Sourcetree fails to authenticate to Bitbucket with git and ssh using yubikey

Hello,

I recently generated a new pair of keys to be used with my Yubikey for SSH logins. I successfully added the ssh public key to Bitbucket and it is correctly installed on my system (ie visible from ssh-add).

When I use the git command line everything works fine: for every remote git command to Bitbucket (even from a terminal launched from Sourcetree), macOS asks me the pin to properly unlock my Yubikey (where the private key is securely stored) and the git command ends with success.

Unfortunately, when I try the very same remote command through Sourcetree GUI, it fails. From the log I see that Sourcetree\git is trying to directly unlock the private key without asking for the pin (in fact, macOS's pin dialog is never shown).

I suspect this error occurs with every external token card for SSH.
Could you please investigate this issue and make sure that Sourcetree properly works with an external token card?

Thanks for your help.

Best Regards,

Nicholas

References:
http://florin.myip.org/blog/easy-multifactor-authentication-ssh-using-yubikey-neo-tokens
https://www.isi.edu/~calvin/yubikeyssh.htm

Note: initially reported to Atalssian Service Desk (code: STSP-5478).