Cover - USD ($)	9 Months Ended
Cover - USD ($)	Dec. 31, 2025	Mar. 16, 2026	Jun. 30, 2025
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2025
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	FY
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 Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Public Float			$ 0
Auditor Name	WithumSmith+Brown, PC
Auditor Firm ID	100
Auditor Location	New York
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, par value $0.0001 per share
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, each whole warrant exercisable for one Class A ordinary share at an exercise price of $11.50
Security Exchange Name	NYSE
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 B Ordinary Shares [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		11,500,000

Bain Capital GSS Investment Corp. 10-K