What is the common spec for Knative? It seems like one runs an app as normal in a container and then the special scaling sauce is handled by Knative.

When I think of a portable spec for serverless, I think of something more like a Trait of an Interface that needs to be implemented, less a app hosting model. If you think about it like that, then Web Assembly component model [1] would be a great fit for defining an interface that could be implemented in a variety of languages.

[1]: https://github.com/WebAssembly/component-model/blob/main/des...

Yes, exactly. Of course experimentation and competition is good to settle on a solid set of building blocks, but in the long run serverless code should absolutely be portable between vendors.

There's a strong incentive for vendors to not allow this as it reduces their pricing power... But think we will see it eventually one way or another.

That would only be implementable by languages with a WASM output target though. Knative says that any container that responds to HTTP will work, and you could host those in different environments. It's much more general.