Lean management has long delivered operational efficiency, yet aggressively lean supply chains have proven fragile under compounding shocks. Industry 4.0 (I4.0) technologies promise visibility and reconfigurability, but isolated technological adoption often fails to deliver durable performance. Drawing on Socio-Technical Systems theory, this study decouples Lean into a technical subsystem (Process-Oriented Lean) and a social subsystem (People-Oriented Lean), and tests whether these subsystems differentially moderate the effects of I4.0 on operational efficiency and supply chain resilience in the Saudi Arabian context. Survey data from 245 supply chain and operations managers were analysed using partial least squares structural equation modelling with 5,000 bootstrap subsamples. I4.0 has significant positive direct effects on both operational efficiency (β = 0.318, p < 0.001) and resilience (β = 0.187, p = 0.002). People-Oriented Lean amplifies both outcomes, with the strongest amplification on resilience (β = 0.294, p < 0.001). Process-Oriented Lean, however, acts asymmetrically: it strengthens the I4.0–efficiency link (β = 0.170, p = 0.002) but attenuates the I4.0–resilience link (β = -0.124, p = 0.030). The model accounts for 47.9% of the variance in efficiency and 41.4% in resilience. Findings clarify the productivity-resilience dilemma: technical leanness amplifies digital efficiency but erodes resilience unless paired with an empowered, problem-solving workforce. The study extends socio-technical theorising of digital transformation and offers concrete guidance for Vision-2030 economies pursuing simultaneous digitalisation and supply chain hardening.