HomeDocs changes
Documentation changes
What the docs quietly changed.
Anthropic's published documentation, fetched on a schedule and diffed against the last copy. Every edit dated, including the ones that never made a release note.
Last poll read all 4 cleanly: Claude Code CLI, Claude Developer Platform, Claude Documentation, Model Context Protocol. A date here is when this site noticed, not when Anthropic edited.
Claude Developer Platform
821pages tracked
767 changed this week · last read 24 Oct 2026
Claude Code CLI
228pages tracked
145 changed this week · last read 24 Oct 2026
Claude Documentation
280pages tracked
65 changed this week · last read 23 Oct 2026
Model Context Protocol
357pages tracked
171 changed this week · last read 23 Oct 2026
100 on this page
10,173 of the ledger's changes in api. Show every change
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8 Oct 2026
171 pages
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api
api/beta/agents/update
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api/beta/agents/update
- `BetaManagedAgentsModel = "claude-sonnet-5-5" or "claude-opus-5-5" or "claude-fable-5-1" or 13 more or string`
- `BetaManagedAgentsModel = "claude-haiku-5-5" or "claude-sonnet-5-5" or "claude-opus-5-5" or 14 more or string`
- `"claude-haiku-5-5"`
Fastest model for high-volume, real-time tasks
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api/beta/agents/retrieve
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api/beta/agents/retrieve
- `"claude-haiku-5-5"`
Fastest model for high-volume, real-time tasks
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api/beta/agents/list
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api/beta/agents/list
- `"claude-haiku-5-5"`
Fastest model for high-volume, real-time tasks
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api/beta/agents/create
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api/beta/agents/create
- `BetaManagedAgentsModel = "claude-sonnet-5-5" or "claude-opus-5-5" or "claude-fable-5-1" or 13 more or string`
- `BetaManagedAgentsModel = "claude-haiku-5-5" or "claude-sonnet-5-5" or "claude-opus-5-5" or 14 more or string`
- `"claude-haiku-5-5"`
Fastest model for high-volume, real-time tasks
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api/beta/agents/archive
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api/beta/agents/archive
- `"claude-haiku-5-5"`
Fastest model for high-volume, real-time tasks
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api/beta/agents
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api/beta/agents
- `BetaManagedAgentsModel = "claude-sonnet-5-5" or "claude-opus-5-5" or "claude-fable-5-1" or 13 more or string`
- `BetaManagedAgentsModel = "claude-haiku-5-5" or "claude-sonnet-5-5" or "claude-opus-5-5" or 14 more or string`
- `"claude-haiku-5-5"`
Fastest model for high-volume, real-time tasks
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api/beta
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api/beta
Whether the model supports code execution tools.
Whether code that the model runs in the code execution tool can call the request's other tools, as in programmatic tool calling and dynamic filtering for web search and web f
- `server_tools: BetaServerToolsCapability`
Whether this model supports the web search and code execution server tools. `supported` is true when the model supports at least one of the tools. A supported tool can still
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agents-and-tools/tool-use/overview
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agents-and-tools/tool-use/overview
| Model | Tool use system prompt tokens: auto, none
| :------------------------------------------------------------------------------------------------------------------------------------ | :----------------------------------------
| Claude Opus 5.5 | 286 tokens
| Claude Opus 5 | 286 tokens
| Claude Opus 4.8 | 290 tokens
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about-claude/use-case-guides/legal-summarization
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about-claude/use-case-guides/legal-summarization
Model accuracy is extremely important when summarizing legal documents. Claude Opus 5 is an excellent choice for use cases such as this where high accuracy is required. If the size
Model accuracy is extremely important when summarizing legal documents. Claude Opus 5 is an excellent choice for use cases such as this where high accuracy is required. If the size
* Input tokens: 86M (assuming 1 token per 3.5 characters)
* Output tokens per summary: 350
* Total output tokens: 350,000
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about-claude/use-case-guides/customer-support-chat
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about-claude/use-case-guides/customer-support-chat
For customer support chat, Claude Opus 5 is well suited to balance intelligence, latency, and cost, including the most complex support scenarios that require deep reasoning across
For customer support chat, Claude Opus 5 is well suited to balance intelligence, latency, and cost, including the most complex support scenarios that require deep reasoning across
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about-claude/pricing
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about-claude/pricing
| Model | Base input tokens | 5m cache writes |
| :------------------------------------------------------------------------------------------------------------------------------------ | :-------------------- | :-------------- |
| Claude Fable 5.1 | $10 / MTok | $12.50 / MTok |
| Claude Mythos 5.1 ([limited availability](https://support.claude.com/en/articles/14604842)) | $10 / MTok | $12.50 / MTok |
| Claude Fable 5 | $10 / MTok | $12.50 / MTok |
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about-claude/models/optimizing-for-cost-and-intelligence
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about-claude/models/optimizing-for-cost-and-intelligence
13. **Chartography:** Surge AI, "Chartography," 2026. The complete released 100-question set, measured August 6 and 9, 2026 (Claude Opus 5 alone) and September 20, 2026 (Claude Opu
13. **Chartography:** Surge AI, "Chartography," 2026. The complete released 100-question set, measured August 6 and 9, 2026 (Claude Opus 5 alone) and September 20, 2026 (Claude Opu
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7 Oct 2026
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models/sonnet-5/overview
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models/sonnet-5/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/sonnet-5-5/overview
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models/sonnet-5-5/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
| [Cache read](https://platform.claude.com/docs/en/build-with-claude/prompt-caching) | $0.20 / MTok |
| [Cache read](https://platform.claude.com/docs/en/build-with-claude/prompt-caching) | $0.10 / MTok |
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models/sonnet-4-6/overview
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models/sonnet-4-6/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/sonnet-4-5/overview
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models/sonnet-4-5/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/overview
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models/overview
* **Pricing:** Base price per million tokens. Batch API requests are 50% off; prompt cache reads cost 10% of the base input price (2.5% on Claude Fable 5.1 and Claude Mythos 5.1, 5
* **Pricing:** Base price per million tokens. Batch API requests are 50% off; prompt cache reads cost 10% of the base input price (2.5% on Claude Fable 5.1 and Claude Mythos 5.1, 5
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models/opus-5/overview
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models/opus-5/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/opus-5-5/overview
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models/opus-5-5/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/opus-4-8/overview
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models/opus-4-8/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/opus-4-7/overview
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models/opus-4-7/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/opus-4-6/overview
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models/opus-4-6/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/opus-4-5/overview
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models/opus-4-5/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/mythos-5/overview
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models/mythos-5/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/mythos-5-1/overview
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models/mythos-5-1/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/haiku-4-5/overview
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models/haiku-4-5/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/fable-5/overview
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models/fable-5/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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models/fable-5-1/overview
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models/fable-5-1/overview
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
* **Price / MTok:** Input / output, base price per million tokens. Batch API requests are 50% off; prompt caching reads cost 10% of the base input price (2.5% on Claude Fable 5.1 a
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build-with-claude/prompt-caching
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build-with-claude/prompt-caching
| Claude Sonnet 5.5 | $2 / MTok | $2.50 / MTok | $4 /
| Claude Sonnet 5.5 | $2 / MTok | $2.50 / MTok | $4 /
*<sup>2 Cache hits and refreshes on Claude Opus 5.5 are priced at 0.05x the base input price.</sup>*
*<sup>2 Cache hits and refreshes on Claude Opus 5.5 and Claude Sonnet 5.5 are priced at 0.05x the base input price.</sup>*
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about-claude/pricing
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| Claude Sonnet 5.5 | $2 / MTok | $2.50 / MTok |
| Claude Sonnet 5.5 | $2 / MTok | $2.50 / MTok |
*<sup>2 Cache hits and refreshes on Claude Opus 5.5 are priced at 0.05x the base input price.</sup>*
*<sup>2 Cache hits and refreshes on Claude Opus 5.5 and Claude Sonnet 5.5 are priced at 0.05x the base input price.</sup>*
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test-and-evaluate/strengthen-guardrails/reduce-latency
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test-and-evaluate/strengthen-guardrails/reduce-latency
description: Reduce Claude's response latency by choosing a faster model like Claude Haiku 4.5, trimming prompt and output tokens, and streaming responses.
description: Reduce Claude's response latency by choosing a faster model like Claude Haiku 5.5, trimming prompt and output tokens, and streaming responses.
For speed-critical applications, **Claude Haiku 4.5** offers the fastest response times while maintaining high intelligence:
For speed-critical applications, **Claude Haiku 5.5** offers the fastest response times while maintaining high intelligence. [Effort](https://platform.claude.com/docs/en/build-with
# For time-sensitive applications, use Claude Haiku 4.5
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test-and-evaluate/strengthen-guardrails/mitigate-jailbreaks
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test-and-evaluate/strengthen-guardrails/mitigate-jailbreaks
* **Harmlessness screens:** Use a lightweight model like Claude Haiku 4.5 to pre-screen user input before it reaches your main conversation. Use [structured outputs](https://platfo
* **Harmlessness screens:** Use a lightweight model like Claude Haiku 5.5 to pre-screen user input before it reaches your main conversation. Use [structured outputs](https://platfo
* **Screen tool outputs before Claude acts on them.** Apply the same lightweight-model screening pattern you use for user input to the content your tools return. Run each tool, pas
* **Screen tool outputs before Claude acts on them.** Apply the same lightweight-model screening pattern you use for user input to the content your tools return. Run each tool, pas
If `injection_suspected` is `true`, return an error or a stripped summary in the `tool_result` block instead of the raw content, and consider surfacing the attempt to the user.
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test-and-evaluate/develop-tests
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![Flowchart of prompt engineering: test cases, preliminary prompt, iterative testing and refinement, final validation, ship](https://platform.claude.com/docs/images/how-to-prompt-e
<Frame>
![Flowchart of prompt engineering: test cases, preliminary prompt, iterative testing and refinement, final validation, ship](https://platform.claude.com/docs/images/how-to-prompt
</Frame>
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resources/overview
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resources/overview
<Card title="Claude Haiku 5.5 System Card" icon="file" href="https://www.anthropic.com/document/claude-haiku-5-5-system-card">
Detailed documentation of Claude Haiku 5.5.
</Card>
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release-notes/system-prompts/overview
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release-notes/system-prompts/overview
<Card id="claude-haiku-5-5" title="Claude Haiku 5.5" icon="file" href="https://platform.claude.com/docs/en/release-notes/system-prompts/claude-haiku-5-5" />
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release-notes/overview
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release-notes/overview
### October 8, 2026
* The [Compliance API](https://platform.claude.com/docs/en/manage-claude/compliance-api) chat endpoints now also return chats from the unified Claude experience, in beta for Claude
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models/sonnet-5/overview
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| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cuto
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :-------------
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Adaptive (always on) | `medium` | Jun 2026
| [Claude Sonnet 5.5](https://platform.claude.com/docs/en/models/sonnet-5-5/overview) | 1M | 128K | $2 / $10 | Adaptive | `high` | Jun 2026
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models/sonnet-5-5/whats-new-sonnet-5-5
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models/sonnet-5-5/whats-new-sonnet-5-5
Claude Sonnet 5.5 has the same prices as Claude Sonnet 5, including prompt caching and batch processing rates. See [Pricing](https://platform.claude.com/docs/en/about-claude/pricin
Claude Sonnet 5.5 has the same prices as Claude Sonnet 5, except for prompt cache reads, which cost $0.10 USD per million tokens, half the Claude Sonnet 5 rate. See [Pricing](https
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models/sonnet-5-5/overview
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| Model | Context | Max output | Price / MTok | Latency | Thinking | Default effort | Knowl
| :-------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------- | :------------------- | :------------- | :----
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Slower | Adaptive (always on) | `high` | Jun 2
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Moderate | Adaptive (always on) | `medium` | Jun 2
| **Claude Sonnet 5.5** (this model) | 1M | 128K | $2 / $10 | Fast | Adaptive | `high` | Jun 2
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models/sonnet-5-5/migration-guide
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Claude Sonnet 5.5 has the same prices as Claude Sonnet 5. See [Claude pricing](https://platform.claude.com/docs/en/about-claude/pricing). For its context window and output limits,
Claude Sonnet 5.5 has the same prices as Claude Sonnet 5, except for prompt cache reads, which cost $0.10 USD per million tokens, half the Claude Sonnet 5 rate. See [Claude pricing
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| Model | Context | Max output | Price / MTok | Thinking | Default effort | Know
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :----------------------------- | :------------- | :---
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Adaptive (always on) | `medium` | Jun
| [Claude Sonnet 5.5](https://platform.claude.com/docs/en/models/sonnet-5-5/overview) | 1M | 128K | $2 / $10 | Adaptive | `high` | Jun
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| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cuto
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :-------------
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Adaptive (always on) | `medium` | Jun 2026
| [Claude Sonnet 5.5](https://platform.claude.com/docs/en/models/sonnet-5-5/overview) | 1M | 128K | $2 / $10 | Adaptive | `high` | Jun 2026
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models/overview
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models/overview
| Feature | Claude Fable 5.1
| :-------------------------------------------------------------------------------------------------------- | :---------------------------------------------------------------------
| Description | For demanding reasoning and long-horizon agentic work
| Model page | [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-
| Comparative latency | Slower
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models/opus-5/overview
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| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cuto
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :-------------
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Adaptive (always on) | `medium` | Jun 2026
| **Claude Opus 5** (this model) | 1M | 128K | $5 / $25 | Adaptive | `high` | May 2026
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models/opus-5-5/overview
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| Model | Context | Max output | Price / MTok | Latency | Thinking | Default effort | Kno
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------- | :------------------- | :------------- | :--
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Slower | Adaptive (always on) | `high` | Jun
| **Claude Opus 5.5** (this model) | 1M | 128K | $4 / $20 | Moderate | Adaptive (always on) | `medium` | Jun
| [Claude Sonnet 5.5](https://platform.claude.com/docs/en/models/sonnet-5-5/overview) | 1M | 128K | $2 / $10 | Fast | Adaptive | `high` | Jun
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| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cuto
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :-------------
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Adaptive (always on) | `medium` | Jun 2026
| **Claude Opus 4.8** (this model) | 1M | 128K | $5 / $25 | Adaptive | `high` | Jan 2026
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| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cuto
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :-------------
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Adaptive (always on) | `medium` | Jun 2026
| **Claude Opus 4.7** (this model) | 1M | 128K | $5 / $25 | Adaptive | `high` | Jan 2026
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| Model | Context | Max output | Price / MTok | Thinking | Default effort | Know
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :----------------------------- | :------------- | :---
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Adaptive (always on) | `medium` | Jun
| **Claude Opus 4.6** (this model) | 1M | 128K | $5 / $25 | Adaptive (extended deprecated) | `high` | May
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| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cuto
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :-------------
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Adaptive (always on) | `medium` | Jun 2026
| **Claude Opus 4.5** (this model) | 200K | 64K | $5 / $25 | Extended | `high` | May 2025
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| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cuto
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :-------------
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026
| **Claude Mythos 5** (this model) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jan 2026
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Adaptive (always on) | `medium` | Jun 2026
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| Model | Context | Max output | Price / MTok | Latency | Thinking | Default effort | Kno
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------- | :------------------- | :------------- | :--
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Slower | Adaptive (always on) | `high` | Jun
| **Claude Mythos 5.1** (this model) | 1M | 128K | $10 / $50 | Slower | Adaptive (always on) | `high` | Jun
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Moderate | Adaptive (always on) | `medium` | Jun
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models/haiku-4-5/overview
description: "Claude Haiku 4.5 at a glance: what it's for, model IDs on every platform, context window, output limits, pricing, availability, and the guides and resources for build
description: "Claude Haiku 4.5 reference: lifecycle status, model IDs on every platform, context window, output limits, pricing, and migration resources. Claude Haiku 5.5 is the cu
**Latest.** Released October 15, 2025.
**Legacy.** Released October 15, 2025.
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models/fable-5/overview
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| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cuto
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :-------------
| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026
| **Claude Fable 5** (this model) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jan 2026
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Adaptive (always on) | `medium` | Jun 2026
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| Model | Context | Max output | Price / MTok | Latency | Thinking | Default effort | Kno
| :---------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------- | :------------------- | :------------- | :--
| **Claude Fable 5.1** (this model) | 1M | 128K | $10 / $50 | Slower | Adaptive (always on) | `high` | Jun
| [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) | 1M | 128K | $4 / $20 | Moderate | Adaptive (always on) | `medium` | Jun
| [Claude Sonnet 5.5](https://platform.claude.com/docs/en/models/sonnet-5-5/overview) | 1M | 128K | $2 / $10 | Fast | Adaptive | `high` | Jun
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ARG ANT_VERSION=1.38.0
ARG ANT_VERSION=1.39.0
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managed-agents/reference
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| Type | Description
| ---------------- | -----------------------------------------------------------------------------------------------------------------------------------------------------------
| `system.message` | Append privileged system-level context that applies to the accompanying turn and all subsequent turns. Supported on Claude Fable 5.1, Claude Mythos 5.1, Cl
| Type | Description
| ---------------- | -----------------------------------------------------------------------------------------------------------------------------------------------------------
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VERSION=1.38.0
VERSION=1.39.0
implementation("com.anthropic:anthropic-java:2.68.0")
implementation("com.anthropic:anthropic-java:2.69.0")
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`system.message` is supported by Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5.5, Claude Opus 5, Claude Opus 4.8, and Claude Sonnet 5.5. If
`system.message` is supported by Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5.5, Claude Opus 5, Claude Opus 4.8, Claude Sonnet 5.5, and Cla
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Host your AI security server where Anthropic can reach it: an `https://` URL on port 443, on a publicly routable host (private, loopback, and carrier-grade NAT ranges are refused a
Host your AI security server where Anthropic can reach it: an `https://` URL on port 443, on a publicly routable host (private, loopback, and carrier-grade NAT ranges are refused a
| Block `type` | Fields
| ------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------
| `text` | `text`: the text content.
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Inference hooks activity is recorded in your organization's [Activity Feed](https://platform.claude.com/docs/en/manage-claude/compliance-activity-feed): configuration changes, deni
Inference hooks activity is recorded in your organization's [Activity Feed](https://platform.claude.com/docs/en/manage-claude/compliance-activity-feed): configuration changes, deni
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 also deletes the sessions in the cloud that were st
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intro
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* [Claude Haiku 4.5](https://platform.claude.com/docs/en/models/haiku-4-5/overview) (`claude-haiku-4-5`) — *The fastest model with near-frontier intelligence* — Fastest · Lowest co
* [Claude Haiku 5.5](https://platform.claude.com/docs/en/models/haiku-5-5/overview) (`claude-haiku-5-5`) — New — *For high-volume, latency-sensitive tasks such as classification, e
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home
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home
* [Claude Haiku 4.5](https://platform.claude.com/docs/en/models/haiku-4-5/overview) (`claude-haiku-4-5`) — *The fastest model with near-frontier intelligence* — Fastest · Lowes
* [Claude Haiku 5.5](https://platform.claude.com/docs/en/models/haiku-5-5/overview) (`claude-haiku-5-5`) — New — *For high-volume, latency-sensitive tasks such as classificatio
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get-started
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implementation("com.anthropic:anthropic-java:2.68.0")
implementation("com.anthropic:anthropic-java:2.69.0")
<version>2.68.0</version>
<version>2.69.0</version>
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For more details on tool use, see [Tool use with Claude](https://platform.claude.com/docs/en/agents-and-tools/tool-use/overview).
For more details on tool use, see [Tool use with Claude](https://platform.claude.com/docs/en/agents-and-tools/tool-use/overview). To run the browser use tool or the computer use to
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To run the browser use tool or the computer use tool with this SDK, see [Browser and computer use with the SDK toolsets](https://platform.claude.com/docs/en/agents-and-tools/tool-u
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implementation("com.anthropic:anthropic-java:2.68.0")
implementation("com.anthropic:anthropic-java:2.69.0")
<version>2.68.0</version>
<version>2.69.0</version>
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VERSION=1.38.0
VERSION=1.39.0
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claude_api_primer
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For fast, cost-effective tasks: Claude Haiku 4.5: claude-haiku-4-5-20251001
For fast, cost-effective tasks: Claude Haiku 5.5: claude-haiku-5-5
Previous Haiku model: Claude Haiku 4.5: claude-haiku-4-5-20251001
* Claude Haiku 5.5 (`claude-haiku-5-5`, adaptive thinking only, on by default)
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build-with-claude/working-with-messages
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On Claude Fable 5.1, [Claude Mythos 5.1](https://platform.claude.com/docs/en/models/mythos-5-1/overview), Claude Fable 5, [Claude Mythos 5](https://platform.claude.com/docs/en/mode
On Claude Fable 5.1, [Claude Mythos 5.1](https://platform.claude.com/docs/en/models/mythos-5-1/overview), Claude Fable 5, [Claude Mythos 5](https://platform.claude.com/docs/en/mode
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| Claude Haiku 5.5 | Adaptive only | On | `"enabled"`, `"disabled"`2 |
*2 Claude Opus 5 accepts `"disabled"` at [effort](https://platform.claude.com/docs/en/build-with-claude/effort) `high` or below; combining it with effort `xhigh` or `max` returns a
*2 Claude Opus 5 and Claude Haiku 5.5 accept `"disabled"` at [effort](https://platform.claude.com/docs/en/build-with-claude/effort) `high` or below; combining it with effort `xhigh
Models marked `Always on` cannot turn thinking off. Models marked `On` default to thinking. Claude Opus 5 and Claude Sonnet 5 accept `thinking: {type: "disabled"}`. On Claude Sonne
Models marked `Always on` cannot turn thinking off. Models marked `On` default to thinking. Claude Opus 5, Claude Sonnet 5, and Claude Haiku 5.5 accept `thinking: {type: "disabled"
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| Effort level | Thinking behavior |
| ------------------------------------- | ------------------------------------------------------------------------------------------------ |
| `max` | Claude thinks the most readily and at the greatest depth, with no constraint on thinking length. |
| `xhigh` | Claude thinks more readily and at greater depth than at `high`, suited to extended exploration. |
| `high` (default on most models) | Claude thinks on most requests that benefit from it. Provides deep reasoning on complex tasks. |
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build-with-claude/thinking
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| Claude Haiku 5.5 | Adaptive thinking | Adaptive thinking | 400 error | 400 error | Thinking off at `high` effo
On Claude Opus 5.5, Claude Opus 5, Claude Sonnet 5.5, Claude Sonnet 5, Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, and Claude Mythos Preview, thinking is
On Claude Opus 5.5, Claude Opus 5, Claude Sonnet 5.5, Claude Sonnet 5, Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Mythos Preview, and Claude Haiku
Claude Haiku 5.5 also has thinking on by default and accepts `thinking: {type: "disabled"}` at [effort](https://platform.claude.com/docs/en/build-with-claude/effort) `high` or belo
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- claude-haiku-5-5
| Claude Haiku 5.5 | Beta (set `task-budgets-2026-03-13` header) |
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build-with-claude/refusals-and-fallback
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build-with-claude/refusals-and-fallback
description: How Claude Fable models, Claude Opus models, and Claude Sonnet 5.5 return classifier refusals and how to retry refused requests on a fallback model.
description: How Claude Fable models, Claude Opus models, Claude Sonnet 5.5, and Claude Haiku 5.5 return classifier refusals and how to retry refused requests on a fallback model.
Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, Claude Opus 5, and Claude Sonnet 5.5 include safety classifiers that can decline a request. When that happens, you receive a norm
Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, Claude Opus 5, Claude Sonnet 5.5, and Claude Haiku 5.5 include safety classifiers that can decline a request. When that happens,
Server-side fallback is in beta on the Claude API. The `fallbacks` parameter is not supported on the [Message Batches API](https://platform.claude.com/docs/en/build-with-claude/b
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build-with-claude/prompt-engineering/claude-prompting-best-practices
This is the reference for prompt engineering with current Claude models, including Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5.5, Claude Opu
This is the reference for prompt engineering with current Claude models, including Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5.5, Claude Opu
For an overview of model capabilities, see the [models overview](https://platform.claude.com/docs/en/models/overview). For Claude Fable 5.1 capabilities and API changes, see [Wha
For an overview of model capabilities, see the [models overview](https://platform.claude.com/docs/en/models/overview). For Claude Fable 5.1 capabilities and API changes, see [Wha
| Claude Haiku 5.5 | [Prompting Claude Haiku 5.5](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-claude-haiku-5-5) | Dif
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build-with-claude/prompt-caching
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| Claude Haiku 5.5 (for prompts up to 100,000 tokens) | $0.10 / MTok | $0.125 / MTok | $0.2
| Claude Haiku 5.5 (for prompts over 100,000 tokens) | $0.50 / MTok | $0.625 / MTok | $1 /
* **Cache reads:** When cached content is used (10% of base input token price, or 2.5% on Claude Fable 5.1 and Claude Mythos 5.1, and 5% on Claude Opus 5.5)
* **Cache reads:** When cached content is used (10% of base input token price, or 2.5% on Claude Fable 5.1 and Claude Mythos 5.1, and 5% on Claude Opus 5.5 and Claude Sonnet 5.5)
* 512 tokens for Claude Fable 5.1, [Claude Mythos 5.1](https://platform.claude.com/docs/en/models/mythos-5-1/overview), Claude Opus 5.5, Claude Opus 5, Claude Sonnet 5.5, Claude Fa
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build-with-claude/preserved-thinking
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Claude Sonnet 5.5's thinking blocks are also tied to the account that produced them. See [Thinking blocks stay with the account that produced them](https://platform.claude.com/docs
Thinking blocks from Claude Sonnet 5.5 and Claude Haiku 5.5 are also tied to the account that produced them. See [Thinking blocks stay with the account that produced them](https://
Also check your integration if it sends Claude Sonnet 5.5 thinking blocks from one account in a request made by a different account. See [Thinking blocks stay with the account that
Also check your integration if it sends Claude Sonnet 5.5 or Claude Haiku 5.5 thinking blocks from one account in a request made by a different account. See [Thinking blocks stay w
Claude Opus 5.5 reads thinking blocks from Claude Opus 5, from earlier Opus, Sonnet, and Haiku models, and, on the Claude API and Google Cloud, from Claude Sonnet 5.5, but not from
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build-with-claude/mid-conversation-system-messages
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This feature is available on Claude Fable 5.1, [Claude Mythos 5.1](https://platform.claude.com/docs/en/models/mythos-5-1/overview), Claude Fable 5, [Claude Mythos 5](https://plat
This feature is available on Claude Fable 5.1, [Claude Mythos 5.1](https://platform.claude.com/docs/en/models/mythos-5-1/overview), Claude Fable 5, [Claude Mythos 5](https://plat
A `role: "system"` message can also carry `output_config.effort` to change the [effort](https://platform.claude.com/docs/en/build-with-claude/effort) level partway through a conver
A `role: "system"` message can also carry `output_config.effort` to change the [effort](https://platform.claude.com/docs/en/build-with-claude/effort) level partway through a conver
The main use is a per-turn reminder in a tool loop. Append the reminder after the `tool_result` message each time you want the model to see it, and leave every earlier copy where i
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build-with-claude/handling-stop-reasons
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A refused request on Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, Claude Opus 5, or Claude Sonnet 5.5 can usually be served by retrying on another Claude model. [Refusals and
A refused request on Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, Claude Opus 5, Claude Sonnet 5.5, or Claude Haiku 5.5 can usually be served by retrying on another Claude mo
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build-with-claude/extended-thinking
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* You use Claude 4.7 or a later model, such as Claude Opus 5.5, Claude Sonnet 5, Claude Sonnet 5.5, or Claude Fable 5.1, where `type: "enabled"` returns a 400 error.
* You use Claude 4.7 or a later model, such as Claude Opus 5.5, Claude Sonnet 5, Claude Sonnet 5.5, Claude Fable 5.1, or Claude Haiku 5.5, where `type: "enabled"` returns a 400 err
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- claude-haiku-5-5
Most Claude models default to high effort, spending as many tokens as needed for excellent results; Claude Opus 5.5 defaults to medium. You can raise the effort level to `max` for
Most Claude models default to high effort, spending as many tokens as needed for excellent results; Claude Opus 5.5 and Claude Haiku 5.5 default to medium. You can raise the effort
Setting `effort` to the model's default (`"medium"` on Claude Opus 5.5, `"high"` on other models) produces exactly the same behavior as omitting the `effort` parameter entirely.
Setting `effort` to the model's default (`"medium"` on Claude Opus 5.5 and Claude Haiku 5.5, `"high"` on other models) produces exactly the same behavior as omitting the `effort`
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build-with-claude/context-windows
<Frame>
</Frame>
Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5.5, Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Opus 4.6, Claude Sonnet 5.5, Claude S
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api
build-with-claude/context-editing
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build-with-claude/context-editing
| Haiku | (none) | All models through Claude Haiku 4.5 |
| Haiku | Claude Haiku 5.5 and later | Claude Haiku 4.5 and earlier |
On Claude Fable 5.1, Claude Opus 5.5, and Claude Sonnet 5.5, server-side context management never invalidates thinking blocks. Client-side edits to earlier turns can invalidate the
On Claude Fable 5.1, Claude Opus 5.5, Claude Sonnet 5.5, and Claude Haiku 5.5, server-side context management never invalidates thinking blocks. Client-side edits to earlier turns
| Configuration option | Default | Description
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api
build-with-claude/compaction-threshold
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build-with-claude/compaction-threshold
- claude-haiku-5-5
On Claude Fable 5.1, Claude Mythos 5.1, Claude Opus 5.5, and Claude Sonnet 5.5, thinking blocks from before a `compaction` block aren't carried forward, so the summary is all the m
On Claude Fable 5.1, Claude Mythos 5.1, Claude Opus 5.5, Claude Sonnet 5.5, and Claude Haiku 5.5, thinking blocks from before a `compaction` block aren't carried forward, so the su
On Claude Fable 5.1, Claude Opus 5.5, and Claude Sonnet 5.5, remove the `thinking` and `redacted_thinking` blocks from any assistant turn you re-insert after the compaction block,
On Claude Fable 5.1, Claude Opus 5.5, Claude Sonnet 5.5, and Claude Haiku 5.5, remove the `thinking` and `redacted_thinking` blocks from any assistant turn you re-insert after the
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api
build-with-claude/compaction-thinking-blocks
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build-with-claude/compaction-thinking-blocks
- claude-haiku-5-5
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api
build-with-claude/compaction-on-demand
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build-with-claude/compaction-on-demand
- claude-haiku-5-5
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build-with-claude/compaction-keep-recent-turns
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build-with-claude/compaction-keep-recent-turns
- claude-haiku-5-5
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api
build-with-claude/compaction-background
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build-with-claude/compaction-background
- claude-haiku-5-5
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build-with-claude/claude-platform-on-aws
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build-with-claude/claude-platform-on-aws
implementation("com.anthropic:anthropic-java:2.68.0")
implementation("com.anthropic:anthropic-java-aws:2.68.0")
implementation("com.anthropic:anthropic-java:2.69.0")
implementation("com.anthropic:anthropic-java-aws:2.69.0")
<version>2.68.0</version>
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api
build-with-claude/claude-on-vertex-ai
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build-with-claude/claude-on-vertex-ai
implementation("com.anthropic:anthropic-java:2.68.0")
implementation("com.anthropic:anthropic-java-vertex:2.68.0")
implementation("com.anthropic:anthropic-java:2.69.0")
implementation("com.anthropic:anthropic-java-vertex:2.69.0")
<version>2.68.0</version>
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build-with-claude/claude-on-amazon-bedrock-legacy
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build-with-claude/claude-on-amazon-bedrock-legacy
implementation("com.anthropic:anthropic-java:2.68.0")
implementation("com.anthropic:anthropic-java-bedrock:2.68.0")
implementation("com.anthropic:anthropic-java:2.69.0")
implementation("com.anthropic:anthropic-java-bedrock:2.69.0")
<version>2.68.0</version>
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api
build-with-claude/claude-in-microsoft-foundry
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build-with-claude/claude-in-microsoft-foundry
This guide shows you how to set up and make API calls to Claude in Microsoft Foundry using one of Anthropic's client SDKs or direct HTTP requests. When you access Claude in Microso
This guide shows you how to set up and make API calls to Claude in Microsoft Foundry using one of Anthropic's client SDKs or direct HTTP requests. When you access Claude in Microso
implementation("com.anthropic:anthropic-java:2.68.0")
implementation("com.anthropic:anthropic-java-foundry:2.68.0")
implementation("com.anthropic:anthropic-java:2.69.0")
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api
build-with-claude/claude-in-amazon-bedrock
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build-with-claude/claude-in-amazon-bedrock
implementation("com.anthropic:anthropic-java:2.68.0")
implementation("com.anthropic:anthropic-java-bedrock:2.68.0")
implementation("com.anthropic:anthropic-java:2.69.0")
implementation("com.anthropic:anthropic-java-bedrock:2.69.0")
<version>2.68.0</version>
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api
build-with-claude/batch-processing
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build-with-claude/batch-processing
| Claude Haiku 5.5 (for prompts up to 100,000 tokens) | $0.05 / MTok | $0.25 / MTok |
| Claude Haiku 5.5 (for prompts over 100,000 tokens) | $0.25 / MTok | $1.25 / MTok |
The `output-300k-2026-03-24` beta header raises the `max_tokens` cap to 300,000 for batch requests using Claude Opus 5.5, Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Op
The `output-300k-2026-03-24` beta header raises the `max_tokens` cap to 300,000 for batch requests using Claude Opus 5.5, Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Op
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api
api/service-tiers
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api/service-tiers
Priority Tier is supported on all available Claude models except Claude Fable 5.1, Claude Mythos 5.1, Claude Mythos 5, [Claude Mythos Preview](https://anthropic.com/glasswing), Cla
Priority Tier is supported on all available Claude models except Claude Fable 5.1, Claude Haiku 5.5, Claude Mythos 5.1, Claude Mythos 5, [Claude Mythos Preview](https://anthropic.c
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api/rate-limits
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api/rate-limits
| Claude Haiku 5.5 | 1,000 | 2,
| Claude Haiku 5.5 | 5,000 | 5,
| Claude Haiku 5.5 | 10,000 | 10
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