Karpenter is a Kubernetes cluster autoscaler that provisions and manages compute capacity (nodes) for pods that cannot be scheduled. It operates as a controller-runtime-based operator, using Custom Resource Definitions (CRDs) like NodePool, NodeClaim, CapacityBuffer, and NodeOverlay to declaratively manage node lifecycle. The system continuously reconciles the desired state (unschedulable pods, disruption budgets, static replicas) with the actual cluster state, creating or deleting NodeClaims via a pluggable CloudProvider interface (with implementations for AWS, Azure, GCP, and a fake/KWOK provider for testing). Key entry points include the operator startup in `pkg/operator/operator.go`, the provisioning loop in `pkg/controllers/provisioning/provisioner.go`, and the disruption controller in `pkg/controllers/disruption/controller.go`. External dependencies are minimal: it requires a Kubernetes cluster with controller-runtime, Prometheus for metrics, and optional DRA (Dynamic Resource Allocation) support via a separate driver. The codebase is production-grade, with extensive unit and integration tests, performance benchmarks, and a well-defined event/metrics system.