# Anthropic Claude API output_format output_config format structured output

Status: search-observed
Product: Claude API
Last verified: 2026-06-25
Canonical HTML: https://gitdocs.org/fix/anthropic-claude-api-output-format-output-config-format-structured-output
Machine JSON: https://gitdocs.org/api/fixes/anthropic-claude-api-output-format-output-config-format-structured-output.json

## Exact Symptom

See the observed Codex queries below.

## Diagnosis

SDK types may still accept fields that the selected hosted model rejects; model retirement, tokenizer, thinking, and tool behavior are external and fast-moving.

## Fix

```
Verifier checks current model ID, accepted payload, structured output/tool parsing, and behavior under retries.
```

## Avoid

- Changing local code without checking the current external contract.
- Retrying the same install, build, or API call with no version/source change.
- Applying a broad unsafe bypass when a narrow compatibility fix is available.

## Observed Codex Queries

- site:docs.anthropic.com Claude API structured outputs output_format output_config format beta
- Anthropic Claude API output_format output_config format structured output
- output_format site:docs.anthropic.com/en/api/messages
- site:docs.anthropic.com/en/docs "structured outputs" "Claude"
- https://docs.anthropic.com/en/api/messages
- "output_config" "format" "Claude"
- "output_config" "output_format" "API"

## Sources

- Claude model migration guide: https://platform.claude.com/docs/en/about-claude/models/migration-guide
- Official reference opened by Codex: https://docs.anthropic.com/en/api/messages