The Open Protocol
A wire contract you can check, not take on faith.
The local API is documented and printing does not depend on our cloud. Read the contract before buying hardware. Our simulator and conformance suite exercise that contract; access to those development tools is currently by arrangement.
Inspectable today
What you can verify before spending a dollar.
The wire contract
Nodes serve a documented HTTP/JSON API on the LAN for printing, status, events, configuration and supported peripherals, plus raw ESC/POS on port 9100. Shared schemas describe request and response shapes; conformance and contract checks compare the firmware, simulator and clients against them. Capabilities still depend on the board and attached devices.
The digital twin
pnpm sim starts a network service for print, status, events and raw port 9100, with fault injection for paper, cover, offline, drawer, weight and scans. It also serves scan and scale data, but does not reproduce scanner rejection policy or API-key gating. Physical USB behavior and routes such as boot history and network configuration need a real node. It is a workspace tool — free of charge, access by arrangement, with no public download.
The conformance suite
146 specs in our development workspace target the twin or a physical node. Access is currently by arrangement, and physical checks without the required hardware skip with a stated reason.
Honest state, by design
When a node can't read something, it says so: the driver layer models unreadable state as known: false instead of guessing. Scanner reads are labeled by provenance — transmitted by the scanner or inferred — and /scans keeps rejected reads with the reason. The protocol is designed to be audited, not to look good.
Why it matters
Local printing uses a documented interface.
Your application can send print jobs directly to the node on your network without a Proxy Nodes cloud account. The documentation explains how to build that integration. Managed firmware updates and other hosted features have separate service dependencies.
What is open here is the protocol, not the firmware source. We have not announced an open-source release of the firmware, and none is promised. A documented wire contract is what this page describes, with a simulator and a runnable conformance suite behind it — both free of charge, both obtained by arrangement rather than downloaded. Public firmware downloads are not published yet — see the firmware page for the current release and download status.
The contract itself is the open surface: read the API reference, explore the twin, and hold us to the 146 specs. The telemetry leg is inspectable the same way: point a node at your own server instead of ours, over the same open PUT /cloud contract — see the self-hosted telemetry guide.