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  "path": "/t/structured-output-schema-validation-changed-without-notice-previously-valid-schemas-now-rejected/1384139#post_1",
  "publishedAt": "2026-06-19T16:35:55.000Z",
  "site": "https://community.openai.com",
  "textContent": "We ran into a serious issue this morning involving the structured‑output JSON Schema validator used by the Responses API. A schema that had been valid—and in production—suddenly began failing validation with no code changes on our side.\n\nWhat Happened\nOur application uses the json_schema structured‑output mode.\n\nThe schema had been accepted for weeks and was generating correct structured output.\n\nAt some point in the evening of 6/18/2026 EDT, the same schema began failing validation.\n\nNo changes were made to:\n\nour schema\n\nour request envelope\n\nour model version\n\nour deployment environment\n\nThe only plausible change was on the server‑side validator.\n\nThe Breaking Change\nThe validator appears to have tightened or altered its interpretation of JSON Schema in a way that is not backward‑compatible.\n\nSpecifically, we observed:\n\nA schema that previously validated now fails unless rewritten in a more restrictive or differently structured form.\n\nFields/constructs that were previously allowed are now rejected.\n\nThe failure is reproducible and tied directly to the schema, not to the request envelope or runtime environment.\n\nThis effectively turned a previously valid production schema into an invalid one overnight.\n\nImpact\nThis caused:\n\nProduction breakage\n\nTime‑consuming debugging to confirm the issue was not on our side\n\nA need to rewrite the schema to satisfy new, undocumented validator behavior\n\nFor teams relying on structured output for deterministic workflows, this kind of unannounced change is extremely disruptive.\n\nWhat We’d Like Clarified\nWas there a change to the structured‑output JSON Schema validator?\n\nIf so, what changed, and when?\n\nIs the validator expected to be backward‑compatible with previously accepted schemas?\n\nIs there a documented subset or profile of JSON Schema that the validator supports?\n\nCan OpenAI provide versioning or changelogs for validator behavior, similar to model releases?\n\nWhy This Matters\nStructured output is a lot less useful if the schema contract is unstable.\nIf validator behavior can change without notice or versioning, it undermines the determinism that structured output is meant to provide.",
  "title": "Structured Output Schema Validation Changed Without Notice — Previously Valid Schemas Now Rejected"
}