I'm not sure I understand why it's necessary to even couple this to a runtime, let alone own the runtime?
Can't you just do it as a library and train/instruct the LLM to prefer using that library?
The whole point every CEO with a toe in the AI pool can't stop bleating on about is that software engineering is dead and replaced by AI.
bun is MIT licensed, they could take bun free of charge and use their Phd level software engineer god machine to iterate on it.