priority: critical

Error Handling Strategy

CRITICAL: OSError/RuntimeError must ALWAYS bubble up (Python + Rust). SystemExit, KeyboardInterrupt, MemoryError too.

Python: Exception-based, inherit from KreuzbergError. OSError patterns: 1) Library misuse→bubble up, 2) Subprocess→analyze stderr for parsing keywords, 3) Cache→ignore, 4) Dependencies→MissingDependencyError or bubble up. Always add ~keep comments.

Rust: KreuzbergError::Io always bubbles up unchanged. Result<T, KreuzbergError>, never .unwrap() in production, use ?.

Exception hierarchy: ValidationError, ParsingError, OCRError, MissingDependencyError.