When TypeScript Types Meet Untrusted AI: Building Type-Safe LLM Pipelines With Runtime Validation

TypeScript can make an LLM integration look safer than it is. A function may promise Promise and every branch may compile under strict settings, yet none of those guarantees prove that a model returned a valid Classification . TypeScript annotations are erased during compilation and do not alter runtime behavior, so data crossing an AI boundary remains untrusted until executable validation proves otherwise.