Automotive wiring harnesses span several kilometres of cable, constitute one of the heaviest vehicle sub-systems and exist in thousands of variants due to customer specific needs. To clarify how emerging “zonal” and “domain” architectures, digital tools and organisational practices can handle this complexity, we combine a systematic literature review (SLR) with five semi-structured expert interviews drawn from Tier-1 suppliers and specialised software providers. The review screens 229 peer-reviewed publications across Scopus, IEEE Xplore and Web of Science. Backward snowballing completes the corpus. The interviews enrich gaps where scholarly sources remain insufficient regarding the display of industrial realities. Results show a convergent definition of zonal architecture as physically partitioned wiring governed by simple, forwarding, zone controllers feeding a central control unit, promising 15–20% weight savings, and domain architecture as the still-dominant, function-centred paradigm. Current practice is characterised by incremental reuse of legacy harnesses, spreadsheet-based variant management and CAD routing applied only to a single “reference vehicle”. Advanced optimisation algorithms appear mainly in prototypes, blocked at scale by fragmented data and unclear responsibilities. We identify three imperatives for progress: adopt hybrid domain-plus-zonal transitions, establish a single cross-domain data spine, and realign organisational KPIs from local cost control toward end-to-end harness efficiency.