• Alphabet shares surged to a record high after Berkshire Hathaway disclosed a $4.9 billion stake in the tech giant.
  • The investment marks a rare technology bet for Warren Buffett's conglomerate, historically cautious about the sector outside of Apple.
  • The move is seen as a major vote of confidence in Alphabet's dominance across digital advertising, cloud computing, and artificial intelligence.

Alphabet Inc. shares climbed to an all-time high on Monday, extending recent gains after a regulatory filing revealed Berkshire Hathaway has taken a substantial position in the Google parent company. The stock was last up 5.4%, pushing its market capitalization further into record territory.

The surge follows the disclosure that Warren Buffett's investment conglomerate purchased approximately $4.9 billion in Alphabet shares, a significant move given Buffett's historical reluctance to make large bets on technology companies beyond Apple Inc. The filing, submitted to regulators late Friday, confirmed the position was established over recent months.

"This is the type of endorsement that moves markets," said a portfolio manager at a large institutional firm, who asked not to be named because they are not authorized to speak publicly. "When Berkshire takes a position of this size, especially in a sector they've largely avoided, it forces every investor to re-evaluate their thesis."

Berkshire's investment comes amid a broader rally in technology stocks, particularly those seen as leaders in the artificial intelligence space. Alphabet has reported robust earnings in recent quarters, driven by continued strength in its core search advertising business and accelerating growth in its Google Cloud division.

Efforts to reach a spokesperson at Berkshire Hathaway for comment were unsuccessful. A representative for Alphabet declined to comment on the stock movement or specific investor positions.

The investment marks only Berkshire Hathaway's second substantial foray into large-cap technology, making it a significant milestone for both companies. While Alphabet continues to face regulatory scrutiny over antitrust and privacy issues globally, the Berkshire stake suggests confidence that these challenges are manageable in the context of the company's long-term prospects.

Trading volume in Alphabet shares was more than double the 30-day average, according to people familiar with the matter, indicating broad-based investor interest following the disclosure. Other major technology stocks also saw modest gains in early trading, though none matched Alphabet's sharp ascent.

Correction: An earlier version of this article misstated the timing of the regulatory filing. It was submitted late Friday.