Mercury Systems officer proposes $76K share sale

The 1,000 shares are listed as acquired through restricted stock vesting from the issuer on February 15, 2025, with compensation recorded as the nature of payment.

Rhea-AI Filing Summary

Mercury Systems Inc. officer Stuart Kupinsky reported a proposed sale of 1,000 common shares, with an aggregate market value of $76,000.00 and an approximate sale date of October 21, 2026, through Fidelity Brokerage Services LLC. The shares are listed as acquired through restricted stock vesting from the issuer on February 15, 2025, with compensation listed as the nature of payment.

Key Figures

Common shares proposed for sale: 1,000 shares Aggregate market value: $76,000.00 Shares outstanding: 60,136,133 shares +5 more

8 metrics

Common shares proposed for sale 1,000 shares Approximate sale date: October 21, 2026

Aggregate market value $76,000.00 For the 1,000 common shares proposed for sale

Shares outstanding 60,136,133 shares Reported in the securities information

Prior sale 1,195 shares August 17, 2026; listed among securities sold during the past three months

Prior sale 1,178 shares August 18, 2026; listed among securities sold during the past three months

Prior sale 1,308 shares August 19, 2026; listed among securities sold during the past three months

Prior sale 1,000 shares August 21, 2026; listed among securities sold during the past three months

Prior sale 1,000 shares September 21, 2026; listed among securities sold during the past three months

Key Terms

Rule 144, Restricted Stock Vesting, attorney-in-fact

3 terms

Rule 144 regulatory

"See the definition of "person" in paragraph (a) of Rule 144."

Rule 144 is a U.S. securities regulation that sets conditions under which restricted or insider-held shares can be legally resold to the public, such as required holding periods, availability of public information, limits on how much can be sold at once, and certain filing requirements. For investors it matters because it determines when previously locked-up shares can enter the market — like a release valve that can increase supply, affect share price, and signal insider intent.

Restricted Stock Vesting financial

"Restricted Stock Vesting"

Restricted stock vesting is the timetable and conditions under which shares granted to employees or insiders become fully owned and can be sold, typically requiring continued work or meeting performance goals. It matters to investors because large blocks of shares can become tradable at once, which can change share supply and price, and because vesting aligns insiders’ incentives with the company’s long‑term performance—think of it like a timed unlock that both rewards and locks in key people.

attorney-in-fact regulatory

"as attorney-in-fact for Stuart Kupinsky"

An attorney-in-fact is the person or entity given legal authority through a power of attorney to act on behalf of another for specific tasks, such as signing documents, voting shares, or handling transactions. For investors, this matters because it lets a trusted representative make timely decisions or complete paperwork when the owner cannot, much like handing keys to someone to run errands on your behalf—so checks on scope and limits of that authority are important.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many MRCY shares did Stuart Kupinsky propose to sell?

Stuart Kupinsky proposed to sell 1,000 common shares, with an aggregate market value of $76,000.00 and an approximate sale date of October 21, 2026, through Fidelity Brokerage Services LLC.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 10/21/2026 - 12:28 PM EDT Accepted by SEC EDGAR 10/21/2026 - 12:27 PM EDT Learn about SEC filing dates

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0001289593
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	MERCURY SYSTEMS INC
SEC File Number	001-41194
Address of Issuer	50 MINUTEMAN ROAD ANDOVER MASSACHUSETTS 01810
Phone	9782561300
Name of Person for Whose Account the Securities are To Be Sold	KUPINSKY STUART
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Officer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common	Fidelity Brokerage Services LLC 900 Salem Street Smithfield RI 02917	1000	76000.00	60136133	10/21/2026	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common	02/15/2025	Restricted Stock Vesting	Issuer			1000	02/15/2025	Compensation

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
Stuart Kupinsky 50 Minuteman Road Andover MA 01810	Common	08/17/2026	1195	131391.33
Stuart Kupinsky 50 Minuteman Road Andover MA 01810	Common	08/18/2026	1178	131179.37
Stuart Kupinsky 50 Minuteman Road Andover MA 01810	Common	08/19/2026	1308	131200.25
Stuart Kupinsky 50 Minuteman Road Andover MA 01810	Common	08/21/2026	1000	95230.00
Stuart Kupinsky 50 Minuteman Road Andover MA 01810	Common	09/21/2026	1000	86520.00

144: Remarks and Signature

Remarks
Date of Notice	10/21/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	05/07/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ Daniel Tucci, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Stuart Kupinsky
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)