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Sweep 02 Oct 2026 · 18:55Z Build v2.1.288 509 read Stable v2.1.285 Latest v2.1.288 Next v2.1.288 Feeds RSS JSON llms.txt llms-full.txt Unofficial
HomeDocsClaude Developer Platform 28 Sep 2026
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API usage primer for Claude changedclaude_api_primer

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1414Recommended default for most work, including complex agentic coding: Claude Opus 5.5: claude-opus-5-5
1515Step up for the hardest long-running agentic and research tasks, at 2.5x Claude Opus 5.5 pricing: Claude Fable 5.1: claude-fable-5-1
1616Previous Opus model: Claude Opus 5: claude-opus-5
17Smart model: Claude Sonnet 5: claude-sonnet-5
17Smart model: Claude Sonnet 5.5: claude-sonnet-5-5
18Previous Sonnet model: Claude Sonnet 5: claude-sonnet-5
1819For fast, cost-effective tasks: Claude Haiku 4.5: claude-haiku-4-5-20251001
1920```
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244245Thinking is supported in the following models:
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246247* Claude Opus 5.5 (`claude-opus-5-5`, adaptive thinking only, always on)
248* Claude Sonnet 5.5 (`claude-sonnet-5-5`, adaptive thinking only, on by default)
247249* Claude Opus 5 (claude-opus-5, adaptive thinking only, on by default)
248250* Claude Sonnet 5 (`claude-sonnet-5`, adaptive thinking only, on by default)
249251* Claude Opus 4.8 (claude-opus-4-8, adaptive thinking only)
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625627* `tool` forces Claude to always use a particular tool.
626628* `none` prevents Claude from using any tools.
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628On Claude Opus 5.5, Claude Fable 5.1, and Claude Mythos 5.1, `any` and `tool` return a 400 error. Leave `tool_choice` at `auto` and set `"strict": true` on the tool definition to guarantee that any call Claude makes matches the tool's `input_schema`. See [Strict tool use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/strict-tool-use).
630On Claude Opus 5.5, Claude Sonnet 5.5, Claude Fable 5.1, and Claude Mythos 5.1, `any` and `tool` return a 400 error. Leave `tool_choice` at `auto` and set `"strict": true` on the tool definition to guarantee that any call Claude makes matches the tool's `input_schema`. See [Strict tool use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/strict-tool-use).
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630632### JSON output
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