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SEGMENT AND GEOGRAPHICAL INFORMATION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jul. 03, 2026 | Jul. 04, 2025 | Jul. 03, 2026 | Jul. 04, 2025
Revenue |  |  |  |
Revenue | $ 231,028 | $ 173,473 | $ 386,142 | $ 325,859
United States |  |  |  |
Revenue |  |  |  |
Revenue | 231,028 | 173,473 | 386,142 | 325,859
Commercial |  |  |  |
Revenue |  |  |  |
Revenue | 60,820 | 19,848 | 82,055 | 35,174
Government |  |  |  |
Revenue |  |  |  |
Revenue | 96,231 | 80,763 | 165,267 | 153,359
Utilities |  |  |  |
Revenue |  |  |  |
Revenue | 73,977 | 72,862 | 138,820 | 137,326
Time-and-materials |  |  |  |
Revenue |  |  |  |
Revenue | 33,188 | 30,632 | 64,088 | 60,294
Unit-based |  |  |  |
Revenue |  |  |  |
Revenue | 69,946 | 64,737 | 126,616 | 118,699
Fixed price |  |  |  |
Revenue |  |  |  |
Revenue | 127,894 | 78,104 | 195,438 | 146,866
Energy |  |  |  |
Revenue |  |  |  |
Revenue | 202,589 | 146,749 | 330,557 | 272,997
Energy | United States |  |  |  |
Revenue |  |  |  |
Revenue | 202,589 | 146,749 | 330,557 | 272,997
Energy | Commercial |  |  |  |
Revenue |  |  |  |
Revenue | 58,849 | 18,093 | 78,238 | 31,608
Energy | Government |  |  |  |
Revenue |  |  |  |
Revenue | 69,834 | 55,839 | 113,680 | 104,163
Energy | Utilities |  |  |  |
Revenue |  |  |  |
Revenue | 73,906 | 72,817 | 138,639 | 137,226
Energy | Time-and-materials |  |  |  |
Revenue |  |  |  |
Revenue | 14,541 | 11,733 | 27,241 | 23,335
Energy | Unit-based |  |  |  |
Revenue |  |  |  |
Revenue | 61,714 | 58,250 | 111,331 | 105,957
Energy | Fixed price |  |  |  |
Revenue |  |  |  |
Revenue | 126,334 | 76,766 | 191,985 | 143,705
Engineering and Consulting |  |  |  |
Revenue |  |  |  |
Revenue | 28,439 | 26,724 | 55,585 | 52,862
Engineering and Consulting | United States |  |  |  |
Revenue |  |  |  |
Revenue | 28,439 | 26,724 | 55,585 | 52,862
Engineering and Consulting | Commercial |  |  |  |
Revenue |  |  |  |
Revenue | 1,971 | 1,755 | 3,817 | 3,566
Engineering and Consulting | Government |  |  |  |
Revenue |  |  |  |
Revenue | 26,397 | 24,924 | 51,587 | 49,196
Engineering and Consulting | Utilities |  |  |  |
Revenue |  |  |  |
Revenue | 71 | 45 | 181 | 100
Engineering and Consulting | Time-and-materials |  |  |  |
Revenue |  |  |  |
Revenue | 18,647 | 18,899 | 36,847 | 36,959
Engineering and Consulting | Unit-based |  |  |  |
Revenue |  |  |  |
Revenue | 8,232 | 6,487 | 15,285 | 12,742
Engineering and Consulting | Fixed price |  |  |  |
Revenue |  |  |  |
Revenue | $ 1,560 | $ 1,338 | $ 3,453 | $ 3,161

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