Companies that assemble the physical hardware inside AI data centers — the racks, power shelves and network switches hyperscale cloud providers design but don't build themselves — pulled back over the past month even as their underlying businesses kept accelerating. Six contract manufacturers in this niche fell an average of 7.6% over 30 days, a shallow and orderly retreat with none of the six landing on either end of the market's list of the period's biggest movers. That pullback followed a 12-month run that averaged 85.8% across the group. The timing matters: the stock declines came before each company reported earnings in late July, and every one of them beat estimates and raised guidance. That sequence — valuation cools first, results confirm demand second — is the opposite of what a genuine order slowdown would look like.

The six companies. Celestica (CLS), a Canadian contract manufacturer that builds servers, 800G/1.6T network switches and full racks for hyperscale cloud customers. Flex (FLEX), a diversified contract manufacturer whose Cloud and Power Infrastructure unit — including its Anord Mardix busway and power-pod business — sits alongside legacy automotive, industrial and health-solutions work. Jabil (JBL), whose Intelligent Infrastructure segment builds AI servers and networking gear next to a broader consumer- and industrial-electronics base. Sanmina (SANM), which acquired AMD's ZT Systems server-manufacturing operation and now derives most of its growth from AI compute builds. Plexus (PLXS), a smaller manufacturer weighted toward aerospace, defense and medical electronics with an emerging data-center power business. Benchmark Electronics (BHE), a similarly sized manufacturer serving aerospace/defense and medical customers whose newer AI-programs segment is growing fastest.

Business versus tape: a real divergence. For five of the six, the fundamentals argue against the price move rather than for it. Celestica's second-quarter revenue rose 62% year-over-year with its cloud/AI segment up 167%, ahead of its own guidance, and it disclosed new multi-year 2027 programs with OpenAI and AMD/Broadcom. Flex's power-infrastructure segment grew 35% with management citing over 90% of bookings already visible for the next three quarters, and its board has approved spinning off that unit into a standalone company by early 2027. Sanmina's AI infrastructure revenue jumped 173% to 62% of total sales, driving a near-tripling of full-year earnings guidance. Plexus posted record revenue and its best cash-conversion cycle in five years, and Benchmark's AI-programs segment grew 71% while its cash cycle improved to 59 days from 90. Jabil is the partial exception: its AI segment guide was raised to 46% growth, but total company revenue growth decelerated to 11.8% in its most recent quarter as its non-AI base drags on the group figure — a genuine, if narrower, business-side caution flag.

Valuation: the multiples did the work, not demand. Forward price-to-earnings ratios compressed sharply across the group even as prices fell, because guidance rose faster than stocks did — Sanmina's forward P/E dropped to 16.0x from a trailing 33.9x, and Flex's roughly halved to 25.0x from 45.3x. Celestica is the exception: its pullback was the shallowest (-2.4%) but its multiple is the richest, at 16.5x forward price-to-gross-profit versus roughly 9x-15x for peers, consistent with a first-phase re-rate from single-digit EMS multiples that this desk's own prior notes describe as largely complete. Its customer concentration has also worsened, with its top three customers now around 65% of revenue, and its free-cash-flow yield, at 1.3%, is the lowest in the group amid heavy capex.

The tape, briefly. All six names — including non-starred Benchmark and Plexus — stepped down from a strong-uptrend reading to a milder one within a three-week window in late June and July, ahead of earnings, which is the technical fingerprint of a valuation pause rather than a fundamentals break. That agrees with the earnings sequencing above rather than contradicting it.

A broader risk sits above this entire group: the hyperscale cloud customers funding this buildout are projected to spend roughly $725 billion on capex in 2026, up 77% from 2025, but three of the four largest hyperscalers lost market value after their own recent earnings calls even as spending guidance rose — a sentiment risk that has not yet shown up as an order-book signal at any of these six suppliers, but bears watching.

The setup

Where it stands — Six AI-hardware contract manufacturers fell 7.6% on average over 30 days, then all beat earnings and raised guidance in late July. Would confirm — Backlog, bookings visibility or segment guidance (e.g., Flex's 65-75% CPI growth target) holding or rising at the next quarterly report. Would invalidate — A guidance cut or customer-concentration loss at any of the six, or rising inventory/cash-conversion-cycle days signaling order digestion. Watch next — Jabil's next earnings report (its last transcript on file predates this pullback) for whether total revenue growth stabilizes or keeps decelerating. Valuation — Group forward P/E ranges roughly 16x (SANM) to 30x (PLXS), down sharply from trailing multiples of 34x-55x across the cohort.