Honda and Nissan announced 31 August that they have reached an agreement to jointly develop software-defined vehicle (SDV) technology, agreeing to standardise the core electronic control units and build a shared in-vehicle operating system. The companies expect that the resulting technology will appear in new vehicles from both brands as early as fiscal year 2029, marking the first time Japanese automakers have joined forces on core SDV technology at the operating system (OS) level.

The deal covers common specifications for multiple core electronic control units within the vehicles’ architecture, as well as the(OS), key middleware and vehicle control software. In a statement, the two companies said the goal is to “improve efficiency, accelerate innovation and enhance competitiveness through reduced development costs and greater economies of scale”. Honda and Nissan had originally planned to use Nissan’s own technology as the project’s foundation, though the final agreement instead describes the arrangement as fully collaborative.

The partnership arrives after a turbulent two years of relations between the two companies, despite their best efforts to closen their ties. Honda and Nissan first began exploring SDV cooperation in March 2024, and subsequently expanded those talks to include full merger negotiations in December that year. After roping Mitsubishi Motors into the merger talks, negotiations collapsed after it reportedly became apparent that Nissan would become a Honda subsidiary, thereby defeating the equal-partners premise of the initial merger talks. 

At the time, Nissan was struggling heavily against losses and has since mounted an extensive restructuring campaign that will ultimately see it lay off up to 20,000 employees worldwide, close seven of its 19 global plants, and unlock around JP¥500bn (US$3.12bn) in savings annually. The turnaround is, thus far, going well: the automaker returned to profitability during Q2 2026 with a 2.6% margin, although its automotive division continues to post a loss. 

Honda, on the other hand, is looking weaker than at the time of those original merger talks. A major reversal on its electric vehicle ambitions is seeing it absorb roughly JP¥2.5tr in costs related to writedowns and compensating affected suppliers. As a result the automaker reported its first-ever annual loss during fiscal 2025. Since merger talks collapsed, the two sides have continued cooperating on individual projects, and the latest SDV agreement has reportedly been in development throughout that entire period.

Combined, the two automakers carry real scale even without a merger. Honda ranked ninth globally by sales volume in 2025 with 3.52 million vehicles, and Nissan eleventh with 3.2 million.  Combined, the 6.72 million total would rank fourth globally, ahead of both General Motors and Stellantis, though still smaller than compatriot Toyota, Volkswagen or the combined Hyundai-Kia group.

The SDV agreement effectively splits Japan’s auto industry into two competing software camps. Toyota already has a substantial head start through its software subsidiary Woven by Toyota, whose Arene operating system is shipping in the redesigned 2026 RAV4 and is being extended across Toyota’s own brand umbrella and its wider partner bloc of Subaru, Mazda and Suzuki. Toyota’s model is a centrally-controlled platform explicitly built as a software development kit for outside developers, while Honda and Nissan’s approach requires standardising hardware first between two historically separate engineering cultures, an inherently slower process given the joint governance involved.

Targeting fiscal 2029 for the first jointly developed vehicles leaves Honda and Nissan with a meaningful gap against Toyota, which will already have years of real-world data and software iteration behind it by the time the new platform reaches the market. It may also position them poorly against Chinese competitors and Tesla, whose legacy-free architectures let them move faster still.