Valve traced a SteamVR Error -203 black screen to a Vulkan ring buffer overflow
Valve has pointed an Error -203 black screen on the SteamVR 2.18.3 beta at an assert inside SteamVR's own Vulkan renderer. A Valve developer quoted two lines back from the reporter's compositor log on October 10, both reading "Vulkan transfer ring buffer overflow" at vrrenderer/vulkanrenderer.cpp line 5502, one at a transfer size of 71,100 and the other at 2,315,040.
SteamVR on its own Steam store page. The assert Valve quoted fires in SteamVR's compositor renderer. Image: Valve Image: Valve
The report had gone up earlier the same day. Launching a VR-capable or VR-only title turns the headset black, the reporter says, with SteamVR showing either "headset not in fullscreen mode" or "Error -203", on Nobara 44 with Steam client build 1791592380 and SteamVR 2.18.3 beta.
The report carries Steam logs, minidumps and two vrcompositor crash dumps, which is what let Valve answer it about 75 minutes after it was filed.
Valve then renamed the issue to match the log. It reads "ASSERT: Vulkan transfer ring buffer overflow" where the reporter had filed it as a launch failure after a beta update, it carries Valve's bug label, and it was still open on October 14.
The assert fires in Valve's code, not the game's
The path in the log, vrcommon/vrrenderer/vulkanrenderer.cpp, is SteamVR's compositor source, so the overflow is Valve's own renderer refusing a transfer bigger than its ring buffer will take. Both failing transfers are recorded with their sizes, nine minutes apart, in a session that produced two compositor crash dumps.
What Valve has not said is what hands the renderer a transfer of 2,315,040 when the earlier one failed at 71,100. The reporter closed their side of the exchange within minutes, saying they do not have the knowledge to take it further, and nothing had been added to the thread as of October 14.
The games named are VRChat and Hot Dogs, Horseshoes & Hand Grenades, and one reporter on one machine is the whole evidence base. No headset model appears anywhere in the report.
2.18.3 shipped two crash fixes of its own
SteamVR Beta 2.18.3 went out at 00:50 UTC on October 10, roughly 12 hours before the report. Valve's patch notes list "Fixed game crash when an invalid texture size is submitted" and "Fixed OpenXR games crashing on launch if SteamVR wasn't already started" among the Linux changes.
The beta itself is opt-in, and Valve's note points owners at its own SteamVR bug report forum rather than the announcement thread, whose replies it says are not tracked. This report went to Valve's GitHub tracker instead, which is where it was answered.
Those are separate entries, and this report was filed against the build that carried them. Valve's own notes for 2.18.3 also misspelt one of the Vulkan extensions it dropped a requirement on.
Valve has taken a numbered SteamVR error apart in public before, when it told Linux owners that mismatched Nvidia driver files are what produce error 303. Error -203 has a source file and a line number behind it now, put there by Valve, and no fix.
