Control and monitor one SteamOS device from another over your local network: a Steam Deck, any handheld running SteamOS, or a living-room PC. Pair once, then wake it, change its display, or fix a screen that went dark, from the Quick Access menu.
SteamOS Companion is a Decky Loader plugin that lets a SteamOS device be controlled from another one on the same network. The same install can run as a Client, a Server, or Both. A client keeps one paired remote device: it shows connection state, wakes the device, sends power commands, previews and saves display modes, and sets the Gaming Mode display order. A server accepts authenticated requests only from clients its owner has approved by comparing a code on both screens. Everything runs over pinned TLS on your LAN. SteamOS Companion is an independent open-source project and is not affiliated with or endorsed by Valve Corporation.
SHA256 are attached to every release.
The SteamOS handheld on the left pairs with a SteamOS living-room PC on the right. Watch what actually crosses the network, and what deliberately never does. Click any step to inspect it.
Each action is an enumerated operation with a confirmation where it matters. Nothing is replayed silently, and nothing on the wire is a shell command.
The Remote device view keeps connection state, the saved display mode and the actions you reach for most in one place: restore the saved display, wake the device, change resolution, reorder screens, or send a power command.
Docked to a TV that shows nothing? Preview a resolution and refresh rate on the paired device. It reverts automatically unless you confirm you can see the picture, and Revert is always offered first.
Choose which physical screen Gamescope should prefer when several are connected. Reorder with gamepad-friendly controls, then save for the next session or save and restart Gaming Mode right away.
Pick a role on first launch. Changing it later is an explicit saved setting: host identities, listener settings, paired clients and recovery profiles are preserved when a role is added, and a pending display recovery is allowed to finish before the Server role stops.
The plugin checks the latest stable GitHub release on start and every six hours. It validates the release assets and SHA256 before asking Decky Loader to download, verify, confirm and replace the plugin. No sudo, no root flag.
The v1 wire contract is a JSON schema with fixtures, shared by the Decky host and the Omarchy client. It never carries raw Steam payloads, arbitrary methods, PIDs, paths, commands or credentials.
At discovery the client records the host's sha256 certificate fingerprint. Every later connection must present exactly that certificate or it is refused.
Both sides compute scrypt(nonce, "steamos-companion:v1:pairing-sas:" + fingerprint) and show eight digits. The code is a verification string, not a bearer credential.
The pairing request carries a binding derived from the exact TLS 1.2 session. The host derives the same value from its socket and rejects a mismatch before anything is stored.
Power is suspend, restart or shutdown. Display changes name a host-issued output and mode. There is no route that takes a command.
Every mutation carries a client-generated request_id and returns 202 Accepted. After a disconnect the client queries the operation journal instead of sending again.
Scopes are status.read, power.control and display.control. Tokens are stored only as hashes, at most four clients can be paired, and approval can never grant a scope that was not requested.
The fingerprint is part of the salt. Whatever presents its own certificate derives a different code than the real host, so the two screens disagree and the owner rejects. The relay cannot repair this by choosing a nonce: finding one that makes the host display the relay's digits is an offline search of 10^8 codes at roughly 50 ms and 16 MiB each, far outside the 120-second request window.
Decky Loader must already be installed. No reboot and no Decky service restart are required.
steamos-companion-decky-<version>.zip from the Releases page.Then open the Quick Access menu, choose a device mode, and follow the pairing flow above.
From a local checkout, install the latest release. Replace steamdeck.local with your device's hostname or IP if it differs:
ssh deck@steamdeck.local 'bash -s' < install.sh
The installer always fetches the latest release; pass a release tag as its only argument to pin one. It copies the plugin to ~/homebrew/plugins/steamos-companion and asks Decky to reload its plugins. Run it as the deck user; sudo is used only to create, replace and update the plugin directory.
From a terminal in Desktop Mode on the device itself:
curl -fsSL https://raw.githubusercontent.com/tuthan/steamos-companion-decky/main/install.sh | bash
If the reload endpoint is unavailable, use Decky's Reload Plugins action afterwards.
Prefer to drive the Deck from a Linux desktop? The Omarchy bar widget speaks the same v1 protocol and uses only the system Python standard library.
omarchy plugin add https://github.com/tuthan/steamos-companion-omarchy.git --enable
Open the widget's Settings, choose Find hosts, request pairing, and approve it on the Deck once the codes match.
The Decky plugin and the Omarchy widget are the first two clients of the v1 protocol. The next one fits in your pocket.
Pair your phone with the same comparison code, then check status, wake the machine, pick a display mode and reorder screens from the couch without picking up a handheld. It speaks the existing v1 protocol, so no server-side update will be needed.
Follow the releases page to hear when the first build lands.
SteamOS Companion is free, MIT-licensed and built in spare time. If it saved you a trip to the TV, a coffee keeps the plugin, the desktop client and the upcoming mobile app moving.
--prefer-output priority list for the next Gaming Mode session, and the current scanout is reported with gamescopectl when available.