Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Oct. 31, 2025	Oct. 31, 2024	Oct. 31, 2023
Revenues:
Total revenues	$ 158,162	$ 112,132	$ 123,394
Costs of revenues:
Total costs of revenues	184,570	148,050	133,929
Gross loss	(26,408)	(35,918)	(10,535)
Operating expenses:
Administrative and selling expenses	60,743	64,604	64,528
Research and development expenses	34,079	55,404	61,021
Restructuring expense	5,337	2,562
Impairment expense	65,781	1,264	2,375
Total costs and expenses	165,940	122,570	125,549
Loss from operations	(192,348)	(158,488)	(136,084)
Interest expense	(10,378)	(9,690)	(7,247)
Interest income	8,313	13,720	15,795
Gain on extinguishment of finance obligations and debt, net			15,337
Other income (expense), net	3,178	(2,295)	4,724
Loss before provision for income taxes	(191,235)	(156,753)	(107,475)
Provision for income taxes	(137)	(25)	(581)
Net loss	(191,372)	(156,778)	(108,056)
Net loss attributable to noncontrolling interests	(3,473)	(30,769)	(488)
Net loss attributable to FuelCell Energy, Inc.	(187,899)	(126,009)	(107,568)
Series B preferred stock dividends	(3,200)	(3,200)	(3,200)
Net loss attributable to common stockholders	$ (191,099)	$ (129,209)	$ (110,768)
Loss per share basic and diluted:
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (7.42)	$ (7.83)	$ (7.92)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (7.42)	$ (7.83)	$ (7.92)
Basic weighted average shares outstanding (in shares)	25,743,252	16,505,257	13,991,593
Diluted weighted average shares outstanding (in shares)	25,743,252	16,505,257	13,991,593
Net loss	$ (191,372)	$ (156,778)	$ (108,056)
Other comprehensive (loss) income:
Foreign currency translation adjustments	(134)	111	80
Total comprehensive loss	(191,506)	(156,667)	(107,976)
Comprehensive loss attributable to noncontrolling interests	(3,473)	(30,769)	(488)
Comprehensive loss attributable to FuelCell Energy, Inc.	(188,033)	(125,898)	(107,488)
Product
Revenues:
Total revenues	69,129	25,675	19,589
Costs of revenues:
Total costs of revenues	82,853	39,582	12,878
Service
Revenues:
Total revenues	20,398	9,969	49,084
Costs of revenues:
Total costs of revenues	22,634	11,098	44,953
Generation
Revenues:
Total revenues	48,013	49,975	37,508
Costs of revenues:
Total costs of revenues	63,967	79,861	62,913
Advanced Technologies
Revenues:
Total revenues	20,622	26,513	17,213
Costs of revenues:
Total costs of revenues	$ 15,116	$ 17,509	$ 13,185