Post-Quantum TLS Verification PXY-5981

Tungsten does two separate TLS handshakes per intercepted connection — client→tungsten and tungsten→origin. Post-quantum (X25519MLKEM768) must be checked on each leg independently.

1. Tungsten → Origin (this connection)

caesium is the origin, so it can inspect this session directly. Loaded through tungsten → reflects the tungsten-to-origin leg. Loaded directly → just confirms caesium supports the group.

TLS version	TLS 1.3
Cipher suite	`TLS13_AES_256_GCM_SHA384`
Key-exchange group	`X25519`
Verdict	classical group (not post-quantum)

2. Client → Tungsten

caesium can't see this leg. Browsers reach tungsten via an explicit-proxy CONNECT tunnel, so probe it the same way with openssl s_client -proxy.

Proxy node Proxy address (host:port)

PQC preferred:

Expect Negotiated TLS1.3 group: X25519MLKEM768. A handshake failure means tungsten isn't offering PQC on this leg.
macOS note: the system /usr/bin/openssl is LibreSSL, which does not support -brief, -proxy, or post-quantum groups. Install OpenSSL 3 (brew install openssl@3) and run via /opt/homebrew/opt/openssl@3/bin/openssl.

Classical fallback:

Expect success — confirms non-PQC clients still work.