Scoop: Fidelity marks up the value of its stake in Elon Musk's X

Behind the scenes: Fidelity, which began marking down the company's shares just a month into Musk's stewardship, doesn't necessarily have any inside information on the X's financial performance, despite being a shareholder.

• It also doesn't disclose how it determines valuations of privately held companies.
• Comparable companies like Meta and Snap didn't experience similar stock price boosts in October, with Meta actually losing value.

Zoom in: The most likely explanation for X's price increase relates to xAI, a separate Musk company that is training its large language model on X data.

• Fidelity invested in xAI's $6 billion Series B round, and held those shares at cost for months until marking them up by around 70% in October.
• The Series B investment was new money, but there have been reports that X Holdings has a significant equity stake in xAI. If so, that could help explain the X Holdings increase.

The bottom line: Fidelity reports on a one-month lag, which means the new mark does not reflect the reelection of Donald Trump, or Musk's informal role in his upcoming administration.