ASML (Lithography): Every advanced chip in the world passes through an ASML machine. There is no alternative supplier for EUV lithography. ASML's order book is the most reliable forward indicator for semiconductor capital expenditure. A deceleration in EUV orders means fabs are pulling back on expansion — visible in ASML's backlog 2-3 quarters before it shows up in chip company earnings.
Advantest (Testing): Every chip must be tested before it ships. Advantest dominates the ATE (automated test equipment) market for advanced logic and HBM. When Advantest reports order surges, it means new chip designs are moving to high-volume production. The testing step is the last gate before revenue — making Advantest the closest real-time indicator of production ramp.
Micron (Memory): Memory is the most cyclical semiconductor segment and the first to signal demand shifts. Micron's HBM (High Bandwidth Memory) pricing and allocation reveals AI demand health. If HBM pricing holds or increases, AI infrastructure demand is real. If HBM inventory builds, the demand story has cracks.
The three sentinels feed directly into the Weekly Signal framework, specifically the Trend and Participation dimensions. A divergence — where one sentinel weakens while others hold — creates a watchlist trigger rather than an immediate action signal. When two of three weaken simultaneously, it escalates to a regime-change warning.
Each sentinel also maps to a specific layer in the 6-Layer Model: ASML represents Silicon, Advantest represents the testing constraint within Silicon, and Micron represents Memory. Together they cover the physical foundation of the AI build-out.
Sentinel Tickers are monitored weekly as part of the Weekly Signal process. Earnings calls, order book updates, and capacity announcements from these three companies receive priority analysis. The Closelook thesis: if you only follow three semiconductor stocks, these are the three — they tell you what's happening before the market knows.
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