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Total fair value at issuance of derivative instrument.

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Total premium on debt.

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Convertible Promissory Notes - Additional Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended					3 Months Ended
	Jan. 31, 2025 USD ($)	Nov. 30, 2024 USD ($)	Oct. 31, 2024 USD ($)	May 31, 2024 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2026 USD ($) $ / shares shares	Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2024
Short-Term Debt [Line Items]
Issuance of conversion of convertible promissory notes							$ 3,695
Kalaris Therapeutics, Inc. \| Series B-2 Redeemable Convertible Preferred Stock
Short-Term Debt [Line Items]
Debt instrument, converted ratio						1
Maximum \| Kalaris Therapeutics, Inc.
Short-Term Debt [Line Items]
Issuance of conversion of convertible promissory notes			$ 7,500
Probability of Achievement \| Minimum
Short-Term Debt [Line Items]
Tranche liability									0
Probability of Achievement \| Maximum
Short-Term Debt [Line Items]
Tranche liability									0.80
Discount Rate
Short-Term Debt [Line Items]
Tranche liability									0.09
2024 Convertible Promissory Note
Short-Term Debt [Line Items]
Outstanding principal amount						$ 10,000
Interest rate					10.00%			10.00%
Aggregate advance				$ 10,000	$ 5,000
Maturity date					2025-03
Estimated fair value					$ 12,100			$ 12,100
Change in the fair value of derivative liability							500	500
Loss on issuance of convertible promissory notes							(200)
Interest expense							800
Contractual interest expense							200
Amortization of debt discount							600
Total premium on debt					2,100
Accrued interest						$ 900
Common shares issued for conversion of debt \| shares						1,757,951
Conversion price per share \| $ / shares						$ 6.2
2024 Convertible Promissory Note \| Kalaris Therapeutics, Inc.
Short-Term Debt [Line Items]
Debt instrument, issued, principal amount	$ 3,750
2024 Convertible Promissory Note \| Maximum
Short-Term Debt [Line Items]
Outstanding principal amount					$ 10,000			$ 10,000
2024 Bridge Notes
Short-Term Debt [Line Items]
Outstanding principal amount		$ 5,000				$ 10,000
Interest rate		8.00%
Maturity date			2025-05
Change in the fair value of derivative liability							500
Recognized gain for change in fair value of tranche liability							400
Total fair value at issuance of derivative instrument			$ 1,000
Accrued interest						$ 300
Common shares issued for conversion of debt \| shares						1,660,888
Conversion price per share \| $ / shares						$ 6.2
Debt instrument, issued, principal amount		$ 1,000	9,000
Additional draw up amount		$ 15,000
2024 Bridge Notes \| Maximum
Short-Term Debt [Line Items]
Outstanding principal amount			15,000
Debt instrument, issued, principal amount			25,000
2025 Bridge Notes
Short-Term Debt [Line Items]
Outstanding principal amount	3,900					$ 3,750
Change in the fair value of derivative liability							200
Total fair value at issuance of derivative instrument	$ 200
Accrued interest						$ 100
Per share price paid by investors	8.50%
2025 Bridge Notes \| Redeemable Convertible Preferred Stock
Short-Term Debt [Line Items]
Difference between the fair value at the issuance date and the principal amount of the note	$ 200
2025 Bridge Notes \| Series B-2 Redeemable Convertible Preferred Stock
Short-Term Debt [Line Items]
Outstanding principal amount	$ 3,750
Common shares issued for conversion of debt \| shares						794,499
Conversion price per share \| $ / shares						$ 4.7851
2025 Bridge Notes \| Minimum
Short-Term Debt [Line Items]
Expected term (in years)	2 months 12 days
2025 Bridge Notes \| Maximum
Short-Term Debt [Line Items]
Expected term (in years)	3 months 18 days
2025 Bridge Notes \| Probability of Achievement \| Minimum
Short-Term Debt [Line Items]
Tranche liability	0.20
2025 Bridge Notes \| Probability of Achievement \| Maximum
Short-Term Debt [Line Items]
Tranche liability	0.80
2025 Bridge Notes \| Tranche \| Series B-2 Redeemable Convertible Preferred Stock
Short-Term Debt [Line Items]
Additional draw up amount	$ 5,000
2025 Bridge Notes \| First and Second Tranches \| Series B-2 Redeemable Convertible Preferred Stock
Short-Term Debt [Line Items]
Additional draw up amount	3,750
2025 Bridge Notes \| Third Tranches \| Series B-2 Redeemable Convertible Preferred Stock
Short-Term Debt [Line Items]
Additional draw up amount	7,500
2024 Bridge Notes and 2025 Bridge Notes
Short-Term Debt [Line Items]
Interest expense							600
Contractual interest expense							200
Amortization of debt discount							$ 400
January 2025 AlloVir Convertible Promissory Note
Short-Term Debt [Line Items]
Outstanding principal amount	$ 3,750
AlloVir Note \| Kalaris Therapeutics, Inc.
Short-Term Debt [Line Items]
Common shares issued for conversion of debt \| shares						160,165
AlloVir Note \| Maximum
Short-Term Debt [Line Items]
Issuance of conversion of convertible promissory notes			$ 7,500