Module error 

DecodeError — decode’s own diagnostic type, in AnalysisError’s style (tagged variants carrying context, not sentinel codes. This is defense in depth against what pysees’s compiler can’t see (engine/schema version skew, a stale snapshot run against a newer/older wasm build) — the compiler is expected to catch entity-level problems (missing tags, unsupported materials, …) first.

Enums

DecodeError

Serialize, not Deserialize — a DecodeError only ever flows out to JS (boundary.rs), as a { kind: "...", ... }-shaped object.

ModelErrorDetail

core::ModelError, restated for the wire. Node and element indices are the rows of the node table and of the element tables in insertion order (all element kinds in decode order), so a caller can map them back.