Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 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 that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * SUMMIT PARTNERS L P 2. Issuer Name and Ticker or Trading Symbol LifeStance Health Group, Inc. [LFST] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 222 BERKELEY STREET, 18TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 08/18/2025 (Street) BOSTON, MA 02116 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) 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 08/18/2025 S 8,407,643(1) D $5.07 33,524,715(2) D(3)(4)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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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 Underlying Securities (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 of Derivative Security: 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

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
SUMMIT PARTNERS L P 222 BERKELEY STREET 18TH FLOOR BOSTON, MA 02116		X
Summit Partners Growth Equity Fund IX-A, L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA 02116				shareholder
Summit Partners Growth Equity Fund IX-B, L.P. 222 BERKELEY STREET, 18TH FLOOR BOSTON, MA 02116				shareholder
SUMMIT INVESTORS GE IX/VC IV, LLC 222 BERKELEY ST, 18TH FLOOR BOSTON, MA 02116				owner
SUMMIT INVESTORS GE IX/VC IV (UK), L.P. 222 BERKELEY ST, 18TH FLOOR BOSTON, MA 02116				Owner
Summit Partners Entrepreneur Advisors Fund II, L.P. 222 BERKELEY ST, 18TH FLOOR BOSTON, MA 02116				Owner

Signatures

Summit Partners Growth Equity Fund IX-A, L.P., by Summit Partners GE IX, L.P., its GP, by Summit Partners GE IX, LLC, its GP, by Summit Partners, L.P., its Manager, by Summit Master Company, LLC, its GP, by /s/ Adam Hennessey, Member		08/20/2025
**Signature of Reporting Person		Date
Summit Partners Growth Equity Fund IX-B, L.P., by Summit Partners GE IX, L.P., its GP, by Summit Partners GE IX, LLC, its GP, by Summit Partners, L.P., its Manager, by Summit Master Company, LLC, its GP, by /s/ Adam Hennessey, Member		08/20/2025
**Signature of Reporting Person		Date
Summit Investors GE IX/VC IV (UK), L.P., by Summit Investors Management, LLC, its General Partner, by Summit Master Company, LLC, its Managing Member, by /s/ Adam Hennessey, Member		08/20/2025
**Signature of Reporting Person		Date
Summit Partners Entrepreneur Advisors Fund II, L.P., by Summit Partners Entrepreneur Advisors GP II, LLC, its General Partner, by /s/ Adam Hennessey, Member		08/20/2025
**Signature of Reporting Person		Date
Summit Investors GE IX/VC IV, LLC, by Summit Investors Management, LLC, its Manager, by Summit Master Company, LLC, its Managing Member, by /s/ Adam Hennessey, Member		08/20/2025
**Signature of Reporting Person		Date

Explanation of Responses:

*	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).
(1)	Represents 5,148,494 shares sold by Summit Partners Growth Equity Fund IX-A, L.P., 3,214,648 shares sold by Summit Partners Growth Equity Fund IX-B, L.P., 35,938 shares sold by Summit Investors GE IX/VC IV, LLC, 4,804 shares sold by Summit Partners Entrepreneur Advisors Fund II, L.P. and 3,759 shares sold by Summit Investors GE IX/VC IV (UK), L.P.
(2)	The reported securities are held as follows: 20,529,149 shares in the name of Summit Partners Growth Equity Fund IX-A, L.P.; 12,818,117 shares in the name of Summit Partners Growth Equity Fund IX-B, L.P.; 143,301 shares in the name of Summit Investors GE IX/VC IV, LLC; 19,157 shares in the name of Summit Partners Entrepreneur Advisors Fund II, L.P.; and 14,991 shares in the name of Summit Investors GE IX/ VC IV (UK), L.P.
(3)	Summit Partners, L.P. is the managing member of Summit Partners GE IX, LLC, which is general partner of Summit Partners GE IX, L.P., which is the general partner of Summit Partners Growth Equity Fund IX-A, L.P. and Summit Partners Growth Equity Fund IX-B, L.P. Summit Master Company, LLC is (i) the sole member of Summit Partners Entrepreneur Advisors GP II, LLC, which is the general partner of Summit Partners Entrepreneur Advisors Fund II, L.P. and (ii) the general partner of Summit Partners L.P., which is the manager of Summit Investors Management, LLC, which is the manager of Summit Investors GE IX/VC IV, LLC, and the general partner of Summit Investors GE IX/VC IV (UK), L.P.
(4)	Summit Master Company, LLC, as the sole member of Summit Partners Entrepreneur Advisors GP II, LLC and the managing member of Summit Investors Management, LLC, has delegated investment decisions, including voting and dispositive power, to Summit Partners, L.P. and its investment committee responsible for voting and investment decisions with respect to LifeStance Health Group, Inc. Summit Partners, L.P., through a four-person investment committee, currently composed of Peter Y. Chung, Mark A. deLaar, Darren M. Black and Craig D. Frances, has voting and dispositive authority over the shares held by each of these entities and therefore beneficially owns such shares. Each of the Summit Funds, Mr. Chung, Mr. deLaar, Mr. Black and Dr. Frances disclaim beneficial ownership of the shares, except, in each case, to the extent of such person's or entity's pecuniary interest therein.

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