Commitments and Contingencies - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($) ft²	Dec. 31, 2024 USD ($)	Dec. 22, 2025 USD ($) ft² leaseCompenent	Sep. 01, 2023 USD ($)
Operating Leases
Operating lease right-of-use assets	$ 397	$ 6,015
Lease liability	1,974
Gain on termination of lease	316	0
General and administrative	17,357	14,923
Research and development	38,202	38,817
Operating lease liabilities, current portion	286	2,994
Operating lease liabilities, net of current portion	1,688	5,493
Impairment of right-of-use asset	$ 494	$ 0
Office space and laboratory space in Cambridge, Massachusetts
Operating Leases
Area of lease (approximately) | ft²	30,000
Accelerated termination period	30 days
Office And Laboratory Space In Watertown, Massachusetts
Operating Leases
Area of lease (approximately) | ft²			44,000
Commencement period following execution			180 days
Number of lease components | leaseCompenent			2
Operating lease right-of-use assets			$ 0
Lease liability			1,100
Gain on termination of lease	$ 300
General and administrative	100
Research and development	$ 200
Lease modification fee			$ 2,100
Initial rent-free period			18 months
Renewal term			5 years
Office and lab space in Boulder, Colorado
Operating Leases
Area of lease (approximately) | ft²	5,300
Operating lease right-of-use assets	$ 400			$ 1,400
Term of lease				5 years
Incremental borrowing rate used for lease				7.12%
Operating lease liabilities, current portion	300			$ 200
Operating lease liabilities, net of current portion	600			$ 1,200
Impairment of right-of-use asset	$ 500