C3.ai Founder Sold Shares Worth $4.78 Million

Thomas Siebel offloaded 444,248 shares in mid-September as part of a pre-established trading plan.

Updated on Sept. 26, 2026 in Artificial Intelligence

Bold flat-color editorial illustration of a stylized server stack, representing enterprise software infrastructure and institutional financial planning. — C3.ai CEO Thomas Siebel sold 444,248 company shares in mid-September, generating $4.78 million through a pre-arranged Rule 10b5-1 trading plan. AI Illustration. Upload story photo >

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C3.ai CEO Thomas Siebel sold 444,248 shares of the company stock across two days in September 2026. The transactions generated approximately $4.78 million in gross proceeds.

Why it matters

The sale follows a Rule 10b5-1 trading plan established in September 2024, providing a scheduled mechanism for equity divestment. It comes as the enterprise AI software company maintains a market capitalization of $1.7 billion.

Siebel realized $3.05 million in pre-tax profit from exercising vested options. The sales occurred at average prices of $10.90 and $10.54, well below the company's 52-week stock price high of $20.22.

The players

Thomas Siebel

The founder and CEO of C3.ai who oversees the company's enterprise-grade AI software development and strategic direction.

C3.ai

A software company focused on providing a platform for developing, deploying, and operating enterprise artificial intelligence applications.

The details

The shares were sold under a Rule 10b5-1 trading plan, a standardized SEC regulation that allows corporate insiders to sell a predetermined number of shares at specific times to avoid allegations of insider trading based on non-public information. Siebel exercised vested stock options — equity grants that have reached their maturity date and are available for purchase at a fixed price — to complete these transactions.

September 2024: Rule 10b5-1 trading plan was established.
September 15, 2026: 282,001 shares were sold at an average price of $10.90.
September 16, 2026: 162,247 shares were sold at an average price of $10.54.
November 2028: The remaining options are scheduled to reach their expiry date.

The Tech Race

The use of SEC Rule 10b5-1 remains the standard protocol for corporate insiders to execute equity sales without triggering market volatility concerns. This mechanism ensures that large-scale divestment by founders remains decoupled from immediate stock market performance or company-specific news cycles.

While the sale does not directly change software functionality or customer service, it represents a significant shift in internal equity holdings for the company. Following these transactions, Siebel continues to hold 722,362 shares in the organization.

The takeaway

Investors should monitor future filings to see if further sales occur as C3.ai navigates its $1.7 billion valuation. Market participants can track the company's performance against its 52-week low of $7.68 to gauge shifting investor sentiment.