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Stock Incentive Plans - Narrative (Details) $ / shares in Units, $ in Thousands |  | 1 Months Ended | 12 Months Ended |  |  |  |
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Nov. 13, 2023 USD ($) $ / shares shares | Jun. 30, 2024 shares | Jan. 31, 2024 shares | Jan. 31, 2023 shares | Dec. 31, 2024 USD ($) $ / shares shares | Dec. 31, 2023 USD ($) $ / shares shares | Mar. 27, 2024 | Mar. 31, 2019 shares | Sep. 30, 2018 shares | Jun. 30, 2016 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Common stock authorized and reserved for future issuance (in shares) | shares |  |  |  |  | 11,512,268 |  |  |  |  |
Stock‑based compensation expense |  |  |  |  | $ 6,582 | $ 25,778 |  |  |  |
Share based compensation arrangement by share based payment award, settlement of awards, amount (in dollars per share) | $ / shares | $ 61.80 |  |  |  |  |  |  |  |  |
Share-based payment arrangement, accelerated cost | $ 13,100 |  |  |  |  |  |  |  |  |
Total cash payment made to the holders of stock options and restricted stock units | 9,400 |  |  |  |  |  |  |  |  |
Adjustments to additional paid in capital, settlement of outstanding equity awards at merger |  |  |  |  |  | 6,169 |  |  |  |
Excess over fair value recognized as additional stock-based compensation expense |  |  |  |  |  | $ 3,200 |  |  |  |
Weighted average grant date fair value of stock options (in dollars per share) | $ / shares |  |  |  |  | $ 15.63 | $ 26.90 |  |  |  |
Intrinsic value of stock options exercised |  |  |  |  | $ 7,000 |  |  |  |  |
Issuance of common stock upon exercise of options (in shares) | shares |  |  |  |  |  | 0 |  |  |  |
Preferred stock, convertible, conversion ratio |  |  |  |  | 33.333 |  | 33.333 |  |  |
Research and development |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Stock‑based compensation expense |  |  |  |  | $ 3,217 | $ 12,985 |  |  |  |
Share-based payment arrangement, accelerated cost | 5,900 |  |  |  |  |  |  |  |  |
Excess over fair value recognized as additional stock-based compensation expense |  |  |  |  |  | 1,500 |  |  |  |
General and administrative |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Stock‑based compensation expense |  |  |  |  | $ 3,365 | 12,793 |  |  |  |
Share-based payment arrangement, accelerated cost | 7,200 |  |  |  |  |  |  |  |  |
Excess over fair value recognized as additional stock-based compensation expense |  |  |  |  |  | 1,700 |  |  |  |
Stock Options |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Common stock authorized and reserved for future issuance (in shares) | shares |  |  |  |  | 1,706,035 |  |  |  |  |
Restricted Stock Units (RSUs) |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Award vesting term |  |  |  |  | 4 years |  |  |  |  |
Weighted average period for recognition |  |  |  |  | 2 years 10 months 24 days |  |  |  |  |
Grants in period (in shares) | shares |  |  |  |  | 477,037 |  |  |  |  |
Grants in period (in dollars per share) | $ / shares |  |  |  |  | $ 19.86 |  |  |  |  |
Estimated forfeitures rate |  |  |  |  | 10.00% |  |  |  |  |
Vested in period (in shares) | shares |  |  |  |  | 0 |  |  |  |  |
Aggregate fair value of RSU awards vested |  |  |  |  |  | $ 700 |  |  |  |
Unrecognized compensation expense |  |  |  |  | $ 5,400 |  |  |  |  |
Common stock |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Issuance of common stock upon exercise of options (in shares) | shares |  |  |  |  | 458,544 |  |  |  |  |
Common stock | Stock Options |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Unrecognized compensation expense related to unvested employee stock options |  |  |  |  | $ 10,300 |  |  |  |  |
Weighted average period for recognition |  |  |  |  | 2 years 10 months 24 days |  |  |  |  |
2016 Plan |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of shares authorized for grants (in shares) | shares |  |  |  |  |  |  |  |  |  | 40,341
Number of shares authorized, increase (in shares) | shares |  | 3,466,544 | 215,903 | 204,056 |  |  |  |  |  |
Common stock authorized and reserved for future issuance (in shares) | shares |  |  |  |  | 3,520,174 |  |  |  |  |
Employment Inducement Incentive Award Plan |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of shares authorized for grants (in shares) | shares |  |  |  |  | 611,960 |  |  |  |  |
Common stock authorized and reserved for future issuance (in shares) | shares |  | 360,000 |  |  | 450,000 | 60,833 |  | 66,667 | 39,166 |
Old Cartesian Plan |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Number of shares authorized for grants (in shares) | shares |  |  |  |  | 27,270 |  |  |  |  |
Award vesting term |  |  |  |  | 4 years |  |  |  |  |
Award expiration term |  |  |  |  | 10 years |  |  |  |  |
Share-based compensation arrangement by share-based payment award, options, outstanding, number (in shares) | shares |  |  |  |  | 0 | 14,112.299 |  |  |  |
Unrecognized compensation expense related to unvested employee stock options | $ 2,600 |  |  |  |  |  |  |  |  |
Stock‑based compensation expense |  |  |  |  | $ 1,300 | $ 200 |  |  |  |
Old Cartesian Plan | Common stock | Old Cartestian |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Share-based compensation arrangement by share-based payment award, options, outstanding, number (in shares) | shares | 776,865 |  |  |  |  |  |  |  |  |
Old Cartesian Plan | Preferred Stock | Old Cartestian |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |
Share-based compensation arrangement by share-based payment award, options, outstanding, number (in shares) | shares | 14,112.299 |  |  |  |  |  |  |  |  |

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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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- Definition The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(1)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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