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COMMON STOCK WARRANTS - Narrative (Details) $ / shares in Units, $ in Thousands					1 Months Ended	3 Months Ended		6 Months Ended
	Aug. 23, 2024	Sep. 21, 2023 USD ($) tradingDay $ / shares shares	Oct. 08, 2021 $ / shares shares	Sep. 21, 2020 shares	Jan. 31, 2026 shares	Jun. 30, 2026 USD ($) $ / shares shares	Jun. 30, 2025 USD ($) shares	Jun. 30, 2026 USD ($) $ / shares shares	Jun. 30, 2025 USD ($) shares	Jan. 30, 2026 $ / shares	Dec. 31, 2025 shares	Oct. 14, 2025 $ / shares shares	Jul. 10, 2025 $ / shares	Dec. 31, 2024 shares	Sep. 16, 2022 $ / shares shares	Nov. 09, 2021 shares
Class of Warrant or Right [Line Items]
Warrants issued (in shares)								5,100,000	0
Warrants outstanding (in shares)						5,224,819	1,943,403	5,224,819	1,943,403		3,124,819			1,943,403
Conversion ratio																1
Net decrease (increase) to warrant liabilities \| $						$ (166)	$ (459)	$ (510)	$ (344)
Number of shares with vesting conditions met (in shares)						833		833			833
Proceeds from issuance of common stock and common stock warrants via RDO, net of issuance costs \| $								$ 13,553	$ 0
Shares issued (in shares)					3,471,428
RDO Warrants \| Senior notes
Class of Warrant or Right [Line Items]
Class of warrant or right, exercise price of warrants or rights (in dollars per share) \| $ / shares										$ 1.75
Yorkville Promissory Note \| Senior notes
Class of Warrant or Right [Line Items]
Class of warrant or right, exercise price of warrants or rights (in dollars per share) \| $ / shares												$ 9.98
Warrant exercisable (in shares)												1,052,104
Scenario two
Class of Warrant or Right [Line Items]
Price of common stock triggering redemption of warrants (in USD per share) \| $ / shares								$ 150.00
Trading days triggering redemption of warrants								20 days
Consecutive trading day period								30 days
STWO \| Common Stock
Class of Warrant or Right [Line Items]
Price per share (in USD per share) \| $ / shares			$ 172.50
STWO \| Public Warrant Holders \| Common Stock
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)			15
stock split ratio	0.667
Issuance of shares (in shares)			1
Public common stock warrants
Class of Warrant or Right [Line Items]
Warrants issued (in shares)								0	0
Warrants outstanding (in shares)						764,081	764,081	764,081	764,081		764,081			764,081
Public common stock warrants \| Scenario one
Class of Warrant or Right [Line Items]
Redemption price per share (in USD per share) \| $ / shares						$ 0.01		$ 0.01
Price of common stock triggering redemption of warrants (in USD per share) \| $ / shares								$ 270.00
Trading days triggering redemption of warrants								20 days
Consecutive trading day period								30 days
Public common stock warrants \| Scenario two
Class of Warrant or Right [Line Items]
Redemption price per share (in USD per share) \| $ / shares						$ 0.10		$ 0.10
Public common stock warrants \| STWO
Class of Warrant or Right [Line Items]
Warrants issued (in shares)			8,333,287
Warrants term (in years)			5 years
Private warrants
Class of Warrant or Right [Line Items]
Warrants vested (in shares)			3,500,000
Private warrants \| Private Placement
Class of Warrant or Right [Line Items]
Warrants issued (in shares)				4,666,667
Warrants forfeited (in shares)			583,333
Warrants outstanding (in shares)			4,083,334
Private warrants \| Private Placement \| Scenario one
Class of Warrant or Right [Line Items]
Warrants vested (in shares)																583,334
Earnout warrants
Class of Warrant or Right [Line Items]
Net decrease (increase) to warrant liabilities \| $						$ 166	$ 459	$ 510	$ 344
SMUD Warrant
Class of Warrant or Right [Line Items]
Warrants issued (in shares)								0	0
Warrants outstanding (in shares)						833	833	833	833		833			833
Class of warrant or right, number of securities called by each warrant or right (in shares)															33,333
Class of warrant or right, exercise price of warrants or rights (in dollars per share) \| $ / shares															$ 64.44
Honeywell warrants
Class of Warrant or Right [Line Items]
Proceeds from issuance of common stock and common stock warrants via RDO, net of issuance costs \| $		$ 27,500
Shares issued (in shares)		1,099,450
Honeywell warrants \| Investment Warrant
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)		708,775
Class of warrant or right, exercise price of warrants or rights (in dollars per share) \| $ / shares		$ 28.35
Honeywell warrants \| IP Warrant
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)		417,997
Class of warrant or right, exercise price of warrants or rights (in dollars per share) \| $ / shares		$ 43.50
Performance warrant
Class of Warrant or Right [Line Items]
Warrants term (in years)		5 years
Class of warrant or right, exercise price of warrants or rights (in dollars per share) \| $ / shares		$ 21.75
Proceeds from issuance of common stock and common stock warrants via RDO, net of issuance costs \| $		$ 300,000
Additional performance warrants \| $		$ 15,000
Number of trading days \| tradingDay		15
Performance warrant \| UOP LLC
Class of Warrant or Right [Line Items]
Warrants term (in years)		5 years
Class of warrant or right, number of securities called by each warrant or right (in shares)		51,717
Exchange for pre-payment of equipment \| $		$ 15,000
Bridge Financing Warrants
Class of Warrant or Right [Line Items]
Warrants issued (in shares)								0
Warrants outstanding (in shares)						129,312		129,312			129,312
Bridge Financing Warrants \| Investment Warrant
Class of Warrant or Right [Line Items]
Class of warrant or right, exercise price of warrants or rights (in dollars per share) \| $ / shares													$ 3.48
Pre-funded warrants \| RDO Warrants \| Senior notes
Class of Warrant or Right [Line Items]
Class of warrant or right, exercise price of warrants or rights (in dollars per share) \| $ / shares										$ 1.74999