Cover - USD ($)	12 Months Ended
	Sep. 30, 2025	Dec. 12, 2025	Mar. 31, 2025
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Financial Statement Error Correction [Flag]	false
Entity Interactive Data Current	Yes
ICFR Auditor Attestation Flag	false
Amendment Flag	false
Document Period End Date	Sep. 30, 2025
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	FY
Entity Information [Line Items]
Entity Registrant Name	EUREKA ACQUISITION CORP
Entity Central Index Key	0002000410
Entity File Number	001-42152
Entity Tax Identification Number	00-0000000
Entity Incorporation, State or Country Code	E9
Current Fiscal Year End Date	--09-30
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Shell Company	true
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Public Float			$ 0
Entity Contact Personnel [Line Items]
Entity Address, Address Line One	Suite 1608
Entity Address, Address Line Two	16th FloorFortress Tower
Entity Address, Address Line Three	250 King’s Road
Entity Address, City or Town	North Point
Entity Address, Country	HK
Entity Address, Postal Zip Code	00000
Entity Phone Fax Numbers [Line Items]
City Area Code	(+1)
Local Phone Number	949 899 1827
Units, consisting of one Ordinary Share, $0.0001 par value, and one Right to acquire one-fifth of one Ordinary Share
Entity Listings [Line Items]
Title of 12(b) Security	Units, consisting of one Class A ordinary share, $0.0001 par value, and one Right to acquire one-fifth of one Class A ordinary share
Trading Symbol	EURKU
Security Exchange Name	NASDAQ
Class A ordinary shares, par value $0.0001 per share
Entity Listings [Line Items]
Title of 12(b) Security	Class A ordinary shares, par value $0.0001 per share
Trading Symbol	EURK
Security Exchange Name	NASDAQ
Rights, each whole right to acquire one-fifth of one Class A ordinary share
Entity Listings [Line Items]
Title of 12(b) Security	Rights, each whole right to acquire one-fifth of one Class A ordinary share
Trading Symbol	EURKR
Security Exchange Name	NASDAQ
Class A Ordinary Shares
Entity Listings [Line Items]
Entity Common Stock, Shares Outstanding		3,388,233
Class B Ordinary Shares
Entity Listings [Line Items]
Entity Common Stock, Shares Outstanding		1,437,500