v3.25.2
Redeemable Convertible Preferred Stock, Redeemable Common Stock, and Stockholders Equity (Deficit) - Common Stock (Q2) (Details)
 6 Months Ended 12 Months Ended
Jun. 30, 2025
votingRight
$ / shares
shares
Dec. 31, 2024
$ / shares
Dec. 31, 2023
Vote
$ / shares
shares
Dec. 31, 2024
shares
Dec. 31, 2024
votingRight
Dec. 31, 2024
Vote
Class of Stock [Line Items]            
Common shares, shares authorized (in shares) 3,400,000,000   469,030,700 690,680,000    
Common shares, par value (usd per share) | $ / shares $ 0.000005 $ 0.000005 $ 0.000005      
Common stock dividends declared (in dollars per share) | $ / shares $ 0 0 $ 0      
Common Class C            
Class of Stock [Line Items]            
Common shares, shares authorized (in shares) 200,000,000     0    
Common shares, par value (usd per share) | $ / shares $ 0.000005 0.000005        
Common shares, shares outstanding (in shares) 0     0    
Common shares, shares issued (in shares) 0     0    
Voting rights for common stock | votingRight 0          
Common Class A            
Class of Stock [Line Items]            
Common shares, shares authorized (in shares) 3,000,000,000   469,031,000 540,680,000    
Common shares, par value (usd per share) | $ / shares $ 0.000005 0.000005 $ 0.000005      
Common shares, shares outstanding (in shares) 340,075,000   203,520,000 114,689,000    
Common shares, shares issued (in shares) 346,663,000   208,003,000 121,277,000    
Voting rights for common stock 1         1
Common Class B            
Class of Stock [Line Items]            
Common shares, shares authorized (in shares) 200,000,000   0 150,000,000    
Common shares, par value (usd per share) | $ / shares $ 0.000005 $ 0.000005 $ 0.000005      
Common shares, shares outstanding (in shares) 118,102,000   0 118,198,000    
Common shares, shares issued (in shares) 118,102,000   0 118,198,000    
Voting rights for common stock 10   1   1 10