OKLO INC., 10-Q filed on 5/12/2026
Quarterly Report
v3.26.1
Cover - shares
 3 Months Ended
Mar. 31, 2026
May 07, 2026
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Transition Report false  
Entity File Number 001-40583  
Registrant Name Oklo Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 86-2292473  
Entity Address, Address Line One 3190 Coronado Dr.  
Entity Address, City or Town Santa Clara  
Entity Address, State or Province CA  
City Area Code 650  
Local Phone Number 550-0127  
Entity Address, Postal Zip Code 95054  
Title of 12(b) Security Class A common stock, par value $0.0001 per share  
Trading Symbol OKLO  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   173,990,987
Document Fiscal Year Focus 2026  
CIK 0001849056  
Amendment Flag false  
Document Fiscal Period Focus Q1  
Current Fiscal Year End Date --12-31  
v3.26.1
Condensed Consolidated Balance Sheets (Unaudited) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Current assets:    
Cash and cash equivalents $ 1,594,103 $ 788,445
Marketable debt securities 614,506 439,526
Prepaid and other current assets 17,049 25,798
Total current assets 2,225,658 1,253,769
Marketable debt securities, net of current portion 328,289 184,568
Property, plant and equipment, net 95,615 42,312
Operating lease right-of-use assets 2,528 1,384
Indefinite-lived intangible assets 27,500 27,500
Goodwill 6,621 6,621
Other assets 17,298 12,303
Total assets 2,703,509 1,528,457
Current liabilities:    
Accounts payable 14,209 4,145
Accrued expenses and other 21,896 20,497
Operating lease liabilities 1,031 904
Total current liabilities 37,136 25,546
Operating lease liabilities, net of current portion 1,589 546
Right of first refusal liability 25,000 25,000
Deferred tax liabilities 1,155 1,155
Total liabilities 64,880 52,247
Commitments and contingencies
Stockholders' equity:    
Class A common stock, $0.0001 par value – 500,000,000 shares authorized; 173,867,839 and 160,514,103 shares issued and outstanding as of March 31, 2026 and December 31, 2025, respectively 17 16
Additional paid-in capital 2,913,931 1,715,787
Accumulated deficit (273,837) (240,772)
Accumulated other comprehensive (loss) income (1,482) 1,179
Total stockholders’ equity 2,638,629 1,476,210
Total liabilities and stockholders’ equity $ 2,703,509 $ 1,528,457
v3.26.1
Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares
Mar. 31, 2026
Dec. 31, 2025
Statement of Financial Position [Abstract]    
Common stock, par value (in dollars per share) $ 0.0001 $ 0.0001
Common stock, authorized (in shares) 500,000,000 500,000,000
Common stock, issued (in shares) 173,867,839 160,514,103
Common stock, outstanding (in shares) 173,867,839 160,514,103
v3.26.1
Condensed Consolidated Statements of Operations (Unaudited) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Operating expenses    
Research and development $ 27,049 $ 7,846
General and administrative 24,200 10,028
Total operating expenses 51,249 17,874
Loss from operations (51,249) (17,874)
Other income    
Interest and dividend income, net 21,339 3,653
Loss before income taxes (29,910) (14,221)
Income tax (expense) benefit (3,155) 4,411
Net loss $ (33,065) $ (9,810)
Net loss per share:    
Basic - Class A common stock (in dollars per share) $ (0.19) $ (0.07)
Diluted - Class A common stock (in dollars per share) $ (0.19) $ (0.07)
Weighted-average common shares outstanding - basic - Class A common stock (in shares) 170,333,746 138,109,974
Weighted-average common shares outstanding - diluted - Class A common stock (in shares) 170,333,746 138,109,974
v3.26.1
Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Statement of Comprehensive Income [Abstract]    
Net loss $ (33,065) $ (9,810)
Other comprehensive loss:    
Unrealized loss on marketable debt securities (2,661) (561)
Total comprehensive loss $ (35,726) $ (10,371)
v3.26.1
Condensed Consolidated Statements of Stockholders’ Equity (Unaudited) - USD ($)
$ in Thousands
Total
At The Market Offering
Common Stock
Common Stock
At The Market Offering
Common Stock
Restricted Stock
Additional Paid-In Capital
Additional Paid-In Capital
At The Market Offering
Accumulated Deficit
Accumulated Other Comprehensive Income (Loss)
Beginning balance of the period (in shares) at Dec. 31, 2024     137,706,596            
Balance as of beginning of the period at Dec. 31, 2024 $ 250,857   $ 14     $ 383,739   $ (135,109) $ 2,213
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Exercise of stock options (in shares)     318,921            
Exercise of stock options $ 720         720      
Issuance of common stock (in shares) 318,921       134,832        
Issuance of common stock in at-the-market offering, net of offering costs $ 720                
Issuance of stock in connection with acquisition of business (in shares)     820,840   274,339        
Issuance of common stock in connection with acquisition of business $ 27,408         27,408      
Common stock withheld for taxes (in shares) (66,724)   (66,724)            
Common stock withheld for taxes $ (1,595)         (1,595)      
Stock-based compensation 2,311         2,311      
Change in unrealized loss on marketable debt securities (561)               (561)
Net loss (9,810)             (9,810)  
Ending balance of the period (in shares) at Mar. 31, 2025     139,188,804            
Balance as of end of the period at Mar. 31, 2025 $ 269,330   $ 14     412,583   (144,919) 1,652
Beginning balance of the period (in shares) at Dec. 31, 2025 160,514,103   160,514,103            
Balance as of beginning of the period at Dec. 31, 2025 $ 1,476,210   $ 16     1,715,787   (240,772) 1,179
Increase (Decrease) in Stockholders' Equity [Roll Forward]                  
Exercise of stock options (in shares)     290,908            
Exercise of stock options $ 737         737      
Issuance of common stock (in shares) 290,908     12,376,352 687,756        
Issuance of common stock in at-the-market offering, net of offering costs $ 737 $ 1,181,897   $ 1     $ 1,181,896    
Common stock withheld for taxes (in shares) (1,280)   (1,280)            
Common stock withheld for taxes $ (75)         (75)      
Stock-based compensation 15,586         15,586      
Change in unrealized loss on marketable debt securities (2,661)               (2,661)
Net loss $ (33,065)             (33,065)  
Ending balance of the period (in shares) at Mar. 31, 2026 173,867,839   173,867,839            
Balance as of end of the period at Mar. 31, 2026 $ 2,638,629   $ 17     $ 2,913,931   $ (273,837) $ (1,482)
v3.26.1
Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Cash flows from operating activities:    
Net loss $ (33,065) $ (9,810)
Adjustments to reconcile net loss to net cash used in operating activities:    
Depreciation and amortization 163 124
Interest income and accretion of discount on marketable debt securities, net (138) (312)
Stock-based compensation 15,586 2,311
Deferred income taxes 0 (4,734)
Change in operating assets and liabilities, net of effect of acquisition:    
Prepaid and other current assets 8,749 336
Other assets 5 (17)
Accounts payable (61) (1,755)
Accrued expenses and other (9,132) 1,606
Operating lease right-of-use assets and liabilities 26 8
Net cash used in operating activities (17,867) (12,243)
Cash flows from investing activities:    
Purchases of property, plant and equipment (32,810) (332)
Purchases of marketable debt securities (451,678) (29,887)
Proceeds from redemptions of marketable debt securities 130,454 37,183
Payment for acquisition of business, net of cash acquired 0 (900)
Purchase of other investments (5,000) 0
Net cash (used in) provided by investing activities (359,034) 6,064
Cash flows from financing activities:    
Payment of taxes from common stock withheld (75) (1,595)
Proceeds from exercise of stock options 737 720
Proceeds from sale of common stock, net of offering costs 1,181,897 0
Net cash provided by (used in) financing activities 1,182,559 (875)
Net increase (decrease) in cash and cash equivalents 805,658 (7,054)
Cash and cash equivalents - beginning of year 788,445 97,132
Cash and cash equivalents - end of period 1,594,103 90,078
Supplemental noncash investing and financing activities:    
Issuance of common stock in connection with acquisition of business 0 27,408
Assumed liabilities in connection with acquisition of business 0 287
Purchases of property, plant and equipment in accounts payable and accrued expense and other $ 20,656 $ 0
v3.26.1
Nature of Operations and Organization
 3 Months Ended
Mar. 31, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Nature of Operations and Organization Nature of Operations and Organization
Oklo Inc. (the "Company" or "Oklo"), a Delaware corporation, and its subsidiaries are developing advanced fission power plants to provide clean, reliable, and affordable energy at scale. Oklo Technologies, Inc., a Delaware corporation and wholly owned subsidiary of Oklo Inc., was incorporated on July 3, 2013.

The Company plans to commercialize its metal-fueled fast reactor technology with the Aurora powerhouse product line. The Aurora product line is designed to produce between 15 and 75 megawatts of electricity (“MWe”) on fresh, recycled, or down-blended nuclear fuel. Advanced fission technology built on a deep history of successful operation, first demonstrated by the Experimental Breeder Reactor-II (“EBR-II”), which sold and supplied power to the grid and showed effective used nuclear fuel recycling capabilities over 30 years of operation. The Company is also commercializing nuclear fuel recycling and fuel fabrication technology that can convert used nuclear fuel and other nuclear materials into usable fuel for its reactors, as well as the production of radioisotopes. The Company’s radioisotope activities are intended to support domestic supply for medical, industrial, space, defense, and other critical applications. The Company is pursuing these activities through dedicated isotope production and processing capabilities, which may also benefit from radioisotope co-products generated through its fuel recycling and reactor platform.

Liquidity and Capital Resources

As of March 31, 2026, the Company’s cash, cash equivalents, and marketable debt securities were $2,536,898. The Company continues to incur significant operating losses. For the three months ended March 31, 2026, the Company had a net loss of $33,065, loss from operations of $51,249, and net cash used in operating activities of $17,867. As of March 31, 2026, the Company had an accumulated deficit of $273,837.

The Company expects to utilize its existing cash, cash equivalents, and marketable debt securities to fund construction of its powerhouses, fuel and radioisotope businesses, operations, and growth plans and believes that its existing cash, cash equivalents, and marketable debt securities will be sufficient to fund its operations for the one-year period following the issuance date of these unaudited condensed consolidated financial statements.
v3.26.1
Summary of Significant Accounting Policies
 3 Months Ended
Mar. 31, 2026
Accounting Policies [Abstract]  
Summary of Significant Accounting Policies Summary of Significant Accounting Policies
Basis of Presentation

The accompanying unaudited condensed consolidated financial statements and accompanying notes are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial reporting.

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and Articles 8 and 10 of Regulation S-X. Certain information or footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted, pursuant to the rules and regulations of the SEC for interim financial reporting. Accordingly, it does not include all the information and footnotes necessary for a complete presentation of financial position, results of operations, or cash flows. The information herein should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025, which was filed on March 17, 2026. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting of a normal recurring nature, which are necessary for a fair statement of the financial position, operating results, and cash flows for the periods presented.
Segment Information

The Company has viewed its financial information on an aggregate basis for the purposes of evaluating financial performance and allocating the Company’s resources. The Company’s principal business consists primarily of research and development and deployment activities for its planned or in-process powerhouses, nuclear fuel recycling and fuel
fabrication facilities, and its radioisotope production facilities. Accordingly, the Company has determined that it conducts its business in one operating and one reportable segment. For more information about the Company’s single operating and reportable segment, see Note 12—Segment Information.
Principles of Consolidation

The unaudited condensed consolidated financial statements include the Company’s accounts and those of its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated.
Use of Estimates

Preparation of financial statements in conformity with U.S. GAAP requires management to make estimates, judgments, and assumptions that affect the amounts reported and disclosed in the unaudited condensed consolidated financial statements and accompanying notes. Actual results could differ materially from these estimates. On an ongoing basis, the Company evaluates its estimates, including those related to the valuation of the operating lease liabilities and operating right-of-use assets, useful lives of property, plant and equipment, valuation allowance on deferred tax assets, and the fair value of acquired intangible assets and goodwill. These estimates, judgments, and assumptions are based on current and expected economic conditions, historical data, and experience available at the date of the accompanying unaudited condensed consolidated financial statements, and various other factors that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities.
Risk and Uncertainties

The Company is subject to continuing risks and uncertainties amidst a range of supply chain, construction, and design complexities and in connection with the market dynamics around fuel costs and the current macroeconomic environment, including as a result of inflation, instability in the global banking system, trade policy (including tariffs, export controls, and sanctions), ongoing or escalating geopolitical factors and military activities, as well as the potential for additional conflicts, war or civil unrest. At this point, the extent to which these effects may impact the Company’s future financial condition or results of operations is uncertain, and as of the date of issuance of these condensed consolidated financial statements, the Company is not aware of any specific event or circumstance that would require the update of any estimates or judgments or an adjustment of the carrying value of any assets or liabilities. These estimates may change as new events occur and additional information is obtained and will be recognized in the condensed consolidated financial statements as soon as they become known.
Net Loss Per Common Share

The Company’s basic net loss per share of common stock is computed based on the average number of outstanding shares of common stock for the period, by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period, without consideration for potential dilutive securities. Diluted net loss per share of common stock is computed by dividing net loss by the weighted-average number of shares of common stock and common share equivalents of potentially dilutive securities outstanding for the period. Potentially dilutive securities include common stock equivalents. Since the Company was in a loss position for the periods presented, basic net loss per share of common stock is the same as diluted net loss per share of common stock since the effects of potentially dilutive securities are antidilutive.

The outstanding potentially dilutive common stock equivalents as of March 31, 2026 and 2025 for: (1) options to purchase shares of common stock of 6,130,247 and 9,151,461, respectively, (2) unvested restricted stock of 426,750 and 640,125, respectively, and (3) unvested restricted stock units of 2,619,465 and 1,624,743, respectively, have been excluded from the calculation of diluted net loss per common share due to their anti-dilutive effect.

Emerging Growth Company Status

The Company is classified as an emerging growth company (“EGC”), as defined under the Jumpstart Our Business Startups Act. Therefore, the Company may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not EGCs. The Company will retain EGC status until December 31, 2026.

Recently Issued and Not Adopted Accounting Standards
In November 2024, the FASB issued ASU 2024-03, Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, which will require disaggregated disclosures in the notes to the financial statements of certain categories of expenses, including purchases of inventory, employee compensation, and depreciation and amortization, that are included in expense line items within the statement of operations. ASU 2024-03 will be applied prospectively; however, retrospective application is permitted. ASU 2024-03, as clarified in ASU 2025-01, Clarifying the Effective Date, requires public business entities to adopt the guidance in annual reporting periods beginning after December 15, 2026, and interim periods within annual reporting periods beginning after December 15, 2027. Early adoption is permitted. The Company is evaluating the impact of ASU 2024-03 on its disclosures in the notes to its financial statements.

In September 2025, the FASB issued ASU 2025‑06, Intangibles—Goodwill and Other—Internal‑Use Software (Subtopic 350‑40): Targeted Improvements to the Accounting for Internal‑Use Software, which updates the guidance for capitalization of internal‑use software costs, including clarifications to the criteria for capitalizing configuration, development, and implementation activities. ASU 2025-06 is effective for the Company beginning with interim reporting for fiscal year 2029. Early adoption is permitted. The Company is currently evaluating the impact of ASU 2025-06 on its accounting policies and related disclosures.

In December 2025, the FASB issued ASU 2025‑10, Government Grants (Topic 832): Accounting for Government Grants Received by Business Entities, which provides updated guidance on how to recognize, measure, and present government grants. ASU 2025‑10 is effective for the Company for annual periods beginning after December 15, 2028, including interim periods within those periods using a modified prospective, modified retrospective, or full retrospective transition approach. Early adoption is permitted. The Company is currently assessing the effect of ASU 2025-10 on its financial statements.
v3.26.1
Business Combination
 3 Months Ended
Mar. 31, 2026
Business Combination [Abstract]  
Business Combination Business Combination
Atomic Alchemy

On February 28, 2025 (the “Acquisition Date”), the Company acquired Atomic Alchemy Inc.’s ("Atomic Alchemy") common stock in a business combination for its radioisotope business located in the U.S. The purchase price of $28,424 was comprised of (i) a cash portion of $900, net of cash acquired, paid at the Acquisition Date to certain Atomic Alchemy equity holders for their respective portion of the consideration, and (ii) the issuance of 820,840 shares of the Company’s common stock representing stock consideration in exchange for Atomic Alchemy’s common stock. At the Acquisition Date, the Company’s common stock public trading price of $33.39 per share was used to measure the stock consideration of $27,408.

In connection with the business combination, the Company issued 274,339 shares of its common stock, subject to certain lock-up provisions, vesting conditions, and substantial risk of forfeiture, representing post-combination services, pursuant to an employment agreement and vesting agreement.

The composition of the purchase price is as follows:

Cash$1,016 
Common stock27,408 
Total purchase consideration$28,424 

The Company incurred $410 in transaction costs related to the acquisition, which primarily consisted of legal and accounting expenses. The acquisition-related expenses were recorded in general and administrative expenses on the condensed consolidated statements of operations.

During the fourth quarter of 2025, the Company adjusted the purchase price allocation as a result of certain measurement period adjustments to the acquired assets and liabilities assumed. The Company finalized its measurement period accounting after filing Atomic Alchemy's short year 2025 federal and state income tax returns, and following revisions to internal estimates and new information obtained about facts and circumstances that existed as of the Acquisition Date. The measurement period adjustments included a decrease in deferred tax liabilities of $99 with a corresponding decrease to goodwill.
The purchase price allocation resulted in the following amounts being allocated to the assets acquired and liabilities assumed at the Acquisition Date based upon their respective fair values as summarized below:

Cash$116 
Prepaid expenses99 
Property and equipment40 
Operating lease right-of-use assets19 
Indefinite-lived intangible assets27,500 
Goodwill6,621 
Operating lease liability(19)
Other current liabilities(268)
Deferred tax liabilities(5,684)
Net assets acquired
$28,424 

The Company utilized an independent appraisal firm to assist in the determination of the fair values of the assets acquired and liabilities assumed, which required certain significant management assumptions and estimates. The fair value of the indefinite-lived intangible assets representing in-process research and development ("IPR&D") were valued using a pre-tax royalty for the hypothetical use of a trade name for a selected royalty rate based on a market licensing agreement benchmarking analysis.

The IPR&D consisted of two separate projects, Abundantia and Meitner. Abundantia’s fair value assigned of $4,600 is expected to produce revenue as early as 2026 from the sale of purified radium and other desired radioisotopes produced via irradiation. Meitner’s fair value of $22,900 is a later stage project which will produce for sale isotopes that are prepared and irradiated into radioisotopes in Versatile Isotope Production Reactors (“VIPR”), which is a thermal pool-type nuclear reactor. Each project has a different risk profile, cash flows, and its own unique process. Abundantia's fair value was determined using a risk-adjusted cash flow approach applied to its potential cash flows, subject to obtaining a certain material handling permit required by the NRC. Meitner is expected to produce revenue once a facility is constructed, with its fair value determined using a risk-adjusted cash flow approach applied to its cash flows, subject to approval of an application for a construction license and operating license by the NRC. There was no estimated useful life assigned given the assets are IPR&D.

The excess of the purchase price over the fair value amounts assigned to the assets acquired and liabilities assumed represents goodwill from the acquisition. Goodwill is recorded as a noncurrent asset that is not amortized but is subject to an annual review for impairment. Goodwill is not deductible for tax purposes.

The results of operations of Atomic Alchemy are included in the condensed consolidated financial statements beginning on the Acquisition Date.
v3.26.1
Balance Sheet Components
 3 Months Ended
Mar. 31, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Balance Sheet Components Balance Sheet Components
Prepaid and Other Current Assets

Prepaid and other current assets are summarized as follows:
As of
March 31, 2026
(unaudited)		December 31, 2025
Prepaid expense$5,670 $18,853 
Accrued interest receivable9,710 4,976 
Other1,669 1,969 
Total prepaid and other current assets$17,049 $25,798 

Prepaid expenses include prepaid consulting fees, insurance premiums, rent and other charges, and construction deposits.

Prepaid expenses are amortized over the straight-line method over the contract term. Construction deposits are reclassified to construction in progress and capitalized when the related work is performed.
Property, Plant and Equipment, Net

Property, plant and equipment, net are summarized as follows:
As of
Estimates Useful Lives (Years)March 31, 2026
(unaudited)		December 31, 2025
Computers and equipment
3 - 7
$366 $366 
Furniture, fixtures and machinery7665 483 
Software31,405 1,405 
Leasehold improvements*62 62 
LandN/A5,145 5,145 
Total property and equipment, gross7,643 7,461 
Less: accumulated depreciation and amortization(1,060)(897)
Construction in progress and equipment deposits89,032 35,748 
Total property, plant and equipment, net$95,615 $42,312 
* Shorter of lease term or estimated useful life of the asset.

Included in property, plant, and equipment is construction in progress and equipment deposits. Costs related to construction of capital projects are accumulated in construction in progress and equipment deposits until the project is complete, as well as equipment that is not yet placed in service. A construction project is considered substantially complete upon the cessation of construction and development activities. Once the project is substantially complete and ready for its intended use these costs will be amortized over the asset’s estimated useful life.

Depreciation and amortization expenses for the three months ended March 31, 2026 and 2025 totaled $163 and $124, respectively.

Other Assets

Other assets are summarized as follows:
As of
March 31, 2026
(unaudited)		December 31, 2025
Other$212 $217 
Other investments17,086 12,086 
Total other assets$17,298 $12,303 
As of March 31, 2026 and December 31, 2025, the Company’s other investments totaled $17,086 and $12,086, respectively, and primarily consist of simple agreements for future equity and preferred equity investments in privately held companies. These investments are recorded at cost, as they do not have readily determinable fair values. As of March 31, 2026, management did not identify any impairment indicators or observable transactions that would require an adjustment to carrying value.
Accrued Expenses and Other

Accrued expenses and other are summarized as follows:
As of
March 31, 2026
(unaudited)		December 31, 2025
Accrued professional fees$1,621 $1,838 
Accrued payroll and bonuses4,769 10,998 
General accrued expenses13,950 7,210 
Other current liabilities1,556 451 
Total accrued expenses and other$21,896 $20,497 
v3.26.1
Leases
 3 Months Ended
Mar. 31, 2026
Leases [Abstract]  
Leases Leases
As of March 31, 2026, the Company had commercial real estate lease agreements for office space under operating leases.

The table below presents supplemental information related to the operating leases:
Three Months Ended March 31,
20262025
Cash payments included in the measurement of operating lease liabilities during the period$279 $150 
Operating lease liabilities arising from obtaining lease right-of-use assets during the period$1,400 $890 
Weighted-average remaining lease term (in months) as of period-end3837
Weighted-average discount rate during the period8.95%8.97%

The Company utilizes its incremental borrowing rates on a collateralized basis, reflecting the Company’s credit quality and the term of the lease at the commencement of the lease in determining the present value of future payments since the implicit rate for the Company’s leases is not readily determinable.

Variable lease expense includes lease payments that vary based on usage or performance and are not fixed at lease commencement. Payments for services such as maintenance, utilities, and real estate taxes are accounted for as non-lease components and expensed as incurred.

The components of operating lease costs were as follows:
Three Months Ended March 31,
20262025
Operating lease costs included in:
Research and development$260 $151 
General and administrative105 80 
Total operating costs (1)
$365 $231 

(1) Month-to-month lease arrangements for the three months ended March 31, 2026 and 2025 of $57 and $71, respectively, are included in the captions within operating lease costs.

The minimum lease payments below do not include non-lease components, which are contractual obligations under the Company’s lease, but are not fixed and can fluctuate from period to period and are expensed as incurred.

As of March 31, 2026, future maturities of the operating lease liabilities were as follows:

2026 (remaining of year)$1,045 
2027614 
2028614 
2029635 
2030106 
Minimum lease payments3,014 
Less imputed interest(394)
Present value of operating lease liabilities$2,620 
Current portion of operating lease liabilities$1,031 
Noncurrent portion of operating lease liabilities1,589 
Total operating lease liabilities$2,620 

On March 16, 2026, the Company entered into a ground lease for land in Caldwell County, Texas. The lease had not commenced as of March 31, 2026 because the premises had not been delivered until April 2026.
v3.26.1
Financial Instruments
 3 Months Ended
Mar. 31, 2026
Investments, Debt and Equity Securities [Abstract]  
Financial Instruments Financial Instruments
The following table shows the Company’s cash, cash equivalents and marketable debt securities by significant investment category:
As of March 31, 2026
Amortized CostUnrealized Gains
Unrealized Losses (1)
Fair ValueCash and Cash EquivalentsCurrent Marketable Debt SecuritiesNoncurrent Marketable Debt Securities
Cash$— $— $— $— $15,571 $— $— 
Level 1:
Money market funds— — — — 1,578,532 — — 
U.S. Treasury securities805,151 289 (1,674)803,766 — 475,477 328,289 
Subtotal805,151 289 (1,674)803,766 1,578,532 475,477 328,289 
Level 2 (2):
Commercial paper139,126 10 (107)139,029 — 139,029 — 
Total $944,277 $299 $(1,781)$942,795 $1,594,103 $614,506 $328,289 

(1) There was no allowance for expected credit losses on available-for-sale marketable debt securities as of March 31, 2026 as the unrealized losses were deemed to be temporary in nature.

(2) The valuation techniques used to measure the fair values of the Company’s Level 2 financial instruments, which generally have counterparties with high credit ratings, are based on quoted market prices or model-driven valuations using significant inputs derived from or corroborated by observable market data.

As of March 31, 2026, interest receivables related to available-for-sale marketable debt securities of $4,143 were included in marketable debt securities on the condensed consolidated balance sheets.

As of March 31, 2026, interest receivables related to marketable debt securities of $4,566 were included in prepaid expenses and other current assets on the condensed consolidated balance sheets.

The following table shows the fair value of the Company’s noncurrent marketable debt securities, by contractual maturity, as of March 31, 2026:

Due within 1 year$614,506 
Due after 1 year through 5 years328,289 
Total fair value$942,795 

The following tables show the Company’s cash, cash equivalents, and marketable debt securities by significant investment category:
As of December 31, 2025
Amortized CostUnrealized GainsFair ValueCash and Cash EquivalentsCurrent Marketable Debt SecuritiesNoncurrent Marketable Debt Securities
Cash$— $— $— $11,022 $— $— 
Level 1:
Money market funds— — — 777,423 — — 
U.S. Treasury securities504,008 1,123 505,131 — 320,563 184,568 
Subtotal504,008 1,123 505,131 777,423 320,563 184,568 
Level 2 (1):
Commercial paper118,907 56 118,963 — 118,963 — 
Total$622,915 $1,179 $624,094 $788,445 $439,526 $184,568 

(1) The valuation techniques used to measure the fair values of the Company’s Level 2 financial instruments, which generally have counterparties with high credit ratings, are based on quoted market prices or model-driven valuations using significant inputs derived from or corroborated by observable market data.

As of December 31, 2025, interest receivables related to available-for-sale marketable debt securities of $4,005 were included in marketable debt securities on the condensed consolidated balance sheets.
As of December 31, 2025, interest receivables related to marketable debt securities of $3,160 were included in prepaid expenses and other current assets on the condensed consolidated balance sheets.
v3.26.1
Right of First Refusal Liability
 3 Months Ended
Mar. 31, 2026
Commitments and Contingencies Disclosure [Abstract]  
Right of First Refusal Liability Right of First Refusal Liability
On February 16, 2024, the Company entered into a letter of intent (the “LOI”) with an unrelated third party (the “third party”) for the purchase of power from the Company’s planned powerhouses to serve certain data centers in the U.S. on a 20-year timeline with the right to renew for additional 20-year terms, and at a rate to be formally specified in one or more future power purchase agreement ("PPA") (subject to the requirement that the price meets certain conditions contained in the agreement).

The LOI provides for the third party to have a continuing right of first refusal for a period of thirty-six (36) months following its execution to purchase energy output produced by certain powerhouses developed by the Company in the U.S., subject to certain provisions and excluded powerhouses (the “ROFR”). In exchange for the ROFR and other rights contained in the LOI, in March 2024, the third party paid the Company $25,000 (the “Payment”). In connection with the Payment, the Company agreed to supply power at a discount to the most favored nation pricing that the Company is required to provide to the third party in a future PPA (location to be determined); provided, that pricing set out in a PPA will include an additional discount if needed such that the total savings against most favored nation pricing over the course of the PPA is equivalent to the Payment. The Payment is effectively a nonrefundable upfront payment that will be attributed to future power delivery. As of March 31, 2026 and December 31, 2025, the outstanding balance under the right of first refusal liability was $25,000, as reflected on the condensed consolidated balance sheets.
v3.26.1
Stockholders’ Equity
 3 Months Ended
Mar. 31, 2026
Equity [Abstract]  
Stockholders’ Equity Stockholders’ Equity
Pursuant to the Second Amended and Restated Certificate of Incorporation of the Company, the Company is authorized to issue 501,000,000 shares of all classes of capital stock consisting of (i) 500,000,000 shares of common stock, par value of $0.0001 per share, and (ii) 1,000,000 shares of preferred stock, par value of $0.0001 per share. Subject to the special rights of the holders of any outstanding series of preferred stock, the number of shares of preferred stock may be increased or decreased (but not below the number of shares then outstanding) by affirmative vote of the holders of a majority of the stock of the Company entitled to vote. There are no shares of preferred stock issued and outstanding.

Equity ATM Program

In December 2025, the Company entered into a sales agreement with sales agents pursuant to which the Company may offer and sell, from time to time and at its sole discretion, shares of its common stock up to an aggregate gross sales price of $1,500,000 in an ATM offering (the "2025 ATM Program"), which was completed during the three months ended March 31, 2026. Under the 2025 ATM Program, the Company agreed to pay the sales agents commissions at a rate equal to 1.5% of the aggregate gross proceeds from each sale of shares.

The following is a summary of the shares issued under the 2025 ATM Program during the three months ended March 31, 2026 (in thousands except shares issued and average price per share):

Period Ended Shares Issued Average Net Price Per Share Gross Proceeds Net Proceeds
March 31, 202612,376,352$96.95$1,199,868 $1,181,897 

Exercise of Stock Options – During the three months ended March 31, 2026 and 2025, the Company issued shares of its common stock upon the exercise of stock options totaling 290,908 and 318,921, respectively, with proceeds of $737 and $720, respectively, as reflected on the condensed consolidated statements of stockholders’ equity.

Restricted Stock Units – The Company issued, in connection with the vesting of restricted stock units, 687,756 and 134,832 shares of the Company’s common stock during the three months ended March 31, 2026 and 2025, respectively, as reflected on the condensed consolidated statements of stockholders’ equity.

Common Stock Withheld for Taxes – The Company withheld 1,280 and 66,724 shares of its common stock upon issuance of vested restricted units, representing a payment for taxes of $75 and $1,595, during the three months ended March 31, 2026 and 2025, respectively, as reflected on the condensed consolidated statements of stockholders’ equity.
v3.26.1
Stock-Based Compensation
 3 Months Ended
Mar. 31, 2026
Share-Based Payment Arrangement [Abstract]  
Stock-Based Compensation Stock-Based Compensation
Stock-based compensation expense charged to operations is summarized as follows:

Three Months Ended March 31,
20262025
Research and development$7,496 $973 
General and administrative8,090 1,338 
Total costs charged to operations$15,586 $2,311 

During the three months ended March 31, 2026, approximately 550,000 shares were granted to acquire shares of the Company's common stock, consisting of restricted stock units, with a grant date fair value of approximately $36,000 under its stock-based compensation plan.

Unrecognized compensation expense and expected weighted-average period to be recognized related to the stock-based compensation awards as of March 31, 2026 were as follows:

Restricted StockStock OptionsTotals
Unrecognized stock-based compensation cost$118,291 $13,757 $132,048 
Weighted-average period over which cost is expected to be recognized (in years)3.443.323.42
v3.26.1
Income Taxes
 3 Months Ended
Mar. 31, 2026
Income Tax Disclosure [Abstract]  
Income Taxes Income Taxes
The provision for income taxes in interim periods is determined using an estimate of the Company’s annual effective tax rate ("ETR"), adjusted for discrete items that arise during the period. Each quarter, the Company updates its estimate of its annual ETR, and if the estimated annual ETR changes, the Company makes a cumulative adjustment in such period. The quarterly provision for income taxes, and estimate of the Company’s annual ETR, are subject to variation due to several factors, including variability in pre-tax income (or loss), the mix of jurisdictions to which such income relates, changes in how the Company conducts business, and tax law developments.

The realization of deferred tax assets is dependent upon a variety of factors, including the generation of future taxable income, the reversal of deferred tax liabilities, and tax planning strategies. The Company's provision for income taxes reflects discrete items and jurisdictional tax expense, which may cause fluctuations in the quarterly and year‑to‑date ETR compared to the Company’s statutory tax rate. During the three months ended March 31, 2026, the Company recorded income tax expense of $3,155 primarily attributable to state income taxes in certain jurisdictions. During the three months ended March 31, 2025, the Company recorded an income tax benefit of $4,411 primarily related to discrete items recognized in connection with the acquisition of Atomic Alchemy. Based on the Company’s cumulative historical operating losses and uncertainty regarding the generation of future taxable income, a valuation allowance was maintained against substantially all deferred tax assets as of March 31, 2026 and 2025.

As of March 31, 2026 and 2025, the Company had unrecognized tax benefits related to federal research credit carryforwards, of which, if fully recognized in the future would have no impact to the ETR and would result in a corresponding adjustment to the valuation allowance. No interest and penalties related to the unrecognized tax benefits are accrued.
v3.26.1
Commitments and Contingencies
 3 Months Ended
Mar. 31, 2026
Commitments and Contingencies Disclosure [Abstract]  
Commitments and Contingencies Commitments and Contingencies
Contract Commitments

The Company enters into contracts in the normal course of business with third-party contract research organizations, contract development and manufacturing organizations and other service providers and vendors. These contracts generally provide for termination on notice and, therefore, are cancellable contracts and not considered contractual obligations and commitments.
Contingencies

From time to time, the Company may become involved in litigation matters arising in the ordinary course of business. The Company is not a party to any legal proceedings, nor is it aware of any material pending or threatened litigation. There were no contingent liabilities as of March 31, 2026.
v3.26.1
Segment Information
 3 Months Ended
Mar. 31, 2026
Segment Reporting [Abstract]  
Segment Information Segment Information
In accordance with criteria under ASC 280, the Company’s chief operating decision maker (“CODM”) has been identified as the Chief Executive Officer. The Company’s CODM reviews consolidated results to assess performance, make decisions, and allocates operating and capital resources of the Company as a whole, therefore, there is only one reportable segment. The CODM does not distinguish its principal business activities for the purpose of internal reporting and uses net loss to allocate resources in the annual budgeting and forecasting process, along with using that measure as a basis for evaluating financial performance quarterly by comparing the actual results with historical budgets.

Significant segment expenses that are provided to CODM on a regular basis and are included within reported measure of segment profit or loss are research and development and general and administrative. Other segment items are interest and dividend income and income taxes.
The condensed consolidated statements of operations for the three months ended March 31, 2026 and 2025, reflect the significant segment expenses and other segment items, as well as the condensed consolidated balance sheets as of March 31, 2026 and December 31, 2025, for the one reportable segment.
v3.26.1
Related Party Transactions
 3 Months Ended
Mar. 31, 2026
Related Party Transactions [Abstract]  
Related Party Transactions Related Party Transactions
On June 25, 2025, the Company entered into an agreement under which M. Klein & Company, through its affiliate, The Klein Group LLC, will provide financial advisory and strategic services. Mr. Michael Klein, who currently serves as a director of the Company, maintains a direct controlling interest in M. Klein & Company. The advisory agreement is for a term of one year and requires the Company to pay a $250 quarterly retainer fee, in addition to other potential fees depending on the outcomes of certain transactions. During the three months ended March 31, 2026, the Company made total payments of $250 under the agreement.
v3.26.1
Subsequent Events
 3 Months Ended
Mar. 31, 2026
Subsequent Events [Abstract]  
Subsequent Events Subsequent Events
The Company performed an evaluation of subsequent events through the date of filing of these unaudited condensed consolidated financial statements with the SEC and determined that there have been no material subsequent events which affected, or could affect, the amounts or disclosures on the unaudited condensed consolidated financial statements.
v3.26.1
Insider Trading Arrangements
 3 Months Ended
Mar. 31, 2026
Trading Arrangements, by Individual  
Rule 10b5-1 Arrangement Adopted false
Non-Rule 10b5-1 Arrangement Adopted false
Rule 10b5-1 Arrangement Terminated false
Non-Rule 10b5-1 Arrangement Terminated false
v3.26.1
Summary of Significant Accounting Policies (Policies)
 3 Months Ended
Mar. 31, 2026
Accounting Policies [Abstract]  
Basis of Presentation
Basis of Presentation

The accompanying unaudited condensed consolidated financial statements and accompanying notes are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial reporting.

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with the instructions to Form 10-Q and Articles 8 and 10 of Regulation S-X. Certain information or footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted, pursuant to the rules and regulations of the SEC for interim financial reporting. Accordingly, it does not include all the information and footnotes necessary for a complete presentation of financial position, results of operations, or cash flows. The information herein should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025, which was filed on March 17, 2026. In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting of a normal recurring nature, which are necessary for a fair statement of the financial position, operating results, and cash flows for the periods presented.
Segment Information
Segment Information

The Company has viewed its financial information on an aggregate basis for the purposes of evaluating financial performance and allocating the Company’s resources. The Company’s principal business consists primarily of research and development and deployment activities for its planned or in-process powerhouses, nuclear fuel recycling and fuel
fabrication facilities, and its radioisotope production facilities. Accordingly, the Company has determined that it conducts its business in one operating and one reportable segment.
Principles of Consolidation
Principles of Consolidation

The unaudited condensed consolidated financial statements include the Company’s accounts and those of its wholly owned subsidiaries. All intercompany transactions and balances have been eliminated.
Use of Estimates
Use of Estimates
Preparation of financial statements in conformity with U.S. GAAP requires management to make estimates, judgments, and assumptions that affect the amounts reported and disclosed in the unaudited condensed consolidated financial statements and accompanying notes. Actual results could differ materially from these estimates. On an ongoing basis, the Company evaluates its estimates, including those related to the valuation of the operating lease liabilities and operating right-of-use assets, useful lives of property, plant and equipment, valuation allowance on deferred tax assets, and the fair value of acquired intangible assets and goodwill. These estimates, judgments, and assumptions are based on current and expected economic conditions, historical data, and experience available at the date of the accompanying unaudited condensed consolidated financial statements, and various other factors that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities.
Risk and Uncertainties
Risk and Uncertainties

The Company is subject to continuing risks and uncertainties amidst a range of supply chain, construction, and design complexities and in connection with the market dynamics around fuel costs and the current macroeconomic environment, including as a result of inflation, instability in the global banking system, trade policy (including tariffs, export controls, and sanctions), ongoing or escalating geopolitical factors and military activities, as well as the potential for additional conflicts, war or civil unrest. At this point, the extent to which these effects may impact the Company’s future financial condition or results of operations is uncertain, and as of the date of issuance of these condensed consolidated financial statements, the Company is not aware of any specific event or circumstance that would require the update of any estimates or judgments or an adjustment of the carrying value of any assets or liabilities. These estimates may change as new events occur and additional information is obtained and will be recognized in the condensed consolidated financial statements as soon as they become known.
Net Loss Per Common Share
Net Loss Per Common Share

The Company’s basic net loss per share of common stock is computed based on the average number of outstanding shares of common stock for the period, by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period, without consideration for potential dilutive securities. Diluted net loss per share of common stock is computed by dividing net loss by the weighted-average number of shares of common stock and common share equivalents of potentially dilutive securities outstanding for the period. Potentially dilutive securities include common stock equivalents. Since the Company was in a loss position for the periods presented, basic net loss per share of common stock is the same as diluted net loss per share of common stock since the effects of potentially dilutive securities are antidilutive.
Recently Issued and Not Adopted Accounting Standards
Recently Issued and Not Adopted Accounting Standards
In November 2024, the FASB issued ASU 2024-03, Income Statement – Reporting Comprehensive Income – Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, which will require disaggregated disclosures in the notes to the financial statements of certain categories of expenses, including purchases of inventory, employee compensation, and depreciation and amortization, that are included in expense line items within the statement of operations. ASU 2024-03 will be applied prospectively; however, retrospective application is permitted. ASU 2024-03, as clarified in ASU 2025-01, Clarifying the Effective Date, requires public business entities to adopt the guidance in annual reporting periods beginning after December 15, 2026, and interim periods within annual reporting periods beginning after December 15, 2027. Early adoption is permitted. The Company is evaluating the impact of ASU 2024-03 on its disclosures in the notes to its financial statements.

In September 2025, the FASB issued ASU 2025‑06, Intangibles—Goodwill and Other—Internal‑Use Software (Subtopic 350‑40): Targeted Improvements to the Accounting for Internal‑Use Software, which updates the guidance for capitalization of internal‑use software costs, including clarifications to the criteria for capitalizing configuration, development, and implementation activities. ASU 2025-06 is effective for the Company beginning with interim reporting for fiscal year 2029. Early adoption is permitted. The Company is currently evaluating the impact of ASU 2025-06 on its accounting policies and related disclosures.

In December 2025, the FASB issued ASU 2025‑10, Government Grants (Topic 832): Accounting for Government Grants Received by Business Entities, which provides updated guidance on how to recognize, measure, and present government grants. ASU 2025‑10 is effective for the Company for annual periods beginning after December 15, 2028, including interim periods within those periods using a modified prospective, modified retrospective, or full retrospective transition approach. Early adoption is permitted. The Company is currently assessing the effect of ASU 2025-10 on its financial statements.
v3.26.1
Business Combination (Tables)
 3 Months Ended
Mar. 31, 2026
Business Combination [Abstract]  
Schedule of Business Acquisitions, by Acquisition
The composition of the purchase price is as follows:

Cash$1,016 
Common stock27,408 
Total purchase consideration$28,424 
Schedule of Assets Acquired and Liabilities Assumed
The purchase price allocation resulted in the following amounts being allocated to the assets acquired and liabilities assumed at the Acquisition Date based upon their respective fair values as summarized below:

Cash$116 
Prepaid expenses99 
Property and equipment40 
Operating lease right-of-use assets19 
Indefinite-lived intangible assets27,500 
Goodwill6,621 
Operating lease liability(19)
Other current liabilities(268)
Deferred tax liabilities(5,684)
Net assets acquired
$28,424 
v3.26.1
Balance Sheet Components (Tables)
 3 Months Ended
Mar. 31, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]  
Schedule of Prepaid and Other Current Assets
Prepaid and other current assets are summarized as follows:
As of
March 31, 2026
(unaudited)		December 31, 2025
Prepaid expense$5,670 $18,853 
Accrued interest receivable9,710 4,976 
Other1,669 1,969 
Total prepaid and other current assets$17,049 $25,798 
Schedule of Property, Plant and Equipment, Net
Property, plant and equipment, net are summarized as follows:
As of
Estimates Useful Lives (Years)March 31, 2026
(unaudited)		December 31, 2025
Computers and equipment
3 - 7
$366 $366 
Furniture, fixtures and machinery7665 483 
Software31,405 1,405 
Leasehold improvements*62 62 
LandN/A5,145 5,145 
Total property and equipment, gross7,643 7,461 
Less: accumulated depreciation and amortization(1,060)(897)
Construction in progress and equipment deposits89,032 35,748 
Total property, plant and equipment, net$95,615 $42,312 
* Shorter of lease term or estimated useful life of the asset.
Schedule of Other Assets
Other assets are summarized as follows:
As of
March 31, 2026
(unaudited)		December 31, 2025
Other$212 $217 
Other investments17,086 12,086 
Total other assets$17,298 $12,303 
Schedule of Accrued Expenses and Other
Accrued expenses and other are summarized as follows:
As of
March 31, 2026
(unaudited)		December 31, 2025
Accrued professional fees$1,621 $1,838 
Accrued payroll and bonuses4,769 10,998 
General accrued expenses13,950 7,210 
Other current liabilities1,556 451 
Total accrued expenses and other$21,896 $20,497 
v3.26.1
Leases (Tables)
 3 Months Ended
Mar. 31, 2026
Leases [Abstract]  
Schedule of Lease Supplemental Information and Lease Cost
The table below presents supplemental information related to the operating leases:
Three Months Ended March 31,
20262025
Cash payments included in the measurement of operating lease liabilities during the period$279 $150 
Operating lease liabilities arising from obtaining lease right-of-use assets during the period$1,400 $890 
Weighted-average remaining lease term (in months) as of period-end3837
Weighted-average discount rate during the period8.95%8.97%
The components of operating lease costs were as follows:
Three Months Ended March 31,
20262025
Operating lease costs included in:
Research and development$260 $151 
General and administrative105 80 
Total operating costs (1)
$365 $231 

(1) Month-to-month lease arrangements for the three months ended March 31, 2026 and 2025 of $57 and $71, respectively, are included in the captions within operating lease costs.
Schedule of Operating Lease Maturities
As of March 31, 2026, future maturities of the operating lease liabilities were as follows:

2026 (remaining of year)$1,045 
2027614 
2028614 
2029635 
2030106 
Minimum lease payments3,014 
Less imputed interest(394)
Present value of operating lease liabilities$2,620 
Current portion of operating lease liabilities$1,031 
Noncurrent portion of operating lease liabilities1,589 
Total operating lease liabilities$2,620 
v3.26.1
Financial Instruments (Tables)
 3 Months Ended
Mar. 31, 2026
Investments, Debt and Equity Securities [Abstract]  
Schedule of Cash, Cash Equivalents and Marketable Debt Securities by Significant Investment Category
The following table shows the Company’s cash, cash equivalents and marketable debt securities by significant investment category:
As of March 31, 2026
Amortized CostUnrealized Gains
Unrealized Losses (1)
Fair ValueCash and Cash EquivalentsCurrent Marketable Debt SecuritiesNoncurrent Marketable Debt Securities
Cash$— $— $— $— $15,571 $— $— 
Level 1:
Money market funds— — — — 1,578,532 — — 
U.S. Treasury securities805,151 289 (1,674)803,766 — 475,477 328,289 
Subtotal805,151 289 (1,674)803,766 1,578,532 475,477 328,289 
Level 2 (2):
Commercial paper139,126 10 (107)139,029 — 139,029 — 
Total $944,277 $299 $(1,781)$942,795 $1,594,103 $614,506 $328,289 

(1) There was no allowance for expected credit losses on available-for-sale marketable debt securities as of March 31, 2026 as the unrealized losses were deemed to be temporary in nature.

(2) The valuation techniques used to measure the fair values of the Company’s Level 2 financial instruments, which generally have counterparties with high credit ratings, are based on quoted market prices or model-driven valuations using significant inputs derived from or corroborated by observable market data.
The following tables show the Company’s cash, cash equivalents, and marketable debt securities by significant investment category:
As of December 31, 2025
Amortized CostUnrealized GainsFair ValueCash and Cash EquivalentsCurrent Marketable Debt SecuritiesNoncurrent Marketable Debt Securities
Cash$— $— $— $11,022 $— $— 
Level 1:
Money market funds— — — 777,423 — — 
U.S. Treasury securities504,008 1,123 505,131 — 320,563 184,568 
Subtotal504,008 1,123 505,131 777,423 320,563 184,568 
Level 2 (1):
Commercial paper118,907 56 118,963 — 118,963 — 
Total$622,915 $1,179 $624,094 $788,445 $439,526 $184,568 

(1) The valuation techniques used to measure the fair values of the Company’s Level 2 financial instruments, which generally have counterparties with high credit ratings, are based on quoted market prices or model-driven valuations using significant inputs derived from or corroborated by observable market data.
Schedule of Fair Value of the Company’s Marketable Debt Securities, by Contractual Maturity
The following table shows the fair value of the Company’s noncurrent marketable debt securities, by contractual maturity, as of March 31, 2026:

Due within 1 year$614,506 
Due after 1 year through 5 years328,289 
Total fair value$942,795 
v3.26.1
Stockholders’ Equity (Tables)
 3 Months Ended
Mar. 31, 2026
Equity [Abstract]  
Schedule of Shares Issued
The following is a summary of the shares issued under the 2025 ATM Program during the three months ended March 31, 2026 (in thousands except shares issued and average price per share):

Period Ended Shares Issued Average Net Price Per Share Gross Proceeds Net Proceeds
March 31, 202612,376,352$96.95$1,199,868 $1,181,897 
v3.26.1
Stock-Based Compensation (Tables)
 3 Months Ended
Mar. 31, 2026
Share-Based Payment Arrangement [Abstract]  
Schedule of Stock-Based Compensation Expense
Stock-based compensation expense charged to operations is summarized as follows:

Three Months Ended March 31,
20262025
Research and development$7,496 $973 
General and administrative8,090 1,338 
Total costs charged to operations$15,586 $2,311 
Schedule of Unrecognized Compensation Expense
Unrecognized compensation expense and expected weighted-average period to be recognized related to the stock-based compensation awards as of March 31, 2026 were as follows:

Restricted StockStock OptionsTotals
Unrecognized stock-based compensation cost$118,291 $13,757 $132,048 
Weighted-average period over which cost is expected to be recognized (in years)3.443.323.42
v3.26.1
Nature of Operations and Organization (Details)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
USD ($)
MWd
Mar. 31, 2025
USD ($)
Dec. 31, 2025
USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]      
Powerhouse production capability, nuclear fuel | MWd 15    
Powerhouse production capability, fresh fuel | MWd 75    
Powerhouse useful life 30 years    
Cash, cash equivalents, and marketable securities $ 2,536,898    
Net loss 33,065 $ 9,810  
Operating loss 51,249 17,874  
Net cash used in operating activities 17,867 $ 12,243  
Accumulated deficit $ 273,837   $ 240,772
v3.26.1
Summary of Significant Accounting Policies (Details)
 3 Months Ended 12 Months Ended
Mar. 31, 2026
segment
shares
Mar. 31, 2025
shares
Dec. 31, 2025
segment
Property, Plant and Equipment [Line Items]      
Number of operating segments | segment 1    
Number of reportable segments | segment 1   1
Stock Options      
Property, Plant and Equipment [Line Items]      
Antidilutive securities excluded from earnings per share (in shares) 6,130,247 9,151,461  
Restricted Stock      
Property, Plant and Equipment [Line Items]      
Antidilutive securities excluded from earnings per share (in shares) 426,750 640,125  
Restricted Stock Units      
Property, Plant and Equipment [Line Items]      
Antidilutive securities excluded from earnings per share (in shares) 2,619,465 1,624,743  
v3.26.1
Business Combination - Narrative (Details)
 3 Months Ended
Feb. 28, 2025
USD ($)
project
$ / shares
shares
Mar. 31, 2026
USD ($)
Dec. 31, 2025
USD ($)
Mar. 31, 2025
USD ($)
Business Combination [Line Items]        
Payment for acquisition of business, net of cash acquired   $ 0   $ 900,000
Atomic Alchemy, Inc.        
Business Combination [Line Items]        
Total purchase consideration $ 28,424,000      
Payment for acquisition of business, net of cash acquired $ 900,000      
Share price (in dollars per share) | $ / shares $ 33.39      
Business combination, consideration transferred, equity $ 27,408,000      
Transaction costs $ 410,000      
Decrease in deferred tax liabilities     $ 99,000  
IPR&D projects, number | project 2      
Indefinite-lived intangible assets $ 27,500,000      
Tax-deductible goodwill 0      
Atomic Alchemy, Inc. | In Process Research and Development, Abundantia Project        
Business Combination [Line Items]        
Indefinite-lived intangible assets 4,600,000      
Atomic Alchemy, Inc. | In Process Research and Development, Meitner Project        
Business Combination [Line Items]        
Indefinite-lived intangible assets $ 22,900,000      
Atomic Alchemy, Inc. | Class A common stock, stock purchase consideration        
Business Combination [Line Items]        
Equity interests issued or issuable (in shares) | shares 820,840      
Atomic Alchemy, Inc. | Class A common stock, post combination services consideration        
Business Combination [Line Items]        
Equity interests issued or issuable (in shares) | shares 274,339      
v3.26.1
Business Combination - Schedule of Purchase Price (Details) - Atomic Alchemy, Inc.
$ in Thousands
Feb. 28, 2025
USD ($)
Business Combination [Line Items]  
Cash $ 1,016
Common stock 27,408
Total purchase consideration $ 28,424
v3.26.1
Business Combination - Schedule of Assets Acquired and Liabilities Assumed (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Feb. 28, 2025
Business Combination [Line Items]      
Goodwill $ 6,621 $ 6,621  
Atomic Alchemy, Inc.      
Business Combination [Line Items]      
Cash     $ 116
Prepaid expenses     99
Property and equipment     40
Operating lease right-of-use assets     19
Indefinite-lived intangible assets     27,500
Goodwill     6,621
Operating lease liability     (19)
Other current liabilities     (268)
Deferred tax liabilities     (5,684)
Net assets acquired     $ 28,424
v3.26.1
Balance Sheet Components - Schedule of Prepaid and Other Current Assets (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]    
Prepaid expense $ 5,670 $ 18,853
Accrued interest receivable 9,710 4,976
Other 1,669 1,969
Total prepaid and other current assets $ 17,049 $ 25,798
v3.26.1
Balance Sheet Components - Schedule of Property, Plant and Equipment, Net (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross $ 7,643 $ 7,461
Less: accumulated depreciation and amortization (1,060) (897)
Construction in progress and equipment deposits 89,032 35,748
Total property, plant and equipment, net 95,615 42,312
Computers and equipment    
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross $ 366 366
Computers and equipment | Minimum    
Property, Plant and Equipment [Line Items]    
Estimates Useful Lives (Years) 3 years  
Computers and equipment | Maximum    
Property, Plant and Equipment [Line Items]    
Estimates Useful Lives (Years) 7 years  
Furniture, fixtures and machinery    
Property, Plant and Equipment [Line Items]    
Estimates Useful Lives (Years) 7 years  
Total property and equipment, gross $ 665 483
Software    
Property, Plant and Equipment [Line Items]    
Estimates Useful Lives (Years) 3 years  
Total property and equipment, gross $ 1,405 1,405
Leasehold improvements    
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross 62 62
Land    
Property, Plant and Equipment [Line Items]    
Total property and equipment, gross $ 5,145 $ 5,145
v3.26.1
Balance Sheet Components - Narrative (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]      
Depreciation and amortization expenses $ 163 $ 124  
Other investments $ 17,086   $ 12,086
v3.26.1
Balance Sheet Components - Schedule of Other Assets (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]    
Other $ 212 $ 217
Other investments 17,086 12,086
Total other assets $ 17,298 $ 12,303
v3.26.1
Balance Sheet Components - Schedule of Accrued Expenses and Other (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]    
Accrued professional fees $ 1,621 $ 1,838
Accrued payroll and bonuses 4,769 10,998
General accrued expenses 13,950 7,210
Other current liabilities 1,556 451
Total accrued expenses and other $ 21,896 $ 20,497
v3.26.1
Leases - Schedule of Supplemental Information (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Leases [Abstract]    
Cash payments included in the measurement of operating lease liabilities during the period $ 279 $ 150
Operating lease liabilities arising from obtaining lease right-of-use assets during the period $ 1,400 $ 890
Weighted-average remaining lease term (in months) as of period-end 38 months 37 months
Weighted-average discount rate during the period 8.95% 8.97%
v3.26.1
Leases - Schedule of Operating Lease Costs (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Lessee, Lease, Description [Line Items]    
Total operating costs $ 365 $ 231
Month-to-Month Lease Arrangements    
Lessee, Lease, Description [Line Items]    
Total operating costs 57 71
Research and development    
Lessee, Lease, Description [Line Items]    
Total operating costs 260 151
General and administrative    
Lessee, Lease, Description [Line Items]    
Total operating costs $ 105 $ 80
v3.26.1
Leases - Schedule of Operating Lease Maturities (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Leases [Abstract]    
2026 (remaining of year) $ 1,045  
2027 614  
2028 614  
2029 635  
2030 106  
Minimum lease payments 3,014  
Less imputed interest (394)  
Current portion of operating lease liabilities 1,031 $ 904
Noncurrent portion of operating lease liabilities 1,589 $ 546
Total operating lease liabilities $ 2,620  
v3.26.1
Financial Instruments - Schedule of Cash, Cash Equivalents, and Marketable Debt Securities by Investment Category (Details) - USD ($)
Mar. 31, 2026
Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash $ 15,571,000 $ 11,022,000
Amortized Cost 944,277,000 622,915,000
Unrealized Gains 299,000 1,179,000
Unrealized Losses (1,781,000)  
Fair Value 942,795,000 624,094,000
Cash and Cash Equivalents 1,594,103,000 788,445,000
Current Marketable Debt Securities 614,506,000 439,526,000
Noncurrent Marketable Debt Securities 328,289,000 184,568,000
Allowance for credit loss 0  
Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Amortized Cost 805,151,000 504,008,000
Unrealized Gains 289,000 1,123,000
Unrealized Losses (1,674,000)  
Fair Value 803,766,000 505,131,000
Cash and Cash Equivalents 1,578,532,000 777,423,000
Current Marketable Debt Securities 475,477,000 320,563,000
Noncurrent Marketable Debt Securities 328,289,000 184,568,000
Level 1 | U.S. Treasury securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Amortized Cost 805,151,000 504,008,000
Unrealized Gains 289,000 1,123,000
Unrealized Losses (1,674,000)  
Fair Value 803,766,000 505,131,000
Current Marketable Debt Securities 475,477,000 320,563,000
Noncurrent Marketable Debt Securities 328,289,000 184,568,000
Level 1 | Money market funds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash and Cash Equivalents 1,578,532,000 777,423,000
Level 2 | Commercial paper    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Amortized Cost 139,126,000 118,907,000
Unrealized Gains 10,000 56,000
Unrealized Losses (107,000)  
Fair Value 139,029,000 118,963,000
Current Marketable Debt Securities $ 139,029,000 $ 118,963,000
v3.26.1
Financial Instruments - Narrative (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Debt securities, available-for-sale, excluding accrued interest, current    
Debt Securities, Available-for-Sale [Line Items]    
Debt securities interest receivable $ 4,143 $ 4,005
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration] Marketable debt securities Marketable debt securities
Prepaid expenses and other current assets    
Debt Securities, Available-for-Sale [Line Items]    
Debt securities interest receivable $ 4,566 $ 3,160
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration] Prepaid and other current assets Prepaid and other current assets
v3.26.1
Financial Instruments - Schedule of Fair Value of the Company’s Marketable Debt Securities, by Contractual Maturity (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Investments, Debt and Equity Securities [Abstract]    
Due within 1 year $ 614,506  
Due after 1 year through 5 years 328,289  
Fair Value $ 942,795 $ 624,094
v3.26.1
Right of First Refusal Liability (Details) - USD ($)
$ in Thousands
 1 Months Ended
Mar. 31, 2024
Mar. 31, 2026
Dec. 31, 2025
Feb. 16, 2024
Commitments and Contingencies Disclosure [Abstract]        
Commitment period       20 years
Purchase power agreement additional extension term       20 years
Right of first refusal term       36 months
Right of first refusal payment $ 25,000      
Right of first refusal liability   $ 25,000 $ 25,000  
v3.26.1
Stockholders’ Equity - Narrative (Details)
$ / shares in Units, $ in Thousands
 3 Months Ended 4 Months Ended
Mar. 31, 2026
USD ($)
$ / shares
shares
Mar. 31, 2025
USD ($)
shares
Mar. 31, 2026
USD ($)
$ / shares
shares
Dec. 31, 2025
$ / shares
shares
Class of Stock [Line Items]        
Common stock and preferred stock, authorized (in shares) 501,000,000   501,000,000  
Common stock, authorized (in shares) 500,000,000   500,000,000 500,000,000
Common stock, par value (in dollars per share) | $ / shares $ 0.0001   $ 0.0001 $ 0.0001
Preferred stock, authorized (in shares) 1,000,000   1,000,000  
Preferred stock, par value (in dollars per share) | $ / shares $ 0.0001   $ 0.0001  
Issuance of common stock (in shares) 290,908 318,921    
Issuance of common stock | $ $ 737 $ 720    
Common stock withheld for taxes (in shares) 1,280 66,724    
Payment of taxes from common stock withheld | $ $ 75 $ 1,595    
Restricted Stock        
Class of Stock [Line Items]        
Vesting of restricted stock units (in shares) 687,756 134,832    
At The Market Offering        
Class of Stock [Line Items]        
Proceeds from issuance of common stock, gross | $ $ 1,199,868   $ 1,500  
Sale of stock, commission percentage     0.015  
Issuance of common stock | $ $ 1,181,897      
v3.26.1
Stockholders’ Equity - Schedule of Shares Issued (Details) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 4 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Mar. 31, 2026
Class of Stock [Line Items]      
Net Proceeds $ 1,181,897 $ 0  
At The Market Offering      
Class of Stock [Line Items]      
Shares Issued (in shares) 12,376,352   12,376,352
Average Net Price Per Share (in dollars per share) $ 96.95   $ 96.95
Gross Proceeds $ 1,199,868   $ 1,500
Net Proceeds $ 1,181,897    
v3.26.1
Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Total costs charged to operations $ 15,586 $ 2,311
Research and development    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Total costs charged to operations 7,496 973
General and administrative    
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]    
Total costs charged to operations $ 8,090 $ 1,338
v3.26.1
Stock-Based Compensation - Narrative (Details) - Restricted Stock
$ in Thousands
 3 Months Ended
Mar. 31, 2026
USD ($)
shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]  
Granted (in shares) | shares 550,000
Issued during period, grant date fair value | $ $ 36,000
v3.26.1
Stock-Based Compensation - Schedule of Unrecognized Compensation Expense (Details)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
USD ($)
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]  
Unrecognized stock-based compensation cost $ 132,048
Weighted-average period over which cost is expected to be recognized (in years) 3 years 5 months 1 day
Restricted Stock  
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]  
Unrecognized stock-based compensation cost $ 118,291
Weighted-average period over which cost is expected to be recognized (in years) 3 years 5 months 8 days
Stock Options  
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]  
Unrecognized stock-based compensation cost $ 13,757
Weighted-average period over which cost is expected to be recognized (in years) 3 years 3 months 25 days
v3.26.1
Income Taxes (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Income Tax Disclosure [Abstract]    
Income tax expense (benefit) $ 3,155 $ (4,411)
v3.26.1
Commitments and Contingencies (Details)
Mar. 31, 2026
USD ($)
Commitments and Contingencies Disclosure [Abstract]  
Loss contingency accrual $ 0
v3.26.1
Segment Information (Details) - segment
 3 Months Ended 12 Months Ended
Mar. 31, 2026
Dec. 31, 2025
Segment Reporting [Abstract]    
Number of reportable segments 1 1
v3.26.1
Related Party Transactions (Details) - Klein Group LLC - USD ($)
$ in Thousands
 3 Months Ended
Jun. 25, 2025
Mar. 31, 2026
Related Party Transaction [Line Items]    
Advisory agreement term 1 year  
Advisory agreement, quarterly retainer fee $ 250  
Advisory agreement, payment of quarterly retainer fee   $ 250