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# 尝试过程

That is because websockets never report their requestHeadersText.
Fixed for the new implementation.

# 解决

I believe it happens when the actual request is not sent. Usually happens when you are loading a cached resource.

Another possible scenario I’ve seen - the exact same request is being sent again just after few milliseconds (most likely due to a bug in the client side).
In that case you’ll also see that the status of the first request is “canceled” and that the latency is only several milliseconds.

# 结论

Provisional headers are shown