599 pages for tail.

whats-new-opus-5-5 Claude Developer Platform · in the page models/opus-5-5/whats-new-opus-5-5 …request returns HTTP 200 with `stop_reason: "refusal"` and a [`stop_details`](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#refusal-response) object naming the policy are… Models overview Claude Developer Platform · in the page models/overview …most extensive and reliable. Training data cutoff (under Additional details) is the broader range of data used. See Anthropic’s Transparency Hub for details. * **Retirement:** Anthropic’s commitment f… Sonnet migration Claude Developer Platform · in the page models/sonnet-5/migration-guide …cing](https://platform.claude.com/docs/en/about-claude/pricing) for details. There are two breaking API changes for code already running on Claude Sonnet 4.6. First, [adaptive thinking](https://platfo… whats-new-sonnet-5 Claude Developer Platform · in the page models/sonnet-5/whats-new-sonnet-5 …tion-guide#migrating-from-claude-sonnet-4-6-to-claude-sonnet-5) for details. ## Next steps <CardGroup> <Card title="Models overview" icon="arrow-right" href="https://platform.claude.com/docs/en/mo… overview Claude Developer Platform · in the page release-notes/overview …uming billing for refusals that arrive before any output when `stop_details.category` is `"bio"`, `"frontier_llm"`, or `"reasoning_extraction"`, the categories where we measure low volumes of false po… claude-fable-5 Claude Developer Platform · in the page release-notes/system-prompts/claude-fable-5 …aude's product knowledge ends here; it has no documentation access, details may have changed, and it doesn't give instructions on how to use the application or other products. For anything not mention… claude-fable-5-1 Claude Developer Platform · in the page release-notes/system-prompts/claude-fable-5-1 …aude's product knowledge ends here; it has no documentation access, details may have changed, and it doesn't give instructions on how to use the application or other products. For anything not mention… claude-haiku-3-5 Claude Developer Platform · in the page release-notes/system-prompts/claude-haiku-3-5 …e information in these tags if asked but it does not know any other details of the Claude 3 model family. If asked about this, Claude should encourage the human to check the Anthropic website for more… claude-haiku-4-5 Claude Developer Platform · in the page release-notes/system-prompts/claude-haiku-4-5 …automate file and task management**. **Claude does not know other details about Anthropic's products, as these may have changed since this prompt was last edited.** Claude can provide the informatio… claude-opus-4 Claude Developer Platform · in the page release-notes/system-prompts/claude-opus-4 …provide the information here if asked, but does not know any other details about Claude models, or Anthropic's products. Claude does not offer instructions about how to use the web application. If th… claude-opus-4-1 Claude Developer Platform · in the page release-notes/system-prompts/claude-opus-4-1 …provide the information here if asked, but does not know any other details about Claude models, or Anthropic's products. Claude does not offer instructions about how to use the web application. If th… claude-opus-4-5 Claude Developer Platform · in the page release-notes/system-prompts/claude-opus-4-5 …automate file and task management**. **Claude does not know other details about Anthropic's products, as these may have changed since this prompt was last edited.** Claude can provide the informatio… claude-opus-4-6 Claude Developer Platform · in the page release-notes/system-prompts/claude-opus-4-6 …s to automate file and task management. Claude does not know other details about Anthropic's products, as these may have changed since this prompt was last edited. Claude can provide the information… claude-opus-4-7 Claude Developer Platform · in the page release-notes/system-prompts/claude-opus-4-7 …Cowork can use all of these as tools. Claude does not know further details about Anthropic's products or their capabilities, as it does not have access to their documentation and they may have change… claude-opus-4-8 Claude Developer Platform · in the page release-notes/system-prompts/claude-opus-4-8 …aude's product knowledge ends here; it has no documentation access, details may have changed, and it doesn't give instructions on how to use the application or other products. For anything not mention… claude-opus-5 Claude Developer Platform · in the page release-notes/system-prompts/claude-opus-5 …aude's product knowledge ends here; it has no documentation access, details may have changed, and it doesn't give instructions on how to use the application or other products. For anything not mention… claude-opus-5-5 Claude Developer Platform · in the page release-notes/system-prompts/claude-opus-5-5 …aude's product knowledge ends here; it has no documentation access, details may have changed, and it doesn't give instructions on how to use the application or other products. For anything not mention… claude-sonnet-3-5 Claude Developer Platform · in the page release-notes/system-prompts/claude-sonnet-3-5 …e information in these tags if asked but it does not know any other details of the Claude 3 model family. If asked about this, Claude should encourage the human to check the Anthropic website for more… claude-sonnet-3-7 Claude Developer Platform · in the page release-notes/system-prompts/claude-sonnet-3-7 …provide the information here if asked, but does not know any other details about Claude models, or Anthropic's products. Claude does not offer instructions about how to use the web application or Cla… claude-sonnet-4 Claude Developer Platform · in the page release-notes/system-prompts/claude-sonnet-4 …provide the information here if asked, but does not know any other details about Claude models, or Anthropic's products. Claude does not offer instructions about how to use the web application. If th… claude-sonnet-4-5 Claude Developer Platform · in the page release-notes/system-prompts/claude-sonnet-4-5 …automate file and task management**. **Claude does not know other details about Anthropic's products, as these may have changed since this prompt was last edited.** Claude can provide the informatio… claude-sonnet-4-6 Claude Developer Platform · in the page release-notes/system-prompts/claude-sonnet-4-6 …s to automate file and task management. Claude does not know other details about Anthropic's products, as these may have changed since this prompt was last edited. Claude can provide the information… overview Claude Developer Platform · in the page resources/overview …claude.com/docs/en/resources/overview description: Model cards with detailed documentation for Claude models. --- <CardGroup cols={3}> <Card title="Claude Opus 5.5 System Card" icon="file" href="ht… develop-tests Claude Developer Platform · in the page test-and-evaluate/develop-tests …information? Can it follow instructions not to use or share certain details? </Accordion> <Accordion title="Context utilization"> How effectively does the model use provided context? How well… handle-streaming-refusals Claude Developer Platform · in the page test-and-evaluate/strengthen-guardrails/handle-streaming-refusals …"text": "Hello.." } ], "stop_reason": "refusal", "stop_details": { "type": "refusal", "category": "cyber", "explanation": "This request was declined because it could enable cy… increase-consistency Claude Developer Platform · in the page test-and-evaluate/strengthen-guardrails/increase-consistency …stent responses. <Tip> When setting up the character, provide detailed information about the personality, background, and any specific traits or quirks. This helps the model better emulate and g… mitigate-jailbreaks Claude Developer Platform · in the page test-and-evaluate/strengthen-guardrails/mitigate-jailbreaks …instruction really came from you before acting. See those pages for details and opt-out information. </Note> ## Continuous monitoring Regularly analyze outputs for signs of successful injection. Use… reduce-latency Claude Developer Platform · in the page test-and-evaluate/strengthen-guardrails/reduce-latency …) puts message.content.first.text ``` </CodeGroup> For more details about model metrics, see the [models overview](https://platform.claude.com/docs/en/models/overview) page. ### 2. Optimize p… reduce-prompt-leak Claude Developer Platform · in the page test-and-evaluate/strengthen-guardrails/reduce-prompt-leak …for more nuanced leaks. </Note> * **Avoid unnecessary proprietary details:** If Claude doesn't need it to perform the task, don't include it. Extra content distracts Claude from focusing on "no leak… Set up Claude Code for your organization Claude Code CLI · in the page admin-setup …Next steps With provider and delivery mechanism chosen, move on to detailed configuration: * [Server-managed settings](/docs/en/server-managed-settings): deliver managed policy from the Claude admin… How the agent loop works Claude Code CLI · in the page agent-sdk/agent-loop …onments. See [Permissions](/docs/en/agent-sdk/permissions) for full details. ### Model Set the `model` option to choose which model runs the session. For more information, see [Choose a model](/docs… Use Claude Code features in the SDK Claude Code CLI · in the page agent-sdk/claude-code-features …. See [Agent Skills in the SDK](/docs/en/agent-sdk/skills) for full details. </Note> ## Hooks The SDK supports two ways to define hooks, and they run side by side: * **Filesystem hooks:** shell com… Track cost and usage Claude Code CLI · in the page agent-sdk/cost-tracking …t caching with the Claude Agent SDK. The Claude Agent SDK provides detailed token usage information for each interaction with Claude. This guide explains how to properly track usage and understand co… Give Claude custom tools Claude Code CLI · in the page agent-sdk/custom-tools …/docs/en/agent-sdk/python#tool) Python reference for full parameter details, including JSON Schema input formats and return value structure. <Tip> To make a parameter optional: in TypeScript, add `… Rewind file changes with checkpointing Claude Code CLI · in the page agent-sdk/file-checkpointing …resume the session later to rewind files. Each step is explained in detail below. The examples in this section use the prompt "Refactor the authentication module". Run them in a project that contains… Intercept and control agent behavior with hooks Claude Code CLI · in the page agent-sdk/hooks …tool name, its arguments, the session ID, and other event-specific details. </Step> <Step title="Your callback returns a decision"> After performing any operations (logging, API calls, valid… Hosting the Agent SDK Claude Code CLI · in the page agent-sdk/hosting …or self-hosted options such as Docker, gVisor, and Firecracker, and detailed isolation configuration, see [Isolation Technologies](/docs/en/agent-sdk/secure-deployment#isolation-technologies). ### Ru… Connect to external tools with MCP Claude Code CLI · in the page agent-sdk/mcp …om tools guide](/docs/en/agent-sdk/custom-tools) for implementation details. An SDK MCP server registered by an [`initialize` control request](/docs/en/agent-sdk/typescript#sdkcontrolinitializerespon… Migrate to Claude Agent SDK Claude Code CLI · in the page agent-sdk/migration-guide …t the [TypeScript SDK Reference](/docs/en/agent-sdk/typescript) for detailed API documentation * Review the [Python SDK Reference](/docs/en/agent-sdk/python) for Python-specific documentation * Learn… Modifying system prompts Claude Code CLI · in the page agent-sdk/modifying-system-prompts …et", preset: "claude_code", append: "Always include detailed docstrings and type hints in Python code." } } })) { messages.push(message); if (message.type === "assi… Observability with OpenTelemetry Claude Code CLI · in the page agent-sdk/observability …``` </CodeGroup> ## Read agent traces Traces give you the most detailed view of an agent run. With `CLAUDE_CODE_ENHANCED_TELEMETRY_BETA=1` set, each step of the agent loop becomes a span you can… Agent SDK overview Claude Code CLI · in the page agent-sdk/overview …ICENSE file. ## Next steps These resources cover deeper technical detail and example projects for building with the Agent SDK. * [Quickstart](/docs/en/agent-sdk/quickstart): build your first agent… Configure permissions Claude Code CLI · in the page agent-sdk/permissions …main(); ``` </CodeGroup> </Tab> </Tabs> ### Mode details #### Accept edits mode (`acceptEdits`) Auto-approves file operations so Claude can edit code without prompting. Other tool… Agent SDK reference - Python Claude Code CLI · in the page agent-sdk/python …See [Structured outputs](/docs/en/agent-sdk/structured-outputs) for details… Quickstart Claude Code CLI · in the page agent-sdk/quickstart …-vertex-ai), or [Microsoft Foundry](/docs/en/microsoft-foundry) for details. <Note> Unless previously approved, Anthropic does not allow third party developers to offer claude.ai login or r… Securely deploying AI agents Claude Code CLI · in the page agent-sdk/secure-deployment …erview) and the system card for the model you deploy for evaluation details. Defense in depth is still good practice though. For example, if an agent processes a malicious file that instructs it to s… Work with sessions Claude Code CLI · in the page agent-sdk/sessions …en/agent-sdk/python#choosing-between-query-and-claudesdkclient) for details on when to use `ClaudeSDKClient` vs the standalone `query()` function. ### TypeScript: `continue: true` The TypeScript SDK… Extend agents with skills Claude Code CLI · in the page agent-sdk/skills …features#control-filesystem-settings-with-settingsources). For more details on `settingSources`/`setting_sources`, see the [TypeScript SDK reference](/docs/en/agent-sdk/typescript#settingsource) or [P… Stream responses in real-time Claude Code CLI · in the page agent-sdk/streaming-output …See [structured outputs](/docs/en/agent-sdk/structured-outputs) for details. ## Next steps Now that you can stream text and tool calls in real-time, explore these related topics: * [Interactive vs… Subagents in the SDK Claude Code CLI · in the page agent-sdk/subagents …**Specialized instructions and knowledge**: each subagent can have a tailored system prompt with specific expertise, best practices, and constraints. A `database-migration` subagent can have detailed…