Honda and Nissan Build Shared Car Software Stack After Merger Collapse

Honda and Nissan are standardizing parts of their next-generation “software-defined vehicle” stacks after their high-profile merger collapsed. On August 31, 2026, they signed a joint development agreement to standardize the core electronic control units (ECUs) and software runtime environment for vehicles starting in fiscal year 2029, without an equity swap or one brand becoming a subsidiary. Mitsubishi, where Nissan holds a 26% stake, said it is actively considering joining. The plan focuses on matching specifications for high-performance main ECUs and zone ECUs, using an automotive Ethernet backbone to enable lighter wiring and over-the-air updates while leaving each brand free to differentiate with application-layer software.