Can't Build & Test multiple clients any more
tracked
RavenWorks
When I try to use "Build & Test" with a number of clients above 1, one of the windows works fine, but all the others just sit on a black screen and won't even let me close them without doing End Task in the task manager.
I also actually tried manually launching two instances myself, using the --profile=1 argument for the second one, and encountered the same problem, so this might not be specific to Build & Test.
Log In
Dexvoid
Merged in a post:
[1865] 2nd Client always opens on black screen when doing Build & Test
Zerithax
When launching the below private world link via Build & Test, the 2nd client always ends up being a black screen. You can confirm it's the 2nd client by launching 3 test clients and noting that the 2nd window thumbnail is black.
VRC Client: Unity-6 Beta
SDK Version: 3.10.1
OS: Win10
Dexvoid
Merged in a post:
[1854] In local world testing, launching multiple clients causes the second and subsequent clients to freeze on a black screen
kurotori
〇 Environment
OS: Windows 11 Pro 25H2 Build 26200.8457
Unity: 2022.3.22f1
VRCSDK: 3.10.3
〇 Summary
When performing local world tests using Build & Test Your World or Test Your Last Build, launching multiple clients simultaneously may cause the second and subsequent clients to become stuck on a black screen.
Launching clients with a delay between each instance can partially mitigate the issue.
〇 Steps to Reproduce
- Open the VRChat SDK in Unity.
- Run Build & Test Your World or Test Your Last Build.
- Launch multiple clients at the same time.
- The second and subsequent clients may remain stuck on a black screen and fail to proceed.
〇 Additional Reproduction Conditions
Based on investigation, this issue appears to be indirectly related to log output.
The issue occurs consistently under the following conditions:
- Disable debug log output for the client.
- Launch the first client.
- Launch the second and subsequent clients.
- The additional clients will consistently become stuck on a black screen.
〇 Possibly Related Issue
A potentially related issue, also suspected to be caused by log output, was observed:
When two clients are running in a local test and are in the same world, performing a rejoin from one client causes VRChat to crash.
After this occurs, VRChat will continue to crash consistently when rejoining the same world, even when running only a single client.
This issue can be resolved by deleting the log files in the following directory:
%HOMEPATH%\AppData\LocalLow\VRChat\VRChat
〇 Suspected Cause
It is likely that a deadlock or similar resource contention involving log files is occurring, causing clients to freeze or crash.
〇 Expected Behavior
All clients should launch and enter the world normally when running multi-client local tests.
Rejoining a world should not cause crashes regardless of log file state.
〇 Actual Behavior
The second and subsequent clients may freeze on a black screen when launched simultaneously.
Under certain conditions, rejoining a world causes VRChat to crash persistently until log files are deleted.
〇 Notes
This issue significantly impacts local multi-client testing workflows and should be addressed with high priority.
Patroll
This is so annoying and it's been happening for months. This is infuriating because it's the basic functionality of world creation. You can't even close any of the black windows
Jar
There is another thread with the same issue,
The workaround posted there (Set debug logging to Full) works for me, for now
Jar
This is still happening
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Jar
Looking forward to a fix for this ASAP, for now I have to keep re uploading to test with a friend or alt account on my phone and it's not ideal
This post was marked as
tracked
Fax
updated the status to
open
Thank you for providing additional details!
Fax
updated the status to
needs more information
Hello, RavenWorks! Thank you for the report.
We're unable to reproduce this issue on our end. Can you please provide additional details that may help narrow down the issue? For example - does your VRChat log contain any unusual errors?
Fuwako
Fax
Hello, I also had that issue. I managed to reliably reproduce the issue for my case. I am uncertain if my case is similar to others, but I also found a workaround for my case.
Description
Subsequent clients that are started after the first client become black and inoperable.
This can also occur when attempting to build and test a VRChat world with 2+ clients.
On the official VRChat Discord, I found that other users mentioned the issue since September 11, 2025.
The issue seems to be dependent on the Logging setting. I can reliably reproduce both the problem and the workaround by changing the setting.
Reproduction steps
- Start VRChat normally.
- In the user menu, navigate to Settings → Debug → Logging.
Set Logging to "None".
- Quit VRChat. By doing this, the new Logging setting should be applied.
- Start a VRChat client via Steam or a shortcut, and allow it to fully load into the home world.
- Start a second client via a shortcut (same VRChat user profile or a different VRChat user profile).
Easy Anti-Cheat starts normally.
It indicates "INITIALIZING".
It indicates "WAITING FOR GAME".
VRChat starts with a white screen which abruptly becomes black after some time.
The VRChat window cannot be closed by clicking the X on the window bar. The process must be manually terminated.
Expected behavior
The first client and subsequent clients should all load and be operable.
Actual behavior
Subsequent clients improperly load and become inoperable.
Workaround
- Start VRChat normally.
- In the user menu, navigate to Settings → Debug → Logging.
Set Logging to "Errors Only" or "Full".
- Quit VRChat. By doing this, the new Logging setting should be applied.
- Multiple clients of the same profile and different profiles can be started.
Environment
OS: Microsoft Windows 11 Home
VRChat: Build 1769
Zebra North
Fuwako Thank you for the workaround! Mine was already set to "Errors Only", changing it to "Full" fixed the issue.