has anyone played with Alchemy? the creator is making some fairly inaccurate claims about Pulumi

SST is on top of Pulumi,

This is true

which is again on top of Terraform.

Not true for the engine, but a number of pulumi providers are built on top of terraform providers.

Terraform and Pulumi are implemented in Go and generate TypeScript "wrappers" that depend on a separate Go process.

This is true, the engine and most providers are written in Go and they do need separate processes for them. And yes that has some downsides, and at a glance doesn't seem as nice as just "everything is TypeScript". But firstly we're not only targeting TypeScript, we've got a lot of devs using Python and C# so Alchemy's all being TypeScript would be kinda moot for them. Secondly we see the process isolation an advantage both in terms of system stability (bad provider code can't knock out the engine) and allowing users to write providers and modules in any language. I think the only interesting part is their claim of being able to use AI tools to generate the provider APIs. Something we've also been experimenting with: https://www.pulumi.com/blog/vibe-clouding/