One card, not a family pocket
Single card share sends one card as its own encrypted payload. It does not add the other person to a pocket, and it does not give them the rest of your wallet. Family sharing is the tool for an ongoing household. This is the tool for one card, once.
Standing next to them
If the other person is beside you, CardWarden can show a QR code. They scan it in the app and receive the card without typing the passphrase. The passphrase is still the key. The QR carries it so nobody has to read it aloud at the counter.
When they are somewhere else
For someone who is not next to you, share the card and tell them the passphrase separately. The card is encrypted with ChaCha20-Poly1305 using a key derived from that passphrase with PBKDF2-HMAC-SHA256 (200,000 iterations). Without the passphrase, the payload does not open. The QR code does not change that. It only saves the typing when you are in the same place.
