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Constraint Decoding

Token-level constraints prevent the model from emitting 'invalid' tokens (Outlines, guidance, llama.cpp grammar).

3 hours1 resources1 prereqs

Outlines (Python), guidance (Microsoft), llama.cpp grammar — apply regex/grammar during sampling so only schema-compliant tokens stay probable.

For open-source models, this is the 100% way to enforce JSON. Closed APIs already do similar work in structured-output mode.

Prerequisites

Schema-driven Output (Pydantic / Zod)
Force output schema with JSON Schema — validate with Pydantic (Python) or Zod (TS).
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