Ageing research has achieved major advances by cataloguing recurrent mechanistic motifs—most prominently in the hallmarks framework—yet it still lacks a sufficiently explicit account of what deteriorates at the level of organism–environment engagement as ageing progresses. This article proposes contextual semiodynamics as a mid-level theoretical object that complements mechanistic pluralism by redescribing ageing as a time-dependent decline in biological sense-making competence, formalized as a minimal profile spanning discrimination, transduction, adaptive response, and organisational coherence. The framework derives a constrained set of dynamical expectations—concerning resilience and recovery kinetics, modular organisation and compensatory coupling, multiscale physiological complexity, and vulnerability to state transitions—thereby reorganizing hallmarks as contributors to competence failure modes rather than as a substitute catalogue. Evo-devo and life-history theory are introduced as principled constraints on trajectory shape and cross-taxon variation, clarifying why similar mechanistic motifs can yield divergent ageing patterns across organisms and environments. Finally, the article specifies a disciplined, conditional role for a quantum-compatible modelling layer: not as a hypothesis about quantum-biological mechanisms, but as a formal resource for cases where context dependence yields empirically robust incompatibilities between partitions, order effects, or failures of a single classical joint-probability representation. Contextual semiodynamics thus offers a parsimonious bridge between mechanistic inventories and dynamical competence trajectories, with a clear agenda for stressor-based, multiscale, and comparative testing.