Against the backdrop of intensifying global technology competition， the “chokepoint” dilemma has emerged as a systemic challenge threatening supply chain security and firm survival. Existing research lacks micro-level explanations of how latecomer firms achieve strategic transformation through the dynamic coordination of open and closed strategies under deglobalization. Drawing on a case study of Jiashite CNC Technology Co.， Ltd.， it developed a cross-stage open-closed decision-making combinatorial model of “technology ecosystem-scenario ecosystem” coordination. The findings reveal that in the dependency-adaptation stage， firms face a technology-dependence context and the challenge of “dependency lock-in”. By adopting the combined strategy of an open technology ecosystem and a closed scenario ecosystem， they accumulate initial capabilities through absorbing external knowledge and protecting niche application scenarios. In the autonomous-reconfiguration stage， supply disruptions force firms to rebuild an autonomous technological system and confront the challenge of reconfiguration and transformation. They shift to a dynamic combination of a closed technology ecosystem and an open scenario ecosystem， accomplishing a leap in value logic from “functional technology” to “high-performance technology”. The conclusion opens the micro-level “black box” of how latecomer firms achieve autonomous technological control under chokepoint conditions， advances both catching-up theory and open innovation theory from a managerial paradox perspective， and offers practical implications for latecomer firms pursuing independent technological breakthroughs.