Repair LLM Structured Output & Schema Failures

The likely issue is a contract mismatch around LLM structured outputs, JSON/schema contracts, parser failures, optional fields, enums, retries, validation, fallbacks, truncation, and provider/model drift. I would first define the invariant: Only schema-valid, semantically acceptable model output may cross into business logic; invalid or incomplete output must remain explicitly invalid and follow a bounded fallback path. Then I would trace the smallest owning boundary, apply or propose a bounded repair/review step, and add deterministic normal, boundary, failure and replay tests. The workflow preserves existing authorization, data-handling, model-selection, public API, and product behavior. If repository/workspace files are available, the findings can be mapped to exact paths and focused local validation; with partial evidence, the result stays an explicit diagnosis/evidence map with assumptions and no invented execution claims.