After creating a new encrypted
id-rsa key file with
ssh-keygen and using it for the first time, I cannot get macOS to forget the passphrase. This is similar to how to make OS X not remember ssh key passphrase question but worse.
I tried rebooting, killing the
ssh-agent, locking all my keychains but it still seems to be stored somewhere. However, I cannot find it in any keychains. This seems to be very insecure. The answers to SSH private key password never removed with Keychain/ssh-agent also do not help.
In fact, the dialog that used to appear asking you whether you wanted to store the passphrase or not does not seem to exist anymore.