SharkWater Trading  •  Data Centers • Insider Filings Nebius COO Sold 500,000 Shares at a $235.53 Average, Over Half His Direct Stake October 7, 2026 Bottom Line Up Front The Form 144 we flagged yesterday is now a completed trade. Ophir Nave of Nebius Group (Nasdaq: NBIS) sold 500,000 shares on October 5, 2026 at a computed average of $235.53, roughly $117.8 million gross, per a Form 4 filed October 7. That is below the $121.4 million the Form 144 implied, which pegged the shares near $242.81. The Form 4 shows 454,685 shares held directly afterward, so the sale took about 52 percent of his directly held shares. It ran under a Rule 10b5-1 plan adopted May 22, 2026. What the Form 4 Shows A Form 144 is a notice. A Form 4 is the receipt. This one reports twelve sale lines on October 5, 2026, all coded as sales, all direct ownership. The weighted average prices run from $231.12 to $243.50. The pre-sale direct balance of 954,685 shares is derived from the first line (938,465 remaining plus 16,220 sold), not stated outright. Shares sold Weighted avg price 16,220 $231.12 61,210 $232.37 56,426 $233.19 48,845 $234.21 106,718 $235.24 73,588 $235.99 18,224 $237.15 48,655 $238.22 48,061 $239.23 14,853 $240.00 1,200 $241.02 6,000 $243.50 500,000 total $235.53 (desk calc) Source: Nebius Group N.V. Form 4, EDGAR, filed October 7, 2026 (accession 0001513845-26-000126), all sales dated October 5, 2026, Rule 10b5-1 plan adopted May 22, 2026. Each row is a weighted average within a price range stated in the filing. Total and average computed by this desk from the rows. The filing remarks say the shares sold were settled restricted share units, about 17 percent of the reporting person's granted equity. Nave is listed as a director and an officer with the title COO. The Form 144 listed him as Director and Officer, so the two filings agree on the person. The Form 144 value of $121,405,000 is an estimate made at filing. Actual proceeds came in about $3.6 million lower on this desk's math, which means the stock traded below the Form 144 reference price for most of the session. Nebius has not issued a press release on this, and none is required. A Form 144 is the weather forecast and a Form 4 is the logbook. The forecast said the boat would leave at $242. The logbook says it left across a dozen tides between $231 and $243, and most of the catch went out in the low to mid $230s. What Is Still Open The plan terms are not public. This desk does not know whether the May 22 plan has more tranches. The September 30 Nebius Form 144 (accession 0001950047-26-009868) was not read, so how it relates to this sale is unknown. Two other officers sold shares on October 1 at $234.16 to cover tax on vested units, which is routine and a different animal at about 9 percent of this size. The Bull Case Pre-scheduled. The plan date of May 22, 2026 predates the sale by more than four months. The timing was set long before October 5. Small against the share count. 500,000 shares was about 0.21 percent of the 238,400,165 shares outstanding cited on the Form 144. Still a large holder. 454,685 shares remain in direct ownership, so he kept a meaningful position. The Bear Case Half the direct stake. Selling about 52 percent of directly held shares in one day is a large reduction, plan or not. Clustered paper. A second Form 144 on September 30 and three Form 4s on October 5 mean insider selling has stacked up over a single week. Sold below the reference. Proceeds came in under the Form 144 estimate, and the 12 line ladder shows the shares went out across a $12 range, mostly in the $230s. The SharkWater Take The 10b5-1 plan takes most of the sting out of the timing argument, and 0.21 percent of shares outstanding will not change the float. What I notice is the size relative to his own position. Half of a direct stake is not a trim. I am not treating this as a sell signal for the company, because a plan sale alone does not tell me the executive's view of the business. I am treating it as a reason to read the next Nebius filings closely, and to check the September 30 Form 144 before drawing any pattern. No edge here for a new position on this alone. Tight lines, SharkWater Educational and informational purposes only. Not personalized investment advice. All figures sourced as noted and accurate as of publication. Options involve substantial risk of loss. The author may hold positions in securities discussed. Do your own work.