Bug 302823 – Safari 26: Websocket fails to connect "The network connection was lost" in case of simultaneous http request to the same server

• Status: RESOLVED
• Resolution: MOVED
• Component: New Bugs

Steps to reproduce:

1. Restart Safari 26 
2. Go to https://jsfiddle.net/qbh8gLne/13/
3. Click "open websocket"

Results: 
- The "error" event fires for the websocket
- console shows error "The network connection was lost"

The problem does not appear to happen if:
- The fetch is to a different server
- The fetch is awaited before opening the websocket
- Safari is not restarted

Sample User Agent strings for users who have encountered this problem:

Mozilla/5.0+(iPhone;+CPU+iPhone+OS+18_7+like+Mac+OS+X)+AppleWebKit/605.1.15+(KHTML,+like+Gecko)+Version/26.1+Mobile/15E148+Safari/604.1 
Mozilla/5.0+(Macintosh;+Intel+Mac+OS+X+10_15_7)+AppleWebKit/605.1.15+(KHTML,+like+Gecko)+Version/26.1+Safari/605.1.15
Mozilla/5.0+(Macintosh;+Intel+Mac+OS+X+10_15_7)+AppleWebKit/605.1.15+(KHTML,+like+Gecko)+Version/26.0.1+Safari/605.1.15
Mozilla/5.0+(Macintosh;+Intel+Mac+OS+X+10_15_7)+AppleWebKit/605.1.15+(KHTML,+like+Gecko)+Version/26.0.1+Safari/605.1.15
Mozilla/5.0+(iPhone;+CPU+iPhone+OS+18_7+like+Mac+OS+X)+AppleWebKit/605.1.15+(KHTML,+like+Gecko)+Version/26.1+Mobile/15E148+Safari/604.1
Mozilla/5.0+(iPhone;+CPU+iPhone+OS+18_7+like+Mac+OS+X)+AppleWebKit/605.1.15+(KHTML,+like+Gecko)+Version/26.1+Mobile/15E148+Safari/604.12
Mozilla/5.0+(iPhone;+CPU+iPhone+OS+18_7+like+Mac+OS+X)+AppleWebKit/605.1.15+(KHTML,+like+Gecko)+Version/26.0.1+Mobile/15E148+Safari/604.1

Could this be related to https://bugs.webkit.org/show_bug.cgi?id=215631?

Is there any update on this, particularly if there is a server side workaround we could implement?  This is starting to affect many of our Safari users.

[Alexey Proskuryakov]

I was about to say that this seemed more like bug 302561, but (1) that one is reported to be an iOS 26.1 regression, and (2) I can reproduce this one without iCloud Private Relay.

Such WebSocket issues are generally in an underlying networking library below WebKit, so I'll move this bug to Apple internal system for Apple engineers to investigate.

> This is starting to affect many of our Safari users. 

If you could describe the impact (how many people are affected and how badly), that would help with prioritization. Please feel free to email me if you prefer to not share this information publicly.

[Radar WebKit Bug Importer]

<rdar://problem/165232100>

[Zhenchao Li]

I can reproduce the websocket error in Safari. However if I try Chrome it is giving me the same error.
I wonder if anything has since changed on the server side?
I can continue to investigate but would be good to confirm whether this is still an issue that only happens in Safari.

I just tried a few different browsers and these are my results:

Chrome on Windows (Version 143.0.7499.170 (Official Build) (64-bit)) - OK
Safari 26.2 on Tahoe desktop - ERROR
Chrome 143 on Tahoe desktop - OK
Chrome on iphone 17 26.0 - OK
Safari on iphone 17 26.0 - ERROR

(In reply to Alexey Proskuryakov from comment #2)
> I was about to say that this seemed more like bug 302561, but (1) that one
> is reported to be an iOS 26.1 regression, and (2) I can reproduce this one
> without iCloud Private Relay.
> 
> Such WebSocket issues are generally in an underlying networking library
> below WebKit, so I'll move this bug to Apple internal system for Apple
> engineers to investigate.
> 
> > This is starting to affect many of our Safari users. 
> 
> If you could describe the impact (how many people are affected and how
> badly), that would help with prioritization. Please feel free to email me if
> you prefer to not share this information publicly.

This is marked "resolved moved".   Was it moved to another bug system?

[Alexey Proskuryakov]

Yes:

> Such WebSocket issues are generally in an underlying networking library below WebKit, so I'll move this bug to Apple internal system for Apple engineers to investigate.

There are no updates to share here.