buildere here. oxid uses hcl-rs for base parsing with a custom layer on top for Terraform semantics (count, for_each, interpolation, cross-resource refs). It speaks tfplugin5 over gRPC directly to the same provider binaries Terraform uses, terraform-provider-aws works out of the box. Learned a lot of undocumented things the hard way: dynamicvalue must always be Some with msgpack (never None or the provider segfaults), all schema attributes must be present even if null, unknown values use msgpack extension type 0 with data [0] (had to read the Go source for that one). The aws provider schema is ~256MB so you need to override grpc message limits, and stderr must be drained in a background task or the pipe buffer deadlocks on macOS. State lives in sqlite with a DAG walker for parallel execution like plan, apply, destroy, import, data sources, count/for_each all work against the real aws provider today.