Between 17 June and 30 July, all six of the publicly traded North American contract electronics manufacturers that assemble artificial-intelligence server racks reported quarters that beat estimates and raised full-year guidance. This is the layer beneath the chip designers: firms paid per box built, on gross margins of 8.8% to 12.3%, that screw together the racks, power shelves, sheet metal and interconnects the cloud operators order.

Celestica, the Toronto assembler of switches, routers and custom racks for hyperscalers, grew June-quarter revenue 62.4% to $4.70bn — accelerating from 52.8% — and raised 2026 guidance to $20.5bn in revenue and $11.30 in earnings per share, up 87%. It disclosed custom-rack work for OpenAI reaching mass production in 2027 and a design-and-manufacturing role on Advanced Micro Devices' Helios platform, plus ten 1.6-terabit networking programmes ramping this half.

Sanmina, the San Jose builder of printed circuit boards, backplanes and enclosures, grew revenue 69.7% and expanded operating margin 173 basis points to 6.43%, the widest expansion in the group. Its cloud and AI end-market hit $2.15bn, 62% of the company, up 173%, with the ZT Systems manufacturing business bought from AMD contributing $1.1bn. Flex, the Singapore-founded maker of switchgear, busway and power-distribution gear for data centres, grew 20.6% — a fourth straight quarterly acceleration — lifted gross margin 72 basis points and guided its cloud-and-power segment to 65–75% growth on booked visibility covering more than 90% of the next three quarters. Benchmark Electronics, the smallest at $2.96bn, grew 17.7% with its AI programmes up 71% and guided to a record $3.0bn year.

The inversion

The two exceptions went the other way in the accounts — and the right way on the tape. Jabil, the Florida manufacturer whose Intelligent Infrastructure segment is now 49% of revenue, saw growth decelerate from 23.1% in February to 11.8% in May, with operating margin slipping to 5.09%; it nonetheless raised full-year revenue to roughly $35bn with AI-related sales of $13.6bn. Plexus, the Wisconsin builder for medical, defence and industrial customers, grew 28.1% but saw operating margin fall to 4.70% from 5.26% and net income decline 4.7%, even as its opportunity funnel reached a record $4.5bn.

Jabil and Plexus are the only two names up over the past 30 days. The four that accelerated and expanded margins are the four that fell. On business momentum, the move CONTRADICTS the fundamentals for Celestica, Flex, Sanmina and Benchmark, and CONFIRMS only for Jabil and Plexus — in reverse.

What actually moved them

The repricing was sector-wide and preceded the results. All six lost their strongest uptrend rating in a rolling sequence between 30 June and 22 July — Celestica first, Benchmark last — every one of them before the 27–30 July reporting cluster. That window covers the global technology selloff of 16–17 July and the late-July session in which Meta said it had built enough capacity to become a net seller of AI compute, erasing roughly $200bn from chip and cloud values. Company-specific damage came after: Sanmina fell 20.5% on 27 July because next-quarter guidance landed 2% below consensus; Flex fell on 29 July despite record adjusted earnings as four banks cut price targets on valuation; Celestica dropped 14.8% on 6 August after pricing a $3bn equity offering, roughly 8–10% dilution for working capital and capital expenditure.

Valuation: two cells, not one

Multiples compressed because estimates rose faster than prices fell. Celestica's trailing price-to-earnings went from 50.2x in early May to 32.7x, its price-to-gross-profit from 28.7x to 20.2x; Flex from 62.2x to 46.9x; Sanmina from 44.2x to 35.6x. Forward multiples now span nearly twofold: Sanmina 16.8x, Flex 25.8x, Jabil 26.8x, Benchmark 27.9x, Celestica 28.0x, Plexus 31.5x. Trailing free-cash-flow yields span more than tenfold — Sanmina 9.46%, Jabil 4.21%, Celestica 1.42%, Plexus 0.86%.

On valuation the verdict is INCONCLUSIVE as a group and splits by name. Plexus carries the highest forward multiple on the lowest consensus earnings growth (19.5%) with margins going backwards. Sanmina carries the lowest on 103% expected earnings growth — but consensus already models deceleration to 15.8% revenue growth in 2027, and management warned working capital will build as the accelerated-compute programme ramps.

The live risks are supply, not demand. Benchmark said complex chip lead times went from 3–5 months to 7–12; Celestica cited 52-week-plus waits and called materials, not factory space, the bottleneck. Server memory contract prices are rising 13–18% quarter over quarter with lead times at 58 weeks — a direct cost pass-through problem for assemblers with no pricing power. Against that, the four largest cloud operators guide to roughly $725bn of 2026 capital spending, up about 77%.

The setup

Where it stands — Six assemblers raised guidance in July; four accelerating names fell hard, the two decelerating names rose. Would confirm — Celestica delivering the guided $20.5bn 2026 revenue and Flex's cloud-and-power segment printing 65%+ growth next quarter. Would invalidate — Sanmina's next quarter landing below its $3.30–3.60bn guide, or any hyperscaler trimming 2027 capital spending. Watch next — Jabil reports fiscal fourth-quarter results in September, its first commentary since 17 June. Valuation — Forward price-to-earnings spans 16.8x (Sanmina) to 31.5x (Plexus); Celestica at 32.7x trailing versus 50.2x in May.