SCHEDULE: JANA Partners Adjusts Mercury Systems Stake to 8.3%

JANA Partners Management, LP, a significant shareholder, has updated its beneficial ownership in Mercury Systems Inc. to 8.3% following a recent share sale and DSU grants.

Summary

• JANA Partners Management, LP filed Amendment No. 3 to its Schedule 13D regarding its beneficial ownership in Mercury Systems Inc.
• JANA Partners now beneficially owns 4,966,675 shares of Mercury Systems Inc., representing approximately 8.3% of the outstanding shares.
• This ownership percentage is based on 60,100,136 shares outstanding as of October 31, 2025, as reported in the Issuer's Quarterly Report on Form 10-Q.
• On November 6, 2025, JANA Partners sold 1,000,000 shares of Mercury Systems Inc. at a price of $75.45 per share.
• The transaction was effected for the purpose of rebalancing the holdings of funds and accounts managed by JANA.
• Mr. Ostfeld, a Board member, was granted 2,362 deferred stock units (DSUs) on October 22, 2025, for his service on the Board, which he assigned to JANA Partners.
• An earlier grant of 4,832 DSUs was made to Mr. Ostfeld on October 23, 2024, also assigned to JANA Partners.
• DSUs vest on the earlier of the first anniversary of the grant date or the next annual meeting of shareholders, but do not convert into shares until Mr. Ostfeld ceases to be a Board member.

Sentiment

Score: 5

Explanation: The sentiment is neutral to slightly negative. While JANA Partners reduced its stake through a share sale, the stated reason was portfolio rebalancing, not a fundamental negative outlook. JANA remains a significant shareholder, indicating continued interest, which balances the impact of the sale.

Positives

• JANA Partners, an activist investor, maintains a significant 8.3% stake in Mercury Systems Inc., indicating continued strategic interest and potential for ongoing engagement.
• The stated reason for the share sale was portfolio rebalancing, suggesting a strategic adjustment rather than a loss of confidence in the company's long-term prospects.

Negatives

• JANA Partners sold 1,000,000 shares, which represents a reduction in their overall stake and could be perceived negatively by the market, potentially signaling a decrease in conviction or a shift in investment focus.

Future Outlook

Deferred stock units granted to Mr. Ostfeld will vest on the earlier of the first anniversary of their grant date or the next annual meeting of shareholders. Vested DSUs will convert into shares only upon Mr. Ostfeld ceasing to be a member of the Board of Directors.

Management Comments

• The transaction reported herein was effected for the purpose of rebalancing the holdings of funds and accounts managed by JANA.

Industry Context

This filing reflects an activist investor's portfolio management decision within the defense technology sector. While not directly indicative of broader industry trends, the continued significant stake of JANA Partners in Mercury Systems Inc. suggests ongoing investor scrutiny and potential for strategic influence within the company.

Related Party Transactions

• Mr. Ostfeld, a member of the Board of Directors of Mercury Systems Inc. and a representative of JANA Partners, assigned all rights to shares issuable from his deferred stock unit grants to JANA Partners Management, LP.

Stakeholder Impact

• Shareholders: The sale of 1,000,000 shares by a major activist investor could lead to short-term price volatility or concern, though the 'rebalancing' explanation may mitigate negative sentiment. JANA's continued 8.3% ownership suggests ongoing influence and potential for value creation initiatives.
• Management: JANA Partners' continued significant stake means management will likely remain under scrutiny regarding strategic direction and shareholder value.

Next Steps

• DSUs granted to Mr. Ostfeld will vest on the earlier of the first anniversary of the grant date or the next annual meeting of shareholders.
• Vested DSUs will convert into shares upon Mr. Ostfeld's departure from the Board of Directors.

Key Dates

Recommendation

JANA Partners, a significant activist investor, reduced its stake in Mercury Systems Inc. by selling 1 million shares. While this might initially appear negative, the stated reason was portfolio rebalancing, not a change in the company's fundamentals or JANA's strategic view. JANA still retains a substantial 8.3% ownership, indicating continued engagement. Therefore, a 'hold' recommendation is appropriate as this filing primarily reflects an investor's portfolio management rather than a direct signal for the company's future performance or a fundamental shift in the company's outlook.

Keywords

JANA Partners, Mercury Systems, Schedule 13D, Share Sale, Beneficial Ownership, Activist Investor, MSI, Deferred Stock Units, Portfolio Rebalancing