Programming Tutorials

  You have deployed a feature using OpenAI’s function calling capabilities. It works perfectly in staging. Then, in production, your error monitoring platform lights up with   SyntaxError: Unexpected token ' in JSON at position...   or   ZodError: Unrecognized key . The LLM returned a Python dictionary with single quotes instead of valid JSON. Or perhaps it hallucinated a parameter that doesn't exist in your TypeScript interface. When building deterministic systems on top of probabilistic models, strict schema validation is the single most common failure point. This article details the root cause of these failures and provides a production-grade TypeScript solution using  Zod ,  JSON5 , and  Recursive Healing . The Root Cause: Why Models Fail at JSON To fix the problem, we must understand why it happens. LLMs are not logic engines; they are autoregressive token predictors. 1. The "Pythonic" Bias LLMs are heavily trained on Python code. In Python, ...