Coldcard Mk 3+ hardware devices are compatible with Casa multisig vaults.
One thing to keep in mind when using your Coldcard is to remember to check for the most recent firmware updates here.
With Coldcard, the instructions for performing a health check and signing a transaction do differ slightly. See the below articles for the instructions for each function:
Some common Coldcard errors are:
Failure. My XFP not involved
Solution: Double-check that the Coldcard is the device used for that vault. If you are performing a key rotation make sure that you are not using the device you marked for replacement to try to sign.
There is an issue with the Coldcard firmware where it looks for the OP_CHECKMULTISIG opcode in the redeem script, but can't find it because it isn't taking into account that we use nested segwit (P2SH-P2WSH). It's assuming all addresses are P2SH or P2WSH.
You can get around this by going to Settings > Multisig Wallets > Skip Checks, and turning that setting on.
Couldn't find signature
Solution: Make sure to upload the correct file to confirm this request. It will prompt you with the file name to look for in the error message.
Failure Invalid PSBT multisig.py 716
This is shown when trying to sign a testnet transaction, but the right setting has not been configured. In order to sign for testnet you must do the following:
In Coldcard settings, select: Advanced > Danger Zone > Have ‘Testnet: BTC’ checked, not ‘Bitcoin’
Failure XPUBs in PSBT do not match any known wallet
This is shown if "Trust PSBT" is not enabled.
In Coldcard settings, select Multisig Wallets > Trust PSBT and select "Trust PSBT."
If you've tried the above steps and are still having issues, please reach out to our support team, and we're happy to assist.