CauslEngineErrorCode:
    | "CAUSL_WASM_ENGINE_UNAVAILABLE"
    | "CAUSL_WASM_NOT_PRELOADED"

The code values the engine-unavailable family carries — the discriminant the barrel's own contract tells callers to branch on.

causl/causl-wasm-ts#363 finding 8 — exported because there was no cast-free spelling of the migration 0.5.0 mandates. CAUSL_WASM_NOT_PRELOADED is declared by the SUBPATH's CauslWasmNotPreloadedError, which the main bundle must not name, so this type is the only main-bundle place both literals can appear. The repo's tsconfig.base.json sets useUnknownInCatchVariables: true, so without it an adopter's switch on err.code needs (err as { code?: string }).code — an unchecked cast against an unexported string, which is what the CHANGELOG's own worked example writes.