Cover - shares	6 Months Ended
	Sep. 30, 2025	Nov. 13, 2025
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2025
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q3
Entity File Number	001-42874
Entity Central Index Key	0002064355
Amendment Flag	false
Entity Registrant Name	Bain Capital GSS Investment Corp.
Entity Tax Identification Number	98-1853296
Entity Incorporation, State or Country Code	E9
Current Fiscal Year End Date	--12-31
Entity Address, Address Line One	200 Clarendon Street
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02116
Country Region	+1
City Area Code	617
Local Phone Number	516-2000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	true
Class A Ordinary Share Redeemable Warrant [Member]
Document Information [Line Items]
Trading Symbol	BCSS.U
Title of 12(b) Security	Units, each consisting of one Class A ordinary share, $0.0001 par value, and one-fifth of one redeemable warrant
Security Exchange Name	NYSE
Class A Ordinary Shares [Member]
Document Information [Line Items]
Trading Symbol	BCSS
Entity Common Stock, Shares Outstanding		46,900,000
Title of 12(b) Security	Class A ordinary shares included as part of the units
Security Exchange Name	NYSE
Class A Ordinary Share Whole Exercise Price [Member]
Document Information [Line Items]
Trading Symbol	BCSS.W
Title of 12(b) Security	Redeemable warrants included as part of the units, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50
Security Exchange Name	NYSE
Class B Ordinary Shares [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		11,500,000