49,917 RSUs granted to Terrestrial Energy (IMSR) General Counsel

Rhea-AI Filing Summary

Terrestrial Energy Inc. reported that its General Counsel, Steven M. Millsap, received a grant of 49,917 restricted stock units (RSUs). Each RSU represents a contingent right to acquire one share of common stock.

The RSUs were granted under the Terrestrial Energy Inc. 2025 Equity Incentive Plan. They vest in one‑third installments on each of the first, second and third anniversaries of the grant date, conditioned on Mr. Millsap’s continued service with the company. After this award, he holds 49,917 RSUs directly.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider Millsap Steven M.

Role General Counsel

Type	Security	Shares	Price	Value
Grant/Award	Restricted Stock Units	49,917	$0.00	--

Holdings After Transaction: Restricted Stock Units — 49,917 shares (Direct)

Footnotes (1)

1. Each restricted stock unit represents a contingent right to acquire one share of Common Stock. Consists of restricted stock units granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive Plan. The restricted stock units vest in one-third increments on each of the first, second and third anniversaries of the grant date, subject to the reporting person's continued service through each applicable vesting date.

Key Figures

RSUs granted: 49,917 restricted stock units Grant price per RSU: $0.00 per unit RSUs held after grant: 49,917 restricted stock units

3 metrics

RSUs granted 49,917 restricted stock units Award to General Counsel on April 12, 2026

Grant price per RSU $0.00 per unit Equity compensation award, no cash paid by insider

RSUs held after grant 49,917 restricted stock units Total RSUs directly owned following the reported transaction

Key Terms

Restricted Stock Units, 2025 Equity Incentive Plan, vest, continued service

4 terms

Restricted Stock Units financial

"Each restricted stock unit represents a contingent right to acquire one share of Common Stock."

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

2025 Equity Incentive Plan financial

"Consists of restricted stock units granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive Plan."

vest financial

"The restricted stock units vest in one-third increments on each of the first, second and third anniversaries 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.

continued service financial

"subject to the reporting person's continued service through each applicable vesting date."

Form 4 Insider Transactions: What Each Field Means →

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^*

Millsap Steven M.

(Last) (First) (Middle)

C/O TERRESTRIAL ENERGY INC.

2730 W. TYVOLA ROAD, SUITE 100

(Street)

CHARLOTTE NORTH CAROLINA 28217

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Terrestrial Energy Inc. /DE/ [ IMSR ]

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

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
04/12/2026

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

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
Restricted Stock Units	(1)	04/12/2026		A		49,917		(2)	(2)	Common Stock	49,917	$0	49,917	D

Explanation of Responses:

1. Each restricted stock unit represents a contingent right to acquire one share of Common Stock.

2. Consists of restricted stock units granted pursuant to the Terrestrial Energy Inc. 2025 Equity Incentive Plan. The restricted stock units vest in one-third increments on each of the first, second and third anniversaries of the grant date, subject to the reporting person's continued service through each applicable vesting date.

	/s/ Steven M. Millsap	04/14/2026
	** 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)

FAQ

What insider transaction did Terrestrial Energy (IMSR) report for Steven M. Millsap?

Terrestrial Energy reported that General Counsel Steven M. Millsap received a grant of 49,917 restricted stock units. These RSUs are a form of equity compensation that may convert into the company’s common stock over time, aligning his interests with shareholders.

How many Terrestrial Energy (IMSR) RSUs were granted to the General Counsel?

Steven M. Millsap was granted 49,917 restricted stock units. Each RSU represents a contingent right to receive one share of Terrestrial Energy common stock, subject to vesting conditions and continued service requirements specified in the company’s 2025 Equity Incentive Plan.

What is the vesting schedule for Steven M. Millsap’s Terrestrial Energy RSUs?

The 49,917 restricted stock units vest in one‑third increments on each of the first, second, and third anniversaries of the grant date. Vesting is conditioned on Mr. Millsap remaining in service with Terrestrial Energy through each applicable vesting date.

Does the Terrestrial Energy (IMSR) RSU grant involve an open‑market stock purchase?

No, the filing describes a grant of restricted stock units as compensation, not an open‑market stock purchase. The RSUs were awarded at no cash cost per unit under the company’s 2025 Equity Incentive Plan, and convert to shares only as they vest over time.

How many Terrestrial Energy RSUs does Steven M. Millsap hold after this transaction?

Following this grant, Steven M. Millsap holds 49,917 restricted stock units directly. These RSUs give him a contingent right to receive an equal number of Terrestrial Energy common shares, assuming all vesting conditions and continued service requirements are fully satisfied.