claude-dev-suite Coldcard (Coinkite)
Bitcoin-only hardware wallet. Industry favorite for airgapped signing. Models: Mk4, Q.
Models
| Model | Year | Notes |
|---|---|---|
| Mk4 | 2022 | USB-C + microSD + NFC, no battery |
| Q | 2024 | Color touchscreen, USB-C, microSD, NFC, full keyboard, battery |
Airgap support
Multiple transport options:
- microSD card: write PSBT to card, sign on device, write back.
- NFC: tap-to-transfer.
- QR codes (Q only): scan + display.
- USB: direct (less airgap).
Bitcoin-only firmware
Coldcard intentionally supports ONLY Bitcoin. No altcoins. Smaller attack surface, simpler mental model.
Trick PINs
Defense against coercion:
- Set up multiple PINs.
- "Real" PIN unlocks main wallet.
- "Duress" PIN unlocks decoy wallet (real-looking but with different seed).
- "Login countdown" — N attempts before wallet wipe.
BIP85
Native support for deriving sub-seeds via BIP85. UI lets you generate:
- BIP39 mnemonic (any word count).
- HEX bytes.
- WIF private key.
- xprv.
MuSig2 (experimental)
Mk4 has experimental MuSig2 support for cooperative Taproot signing. Not yet standard across HW wallets.
Backup
- Standard 24-word seed.
- "Tarot card" backup grids for resilient recovery.
- BIP85-derived sub-seeds.
- Encrypted backups to microSD with a separate backup password.
API
ckcc-protocol Python:
from ckcc_protocol.client import ColdcardDevice
dev = ColdcardDevice()
pk = dev.get_xpub("m/84'/0'/0'")
dev.sign_psbt(psbt_bytes)
Connection
- USB-C.
- microSD (airgap).
- NFC (Mk4, Q).
- Q only: QR code.
Third-party: HWI, Sparrow, Specter, Electrum.
Common issues
- microSD format must be FAT32 (max 32 GB).
- USB driver issues on some Linux distros.
- NFC on iPhone limited to read-only — use Android for tap-to-sign.