Proxyman interferes with WebSocket upgrade request & causes race condition

Description

When using Proxyman to trace a WS connection with SSL Proxying enabled, Proxyman sends an HTTP 101 response back to the client immediately (within 5ms), before the server has actually returned its HTTP response. This causes a race condition in clients that need to wait for the upgrade (101) response before doing additional logic.

Steps to Reproduce

1. Start Proxyman and enable SSL Proxying for a WS API
2. Using any local client, open a WS connection at that URL

Current Behavior

Proxyman receives the HTTP upgrade request from the client and forwards it to the server, but does not wait for the server response before responding to the client. Instead, it immediately sends a fake success (HTTP 101) response to the client:

HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Sec-WebSocket-Accept: pIF19n7SVsW0u4/t7tCDGOzUNnY=
Connection: upgrade

Since the Sec-WebSocket-Accept header is correctly computed, this causes the client to erroneously believe the upgrade process has already completed. If the client waits for the upgrade process to complete before doing additional logic, this causes a race condition and all sorts of bad behavior.

Expected Behavior

Proxyman should wait for the HTTP response (whether 101 or not) and forward that response to the client, just like the behavior for other HTTP requests.

Environment

• App version: 5.16.0
• macOS version: 15.3.2 (24D81)