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So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."}],"balance_after":5909,"derivative":{"underlying":"Common Stock","underlying_shares":882},"source":{"system":"sec-edgar","filing":"0000950138-25-000036","document":"form4.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/2019804/000095013825000036/form4.xml","form_type":"4"}},{"id":961213,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":34662,"kind":"person","name":"Pardee Charles G","position":1,"cik":"0001544340","reported_name":"Pardee Charles G","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Restricted Stock Units","published_at":"2025-12-22T21:35:30.000Z","date":"2025-12-18","kind":"grant","planned":false,"acquired":true,"shares":5027,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."}],"balance_after":5027,"derivative":{"underlying":"Common Stock","underlying_shares":5027},"source":{"system":"sec-edgar","filing":"0000950138-25-000036","document":"form4.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2019804/000095013825000036/form4.xml","form_type":"4"}},{"id":961212,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":70999,"kind":"person","name":"MacDiarmid John Hugh","position":1,"cik":"0002092518","reported_name":"MacDiarmid John Hugh","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Resricted Stock Units","published_at":"2025-12-22T21:31:47.000Z","date":"2025-12-18","kind":"grant","planned":false,"acquired":true,"shares":1029,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."}],"balance_after":6894,"derivative":{"underlying":"Common Stock","underlying_shares":1029},"source":{"system":"sec-edgar","filing":"0000950138-25-000034","document":"form4.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/2019804/000095013825000034/form4.xml","form_type":"4"}},{"id":961211,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":70999,"kind":"person","name":"MacDiarmid John Hugh","position":1,"cik":"0002092518","reported_name":"MacDiarmid John Hugh","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Restricted Stock Units","published_at":"2025-12-22T21:31:47.000Z","date":"2025-12-18","kind":"grant","planned":false,"acquired":true,"shares":5865,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. 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So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."}],"balance_after":5865,"derivative":{"underlying":"Common Stock","underlying_shares":5865},"source":{"system":"sec-edgar","filing":"0000950138-25-000034","document":"form4.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2019804/000095013825000034/form4.xml","form_type":"4"}},{"id":961202,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":30101,"kind":"person","name":"Matthews Shawn","position":1,"cik":"0001855118","reported_name":"Matthews Shawn","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Restricted Stock Units","published_at":"2025-12-22T21:30:08.000Z","date":"2025-12-18","kind":"grant","planned":false,"acquired":true,"shares":735,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. 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So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."}],"balance_after":4925,"derivative":{"underlying":"Common Stock","underlying_shares":735},"source":{"system":"sec-edgar","filing":"0001213900-25-124579","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/2019804/000121390025124579/ownership.xml","form_type":"4"}},{"id":961201,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":30101,"kind":"person","name":"Matthews Shawn","position":1,"cik":"0001855118","reported_name":"Matthews Shawn","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Restricted Stock Units","published_at":"2025-12-22T21:30:08.000Z","date":"2025-12-18","kind":"grant","planned":false,"acquired":true,"shares":4190,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."}],"balance_after":4190,"derivative":{"underlying":"Common Stock","underlying_shares":4190},"source":{"system":"sec-edgar","filing":"0001213900-25-124579","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2019804/000121390025124579/ownership.xml","form_type":"4"}},{"id":961335,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":71026,"kind":"person","name":"BUCKMAN FREDERICK W","position":1,"cik":"0001144845","reported_name":"BUCKMAN FREDERICK W","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Resricted Stock Units","published_at":"2025-12-22T17:25:19.000Z","date":"2025-12-18","kind":"grant","planned":false,"acquired":true,"shares":1176,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."}],"balance_after":7879,"derivative":{"underlying":"Common Stock","underlying_shares":1176},"source":{"system":"sec-edgar","filing":"0000950138-25-000045","document":"form4.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/1144845/000095013825000045/form4.xml","form_type":"4"}},{"id":961334,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":71026,"kind":"person","name":"BUCKMAN FREDERICK W","position":1,"cik":"0001144845","reported_name":"BUCKMAN FREDERICK W","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}}],"security":"Restricted Stock Units","published_at":"2025-12-22T17:25:19.000Z","date":"2025-12-18","kind":"grant","planned":false,"acquired":true,"shares":6703,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. So long as the Reporting Person provides continuous service to Terrestrial Energy, Inc., 100% of the restricted stock units will vest on December 31, 2026."}],"balance_after":6703,"derivative":{"underlying":"Common Stock","underlying_shares":6703},"source":{"system":"sec-edgar","filing":"0000950138-25-000045","document":"form4.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/1144845/000095013825000045/form4.xml","form_type":"4"}},{"id":1000496,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":30101,"kind":"person","name":"Matthews Shawn","position":1,"cik":"0001855118","reported_name":"Matthews Shawn","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}},{"id":73234,"kind":"organization","name":"HCM Investor Holdings II, LLC","position":2,"cik":"0002019800","reported_name":"HCM Investor Holdings II, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":false,"other":true,"other_text":"Former 10% Holder"}}],"security":"Warrants","published_at":"2025-11-13T19:31:34.000Z","date":"2025-11-06","kind":"other","planned":false,"acquired":false,"shares":3500000,"ownership":{"direct":false,"nature":"See Footnote"},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F1","text":"On November 6, 2025, HCM Investor Holdings II, LLC (the \"Sponsor\") distributed an aggregate of 5,675,000 shares of common stock, par value $0.0001 per share of the Issuer (\"Common Stock\") and 4,275,000 Warrants, convertible to 4,275,000 shares of Common Stock, to its members as a distribution for no consideration in accordance with the terms of the Sponsor's limited liability company agreement. 2,755,000 shares of Common Stock and 775,000 Warrants were distributed to Shawn Matthews on such basis. Under Rule 16a-13 promulgated under the Securities Exchange Act of 1934, as a change in form of beneficial ownership, the reported distribution by the Sponsor (as it relates to Mr. Matthews' deemed beneficial ownership of the securities held by the Sponsor) to its members from the Sponsor, were exempt from Section 16 of the Securities Exchange Act of 1934."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"Shawn Matthews is the record holder of such securities. Shawn Matthews is the sole Managing Member of HCM Investor Holdings II, LLC and shares voting and investment discretion with respect to the securities held by HCM Investor Holdings II, LLC."}],"balance_after":775000,"derivative":{"exercise_price":11.5,"exercise_date":"2025-11-27","expiration_date":"2030-10-28","underlying":"Common Stock, par value $0.0001 per share","underlying_shares":3500000},"source":{"system":"sec-edgar","filing":"0001213900-25-110214","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/2019800/000121390025110214/ownership.xml","form_type":"4"}},{"id":1000495,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":30101,"kind":"person","name":"Matthews Shawn","position":1,"cik":"0001855118","reported_name":"Matthews Shawn","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}},{"id":73234,"kind":"organization","name":"HCM Investor Holdings II, LLC","position":2,"cik":"0002019800","reported_name":"HCM Investor Holdings II, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":false,"other":true,"other_text":"Former 10% Holder"}}],"security":"Common Stock, par value $0.0001 per share","published_at":"2025-11-13T19:31:34.000Z","date":"2025-11-06","kind":"other","planned":false,"acquired":false,"shares":2920000,"ownership":{"direct":false,"nature":"See Footnote"},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F1","text":"On November 6, 2025, HCM Investor Holdings II, LLC (the \"Sponsor\") distributed an aggregate of 5,675,000 shares of common stock, par value $0.0001 per share of the Issuer (\"Common Stock\") and 4,275,000 Warrants, convertible to 4,275,000 shares of Common Stock, to its members as a distribution for no consideration in accordance with the terms of the Sponsor's limited liability company agreement. 2,755,000 shares of Common Stock and 775,000 Warrants were distributed to Shawn Matthews on such basis. Under Rule 16a-13 promulgated under the Securities Exchange Act of 1934, as a change in form of beneficial ownership, the reported distribution by the Sponsor (as it relates to Mr. Matthews' deemed beneficial ownership of the securities held by the Sponsor) to its members from the Sponsor, were exempt from Section 16 of the Securities Exchange Act of 1934."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"Shawn Matthews is the record holder of such securities. Shawn Matthews is the sole Managing Member of HCM Investor Holdings II, LLC and shares voting and investment discretion with respect to the securities held by HCM Investor Holdings II, LLC."}],"balance_after":2755000,"source":{"system":"sec-edgar","filing":"0001213900-25-110214","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2019800/000121390025110214/ownership.xml","form_type":"4"}},{"id":1011450,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":73775,"kind":"person","name":"Loveless Jacob","position":1,"cik":"0001855174","reported_name":"Loveless Jacob","relationship":{"director":false,"officer":false,"ten_percent_owner":false,"other":true,"other_text":"Former Director"}}],"security":"Common Stock, par value $0.0001 per share","published_at":"2025-10-31T00:32:23.000Z","date":"2025-10-28","kind":"other","planned":false,"acquired":true,"shares":25000,"ownership":{"direct":true},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F1","text":"Upon closing of the business combination (the \"Business Combination\") between the Issuer (which was formerly known as HCM II Acquisition Corp. or \"HCM II\") and Terrestrial Energy Inc. (\"Terrestrial\") the reporting person acquired these securities in exchange for the reporting person's securities in Terrestrial pursuant to the terms and conditions of the business combination agreement, by and among HCM, Terrestrial and HCM II Merger Sub Inc. (the \"BCA\"). The reporting person resigned as a director of HCM II upon the closing of the Business Combination."}],"balance_after":25000,"source":{"system":"sec-edgar","filing":"0001213900-25-104332","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2019804/000121390025104332/ownership.xml","form_type":"4"}},{"id":1011456,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":65939,"kind":"person","name":"Connor Michael J","position":1,"cik":"0002029946","reported_name":"Connor Michael J","relationship":{"director":false,"officer":false,"ten_percent_owner":false,"other":true,"other_text":"Former Director"}}],"security":"Common Stock, par value $0.0001 per share","published_at":"2025-10-30T20:33:55.000Z","date":"2025-10-28","kind":"other","planned":false,"acquired":true,"shares":25000,"ownership":{"direct":true},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F1","text":"Upon closing of the business combination (the \"Business Combination\") between the Issuer (which was formerly known as HCM II Acquisition Corp. or \"HCM II\") and Terrestrial Energy Inc. (\"Terrestrial\") the reporting person acquired these securities in exchange for the reporting person's securities in Terrestrial pursuant to the terms and conditions of the business combination agreement, by and among HCM, Terrestrial and HCM II Merger Sub Inc. (the \"BCA\"). The reporting person resigned as a director of HCM II upon the closing of the Business Combination."}],"balance_after":25000,"source":{"system":"sec-edgar","filing":"0001213900-25-104334","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2029946/000121390025104334/ownership.xml","form_type":"4"}},{"id":1011455,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":73776,"kind":"person","name":"Brenner Andrew Scott","position":1,"cik":"0002030321","reported_name":"Brenner Andrew Scott","relationship":{"director":false,"officer":false,"ten_percent_owner":false,"other":true,"other_text":"Former Director"}}],"security":"Common Stock, par value $0.0001 per share","published_at":"2025-10-30T20:33:06.000Z","date":"2025-10-28","kind":"other","planned":false,"acquired":true,"shares":25000,"ownership":{"direct":true},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F1","text":"Upon closing of the business combination (the \"Business Combination\") between the Issuer (which was formerly known as HCM II Acquisition Corp. or \"HCM II\") and Terrestrial Energy Inc. (\"Terrestrial\") the reporting person acquired these securities in exchange for the reporting person's securities in Terrestrial pursuant to the terms and conditions of the business combination agreement, by and among HCM, Terrestrial and HCM II Merger Sub Inc. (the \"BCA\"). The reporting person resigned as a director of HCM II upon the closing of the Business Combination."}],"balance_after":25000,"source":{"system":"sec-edgar","filing":"0001213900-25-104333","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2030321/000121390025104333/ownership.xml","form_type":"4"}},{"id":1011454,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":30101,"kind":"person","name":"Matthews Shawn","position":1,"cik":"0001855118","reported_name":"Matthews Shawn","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}},{"id":73234,"kind":"organization","name":"HCM Investor Holdings II, LLC","position":2,"cik":"0002019800","reported_name":"HCM Investor Holdings II, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":false,"other":true,"other_text":"Former 10% owner"}}],"security":"Warrants","published_at":"2025-10-30T20:31:15.000Z","date":"2025-10-28","kind":"other","planned":false,"acquired":false,"shares":1267599,"price":11.5,"value":14577388.5,"ownership":{"direct":false,"nature":"See Footnote"},"footnotes":[{"field":"ownership.nature","element":"natureOfOwnership","label":"F4","text":"Mr. Matthews is the sole managing member of Hondo Holdings LLC, which is registered owner of these warrants, and Mr. Matthews holds voting and investment power with respect to warrants held of record by Hondo Holdings LLC."}],"balance_after":1267599,"derivative":{"exercise_price":11.5,"exercise_date":"2025-11-27","expiration_date":"2030-10-28","underlying":"Common Stock, par value $0.0001 per share","underlying_shares":1267599},"source":{"system":"sec-edgar","filing":"0001213900-25-104331","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":4,"url":"https://www.sec.gov/Archives/edgar/data/2019800/000121390025104331/ownership.xml","form_type":"4"}},{"id":1011453,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":30101,"kind":"person","name":"Matthews Shawn","position":1,"cik":"0001855118","reported_name":"Matthews Shawn","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}},{"id":73234,"kind":"organization","name":"HCM Investor Holdings II, LLC","position":2,"cik":"0002019800","reported_name":"HCM Investor Holdings II, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":false,"other":true,"other_text":"Former 10% owner"}}],"security":"Warrants","published_at":"2025-10-30T20:31:15.000Z","date":"2025-10-28","kind":"other","planned":false,"acquired":false,"shares":4275000,"price":11.5,"value":49162500.0,"ownership":{"direct":false,"nature":"See Footnote"},"footnotes":[{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"Mr. Matthews is the sole managing member of HCM Investor Holdings II, LLC (the \"Sponsor\"), which is registered owner of these shares and warrants, and Mr. Matthews holds voting and investment power with respect to shares and warrants held of record by the Sponsor."}],"balance_after":4275000,"derivative":{"exercise_price":11.5,"exercise_date":"2025-11-27","expiration_date":"2030-10-28","underlying":"Common Stock, par value $0.0001 per share","underlying_shares":4275000},"source":{"system":"sec-edgar","filing":"0001213900-25-104331","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":3,"url":"https://www.sec.gov/Archives/edgar/data/2019800/000121390025104331/ownership.xml","form_type":"4"}},{"id":1011452,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":30101,"kind":"person","name":"Matthews Shawn","position":1,"cik":"0001855118","reported_name":"Matthews Shawn","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}},{"id":73234,"kind":"organization","name":"HCM Investor Holdings II, LLC","position":2,"cik":"0002019800","reported_name":"HCM Investor Holdings II, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":false,"other":true,"other_text":"Former 10% owner"}}],"security":"Common Stock, par value $0.0001 per share","published_at":"2025-10-30T20:31:15.000Z","date":"2025-10-28","kind":"other","planned":false,"acquired":true,"shares":533514,"ownership":{"direct":true},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F3","text":"Upon closing of the Business Combination, between Terrestrial Energy Inc., a Delaware corporation formerly known as HCM II Acquisition Corp. (\"New Terrestrial\"), and Terrestrial Energy Development Inc., a Delaware corporation formerly known as Terrestrial Energy Inc. (\"Legacy Terrestrial\"), the reporting person acquired these securities in exchange for the reporting person's securities in Legacy Terrestrial pursuant to the terms and conditions of the BCA."}],"balance_after":533514,"source":{"system":"sec-edgar","filing":"0001213900-25-104331","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":2,"url":"https://www.sec.gov/Archives/edgar/data/2019800/000121390025104331/ownership.xml","form_type":"4"}},{"id":1011451,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":30101,"kind":"person","name":"Matthews Shawn","position":1,"cik":"0001855118","reported_name":"Matthews Shawn","relationship":{"director":true,"officer":false,"ten_percent_owner":false,"other":false}},{"id":73234,"kind":"organization","name":"HCM Investor Holdings II, LLC","position":2,"cik":"0002019800","reported_name":"HCM Investor Holdings II, LLC","relationship":{"director":false,"officer":false,"ten_percent_owner":false,"other":true,"other_text":"Former 10% owner"}}],"security":"Common Stock, par value $0.0001 per share","published_at":"2025-10-30T20:31:15.000Z","date":"2025-10-28","kind":"other","planned":false,"acquired":true,"shares":5675000,"ownership":{"direct":false,"nature":"See Footnote"},"footnotes":[{"field":"price","element":"transactionPricePerShare","label":"F1","text":"Upon closing of the business combination (the \"Business Combination\") between the Issuer (which was formerly known as HCM II Acquisition Corp. or \"HCM II\") and Terrestrial Energy Inc. (\"Terrestrial\") the reporting person acquired these securities in exchange for the reporting person's securities in Terrestrial pursuant to the terms and conditions of the business combination agreement, dated March 26, 2025 and as amended on October 28, 2025, by and among HCM II, Terrestrial and HCM II Merger Sub Inc. (the \"BCA\"). The reporting person resigned as an officer of HCM II upon the closing of the Business Combination."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F2","text":"Mr. Matthews is the sole managing member of HCM Investor Holdings II, LLC (the \"Sponsor\"), which is registered owner of these shares and warrants, and Mr. Matthews holds voting and investment power with respect to shares and warrants held of record by the Sponsor."}],"balance_after":5675000,"source":{"system":"sec-edgar","filing":"0001213900-25-104331","document":"ownership.xml","document_sequence":1,"table":"nonDerivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2019800/000121390025104331/ownership.xml","form_type":"4"}},{"id":1011475,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":73467,"kind":"person","name":"Irish Simon","position":1,"cik":"0002091865","reported_name":"Irish Simon","relationship":{"director":true,"officer":true,"ten_percent_owner":false,"other":false,"officer_title":"Chief Executive Officer"}}],"security":"Restricted Stock Units","published_at":"2025-10-30T19:56:21.000Z","date":"2025-10-28","kind":"grant","planned":false,"acquired":true,"shares":166298,"price":0,"value":0.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. The restricted stock units vest pro rata over a three year period following the grant date."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. The restricted stock units vest pro rata over a three year period following the grant date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"Each restricted stock unit represents a contingent right to acquire one share of Common Stock. The restricted stock units vest pro rata over a three year period following the grant date."}],"balance_after":166298,"derivative":{"underlying":"Common Stock","underlying_shares":166298},"source":{"system":"sec-edgar","filing":"0001213900-25-104323","document":"ownership.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2091865/000121390025104323/ownership.xml","form_type":"4"}},{"id":1427927,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":73775,"kind":"person","name":"Loveless Jacob","position":1,"cik":"0001855174","reported_name":"Loveless Jacob","relationship":{"director":true}}],"security":"Class B Ordinary Shares","published_at":"2024-08-21T00:37:25.000Z","date":"2024-08-19","kind":"other","planned":false,"acquired":true,"shares":25000,"price":0.004,"value":100.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors."},{"field":"kind","element":"transactionCoding","label":"F2","text":"As contemplated by the securities purchase agreement between HCM Investor Holdings II, LLC (the \"Sponsor\") and the reporting person, dated August 19, 2024, the Sponsor assigned 25,000 Class B ordinary shares to the reporting person in connection with reporting person's appointment to the Issuer's Board of Directors."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors."}],"balance_after":25000,"derivative":{"underlying":"Class A Ordinary Shares","underlying_shares":25000},"source":{"system":"sec-edgar","filing":"0001140361-24-037978","document":"form4.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2019804/000114036124037978/form4.xml","form_type":"4"}},{"id":1427943,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":73776,"kind":"person","name":"Brenner Andrew Scott","position":1,"cik":"0002030321","reported_name":"Brenner Andrew Scott","relationship":{"director":true}}],"security":"Class B Ordinary Shares","published_at":"2024-08-20T20:52:54.000Z","date":"2024-08-19","kind":"other","planned":false,"acquired":true,"shares":25000,"price":0.004,"value":100.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors."},{"field":"kind","element":"transactionCoding","label":"F2","text":"As contemplated by the securities purchase agreement between HCM Investor Holdings II, LLC (the \"Sponsor\") and the reporting person, dated August 19, 2024, the Sponsor assigned 25,000 Class B ordinary shares to the reporting person in connection with reporting person's appointment to the Issuer's Board of Directors."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors."}],"balance_after":25000,"derivative":{"underlying":"Class A Ordinary Shares","underlying_shares":25000},"source":{"system":"sec-edgar","filing":"0001140361-24-037986","document":"form4.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2030321/000114036124037986/form4.xml","form_type":"4"}},{"id":1427928,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":30101,"kind":"person","name":"Matthews Shawn","position":1,"cik":"0001855118","reported_name":"Matthews Shawn","relationship":{"director":true,"officer":true,"ten_percent_owner":true,"officer_title":"Chairman and CEO"}},{"id":73234,"kind":"organization","name":"HCM Investor Holdings II, LLC","position":2,"cik":"0002019800","reported_name":"HCM Investor Holdings II, LLC","relationship":{"ten_percent_owner":true}}],"security":"Class B Ordinary Shares","published_at":"2024-08-20T20:47:18.000Z","date":"2024-08-19","kind":"other","planned":false,"acquired":false,"shares":75000,"price":0.004,"value":300.0,"ownership":{"direct":false,"nature":"See Footnote"},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date."},{"field":"kind","element":"transactionCoding","label":"F2","text":"In connection with the Issuer's initial public offering and the appointment of Messrs. Andrew Brenner, Michael Connor, and Jacob Loveless to the Issuer's Board of Directors, HCM Investor Holdings II, LLC (the \"Sponsor\") assigned 25,000 Class B ordinary shares to each of Messrs. Andrew Brenner, Michael Connor, and Jacob Loveless."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date."},{"field":"ownership.nature","element":"natureOfOwnership","label":"F3","text":"These Class B ordinary shares are held directly by the Sponsor, acquired pursuant to a subscription agreement dated as of April 4, 2024 by and among the Sponsor and the registrant and a share capitalization authorized by the SPAC on April 4, 2024. Shawn Matthews, the Chairman and Chief Executive Officer of the registrant, is the managing member of the Sponsor. Mr. Matthews has sole voting and dispositive control over the shares held by the Sponsor and may be deemed the beneficial owner of such shares. Mr. Matthews disclaims beneficial ownership over any securities owned by the Sponsor in which he does not have any pecuniary interest."}],"balance_after":5675000,"derivative":{"underlying":"Class A Ordinary Shares","underlying_shares":75000},"source":{"system":"sec-edgar","filing":"0001140361-24-037984","document":"form4.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2019800/000114036124037984/form4.xml","form_type":"4"}},{"id":1427941,"issuer":{"id":5288,"kind":"organization","name":"Terrestrial Energy Inc. /DE/","symbol":"IMSR"},"owners":[{"id":65939,"kind":"person","name":"Connor Michael J","position":1,"cik":"0002029946","reported_name":"Connor Michael J","relationship":{"director":true}}],"security":"Class B Ordinary Shares","published_at":"2024-08-20T20:42:15.000Z","date":"2024-08-19","kind":"other","planned":false,"acquired":true,"shares":25000,"price":0.004,"value":100.0,"ownership":{"direct":true},"footnotes":[{"field":"derivative.exercise_price","element":"conversionOrExercisePrice","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors."},{"field":"kind","element":"transactionCoding","label":"F2","text":"As contemplated by the securities purchase agreement between HCM Investor Holdings II, LLC (the \"Sponsor\") and the reporting person, dated August 19, 2024, the Sponsor assigned 25,000 Class B ordinary shares to the reporting person in connection with reporting person's appointment to the Issuer's Board of Directors."},{"field":"derivative.exercise_date","element":"exerciseDate","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors."},{"field":"derivative.expiration_date","element":"expirationDate","label":"F1","text":"The Class B ordinary shares are automatically convertible into the shares of the Issuer's Class A ordinary shares at the time of the Issuer's initial business combination on a one-for-one basis, subject to adjustment pursuant to certain anti-dilution rights, and have no expiration date. The Class B ordinary shares are subject to forfeiture under certain circumstances relating to the reporting person's service on the Issuer's Board of Directors."}],"balance_after":25000,"derivative":{"underlying":"Class A Ordinary Shares","underlying_shares":25000},"source":{"system":"sec-edgar","filing":"0001140361-24-037982","document":"form4.xml","document_sequence":1,"table":"derivative","row_type":"transaction","position":1,"url":"https://www.sec.gov/Archives/edgar/data/2029946/000114036124037982/form4.xml","form_type":"4"}}]}