Cover - USD ($)	12 Months Ended
Cover - USD ($)	Nov. 30, 2025	Feb. 10, 2026	May 31, 2025
Document Type	10-K/A
Amendment Flag	true
Amendment Description	This Amendment No. 1 (this “Amendment”) on Form 10-K/A amends the Annual Report on Form 10-K for the year ended November 30, 2025 of Legato Merger Corp. III (the “Company”), filed with the Securities and Exchange Commission on February 10, 2026 (the “Original Form 10-K”) to include certain additional disclosure in Item 9A of such Original Form 10-K. Other than as set forth above, this Amendment does not reflect events occurring after the filing of the Original Form 10-K, and no other information in the Original Form 10-K is amended hereby. Other events or circumstances occurring after the date of the Original Form 10-K or other disclosures necessary to reflect subsequent events have not been updated subsequent to the date of the Original Form 10-K. Accordingly, this Amendment should be read in conjunction with the Original Form 10-K and our filings with the SEC subsequent thereto.
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Nov. 30, 2025
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2025
Current Fiscal Year End Date	--11-30
Entity File Number	001-41945
Entity Registrant Name	Legato Merger Corp. III
Entity Central Index Key	0002002038
Entity Tax Identification Number	98-1761148
Entity Incorporation, State or Country Code	E9
Entity Address, Address Line One	777 Third Avenue
Entity Address, Address Line Two	37th Floor
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10017
City Area Code	(212)
Local Phone Number	319-7676
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
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
Elected Not To Use the Extended Transition Period	false
Entity Shell Company	true
Entity Public Float			$ 213,727,500
Entity Common Stock, Shares Outstanding		25,799,375
Document Financial Statement Error Correction [Flag]	false
Units, each consisting of one ordinary share, $0.0001 par value, and one-half of one redeemable warrant
Title of 12(b) Security	Units, each consisting of one ordinary share, $0.0001 par value, and one-half of one redeemable warrant
Trading Symbol	LEGT U
Security Exchange Name	NYSEAMER
Ordinary Shares, par value $0.0001 per share
Title of 12(b) Security	Ordinary Shares, par value $0.0001 per share
Trading Symbol	LEGT
Security Exchange Name	NYSEAMER
Redeemable warrants, exercisable for ordinary shares at an exercise price of $11.50 per share
Title of 12(b) Security	Redeemable warrants, exercisable for ordinary shares at an exercise price of $11.50 per share
Trading Symbol	LEGT WS
Security Exchange Name	NYSEAMER

Legato Merger Corp. III 10-K/A