thinking

 
 On current models, thinking is on by default or one parameter away. Which configuration each model accepts, and what it defaults to, is listed in the [per-model configuration table](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#supported-models) on the Troubleshooting page.
 
-On Claude Opus 5, Claude Sonnet 5, Claude Fable 5, Claude Mythos 5, and Claude Mythos Preview, thinking is already on: no configuration needed. The first thing most developers need on these models is to see the thinking text, because `display` defaults to `"omitted"` there. Opt in with `thinking: {"type": "adaptive", "display": "summarized"}`, which is exactly the following request with the [model string](https://platform.claude.com/docs/en/about-claude/models/overview) swapped.
+On Claude Opus 5, Claude Sonnet 5, Claude Fable 5, Claude Mythos 5, and Claude Mythos Preview, thinking is already on: no configuration needed. The first thing most developers need on these models is to see the thinking text, because `display` defaults to `"omitted"` there. Opt in with `thinking: {"type": "adaptive", "display": "summarized"}`, which is exactly the following request with the [model string](https://platform.claude.com/docs/en/models/overview) swapped.
 
 On Claude Opus 4.8, Claude Opus 4.7, Claude Opus 4.6, and Claude Sonnet 4.6, thinking is off until you set `thinking: {type: "adaptive"}`, which lets Claude decide when and how deeply to think based on the request. The following examples do that, set `display: "summarized"` so the thinking text is visible, and use a roomy `max_tokens`:
 

 
 **Response prefill and forced tool use.** You can't pre-fill the assistant response while thinking is on. Forced tool use (`tool_choice: {"type": "any"}` or `{"type": "tool", ...}`) is incompatible with manual extended thinking but works with adaptive thinking. See [Thinking with tool use](https://platform.claude.com/docs/en/build-with-claude/thinking#thinking-with-tool-use).
 
-**Output limits.** Claude Fable 5, Claude Mythos 5, Claude Mythos Preview, Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Sonnet 5, Claude Opus 4.6, and Claude Sonnet 4.6 support up to 128k output tokens per request. Claude Haiku 4.5, Claude Sonnet 4.5, and Claude Opus 4.5 support up to 64k. On the [Message Batches API](https://platform.claude.com/docs/en/build-with-claude/batch-processing#extended-output-beta), the `output-300k-2026-03-24` [beta header](https://platform.claude.com/docs/en/api/beta-headers) raises the limit to 300k for Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Sonnet 5, Claude Opus 4.6, and Claude Sonnet 4.6. See the [models overview](https://platform.claude.com/docs/en/about-claude/models/overview) for limits on legacy models.
+**Output limits.** Claude Fable 5, Claude Mythos 5, Claude Mythos Preview, Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Sonnet 5, Claude Opus 4.6, and Claude Sonnet 4.6 support up to 128k output tokens per request. Claude Haiku 4.5, Claude Sonnet 4.5, and Claude Opus 4.5 support up to 64k. On the [Message Batches API](https://platform.claude.com/docs/en/build-with-claude/batch-processing#extended-output-beta), the `output-300k-2026-03-24` [beta header](https://platform.claude.com/docs/en/api/beta-headers) raises the limit to 300k for Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Sonnet 5, Claude Opus 4.6, and Claude Sonnet 4.6. See each model's page under [Models](https://platform.claude.com/docs/en/models/overview) for its limits.
 
 **Long requests.** The SDKs require streaming when `max_tokens` is greater than 21,333, to avoid HTTP timeouts on long-running requests. This is a client-side validation, not an API restriction. If you don't need to process events incrementally, use `.stream()` with `.get_final_message()` (Python) or `.finalMessage()` (TypeScript) to get the complete `Message` object without handling individual events. See [Streaming Messages](https://platform.claude.com/docs/en/build-with-claude/streaming#get-the-final-message-without-handling-events). Expect longer response times when thinking is active, because generating thinking blocks adds processing time. For workloads that push thinking above roughly 32k tokens per request, use [batch processing](https://platform.claude.com/docs/en/build-with-claude/batch-processing) to avoid networking issues: such requests can run long enough to hit system timeouts and open connection limits.