Shares of Uber Technologies (UBER 5.74%) were moving higher for the second day in a row, seemingly in response to billionaire Bill Ackman's announcement that he has invested more than $2 billion into Uber stock. Additionally, investors seemed to shrug off some news about a rival or even saw it as a positive sign.

As of 2:40 p.m. EST, the stock was up 5.4%.

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Uber's post-earnings rebound continues

Uber sold off following its fourth-quarter earnings report last week even as the company delivered strong results on the top and bottom lines. Guidance was solid as well, but it was just below analyst expectations, which led to a sell-off for the high-priced stock.

On Friday, the stock jumped after Ackman announced his position in the stock on the social media platform X, and praised the company, calling it "one of the best-managed and highest-quality businesses in the world."

Today, the stock continued to rise on that news and broader gains in the market, despite President Donald Trump's announcement of additional tariffs on steel and aluminum imports.

The other piece of news potentially impacting Uber was that Lyft is planning on launching robotaxis in 2026 in partnership with Mobileye. The news follows a similar announcement from Uber, which said last week that customers in Austin, Texas, would be able to order an autonomous vehicle through Uber in March as part of a partnership with Alphabet's Waymo.

Lyft's announcement makes it clearer that Tesla won't dominate the robotaxi market without a fight. In the past, Uber stock has moved in response to developments with Tesla's robotaxi, indicating are wary of the threat.

What's next for Uber

Robotaxis have been promised for nearly a decade, but they could finally be here as Waymo is already offering driverless rides in a number of cities, and Tesla now says it will ramp up production of its driverless Cybercab next year.

Uber's partnership with Waymo should prepare it well for the transition, and the business fundamentals look rock-solid after the latest earnings report. It's not a surprise that Ackman has taken a position in the stock. The leading ridesharing company looks poised for more growth and more gains.