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SEGMENT AND GEOGRAPHICAL INFORMATION - Disaggregation of Revenue (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Oct. 03, 2025 | Sep. 27, 2024 | Oct. 03, 2025 | Sep. 27, 2024
Revenue |  |  |  |
Revenue | $ 182,006 | $ 158,252 | $ 507,865 | $ 421,737
United States |  |  |  |
Revenue |  |  |  |
Revenue | 182,006 | 158,252 | 507,865 | 421,737
Commercial |  |  |  |
Revenue |  |  |  |
Revenue | 17,887 | 9,932 | 53,061 | 29,139
Government |  |  |  |
Revenue |  |  |  |
Revenue | 89,843 | 83,270 | 243,202 | 212,017
Utilities |  |  |  |
Revenue |  |  |  |
Revenue | 74,276 | 65,050 | 211,602 | 180,581
Time-and-materials |  |  |  |
Revenue |  |  |  |
Revenue | 31,248 | 25,720 | 91,542 | 76,383
Unit-based |  |  |  |
Revenue |  |  |  |
Revenue | 65,217 | 57,480 | 183,916 | 161,397
Fixed price |  |  |  |
Revenue |  |  |  |
Revenue | 85,541 | 75,052 | 232,407 | 183,957
Energy |  |  |  |
Revenue |  |  |  |
Revenue | 154,750 | 134,036 | 427,747 | 352,634
Energy | United States |  |  |  |
Revenue |  |  |  |
Revenue | 154,750 | 134,036 | 427,747 | 352,634
Energy | Commercial |  |  |  |
Revenue |  |  |  |
Revenue | 15,942 | 7,964 | 47,550 | 23,858
Energy | Government |  |  |  |
Revenue |  |  |  |
Revenue | 64,587 | 61,115 | 168,750 | 148,403
Energy | Utilities |  |  |  |
Revenue |  |  |  |
Revenue | 74,221 | 64,957 | 211,447 | 180,373
Energy | Time-and-materials |  |  |  |
Revenue |  |  |  |
Revenue | 12,866 | 7,953 | 36,201 | 25,190
Energy | Unit-based |  |  |  |
Revenue |  |  |  |
Revenue | 58,252 | 52,487 | 164,209 | 147,022
Energy | Fixed price |  |  |  |
Revenue |  |  |  |
Revenue | 83,632 | 73,596 | 227,337 | 180,422
Engineering and Consulting |  |  |  |
Revenue |  |  |  |
Revenue | 27,256 | 24,216 | 80,118 | 69,103
Engineering and Consulting | United States |  |  |  |
Revenue |  |  |  |
Revenue | 27,256 | 24,216 | 80,118 | 69,103
Engineering and Consulting | Commercial |  |  |  |
Revenue |  |  |  |
Revenue | 1,945 | 1,968 | 5,511 | 5,281
Engineering and Consulting | Government |  |  |  |
Revenue |  |  |  |
Revenue | 25,256 | 22,155 | 74,452 | 63,614
Engineering and Consulting | Utilities |  |  |  |
Revenue |  |  |  |
Revenue | 55 | 93 | 155 | 208
Engineering and Consulting | Time-and-materials |  |  |  |
Revenue |  |  |  |
Revenue | 18,382 | 17,767 | 55,341 | 51,193
Engineering and Consulting | Unit-based |  |  |  |
Revenue |  |  |  |
Revenue | 6,965 | 4,993 | 19,707 | 14,375
Engineering and Consulting | Fixed price |  |  |  |
Revenue |  |  |  |
Revenue | $ 1,909 | $ 1,456 | $ 5,070 | $ 3,535

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