Claude: Issues with responses using structured outputs on the API
Timeline of updates
- resolved
We have identified and resolved an issue which resulted in issues with model responses when making use of structured outputs via the Anthropic API between 16:10 UTC on April 22 and 01:59 UTC on April 23. During this period, structured outputs containing some forms of grammar requirements returned with reduced quality. This did not impact any requests not using structured outputs, as detailed here: https://platform.claude.com/docs/en/build-with-claude/structured-outputs (opens in new tab).
From Claude’s published incident history: for incidents before Rewindex began polling this status page, only the final update text is available.
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This incident predates live tracking (October 17, 2026). It came from the vendor’s own published history, which is not covered by checkpoints.
Impact, status and times are the vendor’s own, as last archived. View on status.claude.com (opens in new tab).
Cite this
Status incident (vendor impact label: none) posted by Claude, started 2026-04-23 02:00 UTC, resolved after 0 min, 1 update(s).
- Title
- Issues with responses using structured outputs on the API
- Vendor
- Claude
- Date
- URL
- https://rewindex.com/company/claude/incidents/t6v0k97s0802
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