume it will always stop.
What ran is written down: which tool, what it was given, and what it returned. It’s a readable record, not a black box — you can see exactly what happened after the fact, not just a spinner that finished. Honesty about what ran, kept where you can check it.
Those entries add up to a local audit trail of everything SynthOS has done on your machine — what ran, in what order, and why. It lives on your Mac, so you can review a run, see what an agent touched, and trace any change back to the request that caused it.
Plainly stated: the audit trail is a local record kept for your review — it is not a tamper-proof or legally-notarized log, and we don’t claim it to be one. Its value is transparency: you can always read what an autonomous system did on your machine.
SPEND & STOPPING
See what it costs. Stop what you’re watching.
Two limits are ours to give, and the strongest one isn’t: SynthOS shows what a run is spending as it happens and lets you stop the run you’re watching. The only guaranteed dollar ceiling is the one you set at your provider.
A run shows what it is costing while it runs, on your own provider key. That bill stays between you and your provider — we never meter it — so the cost of a long run isn’t hidden behind a spinner you can’t read.
You can stop a run you are watching, the moment you want it stopped. That stop is scoped to that run. There is no single control that halts everything at once, and we won’t describe one until there is.
The only thing that can guarantee a dollar figure is never exceeded is your provider’s own hard limit on the account that owns your key. Set that first — it is the real ceiling, and it is the one that cannot be talked out of stopping.
This page used to describe a spend ceiling you set and a kill-switch that halted everything at once. Neither is in the app today, so neither is on this page.
YOUR PROVIDER KEY & DATA HANDLING
Your key. No markup.
SynthOS runs on a key you bring. You own the account that powers it, the bill stays between you and your provider, and the key itself never leaves your Mac for our servers.
Bring your own key, stored locally. You connect your own AI provider account, and your key is stored on your Mac — not on our servers. SynthOS uses it from your machine to talk to your provider directly.
No token markup. The usage bill stays between you and your provider — we don’t resell tokens or add a margin on top. What the model costs is what your provider charges you, nothing more from us.
What actually leaves your Mac. To do its work, SynthOS sends the specific request you asked for to your provider’s API — that’s how the model thinks. Your provider’s own terms and data-handling apply to those requests. Everything else — vault, history, credentials — stays local.
The split is deliberate: your machine runs the tools, holds the files, and keeps the run log; your provider’s cloud runs the model. Choosing your own provider means you also choose whose data terms your requests are governed by.
REPORTING A SECURITY ISSUE
Found something? Tell us.
We practise coordinated disclosure. If you’ve found a vulnerability, email us directly and give us a chance to fix it before it’s public — please don’t open a public issue for a security report.
Email [email protected] with what you found and how to reproduce it. We’ll acknowledge your report and work with you on a fix and a coordinated timeline for disclosure.
Don’t open a public issue for a security report, and don’t disclose the details publicly before we have had a chance to address them. Coordinated disclosure protects the people using SynthOS while the fix ships.
Our machine-readable policy lives at /.well-known/security.txt (RFC 9116) — the same contact address and the same coordinated-disclosure request, in the standard format security researchers expect.
SECURITY CONTACT[email protected]/.well-known/security.txtFor anything that isn’t a security report — questions, bugs, feedback — write to [email protected] instead.
WHAT WE DON’T CLAIM
The honest fine print.
Trust is easier to earn by being clear about the limits. Here is what SynthOS does not claim — so you never have to read between the lines.
We don’t claim the audit trail is notarized. It’s a local, readable record of what ran — useful for review and tracing a change back to its cause. It is not a tamper-proof, cryptographically-sealed, or legally-notarized log, and we won’t describe it as one.
We don’t say it runs “while you sleep.” SynthOS can run automated and scheduled work, but it does so within limits you can see: the agent checks in before consequential steps, a run shows what it is spending, and you can stop the run you are watching. Scheduled work fires while SynthOS is open and catches up what it missed at the next launch. We won’t market unattended autonomy as if it were more supervised than it is.
We don’t make absolute security guarantees. Your keys and your run log never leave your Mac, and your vault syncs to storage bound to your account — real reductions in exposure, not a promise that nothing can ever go wrong. Securing your own machine, your provider account, and your backups is part of the picture too.
If a claim isn’t on this site, we’re not making it. The things we do say — your files stay yours, sync you can switch off, check-ins before consequential steps, a local record of what ran — are the things we’re prepared to stand behind.
WHERE TO GO NEXT
Read the rest of the model.
Security and privacy are the floor. The core concepts explain how the whole operating model fits on top of them.
Private cloud sync · Bring your own key · A local record of what ran.