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Stock Incentive Plans - Narrative (Details) $ / shares in Units, $ in Thousands | 1 Months Ended | 3 Months Ended | 9 Months Ended |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 30, 2024 shares | Jan. 31, 2024 shares | Sep. 30, 2024 USD ($) $ / shares shares | Sep. 30, 2023 USD ($) | Sep. 30, 2024 USD ($) $ / shares shares | Sep. 30, 2023 USD ($) $ / shares | Mar. 27, 2024 | Dec. 31, 2023 shares | Nov. 13, 2023 USD ($) shares | Mar. 31, 2019 shares | Sep. 30, 2018 shares | Jun. 30, 2016 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Total (in shares) |  |  | 13,215,543 |  | 13,215,543 |  |  |  |  |  |  |
Stock‑based compensation expense | $ |  |  | $ 1,695 | $ 2,321 | $ 4,717 | $ 8,380 |  |  |  |  |  |
Weighted average grant date fair value of stock options (in dollars per share) | $ / shares |  |  | $ 14.23 |  | $ 15.75 | $ 26.89 |  |  |  |  |  |
Rounding down per-share exercise price (in shares) |  |  |  |  |  |  | 33.333 |  |  |  |  |
Outstanding Series A Preferred Stock options |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Total (in shares) |  |  | 1,972,189 |  | 1,972,189 |  |  |  |  |  |  |
Restricted Stock Units (RSUs) |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award vesting term |  |  |  |  | 4 years |  |  |  |  |  |  |
Weighted average period |  |  |  |  | 3 years 2 months 12 days |  |  |  |  |  |  |
Grants in period (in shares) |  |  |  |  | 477,037 |  |  |  |  |  |  |
Grants in period (in dollars per share) | $ / shares |  |  |  |  | $ 19.86 |  |  |  |  |  |  |
Estimated forfeitures rate |  |  |  |  | 10.00% |  |  |  |  |  |  |
Unrecognized compensation expense | $ |  |  | $ 5,800 |  | $ 5,800 |  |  |  |  |  |  |
Common stock | Outstanding Series A Preferred Stock options |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Unrecognized compensation expense related to unvested employee stock options | $ |  |  | $ 10,300 |  | $ 10,300 |  |  |  |  |  |  |
Weighted average period |  |  |  |  | 3 years |  |  |  |  |  |  |
2016 Plan |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of shares authorized for grants (in shares) |  |  |  |  |  |  |  |  |  |  |  | 40,341
Number of shares authorized, increase (in shares) | 3,466,544 | 215,903 |  |  |  |  |  |  |  |  |  |
Total (in shares) |  |  | 3,511,101 |  | 3,511,101 |  |  |  |  |  |  |
Employment Inducement Incentive Award Plan |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of shares authorized for grants (in shares) |  |  | 253,377 |  | 253,377 |  |  |  |  |  |  |
Total (in shares) | 360,000 |  |  |  |  |  |  | 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) |  |  | 27,270 |  | 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) |  |  | 0 |  | 0 |  |  | 14,112.299 |  |  |  |
Unrecognized compensation expense related to unvested employee stock options | $ |  |  |  |  |  |  |  |  | $ 2,600 |  |  |
Stock‑based compensation expense | $ |  |  | $ 300 |  | $ 1,000 |  |  |  |  |  |  |
Old Cartesian Plan | Old Cartestian | Common stock |  |  |  |  |  |  |  |  |  |  |  |
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) |  |  |  |  |  |  |  |  | 776,865 |  |  |
Old Cartesian Plan | Old Cartestian | Preferred stock |  |  |  |  |  |  |  |  |  |  |  |
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) |  |  |  |  |  |  |  |  | 14,112.299 |  |  |

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