Description of the Business (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Dec. 06, 2023	Dec. 05, 2023	Nov. 13, 2023	Dec. 31, 2025	Dec. 31, 2024
Cash and Cash Equivalents [Line Items]
Common stock, par value (in dollars per share)			$ 0.0001	$ 0.0001	$ 0.0001
Preferred Stock, par value (in dollars per share)			$ 0.0001
Accumulated deficit				$ (822,373)	$ (692,071)
Cash, cash equivalents, restricted cash and marketable securities				126,900
Restricted cash and cash equivalents				$ 1,700
Old Cartesian
Cash and Cash Equivalents [Line Items]
Contingent value right, percentage of milestone payments, royalties and other amounts to be distributed	100.00%			100.00%
Old Cartesian | Common stock
Cash and Cash Equivalents [Line Items]
Issuance of shares (in shares)			224,099
Old Cartesian | Preferred Stock
Cash and Cash Equivalents [Line Items]
Issuance of shares (in shares)		384,930.724
Old Cartesian | Preferred Stock | Series A Preferred Stock
Cash and Cash Equivalents [Line Items]
Issuance of shares (in shares)			384,930.724