Organization	12 Months Ended
Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. ORGANIZATION West Bay BDC LLC (the “Company”) is a Delaware limited liability company that was formed on February 26, 2024. The Company has elected to be regulated as a business development company (“BDC”) under the Investment Company Act of 1940, as amended (the “Investment Company Act”). In addition, the Company has elected to be treated as a regulated investment company (“RIC”), and the Company expects to qualify annually for tax treatment as a RIC, under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”), commencing with its taxable year ended December 31, 2024. The Company’s investment objective is to generate current income and, to a lesser extent, long-term capital appreciation primarily through direct originations of secured debt, including first lien, unitranche, and last-out portions of such loans, second lien debt, unsecured debt, including mezzanine debt, and select equity investments. Goldman Sachs Asset Management, L.P. (“GSAM”), a Delaware limited partnership and an affiliate of Goldman Sachs & Co. LLC (including its predecessors, “GS & Co.”), is the investment adviser (the “Investment Adviser”) of the Company. The term “Goldman Sachs” refers to The Goldman Sachs Group, Inc. (“GS Group Inc.”), together with GS & Co., GSAM and its other subsidiaries. The Company is conducting a private offering, in which investors will make a capital commitment (a “Commitment”) to purchase common units of the Company’s limited liability company interests (the “Units”). Each investor will enter into a subscription agreement with the Company, pursuant to which the investor will agree to purchase Units for an aggregate purchase price equal to its Commitment. Each investor will be required to purchase the Units each time the Company delivers a drawdown notice at least ten business days on which banks are open for business in the state of Qatar (“Qatari Business Days”) prior to the required funding date. The private offering and sale of Units will be made in reliance on one or more exemptions from the registration requirements of the Securities Act of 1933, as amended (the “Securities Act”), including Section 4(a)(2) of the Securities Act and Regulation D and Regulation S under the Securities Act. On May 1, 2024 (the “Inception Date”), the Company received a capital commitment of $10 from an affiliate of the Investment Adviser (the “Initial Member”). The Initial Member was the sole owner of the Company’s interests until the period beginning on the first date on which investors in the Company, other than the Initial Member, were required to make the initial capital contributions to purchase Units, and Units were issued in respect thereof (the “Initial Drawdown Date”). On September 23, 2024, the Company began accepting subscription agreements ("Subscription Agreements") from investors acquiring Units of the Company in the Company's private offering. Under the terms of the Subscription Agreements, investors are required to make capital contributions up to the undrawn amount of their Commitment to purchase Units each time the Company delivers a drawdown notice. On November 27, 2024, the Company commenced investment operations.

West Bay BDC LLC (the “Company”) is a Delaware limited liability company that was formed on February 26, 2024. The Company has elected to be regulated as a business development company (“BDC”) under the Investment Company Act of 1940, as amended (the “Investment Company Act”). In addition, the Company has elected to be treated as a regulated investment company (“RIC”), and the Company expects to qualify annually for tax treatment as a RIC, under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”), commencing with its taxable year ended December 31, 2024.

The Company’s investment objective is to generate current income and, to a lesser extent, long-term capital appreciation primarily through direct originations of secured debt, including first lien, unitranche, and last-out portions of such loans, second lien debt, unsecured debt, including mezzanine debt, and select equity investments.

Goldman Sachs Asset Management, L.P. (“GSAM”), a Delaware limited partnership and an affiliate of Goldman Sachs & Co. LLC (including its predecessors, “GS & Co.”), is the investment adviser (the “Investment Adviser”) of the Company. The term “Goldman Sachs” refers to The Goldman Sachs Group, Inc. (“GS Group Inc.”), together with GS & Co., GSAM and its other subsidiaries.

The Company is conducting a private offering, in which investors will make a capital commitment (a “Commitment”) to purchase common units of the Company’s limited liability company interests (the “Units”). Each investor will enter into a subscription agreement with the Company, pursuant to which the investor will agree to purchase Units for an aggregate purchase price equal to its Commitment. Each investor will be required to purchase the Units each time the Company delivers a drawdown notice at least ten business days on which banks are open for business in the state of Qatar (“Qatari Business Days”) prior to the required funding date. The private offering and sale of Units will be made in reliance on one or more exemptions from the registration requirements of the Securities Act of 1933, as amended (the “Securities Act”), including Section 4(a)(2) of the Securities Act and Regulation D and Regulation S under the Securities Act.

On May 1, 2024 (the “Inception Date”), the Company received a capital commitment of $10 from an affiliate of the Investment Adviser (the “Initial Member”). The Initial Member was the sole owner of the Company’s interests until the period beginning on the first date on which investors in the Company, other than the Initial Member, were required to make the initial capital contributions to purchase Units, and Units were issued in respect thereof (the “Initial Drawdown Date”).

On September 23, 2024, the Company began accepting subscription agreements ("Subscription Agreements") from investors acquiring Units of the Company in the Company's private offering. Under the terms of the Subscription Agreements, investors are required to make capital contributions up to the undrawn amount of their Commitment to purchase Units each time the Company delivers a drawdown notice. On November 27, 2024, the Company commenced investment operations.