@ShogunPanda Sorry to bother you again, while updating everything and running our full test suite, it appears we've found a regression introduced in 9.1.0.

When given a response like this:
HTTP/1.1 100 Continue\r\n\r\nHTTP/1.1 404 Not Found\r\nContent-Type: text/plain; charset=utf-8\r\nContent-Length: 14\r\nDate: Fri, 15 Sep 2023 19:47:23 GMT\r\nServer: Python/3.10 aiohttp/4.0.0a2.dev0\r\n\r\n404: Not Found

In 9.1+ this only parses the initial 100 response and nothing more. In older releases this would parse the 100 response and then parse the 404 response. This causes our client to hang and then timeout, thinking that the server never sent a response.