Admittedly, "How is this different to Java [planned]?" isn't an entirely unreasonable question to ask in this context. :) What's your theory on why it doesn't/

Admittedly, "How is this different to Java [planned]?" isn't an entirely unreasonable question to ask in this context. :) What's your theory on why it doesn't/didn't work out in practice in Java's case? There is one key difference in our respective wording which might point to a difference of perspective: I referred to "the same code" and you referred to "portability of applications". I don't really foresee "portability of applications" so much as "portability of modules/functions" (or "portability of libraries/plugins", I guess). In which case, you're still correct when you say a common byte-code interpreter isn't enough--there also needs to be common specification/API for specific domains. (Which is where WASI is aiming for in terms of general system-level APIs; interface types are aiming for lower levels; and, other higher level domain/application-specific solutions may be developed for other situations.)