On Monday, the U.S. ride-hailing company announced it’s opening up its software for third-parties to integrate and its first such partnership is with Facebook’s (FB) Messenger app. The integration is available in 11 U.S. cities, including Austin, New York, San Francisco and Washington, D.C.

The partnership with Messenger puts Lyft squarely in competition with its biggest rival, Uber, yet again. In December, Messenger added an identical ability to order rides from Uber. The obvious advantage is for customers who use both services, and will now have both at their disposal within the Facebook’s messaging app.

Monday’s announcement from Lyft is also a more formal continuation of the individual partnerships the company has been making in the last few months. In November, Lyft announced a similar integration with Slack, the increasingly popular workplace chat app. Lyft has also partnered with transit apps like CityMapper and RideScout, and last fall, it teamed up with ride-hailing companies Didi Kuaidi, Grab, and Ola to let their respective customers book rides through each other’s services.

Uber’s own toolkit for integrating its software into third-parties has been available to developers since August 2014.