A Janus Device Is a Pure Rust Alternative to the Cloud

A Janus device is a pure Rust alternative to the cloud for a camera, a microphone, or a presence sensor that should answer to the household. The market standard is a vendor server: the device uploads, the app downloads, and a policy you did not write decides who else can see the hallway. This page is the comparison. The builder field note on a smart home without the cloud is the argument in full. It belongs to In Your Home and the Own vision.

What the cloud path actually buys

The usual path runs every reading through someone else's computer. Espressif ships good tools for it: RainMaker, device SDKs for the big providers, and MQTT to a broker. The Janus plan lists them under one word: replace. On a Janus device the mesh is the cloud, an iroh endpoint dialed by public key. That mesh is rusty_esp_iroh, the pure Rust alternative to MQTT.

What you stop sending

A picture of the hallway, a recording of the kitchen, the fact that someone walked through at 2 a.m. A pure Rust alternative to the cloud is a decision about those bytes. They stay on the LAN. The browser page for a camera is rusty_esp_video. Presence without a picture is rusty_esp_sense.

What "pure Rust" does not mean

There is no C in our crates. There is C underneath. Track A firmware runs on Espressif's ESP-IDF, and every Wi-Fi radio runs Espressif's binary blob. A pure Rust alternative to the cloud that claimed a C-free radio would be false while the radio is up. The esp-rs book is the toolchain that builds Track A.

How ownership works when there is no account

The device mints a P-256 key and a did:mata, and an owner adopts it. That is rusty_esp_mid, the pure Rust alternative to a vendor account. No vendor account claims the device, and no cloud certificate has to be renewed.

The price of the trade

Janus does not target Matter, RainMaker, or Home Assistant core. You will not get a voice-assistant skill or a vendor app. Remote access is a real question: the PSRAM tier can use a relay so a short ticket works from anywhere, but that path is written and not yet measured on a board. The no-PSRAM tier is LAN-direct. Boards with 4 MB of flash, such as the ESP32-CAM, never run iroh and reach the mesh through a bridge. Choosing an ESP32 board is where those limits come from.

Two defects, written down

An adopted device can still advertise itself as free to claim, because that record is composed once at boot. The home computer's media controller is not yet wired to receive a Janus stream. A pure Rust alternative to the cloud does not get to bury either sentence.

Where the cloud still wins

Keep the vendor app when you want their remote access, their voice assistant, and their warranty. A local device will not grow those by being patient.

Honest limits

• Off-LAN reach is not a measured row.
• Current dev firmware stores the identity key in a plaintext partition. The field note on identity says so.
• The first afternoon is still a toolchain: Rust, espup, and espino. Deploy an ESP32 at home in an afternoon is that sequence.

Try the unplugged test before you argue about architecture. Turn off the WAN, leave the LAN up, and see whether the page still opens and the owner is still the owner. A pure Rust alternative to the cloud has to pass that afternoon. If it only works when a vendor DNS name resolves, it is the cloud with a local sticker. The measured pieces today are the ones the other pages time: a flash, a microphone soak, a camera packet count, an adoption refusal. A pure Rust alternative to the cloud is the sum of those rows, not a third row that erases their gaps. A pure Rust alternative to the cloud still owes you a measured relay, a hardware-wrapped key, and a media controller that is actually wired. Until those exist, the claim is the LAN, and the LAN is already a lot. A pure Rust alternative to the cloud that promised the missing rows would be the vendor brochure again. The brochure is the thing this page is here to refuse, including when the missing row would make the title sound larger.

Where to start

Start with the afternoon guide, then the Learn index for how far each package is proven. The Flash vision is the tool end of the same path.

The household computer this device is for lives at MATA. The crates are Remade With Rust. When a policy note or a datasheet needs to become a retrieval corpus, the same house runs RAG Converter.