Valid JSON Can Still Mean Empty Extractions

mattjcoles · reddit · 2026-07-14

The author reiterates a common pitfall: **just because the JSON syntax is valid doesn't mean the model actually extracted any content**. Their extraction schema consists of near-duplicate objects. Under GBNF constraints, Qwen3-VL repeats the same item endlessly; increasing the repetition penalty stops the loop, but the model may then output **valid but completely empty JSON**. The author advises validating entry counts and actual content, rather than just the format, for such tasks.

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