Tesla Inc. (TSLA) dropped some interesting news in its fourth-quarter earnings release: the electric vehicle maker is investing about $2 billion into xAI, the artificial intelligence startup that happens to be run by Tesla's own CEO, Elon Musk.

Breaking Down the Numbers

Tesla is joining xAI's Series E funding round, which just pulled in a total of $20 billion and pegged the AI company's valuation at a jaw-dropping $230 billion. Tesla's $2 billion contribution represents 10% of this particular funding round, though it works out to less than 1% ownership of xAI overall.

The Rationale

Tesla is positioning this investment as a central element of its Master Plan Part IV. The company's argument? While xAI tackles digital intelligence through products like its Grok large language model, Tesla focuses on physical AI. The two companies have inked a framework agreement to explore potential collaborations, which Tesla says will accelerate development of its autonomous driving and robotics technologies.

Here's where things get complicated: this $2 billion investment lands amid a pending shareholder lawsuit from June 2024 that accuses Musk of breaching his fiduciary duties by creating xAI in the first place. The plaintiffs claim Musk redirected talent and business opportunities away from Tesla to prop up his private AI venture.

What's Next

The investment is expected to close in the first quarter of 2026, assuming it passes regulatory review. Tesla also revealed plans to introduce the Gen 3 version of its Optimus humanoid robot in the first quarter of this year, with large-scale production of both the Tesla Semi and CyberCab slated to begin in the first half of 2026.

Tesla shares climbed on the earnings beat and investment announcement, rising 4.15% to $448.33 in extended trading Wednesday.