Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025 USD ($) platform	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) platform	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash equivalents included in prepaid expenses and other current assets	$ 200	$ 0	$ 200	$ 0
Restricted cash equivalents	$ 1,256	1,256	$ 1,256	1,256	$ 1,300
Number of primary battery platforms | platform	1		1
Revenue	$ 15,067	$ 3,345	$ 26,351	$ 5,681
Accounts receivable | Customer concentration risk | Two Customers
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk percentage			71.00%		50.00%
Revenue benchmark | Customer concentration risk | Customer One
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk percentage	41.00%	15.00%	35.00%	14.00%
Revenue benchmark | Customer concentration risk | Customer Two
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk percentage	11.00%	12.00%	13.00%
Revenue benchmark | Customer concentration risk | Customer Three
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Concentration risk percentage		11.00%	11.00%
Level 1 | Money Market Funds
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash equivalents	$ 25,700		$ 25,700		$ 23,500