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Livermore
Livermore
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Deep Fission, Inc.

FISN
Exchange
Nasdaq
Industry
Electric Services
SEC CIK
0001918102

No open-market purchases or sales by Deep Fission, Inc. insiders were filed in the last 90 days; 21 institutions reported holding it in 13F filings for Q2 2026, worth $25.2M in total; no superinvestor holds it.

Holders of 5% or more of FISN

Holders whose latest Schedule 13D or 13G filing reports 5% or more of Deep Fission, Inc., largest stake first. The change is against the holder's previous filing.

Holders of 5% or more of FISN
HolderLatest formStakeChangeFirst filedLatest filingFiling
Muller Elizabeth13D20.60%10.5M sharesNewSep 23, 20251 filingSep 23, 2025SEC
Muller Richard13D10.60%5.43M sharesNewSep 23, 20251 filingSep 23, 2025SEC
Tompkins Mark N.13G/A5.60%3.16M shares−0.22 ppfrom 5.82%Nov 14, 20252 filingsMay 15, 2026SEC
EE Holdings Ltd13G5.50%2.87M sharesNewNov 3, 20251 filingNov 3, 2025SEC

Stakes are as of each holder's latest filing. Holders whose last filing was in the old format (before December 18, 2024) have no stake on record and are not listed, and after an acquisition or delisting holders usually stop filing.

13D and 13G filings

5 Schedule 13D and 13G filings on Deep Fission, Inc., newest first, including old-format filings without a stake.

Schedule 13D and 13G filings on FISN
Filed (ET)FilerFormStakeChangeEvent dateFiling
May 15, 20264:39 PM ETTompkins Mark N.13G/A5.60%3.16M shares−0.22 ppfrom 5.82%Mar 31, 2026SEC
Nov 14, 20253:36 PM ETTompkins Mark N.13G/A5.82%2.96M shares–Sep 30, 2025SEC
Nov 3, 202511:38 AM ETEE Holdings Ltdand 1 other13G5.50%2.87M sharesNewSep 30, 2025SEC
Sep 23, 20259:44 PM ETMuller Richard13D10.60%5.43M sharesNewSep 5, 2025SEC
Sep 23, 20259:43 PM ETMuller Elizabeth13D20.60%10.5M sharesNewSep 5, 2025SEC

Form 144: proposed insider sales

Notices from officers, directors and other affiliates planning to sell Deep Fission, Inc. shares.

No Form 144 notices for Deep Fission, Inc. are on file.