Structured Outputs for Local LLMs 2026: Outlines & XGrammar
Struggling with structured outputs local LLM setups? See how Outlines and XGrammar enforce valid JSON at the token level in 2026 — no retries, no regex hacks.
Chapter 1: Why Structured Output Broke Your Local LLM Stack (And What Changed by 2026) You built the demo. A 7B model running on your own GPU, a prompt that ends with "Respond only with valid JSON," and a json.loads() call on the other side. It worked on the first twelve requests. Then it returned a JSON object wrapped in a markdown fence. Then it returned two objects. Then it apologized for its previous answer and offered a third. Somewhere around request 400 it emitted a trailing comma and your ingestion job died at 3 a.m. This is the single...