Fitting Error
Structured failure cause carried by a terminal failed FitResult.
The current taxonomy is intentionally narrow: a pre-flight configuration problem, a data-import problem, or anything else thrown by the fitting runner. Later phases will widen this hierarchy as concrete failure categories warrant distinct front-end treatment (per-estimator failures, database-specific errors, etc.).
Inheritors
Types
Pre-flight validation rejected the submitted spec. The carried validationResult lists each offending field so a front-end can highlight inputs directly.
Data import failed: file not found, layout mismatch, non-numeric values, empty group, and so on. The cause is typically the underlying ImportException.
Anything else thrown while running the fit: PDFModeler numeric failure, a not-yet-supported feature guard, an unexpected JVM exception. The cause carries the original throwable.