Alphabet (GOOGL.US) shares rose over 2% at the opening on Monday, reaching a new all-time high of $406.41. The surge follows a recent regulatory filing showing Berkshire Hathaway (BRK.A.US) significantly increased its position in the company during the first quarter. Berkshire Hathaway added to its holdings of Alphabet Class A shares and initiated a new position in Alphabet Class C shares, with the total estimated purchase amounting to approximately $11.5 billion. This represents Berkshire's largest acquisition for the quarter. Since initially establishing a position worth $4 billion in the third quarter of 2025, Berkshire's stake in Alphabet has grown to $16.6 billion by the end of the latest quarter, elevating the company from the 10th to the 7th largest holding in its portfolio.