When Structured Output Breaks: A Repair-and-Recovery Playbook for LLM JSON
Strict mode kills the invalid-JSON problem you used to spend afternoons on. But three failures walk right through it — truncation, refusal, and a safety stop — and each one wants a different move, not another retry.
5 min
Structured Outputs Across Claude, GPT-5.6, and Grok: One Schema, Three API Shapes
All three frontier APIs now take a JSON Schema and hand you back guaranteed-valid JSON. But the same schema does not drop into all three unchanged — and the place it breaks is the one line most people copy from OpenAI's docs.
6 min
How to Pull Structured Data From Long Documents — and Trace Every Field Back to the Source
Schema-constrained output gives you a valid object. It can't tell you whether a value was read from the document or invented to satisfy the schema. Google's LangExtract returns the exact character span each field came from — which turns extraction from a trust exercise into a verification one.
4 min
Does Structured Output Hurt LLM Accuracy? The Format Tax, Measured
Forcing JSON can cost a reasoning model 10–15% — but the tax is paid during thinking, not from structure itself. The fix is where you put the reasoning, not whether you constrain.
4 min
Streaming Structured Output From an LLM: How to Render JSON Before It's Done
A JSON object isn't valid until its closing brace — but your UI shouldn't wait for it. The trick is realizing a streamed object is a view, not a value, and validating it exactly once: at the end.
5 min
Outlines vs XGrammar vs llguidance: Constrained Decoding Without the Throughput Tax
Forcing a model to emit valid JSON is a solved problem. Doing it without slowing generation to a crawl is the one that produced three new engines — and your serving stack probably already picked one for you.
4 min
Instructor vs Outlines vs BAML: Getting Structured Output From an LLM
Three libraries promise the same thing — reliable JSON from a language model — and disagree completely on where to enforce it. The right pick follows one question: do you control the decoder?
4 min