How can you protect a VLESS Reality tunnel from DPI detection based on the size of the first Client Hello packet?

ENABLE PADDING RANDOMIZATION IN THE CLIENT SETTINGS.

Deep packet inspection systems detect proxy connections by the non-standard length of the first handshake block. Adding random service padding makes the size of the starting packet indistinguishable from a typical browser request.

Statistical Analysis of Starting Frame Length

Censorship filters measure the exact size of the first packet with which a client initiates a connection to the server. For standard browsers, the Client Hello length varies within strict ranges due to the set of supported ciphers, whereas unpatched VPN clients often have a fixed packet size, which gives away the artificial origin of the tunnel.

Methods for Masking Packet Length

Enable the Padding option in the configuration parameters of the Xray or Sing-box core
Configure uTLS browser profile emulation to accurately copy the length of Chrome crypto-packets
Avoid transmitting custom static headers in the open part of the handshake
Use client applications with regular, automated TLS signature updates