v3.25.4
Document and Entity Information
Mar. 03, 2026
Cover [Abstract]  
Amendment Flag false
Entity Central Index Key 0002020354
Document Type 8-K
Document Period End Date Mar. 03, 2026
Entity Registrant Name West Bay BDC LLC
Entity Incorporation State Country Code DE
Entity File Number 814-01758
Entity Tax Identification Number 99-1657525
Entity Address, Address Line One 200 West Street
Entity Address, City or Town New York
Entity Address, State or Province NY
Entity Address, Postal Zip Code 10282
City Area Code (312)
Local Phone Number 655-4419
Written Communications false
Soliciting Material false
Pre Commencement Tender Offer false
Pre Commencement Issuer Tender Offer false
Entity Emerging Growth Company true
Entity Ex Transition Period true