After five major contributions across error handling, type safety, and safety utilities, here are the production patterns that work and the ones that do not. A practical summary of trade-offs, guardrails, and what we kept in llm4s.

Stop swallowing errors in try-catch blocks. Build safety utilities that preserve context, enable composition, and make errors type-safe. Real refactor from llm4s eliminated 47 try-catch blocks, fixed a streaming bug, and simplified code.

Stop runtime exceptions from crashing LLM pipelines. Build type-safe error hierarchies with Scala Either, ADTs, and smart constructors. Real refactor from llm4s turned generic exceptions into 12+ structured error types and debugging.