I maintain a cross-platform client side network library for persistent TCP connections targeting Win32, Darwin and FreeBSD platforms. I recently upgraded to a Mac Studio w/ M1 Max (Ventura 13.1) from a late 2015 Intel Macbook Pro (Monterey 12.6.2) and I've encountered a discrepancy between the two. For secure TCP connections my lib uses WolfSSL across all platforms but also supports use of system provided Security libraries. On Darwin platforms this is SecureTransport. Yes I am aware SecureTransport is deprecated in favor of Network. I intend to attempt to integrate with Network later but for now my architecture dictates that I use similar C-style callbacks akin to WolfSSL, OpenSSL, MBedTLS etc. On the first call to SSLHandshake the SecureTransport write callback generates 151 bytes for my TLS 1.2 connection to example.com:443 on both platforms. However, while on Intel MBP I am able to continue with the full handshake I immediately receive 0 bytes with EOF. In Wireshark on the Intel MBP the 151 bytes are observed as a TLS 1.2 client hello while on M1 it is observed as an SSL continuation message and that is the last message observed.