mrambossekandClaude Opus 5
1472a86508
A connection opening with a TLS handshake (first byte 0x16) and ALPN elt-echo gets the ClientHello it sent back raw (b64) and as a JA4 fingerprint (sec.clienthello_echo), then a TLS byte-echo; plain connections are unchanged. One port, multiplexed by a timed peek: plain echo is server-speaks-first, so a silent client (peek timeout) is greeted, while a TLS client's immediate ClientHello (0x16) routes to the TLS path — 500ms tolerates ~1s RTT before misdetection. JA4 (FoxIO): full ClientHello parser (ciphers, extensions, ALPN, supported_versions, sig algs) with GREASE exclusion; a_b_c fingerprint, unit-tested for structure + GREASE invariance. Live-verified: elt-echo negotiated, JA4 t13d1712eo computed, 1530-byte ClientHello returned. Capability tls-echo. This completes spec §4. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>