Purpose <p>This study investigates how trait-level personality differences and day-level situational demands jointly shape proactive work behaviors in the form of job crafting. Building on Trait Activation Theory, we argue that emotional demands in the workplace function as trait-relevant situational cues that make stable personality differences more behaviorally salient in daily job crafting behavior. Drawing on Density Distribution reasoning as a conceptual lens, we further note that stable traits can coexist with meaningful daily variability in behavior across days.</p> Originality <p>Although the Big Five personality traits are well-established predictors of workplace behavior, relatively little is known about how their effects vary in response daily situational demands.</p> Design/methodology <p>The study followed a daily diary design with 1884 observations nested in 157 doctors from different hospitals. We employed multilevel modelling in MPLUS to disentangle within-person and between-person effects.</p> Findings <p>The findings showed that openness, conscientiousness, extraversion and agreeability were positively associated to average daily job crafting, whereas neuroticism was negatively associated. Cross-level interactions further revealed that openness, extraversion and conscientiousness strengthened the positive relationship between daily emotional demands and job crafting, whereas neuroticism attenuated this relationship.</p> Implications <p>These results highlight the value of integrating a stable traits perspective with daily behavioral variability to better understand when personality differences are most visible at work.</p>