Document and Entity Information Document Information [Table] Document Information [Line Items] Document and Entity Information Document Type Entity Registrant Name Entity Filer Category Entity Small Business Entity Emerging Growth Company Entity Ex Transition Period Entity Central Index Key Amendment Flag BALANCE SHEET Statement [Table] Class of Stock [Axis] Class of Stock [Domain] Common Class A [Member] Class A ordinary shares Classification of common stock representing ownership interest in a corporation that is subject to redemption. Common Classa Subject To Redemption [Member] Class A ordinary shares subject to possible redemption Classification of common stock representing ownership interest in a corporation that is not subject to redemption. Common Classa Subject Not To Redemption [Member] Class A ordinary shares subject not to possible redemption Common Class B [Member] Class B Ordinary Shares Class B ordinary shares Legal Entity [Axis] Entity [Domain] Represents the information about Spring Valley Acquisition Corp. II. CIK_0001843477_Spring Valley Acquisition Corp. II Statement [Line Items] Statement Assets [Abstract] Assets Assets: Assets, Current [Abstract] Current assets Current assets: Cash Cash Prepaid Expense, Current Prepaid expenses Assets, Current Total current assets Assets, Noncurrent [Abstract] Non-current assets: Non-current assets Assets Held-in-trust, Noncurrent Trust Account Cash and investments held in Trust Account Assets, Noncurrent Total non-current assets Assets Total assets Liabilities and Equity [Abstract] Liabilities, Mezzanine Equity, and Stockholders' Equity (Deficit) Liabilities, Class A Ordinary Shares Subject to Possible Redemption and Shareholders' Deficit: Liabilities, Current [Abstract] Current liabilities Current liabilities: Accounts Payable, Current Trade payables Accounts payable Convertible Notes Payable, Current Convertible promissory note - related party Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered, excluding offering costs (due within one year or within the normal operating cycle if longer). Accrued Liabilities Excluding Offering Costs, Current Accrued expenses Carrying value as of the balance sheet date of the portion of long-term debt due within one year or the operating cycle if longer identified as extension note. Extension Notes Payable Current Extension promissory notes - related party Notes payable Liabilities, Current Total current liabilities The carrying value of deferred underwriting commissions, classified as noncurrent as on the balance sheet date. Deferred Underwriting Commissions, Noncurrent Deferred underwriting commissions Liabilities Total liabilities Commitments and Contingencies. Commitments and contingencies (Note 11) Commitments and Contingencies Temporary Equity, Carrying Amount, Attributable to Parent Common stock subject to possible redemption, November 30, 2025 Common stock subject to possible redemption, November 30, 2024 Redeemable common stock, $0.0001 par value, 350,000,000 shares authorized; 15,951,675 shares issued and subject to possible redemption at $0.02 per share as of November 30, 2025 (none as of November 30, 2024) Class A ordinary shares, $0.0001 par value; 300,000,000 shares authorized; 2,213,278 and 2,213,429 shares subject to possible redemption at $12.02 and $11.55 per share as of December 31, 2025 and 2024, respectively Equity, Attributable to Parent [Abstract] Stockholders' equity (deficit) Shareholders' Deficit: Preferred Stock, Value, Issued Preferred stock, $0.0001 par value, 50,000,000 shares authorized; none issued and outstanding as of November 30, 2025 and 2024 Preference shares, $0.0001 par value 1,000,000 shares authorized none issued and outstanding as of December 31, 2025 and 2024, respectively Common Stock, Value, Issued Common stock, $0.0001 par value, 350,000,000 shares authorized; 110,211,574 shares issued and outstanding, excluding 15,951,675 shares subject to possible redemption, as of November 30, 2025 (96,000,040 shares as of November 30, 2024) Ordinary shares Additional Paid in Capital Additional paid-in capital Retained Earnings (Accumulated Deficit) Accumulated deficit Accumulated deficit Equity, Attributable to Parent Balance ending Balance beginning Total stockholders' equity (deficit) Liabilities and Equity Total liabilities, mezzanine equity and stockholders' equity (deficit) Temporary Equity, Par or Stated Value Per Share Ordinary shares subject to possible redemption, par value (in dollars per share) Temporary Equity, Shares Authorized Ordinary shares subject to possible redemption, shares authorized (in shares) Temporary Equity, Shares Outstanding Ordinary shares subject to possible redemption, shares outstanding (in shares) Temporary Equity, Redemption Price Per Share Temporary equity, redemption price per share Redemption price Preferred Stock, Par or Stated Value Per Share Preferred stock, par value per share Preferred stock, par value (in dollars per share) Preferred Stock, Shares Authorized Preferred stock, shares authorized Preferred stock, shares authorized (in shares) Preferred Stock, Shares Issued Preferred stock, shares issued Preferred stock, shares issued (in shares) Preferred Stock, Shares Outstanding Preferred stock, shares outstanding Preferred stock, shares outstanding (in shares) Common Stock, Par or Stated Value Per Share Common stock, par value per share Common shares, par value (in dollars per share) Common Stock, Shares Authorized Common stock, shares authorized Common shares, shares authorized (in shares) Common Stock, Shares, Issued Common stock, shares issued Common shares, shares issued (in shares) Common Stock, Shares, Outstanding Common stock, shares outstanding Common shares, shares outstanding (in shares) STATEMENT OF OPERATIONS General and Administrative Expense General and administrative expenses Total General and administration costs Operating Income (Loss) Loss from operations Nonoperating Income (Expense) [Abstract] Other income (expense) Other Income (Expense): Interest Income, Operating Interest income on operating account Investment Income, Interest Income from investments held in the Trust Account Income from investments held in Trust Account Derivative, Gain (Loss) on Derivative, Net Change in fair value of derivative liability Change in fair value of derivative liability Nonoperating Income (Expense) Total other expense Net Income (Loss) Attributable to Parent Net loss for the year Net loss Net loss Net income (loss) Weighted Average Number of Shares Outstanding, Basic Weighted average number of shares outstanding - Basic (in shares) Weighted average ordinary shares outstanding - basic (in shares) Weighted Average Number of Shares Outstanding, Diluted Weighted average number of shares outstanding - Diluted (in shares) Weighted average ordinary shares outstanding - diluted (in shares) Earnings Per Share, Basic Loss per share - Basic (in dollars per share) Net (loss) income per ordinary share - basic (in dollars per share) Earnings Per Share, Diluted Loss per share - Diluted (in dollars per share) Net (loss) income per ordinary share - diluted (in dollars per share) STATEMENT OF CHANGES IN STOCKHOLDERS' DEFICIT Equity Components [Axis] Equity Component [Domain] Common Stock [Member] Common Stock Ordinary Shares Additional Paid-in Capital [Member] Additional Paid-In Capital Additional Paid-in Capital Retained Earnings [Member] Accumulated Deficit Accumulated deficit Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Deficit Shares, Issued Balance ending (in shares) Balance beginning (in shares) Amount of increase in additional paid in capital resulting from forgiveness of accrued administrative fees. Adjustments to Additional Paid in Capital, Forgiveness of Accrued Administrative Fees Forgiveness of accrued administrative fees Temporary Equity, Accretion to Redemption Value Accretion of Class A ordinary shares to redemption amount subject to possible redemption Plus: adjust carrying value to redemption value Represents the equity impact of shares converted to another class of common stock. Value of Shares Converted to Another Class of Common Stock Conversion of Class B ordinary shares to Class A ordinary shares not subject to possible redemption Represents the number of shares converted to another class of common stock Number of Shares Converted to Another Class of Common Stock Conversion of Class B ordinary shares to Class A ordinary shares not subject to possible redemption (in shares) Amount of deferred underwriting commission waived during the period. Deferred Underwriting Commissions Waived Waiver of deferred underwriting fees Deferred underwriting commission waiver STATEMENT OF CASH FLOWS Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Cash flows from operating activities Cash Flows from Operating Activities: Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net loss Net (loss) income Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Adjustments to reconcile net loss to net cash used in operating activities: Adjustments to reconcile net (loss) income to net cash used in operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Changes in operating working capital: Increase (Decrease) in Prepaid Expense Prepaid expenses Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Accrued Liabilities Accrued expenses Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Net cash used in operating activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Cash flows from investing activities Cash Flows from Investing Activities: The amount of cash outflow associated with cash deposited in Trust Account. Payments for Cash Deposited in Trust Account Cash deposited in the trust account for the extension The cash inflow from trust account for redemption of shares. Proceeds From Cash Withdrawn From Trust Account For Redemption of Shares Cash withdrawn from trust account for redemption of Class A ordinary shares Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Net cash used in investing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Cash flows from financing activities Cash Flows from Financing Activities: The cash inflow from a borrowing supported by a written promise to pay an obligation identified as an extension note. Proceeds From Extension Notes Payable Proceeds from promissory note to related party-extension The cash inflow from a borrowing supported by a written promise to pay an obligation that can be exchanged for a specified amount of one or more securities at the option of the issuer or holder. Proceeds From Convertible Notes Payable Convertible promissory note - related party Borrowings against the note Payments for Repurchase of Common Stock Redemption of Class A ordinary shares Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Net cash provided by financing activities Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Increase in cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Cash, end of period Cash, beginning of period Cash and restricted cash at the end of the period Supplemental Cash Flow Information [Abstract] Supplemental disclosure of non-cash information Supplemental Disclosure of Cash Flow Information Amount of capital contributed by sponsor for the forgiveness of accrued expenses. Forgiveness of Accrued Liabilities, By Sponsor Capital Sponsor contributed capital for the forgiveness of accrued expenses Description of Organization, Business Operations and Liquidity Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Subsidiary, Sale of Stock [Line Items] Initial Public Offering Description of Organization, Business Operations and Liquidity Nature of Operations [Text Block] NATURE OF OPERATIONS Description of Organization, Business Operations and Liquidity SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Disclosure of information about summary of significant policies Summary of Significant Accounting Policies [Table] Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Summary of Significant Accounting Policies [Line items] Summary of Significant Accounting Policies SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [TEXT BLOCK] Summary of Significant Accounting Policies No definition available. Initial Public Offering The entire disclosure on information about initial public offering. Initial Public Offering [Text Block] Initial Public Offering RELATED PARTY TRANSACTIONS Related Party Transaction [Table] Related Party Transaction [Line Items] RELATED PARTY TRANSACTIONS Related Party Transactions Related Party Transactions Disclosure [Text Block] RELATED PARTY TRANSACTIONS Related Party Transactions COMMITMENTS AND CONTINGENCIES Other Commitments [Table] Other Commitments [Line Items] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Shareholders' Deficit Class of Warrant or Right [Table] Class of Warrant or Right [Line Items] Shareholders' Deficit Equity [Text Block] STOCKHOLDERS' EQUITY (DEFICIT) AND MEZZANINE EQUITY Shareholders' Deficit Fair Value Measurements Fair Value, Recurring and Nonrecurring [Table] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value Measurements Fair Value Disclosures [Text Block] Fair Value Measurements Segment Information Schedule of Segment Reporting Information, by Segment [Table] Segment Reporting Information [Line Items] Segment Information Segment Reporting Disclosure [Text Block] Segment Information SUBSEQUENT EVENTS Subsequent Event [Table] Subsequent Event [Line Items] Subsequent event SUBSEQUENT EVENTS Subsequent Events [Text Block] SUBSEQUENT EVENTS Subsequent Events Basis of Accounting, Policy [Policy Text Block] Basis of Presentation Consolidation, Policy [Policy Text Block] Principles of Consolidation Represents the accounting policy on Emerging Growth Company. Emerging Growth Company [Policy Text Block] Emerging Growth Company Use of Estimates, Policy [Policy Text Block] Use of Estimates Concentration Risk, Credit Risk, Policy [Policy Text Block] Concentration of Credit Risk Cash and Cash Equivalents, Policy [Policy Text Block] Cash Cash and Cash Equivalents Disclosure of accounting policy for Cash and Investments Held in the Trust Account Cash and Investments Held in the Trust Account, Policy [Policy Text Block] Cash and Investments Held in the Trust Account Fair Value of Financial Instruments, Policy [Policy Text Block] Financial instruments measurements and fair value of financial instruments Fair Value of Financial Instruments Fair Value Measurement, Policy [Policy Text Block] Fair Value Measurements The disclosure of derivative warrant liabilities Derivative Warrant Liabilities [Policy Text Block] Derivative Financial Instruments Offering Costs Associated with the Initial Public Offering Disclosure of accounting policy for temporary equity. Temporary Equity, Policy [Policy Text Block] Redeemable common stock Class A Ordinary Shares Subject to Possible Redemption Earnings Per Share, Policy [Policy Text Block] Loss per share Net (Loss) Income per Ordinary Share Income Tax, Policy [Policy Text Block] Income taxes Income Taxes New Accounting Pronouncements, Policy [Policy Text Block] Recent accounting pronouncements Recent Accounting Pronouncements Temporary Equity [Table Text Block] Schedule of amount of common stock subject to possible redemption Schedule of class A ordinary shares reflected on the unaudited condensed balance sheets are reconciled Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of calculation of basic and diluted net income per ordinary share Tabular disclosure of the significant assumptions used during the year to estimate the fair value of shares, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. Schedule of Share-Based Payment Award, Shares Issued, Valuation Assumptions [Table Text Block] Schedule of assumptions were used for the determination of grant date fair value for the shares transferred to directors Summary of Company's financial assets that are measured at fair value on a recurring basis by level within the fair value hierarchy Schedule of company's financial assets that are measured at fair value on a recurring basis Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Schedule of the key inputs into the monte-carlo simulation model for the non-redemption agreements derivative liability Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Schedule of changes in the fair value of the non-redemption agreements Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of several key metrics in making decisions by CODM included in net income or loss and total assets Sale of Stock [Axis] Sale of Stock [Domain] IPO [Member] Initial Public Offering Private Placement [Member] Private Placement Over Allotment Option [Member] Over-allotment option Class of Warrant or Right [Axis] Class of Warrant or Right [Domain] Represents information pertaining to private warrants. Private Warrants Private Warrants Related and Nonrelated Parties [Axis] Related and Nonrelated Parties [Domain] Related Party [Member] Related party Related Party This member stands for sponsor. Sponsor [Member] Sponsor Director [Member] Company controlled by a director Director Related Party Transaction [Axis] Related Party Transaction [Domain] Represents information about unsecured promissory notes. Unsecured Promissory Note [Member] Unsecured promissory note Represents the information pertaining to founder shares. Founder Share [Member] Founder shares Series A Preferred Stock [Member] Series A Preferred Stock Stock Issued During Period, Shares, New Issues Issuance of common shares (in shares) Common stock issued Shares Issued, Price Per Share Purchase price, per unit Common stock issuance price Proceeds from Issuance Initial Public Offering Gross proceeds Class of Warrant or Right, Exercise Price of Warrants or Rights Exercise price of warrants (in dollars per share) Exercise price of warrants Amount of offering costs incurred for offerings during the period. Offering Costs Offering costs The carrying value as of balance sheet date of underwriting fees payable or deferred, classified as noncurrent. Deferred Offering Costs Noncurrent Deferred underwriting commissions Represents the number of shares in a unit. Number of Shares Issued Per Unit Number of shares issued per unit Number of shares issued per right, during the transaction. Number Of Shares Issued Per Right Number of shares issued per right Represents the number of warrants in a unit. Number of Warrants Issued Per Unit Number of warrants in a unit Class of Warrant or Right, Number of Securities Called by Warrants or Rights Number of warrants issuable Sale of private placement warrants (in shares) Price per share or per unit of warrants or rights outstanding. Class of Warrant or Right, Price of Warrants or Rights Price of warrant Class of Warrant or Right, Outstanding Warrants outstanding Number of rights outstanding Proceeds from Issuance of Warrants Proceeds from sale of private placement warrants