Mercury Systems director Ostfeld gets 2,348 stock units

Vested units convert to common stock only when Scott Ostfeld ceases to serve on Mercury Systems Inc.’s board.

Available on EDGAR 10/30/2026 - 08:55 AM EDT Accepted by SEC EDGAR 10/30/2026 - 08:54 AM EDT Learn about SEC filing dates

Rhea-AI Filing Summary

Mercury Systems Inc. director Scott Ostfeld was granted 2,348 deferred stock units on October 28, 2026, in connection with board service. He assigned all rights to shares issuable under the award to JANA Partners Management, LP, and settlement on vesting will be made to JANA. The units vest on the earlier of the first anniversary of the grant date and the next annual meeting. Based on its current structure, JANA will no longer file as a director-by-deputization for Section 16 purposes.

Insider Trade Summary

Grant/Award: 2,348 shares

Grant/Award 1 txn

Insider Ostfeld Scott

Role Director

Type	Security	Shares	Price	Value
Grant/Award	Common Stock, par value $0.01 per share F1, F2	2,348	$0.00	$0.00

Holdings After Transaction: Common Stock, par value $0.01 per share — 0 shares (Indirect, See footnote)

Footnotes (2)

1. F1. Represents deferred stock units ("DSUs") granted to Scott Ostfeld ("Mr. Ostfeld"), a Managing Partner and Portfolio Manager of JANA Partners Management, LP ("JANA"), in connection with his service on the Issuer's Board of Directors. The DSUs vest on the earlier of the first anniversary of the grant date and the next annual meeting of shareholders. Vested DSUs do not convert into shares of common stock until the date on which Mr. Ostfeld ceases to be a member of the Issuer's Board of Directors.
2. F2. Mr. Ostfeld has assigned all rights to any shares issuable pursuant to the grant to JANA. Pursuant to the assignment, settlement of the award on vesting will be made to JANA.

Key Figures

Deferred stock units granted: 2,348 units Grant date: October 28, 2026 Reported shares following transaction: 0 shares

3 metrics

Deferred stock units granted 2,348 units Award to Scott Ostfeld for board service on October 28, 2026

Grant date October 28, 2026 Deferred stock unit award

Reported shares following transaction 0 shares Reported resulting position

Key Terms

deferred stock units, vest, director-by-deputization

3 terms

deferred stock units financial

"Represents deferred stock units ("DSUs") granted to Scott Ostfeld"

Deferred stock units are promises from a company to give an employee shares of stock at a future date, often after certain conditions are met or after leaving the company. They function like a form of delayed compensation, allowing employees to earn shares over time. For investors, they represent potential future ownership in the company, but do not provide immediate voting rights or dividends until the shares are actually received.

vest financial

"The DSUs vest on the earlier of the first anniversary of the grant date"

A vest is the process by which an employee earns the right to receive certain benefits or ownership interests, such as stock or retirement funds, over time. It’s similar to earning a reward gradually, ensuring that the benefit becomes fully yours only after a set period or meeting specific conditions. This makes it important for investors because it determines when they can actually claim or use those benefits.

director-by-deputization regulatory

"JANA will no longer file as a director-by-deputization for purposes of Section 16"

FAQ

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

How many deferred stock units did MRCY director Scott Ostfeld receive?

Scott Ostfeld received 2,348 deferred stock units on October 28, 2026, in connection with service on Mercury Systems Inc.'s board. He assigned all rights to shares issuable under the award to JANA Partners Management, LP, and settlement on vesting will be made to JANA.

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

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SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Ostfeld Scott

(Last) (First) (Middle)

888 SEVENTH AVENUE, 24TH FLOOR

(Street)

NEW YORK NEW YORK 10106

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
MERCURY SYSTEMS INC [ MRCY ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/28/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock, par value $0.01 per share	10/28/2026		A		2,348(1)	A	$0	0	I	See footnote(2)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Represents deferred stock units ("DSUs") granted to Scott Ostfeld ("Mr. Ostfeld"), a Managing Partner and Portfolio Manager of JANA Partners Management, LP ("JANA"), in connection with his service on the Issuer's Board of Directors. The DSUs vest on the earlier of the first anniversary of the grant date and the next annual meeting of shareholders. Vested DSUs do not convert into shares of common stock until the date on which Mr. Ostfeld ceases to be a member of the Issuer's Board of Directors.

2. Mr. Ostfeld has assigned all rights to any shares issuable pursuant to the grant to JANA. Pursuant to the assignment, settlement of the award on vesting will be made to JANA.

Remarks:

Based on the current structure of JANA, JANA will no longer file as a director-by-deputization for purposes of Section 16 under the Securities Exchange Act of 1934.

	/s/ Scott Ostfeld	10/30/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)