• Emit required Connection options for HTTP/1 response upgrade advertisements without changing connection state.
• Parse all HTTP/1 Connection header options consistently.
• Only treat Expect: 100-continue as a continue expectation in HTTP/1.1 requests.
• Reject WebSocket handshakes with a Sec-WebSocket-Key value that is not valid Base64 or does not decode to 16 bytes.
• Reject WebSocket Close frames with payloads larger than 125 bytes.
• Return a 426 Upgrade Required response when an unsupported WebSocket version is requested.