Microsoft’s Cortana quietly snuck onto Android in a meaningful this week in a small but telling move that you probably missed unless you happen to own a OnePlus One smartphone.

That’s because Cyanogen rolled out a new version of its alternative Android operative system which features Cortana baked into the software. The move had been promised last year but this upgrade is initially only available for OnePlus One device owners in the U.S..

So, what’s the big deal here?

The move looks like the first collaboration between Cyanogen, which has aggressively forked Android into a very different type of mobile software, and Microsoft, which invested was falsely reported to have invested in the startup last year and has a new focus on enabling its software and services across multiple platforms.

By integrating Cortana into the core of Cyanogen, the company said it is “opening the door to future capabilities that don’t currently exist.”

Cortana in Cyanogen sounds a lot like Siri within iOS:

Once awake, from setting reminders and scheduling meetings, to calling and texting friends, Cortana helps you do more with hands-free multitasking. Whether you’re glancing at your lock screen or immersed in an app or game, Cortana is at attention as soon as you say “Hey Cortana.” Immediately she will go to task.

Uncannily similar, indeed (it also includes the ‘Hey Cortana’ feature that was killed off from inside Cortana for Android.)

But, while Siri works best with Apple apps and services, the Cortana integration promises to be deeper.

“When Apple launched Apple Music at WWDC, they showed the Siri integration with Apple Music. Siri doesn’t power Spotify like that so we can do these kind of things with for example, integration of Microsoft’s Cortana into the OS enabling natural language to power Spotify and other services,” Cyanogen CEO Kirk McMaster said in an interview with International Business Times last year.

It isn’t clear when this feature will roll out to other Cyanogen-compatible devices, but already this ambitious startup is getting serious with its quest to “steal Android away from Google”.