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STOCK-BASED COMPENSATION (Tables)
 12 Months Ended
Dec. 31, 2025
Share-Based Payment Arrangement [Abstract]  
Summary of Share Option Activities
The following table summarizes the ACM’s employee share option activities:
Number of
Option Shares 		Weighted
Average Grant
Date Fair Value 		Weighted
Average
Exercise Price 		Aggregate Intrinsic Value (In thousands) Weighted Average
Remaining
Contractual Term
Outstanding at December 31, 20248,851,595$6.18 $10.84 5.81 years
Granted255,00018.35 25.53 
Exercised(2,344,035)3.23 6.56 $52,606 
Forfeited/cancelled(135,131)15.21 23.39 
Outstanding at December 31, 20256,627,4297.50 $12.66 $177,514 5.59 years
Vested and exercisable at December 31, 20254,669,1046.64 $11.94 $128,455 5.02 years
The following table summarizes the Company's non-employee share option activities:
Number of
Option Shares (1)		Weighted
Average Grant
Date Fair Value (1)		Weighted
Average
Exercise Price 		Aggregate Intrinsic Value (In thousands) Weighted Average
Remaining
Contractual Term
Outstanding at December 31, 2024784,132$0.52 $1.68 2.12 years
Exercised(307,097)0.25 0.84 $9,490 
Forfeited/cancelled(94,152)0.49 1.81 
Outstanding at December 31, 2025382,883 0.74 $2.32 $14,215  1.63 years
Vested and exercisable at December 31, 2025382,883 0.74 2.32 $14,215  1.63 years
The following table summarizes the ACM Shanghai 2023 Subsidiary Stock Option Plan’s stock option activities:

Number of
Option Shares in
ACM Shanghai		Weighted
Average Grant
Date Fair Value		Weighted
Average
Exercise Price		Aggregate Intrinsic Value (In thousands)Weighted Average
Remaining
Contractual Term
Outstanding at December 31, 202411,604,310$9.01 $7.00 2.48 years
Exercised(2,822,710)7.786.97$23,638 
Forfeited/cancelled(630,700)8.246.97
Outstanding at December 31, 20258,150,900 9.08 $6.97 $144,090  0.98 years
Vested and exercisable at December 31, 20252,448,750 9.086.97$43,289 0.00 years
Assumptions Used to Determine Fair Value of Options Granted
The fair value of options granted to employees is estimated on the grant date using the Black-Scholes valuation model with the following assumptions:
Year ended December 31,
202520242023
Fair value of common stock(1)
$24.33-$32.95
$18.67-$31.92
$11.85-$17.23
Expected term in years(2)
5.50-6.25
5.50-6.25
5.50-6.25
Volatility(3)
82.78%-83.59%
83.85%-85.48%
84.95%-86.45%
Risk-free interest rate(4)
3.90-4.25%
3.80-4.49%
4.16-4.69%
Expected dividend(5)0 %0 %0 %
(1)Fair value of Class A common stock value was the closing market price of the Class A common stock on the grant date.
(2)Expected term of share options is based on the average of the vesting period and the contractual term for each grant.
(3)Volatility is calculated based on the historical volatility of ACM in the period equal to the expected term of each grant.
(4)Risk-free interest rate is based on the yields of U.S. Treasury securities with maturities similar to the expected term of the share options in effect at the time of grant.
(5)Expected dividend is assumed to be 0% as ACM has no history or expectation of paying a dividend on its common stock.
The fair value of options granted to employees is estimated on the grant date using the Black-Scholes valuation with following assumptions:
Year Ended December 31, 2024
Year Ended December 31, 2023
Fair value of common stock(1)
$4.93-$6.89
$14.87
Expected term in years(2)
1.50-4.50
1.50-4.50
Volatility(3)
45.92%-56.18%
60.00%-60.60%
Risk-free interest rate(4)
1.50%-2.75%
1.50%-2.75%
Expected dividend (5)— %— %

(1) Equal to closing value on the grant date.
(2) Expected term of share options is based on the average of the vesting period and the contractual term for each grant.
(3) Volatility is calculated based on the historical volatility of ACM in the period equal to the expected term of each grant.
(4) Risk-free interest rate is based on the yields of RMB deposit in mainland China with maturities similar to the expected term of the share options in effect at the time of grant.
(5) Expected dividend is assumed to be 0% as the impact is adjusted on the value of share of common stock.
Components of Stock-based Compensation Expense
The following table summarizes the components of stock-based compensation expense included in the consolidated statements of comprehensive income:
Year Ended December 31,
202520242023
Cost of revenue$1,343 $2,385 $1,406 
Sales and marketing expense6,629 10,552 5,684 
Research and development expense8,783 14,112 8,459 
General and administrative expense16,822 22,527 11,789 
 Total stock-based compensation expense
$33,577 $49,576 $27,338