Engram’s multi-device sync is now live through a public relay at sync.ellmstack.dev — the piece that lets your vault exist on more than one machine without ever existing in a cloud.
Here’s the design, and the tradeoff:
The vault is local. The relay is a courier. Your memory lives in an encrypted vault on your devices — SQLCipher at rest, keys bound to your hardware. The relay’s only job is delivery: when you enable sync, your devices exchange encrypted blobs through it. The relay holds only ciphertext in transit — queued until your other device comes online — and it has no keys, no plaintext, and nothing to decrypt with. A compromised relay sees a pile of unreadable envelopes.
Why a relay at all? Because your laptop and your workstation are rarely online at the same time. Direct device-to-device sync needs a rendezvous point; the alternative — a cloud vault — means your memory lives on someone else’s disk. A relay gets you multi-device sync without that.
What it costs us. Running a public relay is an ongoing expense with no direct revenue — it’s subsidized by the products that are for sale, and it’s why supporting the work keeps the free infrastructure running. The relay is also why the Engram privacy page is worded carefully: nothing you write ever passes through it in a form it could read.
Sync is opt-in. The vault is local-first and works fully offline; if you never enable sync, nothing leaves your machine but the context you choose to send to your model provider. The relay simply removes “one machine only” from the list of local-first tradeoffs.