Errors are values, and defects are separate

Every fallible entry point returns Result<T, InvalidEntity>. Bad input is modelled; a bug in domain code is not.

The line: a field failing its schema or a broken invariant is InvalidEntity — expected, caller-caused. A computed function throwing or producing data its own schema rejects is a defect: computed is pure, total and typed, so a violation is a bug rather than bad input. An async generator rejecting is a defect for the same reason — infrastructure failing is not bad domain input.

A defect is never folded into a validation issue, even when the entity is nested inside another schema. An unmodelled bug stays distinguishable from bad caller input all the way to the edge.

Issues are carried structured, exactly as the validator produced them, so keying a field-level error response is a path lookup rather than a string parse.

Errors tabulates which failure takes which channel; the unthrown docs explain the defect channel itself.