Module registry 

Structs

CoreEnvoyHandle

CoreEnvoyStatus

CoreRegistry

ServeConfig

Enums

EngineSpawnMode

RuntimeMode

Selects how Registry::start runs, mirroring the TypeScript RIVETKIT_RUNTIME_MODE env var. Envoy holds one long-lived outbound envoy for the process lifetime; Serverless runs an HTTP listener that lazily starts and caches an envoy on the first request.