Broadly enjoyed my read, though I do have a nitpick here:

>The absence of side effects or stalls cannot be enforced by the type system ...

Side effects is probably correct, but stalls would imply wasm code that calls out to a long-time blocking function - that's generally quite easy to type-system-ify, and wasm stuff often does so with promise-like constructs. So there would be a need for spacetimedb-side markers for "this func might do HTTP", but that kind of marker for WASM-contact-able code is very much a normal expectation.

If they don't have that kind of marker, and do allow blocking calls in their beta API, then yeah - huge problem with that kind of internal structure (shared global lock), completely agreed.