Valve’s SteamVR 2.18.1 beta quietly revised the proprietary DRIVER INTERFACES third-party add-ons build against, and it also changed the OSC OUTPUT that the Steam Link driver exposes. Neither change appears in Valve’s public NOTES for the build. The company spelled them out only in a reply to an owner whose paid SteamVR add-on had STOPPED WORKING, as Mixed News reported on September 27, 2026.
That same beta is the RELEASE that added tethered Quest STREAMING over USB — the headline most owners went looking for, and a change this site already covered. The INTERFACE work reaches a much smaller group: anyone running a community or paid SteamVR DRIVER that hooks Valve’s proprietary surfaces.
Valve’s first fix tip is an OSC toggle
In the support reply quoted by Mixed News, Valve wrote that SteamVR “updated a few INTERFACES in the latest RELEASE, as well as modifying the OSC OUTPUT that the Steam Link DRIVER exposes,” and recommended starting by toggling the OSC OUTPUT in Steam Link settings. OSC — Open Sound Control — is the messaging protocol social VR tools use to pass TRACKER data and avatar parameters between applications. A change in what Steam Link sends out lands on anything listening for it.
Valve’s second pointer targets drivers that hook interfaces to pull data from other drivers DIRECTLY. That pattern is UNSUPPORTED, Valve says. A driver doing it should hook the LATEST INTERFACE versions, because that is what every proprietary SteamVR DRIVER builds against.
One paid add-on is named in the report
The report names the Linux beta of SizeOSC, a paid third-party project that brings Resonite’s resize gesture into VRChat. The owner said it STAYED BROKEN even after rolling SteamVR back to the STABLE BUILD, and passed Valve’s explanation to the add-on’s developer. No other add-on has been named. Valve neither confirmed a bug nor promised a FIX. It closed the report on September 25, saying the problem as described was not what was actually going on and that there was too little to work with, while inviting a fresh report if anything else looked wrong with SteamVR.
Aurora and Steam Link fixes share the same beta
Valve’s own NOTES for SteamVR Beta 2.18.1 list a new default environment called Aurora, content-aware color tinting in the theater environment, gamepad navigation in the System UI, an “Additional Options” menu for lesser-used controls, and a setting to stop games dimming while the dashboard is up. Steam Link gets FIXES for video corruption, checkerboarding and stuck streams plus improved automatic bitrate selection. On Linux, async reprojection no longer fails on AMD GPUs. None of those bullets mention DRIVER INTERFACES or OSC.
Anyone whose SteamVR add-on has STOPPED WORKING has the OSC TOGGLE to try first, and after that a wait for the add-on’s author to REBUILD against the CURRENT INTERFACES. The beta is OPT-IN, so the STABLE BRANCH keeps the old interfaces for now. This angle is DISTINCT from the USB-tether Quest STREAMING story: same BUILD, different breakage SURFACE for third-party tooling.
Sources: Mixed News (September 27, 2026); Valve SteamVR Beta 2.18.1 release notes.