Hi, Do you know any ways to debug node js native provider (adding flags to pkg or run it through bash as in python) and core engine (cli)?

You can start the provider up in whatever IDE/debugger your using and then take the port number it prints out and set the PULUMI_DEBUG_PROVIDERS environment variable to "<provider name>:<port number>". With that set then run "pulumi preview/up" like normal and the engine will connect to your running provider rather than starting a new process up.

Thank you very much. In case if I want to debug the CLI, I will build it locally, so can you please send a link to the git of CLI (if there is any, because when I checked the github I found only an engine folder in pulumi/pkg/engine) or give me some other advice how to do this?

The CLI is pkg/cmd in that git repo, "make build" in the root of the repo should build it and put it on GOPATH