The Format Tax: Answer-Only JSON Contracts Suppress Multi-Step Reasoning in Claude Sonnet 4.6, and One Schema Field Buys It Back

Yash Singh - IIIT Una

Production LLM pipelines routinely instruct models to answer in strict JSON so that downstream code can parse the output. Prior work disagreed on whether such format restrictions degrade reasoning, but that debate predates current frontier models. We measure the effect directly on two current models...

Download PDF - LaTeX source

All papers