# Anthropic "thinking" "disabled" "Claude" API

Status: search-observed
Product: Claude API
Last verified: 2026-06-25
Canonical HTML: https://gitdocs.org/fix/anthropic-thinking-disabled-claude-api
Machine JSON: https://gitdocs.org/api/fixes/anthropic-thinking-disabled-claude-api.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 latency 400 SDK accepts field service_tier latency_sensitive
- site:docs.anthropic.com/en/docs Claude API thinking disabled 400 adaptive thinking model
- Anthropic "thinking" "disabled" "Claude" API
- Anthropic docs extended thinking API
- site:docs.anthropic.com "adaptive thinking" Claude API
- docs.anthropic.com claude api adaptive thinking effort levels
- https://docs.anthropic.com/en/api/messages
- https://platform.claude.com/docs/llms.txt
- site:anthropic.com/news "adaptive thinking" "disabled"
- "Claude Opus 4.6: Adaptive thinking and 1M context window"
- github anthropics anthropic-sdk-typescript thinking disabled adaptive thinking
- github.com anthropics anthropic-sdk-typescript "type": "disabled" "thinking"
- https://raw.githubusercontent.com/anthropics/anthropic-sdk-typescript/main/src/resources/messages/messages.ts
- 'ThinkingConfig' in https://raw.githubusercontent.com/anthropics/anthropic-sdk-typescript/main/src/resources/messages/messages.ts
- https://platform.claude.com/docs/en/build-with-claude/adaptive-thinking

## 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
- Official reference opened by Codex: https://platform.claude.com/docs/llms.txt
- Official reference opened by Codex: https://raw.githubusercontent.com/anthropics/anthropic-sdk-typescript/main/src/resources/messages/messages.ts
- Official reference opened by Codex: https://platform.claude.com/docs/en/build-with-claude/adaptive-thinking