Docs and Settings > OS X Code Signing page state that there is multiple code signing support, but once we upload second key, the first one gets replaced every time, so there’s always only one code signing key stored.
The following code-signing identities will be added to the system keychain when your build begins…
We install any P12 certificates that you have uploaded in project settings to circle.keychain
No code-signing identities found. You can add code-signing identities in project settings.