||A major potential benefit of software-defined SDx architectures is agility achieved through logically centralized programmability. The dependency on a centralized control plane (CP), however, can have substantial reliability issues, when the CP can be weakly connected to the data plane (DP), or even disconnected from the DP. Distributed CPs such as MANET (e.g., OLSRv2) can be more reliable but are less programmable and cannot provide global policy guarantees. In this work, we design Carbide, a novel, fundamental control architecture for SDC that achieves a high level of reliability and programmability through the composition of multiple control planes. Introducing both a novel distributed verification framework and a general resource management framework, Carbide selects CPs intelligently and in distributed manner such that they satisfy global constraints. We conduct data-driven evaluations in military settings using EMANE, and demonstrate that Carbide can achieve average downtime that is only 1/3 of the most reliable individual CPs. This work provides a highly reliable, verifiable, secure, and flexible CP design tailored for SDC. Preliminary results appeared in DAIS 2019.