978 pages for system.

effort Claude Developer Platform · in the page build-with-claude/effort …ocs/en/build-with-claude/effort-per-message) sets a new level with a `system` message in `messages`. ### Top-level effort on the next request The top-level `output_config.effort` applies to the whol… effort-per-message Claude Developer Platform · in the page build-with-claude/effort-per-message …e.com/docs/en/build-with-claude/effort-per-message description: Use a system message to change the effort level partway through a conversation and keep the prompt cache. featureMetadata: status: bet… This will automatically use the environment variable VOYAGE_API_KEY. Claude Developer Platform · in the page build-with-claude/embeddings …vide water, irrigation, and habitat for aquatic species, vital for ecosystems.", "Apple's conference call to discuss fourth fiscal quarter results and business updates is scheduled for Thursday, N… extended-thinking Claude Developer Platform · in the page build-with-claude/extended-thinking …o think beyond 32k tokens produces long-running requests that can hit system timeouts and open-connection limits. To track what a budget actually costs you, monitor the `usage.output_tokens_details.t… fallback-credit Claude Developer Platform · in the page build-with-claude/fallback-credit …------------------------------------ | | Must match exactly | `system`, `messages`, `tools`, `tool_choice`, `thinking`, and `cache_control`, plus `output_config`, `mcp_servers`, `context_manage… files Claude Developer Platform · in the page build-with-claude/files ….build()) .build() ); String fileId = file.id(); System.out.println(fileId); ``` ```php PHP $file = $client->files->upload( file: FileParam::fromResource(fopen('/path… handling-stop-reasons Claude Developer Platform · in the page build-with-claude/handling-stop-reasons …content: "6912" }] } ]; ``` ```csharp C# using System.Text.Json; using Anthropic.Models.Messages; var input = JsonSerializer.Deserialize<Dictionary<string, JsonElement>… message-threads Claude Developer Platform · in the page build-with-claude/message-threads …bility: not-eligible note: A thread's contents (the conversation, system prompt, and tools) are held in memory, encrypted under a server-managed key, never written to durable storage, and deleted… mid-conversation-effort-example Claude Developer Platform · in the page build-with-claude/mid-conversation-effort-example …ent for multiagent fan-out, switched on and off with mid-conversation system messages. --- An orchestration mode is a session-level switch: when it is on, the model puts maximum thoroughness behind e… multilingual-support Claude Developer Platform · in the page build-with-claude/multilingual-support …target language explicitly. The most reliable place to do this is the system prompt, which keeps the instruction stable across every turn of a conversation. <CodeGroup> ```bash cURL curl https://… overview Claude Developer Platform · in the page build-with-claude/overview …n. | | [Mid-conversation system messages](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages)… pdf-support Claude Developer Platform · in the page build-with-claude/pdf-support ….build(); Message message = client.messages().create(params); System.out.println(message.content()); ``` ```php PHP $client = new Client(); $message = $client->messages->create(… preserved-thinking Claude Developer Platform · in the page build-with-claude/preserved-thinking …stable --- The API checks each block: * **Prefix:** The top-level `system` prompt, `tools`, and `messages` before a block are its prefix. If the prefix differs from what you sent when the block was… Request 2 caches its request content (not the response) Claude Developer Platform · in the page build-with-claude/prompt-caching …a single `cache_control` field at the top level of your request. The system automatically applies the cache breakpoint to the last cacheable block and moves it forward as conversations grow. Best for… claude-prompting-best-practices Claude Developer Platform · in the page build-with-claude/prompt-engineering/claude-prompting-best-practices …s, covering clarity, examples, XML structuring, thinking, and agentic systems. --- This is the reference for prompt engineering with current Claude models, including Claude Fable 5.2, Claude Mythos 5… prompting-claude-fable-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-fable-5 …ied problems.** Early testers reported single-pass implementations of systems that previously took days of iteration. * **Vision.** Claude Fable 5 interprets dense technical images, web applications,… Delivering work Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-fable-5-1 …Some earlier models gave frequent updates while working, which led to system prompt lines such as “hold all findings for the final response.” Remove lines like that before adding anything. If you sti… Finishing work Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-fable-5-2 …eering/prompting-claude-fable-5-2#keep-caution-from-piling-up) * Your system prompt, skills, or harness was written for Claude Fable 5.1 or Claude Opus 5.5: [Review prompts and harnesses designed for… prompting-claude-haiku-5-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-haiku-5-5 …n tools, early stopping, coding verification, mid-turn user messages, system prompt adherence in chatbots, reasoning in user-facing text, and refusals." --- This guide covers the prompting patterns s… prompting-claude-opus-4-8 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-opus-4-8 …since Claude Opus 4.7 (1M context window default and mid-conversation system messages), see [Migrating to Claude Opus 5.5 from Claude Opus 4.7](https://platform.claude.com/docs/en/models/opus-5-5/migr… prompting-claude-opus-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-opus-5 …ess an in-depth explanation is specifically requested. ``` In a long system prompt, pair the instruction with a short reminder near the end of the prompt: ```text wrap <tone_preference> Keep outputs… prompting-claude-opus-5-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-opus-5-5 …ause the model thinks at length first: [Thinking instructions in chat system prompts](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-claude-opus-5-5#thinking-instru… prompting-claude-sonnet-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-sonnet-5 …cks more often than you’d like, which can occur with large or complex system prompts, add guidance to steer it. As always, measure the effect of any prompting changes on performance. Example: ```text… prompting-claude-sonnet-5-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-sonnet-5-5 …To get less thinking, lower the effort level. Asking the model in the system prompt to think less doesn’t reliably reduce its thinking. Changing the top-level `effort` value between requests invalida… refusals-and-fallback Claude Developer Platform · in the page build-with-claude/refusals-and-fallback …g * Reasoning asked for verbatim or in full The wording can sit in a system prompt, a skill, or a tool description, so check those too. You can still ask Claude to explain its answer. Ask for a shor… search-results Claude Developer Platform · in the page build-with-claude/search-results …finalResponse = client.messages().create(finalParams); System.out.println(finalResponse); }); } static List<ToolResultBlockParam.Content.Block> searchKnowledgeBase(String… skills-guide Claude Developer Platform · in the page build-with-claude/skills-guide …(); Message response = client.messages().create(params); System.out.println(response); } ``` ```php PHP $client = new Client(); $message = $client->messages->create( max… streaming Claude Developer Platform · in the page build-with-claude/streaming …deltaEvent.delta().text().ifPresent(textDelta -> System.out.print(textDelta.text()) ) ); }); } ``` ```php PHP $client = new Client(); $st… structured-outputs Claude Developer Platform · in the page build-with-claude/structured-outputs …'Pro' } ``` </Tab> <Tab title="C#"> ```csharp using System.Text.Json; using Anthropic; using Anthropic.Models.Messages; var client = new AnthropicClient(); var resp… thinking Claude Developer Platform · in the page build-with-claude/thinking …expected behavior, especially for thinking content. The streaming system processes content in batches, which can delay and group streaming events into this “chunky” delivery pattern. </Note> For… thinking-steering-and-cost Claude Developer Platform · in the page build-with-claude/thinking-steering-and-cost …ion: Steer how often and how deeply Claude thinks with effort levels, system prompt guidance, and per-message steering, and understand thinking's cost and pricing. --- <Note> To learn how zero data… thinking-troubleshooting Claude Developer Platform · in the page build-with-claude/thinking-troubleshooting …` The message usually ends with a sentence naming what changed: the `system` prompt, the `tools` list, the first message or block that differs, content that is missing or new, or an earlier thinking… token-counting Claude Developer Platform · in the page build-with-claude/token-counting …ructured list of inputs for creating a message, including support for system prompts, [tools](https://platform.claude.com/docs/en/agents-and-tools/tool-use/overview), [images](https://platform.claude.… vision Claude Developer Platform · in the page build-with-claude/vision …} ] }); console.log(message); ``` ```csharp C# using System.Collections.Generic; using Anthropic; using Anthropic.Models.Messages; AnthropicClient client = new(); string ima… vision-coordinates Claude Developer Platform · in the page build-with-claude/vision-coordinates …cannot pre-resize (for example, when the image comes from an upstream system you can’t modify), use the resize helper from [Resize your image before uploading](https://platform.claude.com/docs/en/buil… working-with-messages Claude Developer Platform · in the page build-with-claude/working-with-messages ….build(); Message response = client.messages().create(params); System.out.println(response); ``` ```php PHP $client = new Client(); $message = $client->messages->create( maxToke… apply Claude Developer Platform · in the page cli-sdks-libraries/cli/apply …m.claude.com/docs/en/managed-agents/agent-setup)) and the body is its system prompt. `ant apply` [infers](https://platform.claude.com/docs/en/cli-sdks-libraries/cli/apply#kind-inference) that the file… using Claude Developer Platform · in the page cli-sdks-libraries/cli/using …ta:agents create <<'YAML' name: Research Agent model: claude-opus-5-5 system: | You are a research assistant. Cite sources for every claim. tools: - type: agent_toolset_20260401 YAML ``` ### File… apple-foundation-models Claude Developer Platform · in the page cli-sdks-libraries/libraries/apple-foundation-models …} ``` A common pattern is to catch `.rateLimited` and fall back to `SystemLanguageModel` for that turn, queue the request, or surface a retry affordance. ## Feature support The package surfaces th… openai-sdk Claude Developer Platform · in the page cli-sdks-libraries/libraries/openai-sdk …-opus-5-5", # Claude model name messages=[ {"role": "system", "content": "You are a helpful assistant."}, {"role": "user", "content": "Who are you?"}, ], ) print(… csharp Claude Developer Platform · in the page cli-sdks-libraries/sdks/csharp …brary requires .NET Standard 2.0 or later. ## Usage ```csharp using System; using Anthropic; using Anthropic.Models.Messages; AnthropicClient client = new(); MessageCreateParams parameters = new()… go Claude Developer Platform · in the page cli-sdks-libraries/sdks/go …"%+v\n", message.Content) ``` </Accordion> <Accordion title="System prompts"> ```go message, err := client.Messages.New(context.TODO(), anthropic.MessageNewParams{ Model: ant… java Claude Developer Platform · in the page cli-sdks-libraries/sdks/java …ile an example on an earlier version, replace `IO.println(...)` with `System.out.println(...)` and place the body inside `public static void main(String[] args)` within a class. </Note> ## Quick star… For Amazon Bedrock support Claude Developer Platform · in the page cli-sdks-libraries/sdks/python …xtra_headers={"anthropic-version": "My-Custom-Value"}, ) ``` ## Type system ### Request parameters Nested request parameters are [TypedDicts](https://docs.python.org/3/library/typing.html#typing.Ty… get-started Claude Developer Platform · in the page get-started …with-claude/working-with-messages"> Learn multi-turn conversations, system prompts, stop reasons, and other core patterns. </Card> Once you’re comfortable with the basics, explore further: <CardGr… home Claude Developer Platform · in the page home …: msg.content()) { block.text().ifPresent( textBlock -> System.out.println(textBlock.text())); } ``` ```ruby Ruby require "anthropic" client = Anthropic::Client.new… intro Claude Developer Platform · in the page intro …e request and response structure, including multi-turn conversations, system prompts, and stop reasons. [Read the Messages API guide](https://platform.claude.com/docs/en/build-with-claude/working… access-transparency Claude Developer Platform · in the page manage-claude/access-transparency …uman access, not automated processing.** Anthropic’s automated safety systems process your content in a secured pipeline with no interactive human access; that processing does not generate `anthropic_… api-and-data-retention Claude Developer Platform · in the page manage-claude/api-and-data-retention …| | [Mid-conversation system messages](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages) | `/v1/messages` with `ro… authentication Claude Developer Platform · in the page manage-claude/authentication …y") .build(); // From ANTHROPIC_API_KEY (or anthropic.apiKey system property) AnthropicClient clientFromEnv = AnthropicOkHttpClient.fromEnv(); ``` ```php PHP // Reads ANTHROPIC_API_K…