FHAT Technical Note #011: Cross-Market Overnight Co-Movement: KOSPI Strength, SOXL's Two-Phase Decline, and FHAT Structural Transition (August 19–20, 2026)

This FHAT Technical Note presents an ex-post empirical case study of the August 19–20, 2026 overnight co-movement between South Korea’s KOSPI Composite Index and the Direxion Daily Semiconductor Bull 3X Shares (SOXL). It separates the decline following SOXL’s USD 127.28 overnight peak into two analytically distinguishable but potentially interacting windows: a moderate post-4:00 AM EDT pullback and a larger move surrounding the 8:30 AM EDT U.S. macroeconomic data release. The note also documents a timestamped, pre-peak exploratory calculation. Using contemporaneous KOSPI and SOXL readings, a session-specific sensitivity ratio of approximately 0.74 produced a conditional SOXL estimate of USD 127.65–127.68 if KOSPI tested its cursor-identified 5-minute prior high at 6,971.41. Independently, the author’s pivot and declining 5-minute MA500 analysis identified a broader USD 127–129 structural ceiling range. SOXL subsequently peaked at USD 127.28. These observations are retained as temporally prior but non-scorable exploratory evidence—not as validation of a stable cross-market transmission coefficient. Following the rapid recovery from USD 115.90, SOXL entered what FHAT classifies as an upward-biased consolidation/transition phase—震(横偏上)/转期. Acceptance above the declining 5-minute MA500, followed by a break and hold above USD 127.28, is defined as the sequential condition for structural repair. The note emphasizes methodological discipline: timestamped evidence is not equivalent to preregistration, algebraic consistency is not independent validation, and coincident cross-market movement does not establish causality. This document is intended for research and educational purposes only and does not constitute financial advice.