v3.24.4
Stockholders Equity - Narrative (FY) (Details)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 15, 2024
USD ($)
$ / shares
shares
Mar. 04, 2024
USD ($)
$ / shares
shares
Jan. 12, 2024
USD ($)
$ / shares
shares
Nov. 09, 2023
USD ($)
$ / shares
shares
Nov. 08, 2023
shares
Oct. 04, 2023
USD ($)
Oct. 02, 2023
USD ($)
$ / shares
shares
Sep. 11, 2023
USD ($)
Sep. 07, 2023
USD ($)
$ / shares
shares
Aug. 22, 2023
$ / shares
shares
Feb. 27, 2023
USD ($)
Feb. 23, 2023
$ / shares
shares
Sep. 28, 2022
USD ($)
Aug. 13, 2021
$ / shares
shares
Aug. 12, 2021
USD ($)
$ / shares
shares
Jun. 30, 2021
USD ($)
Sep. 30, 2024
USD ($)
$ / shares
shares
Sep. 30, 2023
USD ($)
Mar. 31, 2023
USD ($)
Sep. 30, 2024
USD ($)
$ / shares
shares
Sep. 30, 2023
USD ($)
Dec. 31, 2023
USD ($)
$ / shares
shares
Dec. 31, 2022
USD ($)
$ / shares
shares
Nov. 06, 2023
$ / shares
shares
Oct. 01, 2023
Sep. 10, 2023
Mar. 31, 2022
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Shares of stock authorized (in shares)                   274,312,500                                  
Preferred stock, number of shares authorized (in shares)                                 20,000,000     20,000,000   20,000,000 20,000,000        
Preferred stock, par value (in dollars per share) | $ / shares                                 $ 0.00001     $ 0.00001   $ 0.00001 $ 0.00001        
Number of warrants exercised on net basis (in shares)       2,904,269                                              
Exercise price (in dollars per share) | $ / shares     $ 0.96 $ 2                                              
Warrant term (years)   5 years 5 years                           5 years     5 years   5 years          
Proceeds from issuance of warrants | $ $ 2,400 $ 3,500 $ 3,600 $ 6,500     $ 3,600   $ 4,600   $ 9,300                                
Offering fees and other expenses payable | $       $ 500                                              
Warrants consideration (in dollars per share) | $ / shares       $ 0.25                                              
Proceeds from exercise of warrants | $       $ 6,000                                   $ 7,881 $ 0        
Shares issued upon exercise of warrant (in shares)         1,188,269                                            
Number of warrants outstanding (in shares)         1,716,000                                            
Aggregate cost | $ 2,800 4,000 4,000       4,000   5,000   10,000                                
Agent fees and other offering costs | $ $ 300 $ 500 $ 400       $ 400   $ 400   700                 $ 1,137 $ 1,135 2,048 0        
Equity related to warrants | $                                 $ 2,443                    
Percentage of equity interest sold by co-founders                               100.00%                      
Additional payments owed to co-founders | $                     10,000         $ 10,000                      
Minimum proceeds from sale of business and other capital raising transactions | $                               250,000                      
Additional funding received in connection with business combination | $                     247,300       $ 247,300                        
Payment of liability | $                                     $ 10,000                
Change in fair value of warrant liability | $                                 $ 0 $ (221)   $ 0 $ (559) (561) (5,185)        
Deferred offering costs | $                                           300          
ATM Sales Agreement                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Aggregate cost | $                                           $ 0          
Commission rate percentage                         3.00%                            
Consideration From Funds Legally Available                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Additional payments owed to co-founders | $                               $ 40,000                      
Common Stock                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of shares sold (in shares)                       187,920                              
Purchase price (in dollars per share) | $ / shares                       $ 43.23                              
Aggregate cost | $                     $ 10,000                                
November Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares)                                               5,808,538      
Exercise price (in dollars per share) | $ / shares                                               $ 3.86      
Warrant term (years)                                               5 years      
Series A Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares)             672,948                                 672,948      
Exercise price (in dollars per share) | $ / shares             $ 7.18                                        
Warrant term (years)                 5 years                               4 years 11 months 8 days    
February Class A Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares)             231,321                                 231,321      
Exercise price (in dollars per share) | $ / shares             $ 7.18         $ 57.5                              
Warrant term (years)               5 years 3 days       5 years 6 months 3 days                           4 years 11 months 19 days  
Equity related to warrants | $               $ 600                                      
October Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares)             2,000,000                                 2,000,000      
Exercise price (in dollars per share) | $ / shares             $ 2                                        
Warrant term (years)             5 years                                        
Estimated fair value of warrants | $       $ 500                                              
Equity related to warrants | $             $ 1,000                                        
Prefunded Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares)             1,710,000   462,948                                    
Exercise price (in dollars per share) | $ / shares             $ 0.00001   $ 0.00001                                    
Prefunded Warrants | Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Exercise price (in dollars per share) | $ / shares                       $ 0.00001                              
Number of shares sold (in shares)                       43,401                              
Series B Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares)             672,948   672,948                                    
Exercise price (in dollars per share) | $ / shares             $ 7.18                                        
Warrant term (years)                 1 year                               11 months 12 days    
Proceeds from exercise of warrants | $           $ 1,300                                          
Public Warrant                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants outstanding (in shares)                                 172,500     172,500   172,500          
Equity related to warrants | $                             $ 20,200                        
Private Placement Warrant                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants outstanding (in shares)                                 225,450     225,450   225,450          
Other Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares)                                                     5,563
Exercise price (in dollars per share) | $ / shares                                           $ 10          
Number of warrants outstanding (in shares)                                           6,171          
Private Warrant                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Change in fair value of warrant liability | $                                           $ (600) $ (5,200)        
October Pre-Funded Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares)                                           1,710,000          
September Prefunded Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares)                                           462,948          
Exercise price (in dollars per share) | $ / shares $ 0.00001                                                    
February Prefunded Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares)                                           43,401          
Common Class A                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Stock split ratio                   0.02                                  
Common stock, number of shares authorized (in shares)                   250,000,000             250,000,000     250,000,000   250,000,000 250,000,000        
Common stock, par value (in dollars per share) | $ / shares                   $ 0.00001             $ 0.00001     $ 0.00001   $ 0.00001 $ 0.00001        
Number of warrants exercised on net basis (in shares) 10,000,000                                                    
Exercise price (in dollars per share) | $ / shares                                 $ 575     $ 575   $ 575          
Number of shares sold (in shares)   1,320,000 900,000       290,000   210,000                                    
Purchase price (in dollars per share) | $ / shares $ 0.55 $ 0.87 $ 1.09       $ 2   $ 7.43                                    
Common Class A | ATM Sales Agreement                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Aggregate cost | $                         $ 50,000                            
Common Class A | Contingent Sponsor Earnout Shares                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of shares modified (in shares)                           28,750 28,750                        
Common Class A | Contingent Sponsor Earnout Shares | Weighted Average Closing Price of $12.50                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Weighted-average closing sale price (in dollars per share) | $ / shares                           $ 625 $ 625                        
Common Class A | Contingent Sponsor Earnout Shares | Weighted Average Closing Price of $15.00                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Weighted-average closing sale price (in dollars per share) | $ / shares                           750 750                        
Common Class A | Contingent Sponsor Earnout Shares | Weighted Average Closing Price of $17.50                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Weighted-average closing sale price (in dollars per share) | $ / shares                           $ 875 $ 875                        
Common Class A | Common Stock                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Shares issued upon exercise of warrant (in shares)                                           3,577,217 5,563        
Common Class A | September Prefunded Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Number of warrants exercised on net basis (in shares) 5,000,000                                                    
Exercise price (in dollars per share) | $ / shares $ 0.575                                                    
Warrant term (years) 5 years 6 months                                                    
Common Class B                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Common stock, number of shares authorized (in shares)                   4,312,500             4,312,500     4,312,500   4,312,500 4,312,500        
Common stock, par value (in dollars per share) | $ / shares                   $ 0.00001             $ 0.00001     $ 0.00001   $ 0.00001 $ 0.00001        
Number of warrants exercised on net basis (in shares) 5,000,000                                                    
Common Class B | September Prefunded Warrants                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Warrant term (years) 1 year 6 months                                                    
Preferred Stock                                                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                                      
Preferred stock, number of shares authorized (in shares)                   20,000,000                                  
Preferred stock, par value (in dollars per share) | $ / shares                   $ 0.00001