50 pages for systemmessage.

Beta Claude Developer Platform · in the page api/beta …ontent: BetaMessageContentParam` - `role: "assistant"` - `BetaSystemMessageParam object` - `role: "system"` - `clear_at: optional "next_user_message" or "never" or null` How l… Deployments Claude Developer Platform · in the page api/beta/deployments …ng up. Default 3, max 20. format: int32 - `BetaManagedAgentsSystemMessageEventParams object` Privileged context for the accompanying turn and all subsequent turns, appended to the sessi… Archive Deployment Claude Developer Platform · in the page api/beta/deployments/archive …3, max 20. format: int32 - `BetaManagedAgentsDeploymentSystemMessageEvent object` Privileged context for the accompanying turn and all subsequent turns, appended to the session's… Create Deployment Claude Developer Platform · in the page api/beta/deployments/create …ng up. Default 3, max 20. format: int32 - `BetaManagedAgentsSystemMessageEventParams object` Privileged context for the accompanying turn and all subsequent turns, appended to the sessi… List Deployments Claude Developer Platform · in the page api/beta/deployments/list …3, max 20. format: int32 - `BetaManagedAgentsDeploymentSystemMessageEvent object` Privileged context for the accompanying turn and all subsequent turns, appended to the session's… Pause Deployment Claude Developer Platform · in the page api/beta/deployments/pause …3, max 20. format: int32 - `BetaManagedAgentsDeploymentSystemMessageEvent object` Privileged context for the accompanying turn and all subsequent turns, appended to the session's… Get Deployment Claude Developer Platform · in the page api/beta/deployments/retrieve …3, max 20. format: int32 - `BetaManagedAgentsDeploymentSystemMessageEvent object` Privileged context for the accompanying turn and all subsequent turns, appended to the session's… Unpause Deployment Claude Developer Platform · in the page api/beta/deployments/unpause …3, max 20. format: int32 - `BetaManagedAgentsDeploymentSystemMessageEvent object` Privileged context for the accompanying turn and all subsequent turns, appended to the session's… Update Deployment Claude Developer Platform · in the page api/beta/deployments/update …ng up. Default 3, max 20. format: int32 - `BetaManagedAgentsSystemMessageEventParams object` Privileged context for the accompanying turn and all subsequent turns, appended to the sessi… Messages Claude Developer Platform · in the page api/beta/messages …ontent: BetaMessageContentParam` - `role: "assistant"` - `BetaSystemMessageParam object` - `role: "system"` - `clear_at: optional "next_user_message" or "never" or null` How l… Batches Claude Developer Platform · in the page api/beta/messages/batches …BetaMessageContentParam` - `role: "assistant"` - `BetaSystemMessageParam object` - `role: "system"` - `clear_at: optional "next_user_message" or "never" or null`… Create a Message Batch Claude Developer Platform · in the page api/beta/messages/batches/create …BetaMessageContentParam` - `role: "assistant"` - `BetaSystemMessageParam object` - `role: "system"` - `clear_at: optional "next_user_message" or "never" or null`… Count tokens in a Message Claude Developer Platform · in the page api/beta/messages/count_tokens …ontent: BetaMessageContentParam` - `role: "assistant"` - `BetaSystemMessageParam object` - `role: "system"` - `clear_at: optional "next_user_message" or "never" or null` How l… Create a Message Claude Developer Platform · in the page api/beta/messages/create …ontent: BetaMessageContentParam` - `role: "assistant"` - `BetaSystemMessageParam object` - `role: "system"` - `clear_at: optional "next_user_message" or "never" or null` How l… Events Claude Developer Platform · in the page api/beta/sessions/events …itle. Present only when the update changed it. - `BetaManagedAgentsSystemMessageEvent object` A mid-conversation system message event. Carries system-role content that is appended to the sessi… List Events Claude Developer Platform · in the page api/beta/sessions/events/list …itle. Present only when the update changed it. - `BetaManagedAgentsSystemMessageEvent object` A mid-conversation system message event. Carries system-role content that is appended to the sessi… Send Events Claude Developer Platform · in the page api/beta/sessions/events/send …ether the tool execution resulted in an error. - `BetaManagedAgentsSystemMessageEventParams object` Privileged context for the accompanying turn and all subsequent turns, appended to the sessi… Stream Events Claude Developer Platform · in the page api/beta/sessions/events/stream …he buffered event that reconciles the preview. - `BetaManagedAgentsSystemMessageEvent object` A mid-conversation system message event. Carries system-role content that is appended to the sessi… Threads Claude Developer Platform · in the page api/beta/sessions/threads …he buffered event that reconciles the preview. - `BetaManagedAgentsSystemMessageEvent object` A mid-conversation system message event. Carries system-role content that is appended to the sessi… Events Claude Developer Platform · in the page api/beta/sessions/threads/events …itle. Present only when the update changed it. - `BetaManagedAgentsSystemMessageEvent object` A mid-conversation system message event. Carries system-role content that is appended to the sessi… List Session Thread Events Claude Developer Platform · in the page api/beta/sessions/threads/events/list …itle. Present only when the update changed it. - `BetaManagedAgentsSystemMessageEvent object` A mid-conversation system message event. Carries system-role content that is appended to the sessi… Stream Session Thread Events Claude Developer Platform · in the page api/beta/sessions/threads/events/stream …he buffered event that reconciles the preview. - `BetaManagedAgentsSystemMessageEvent object` A mid-conversation system message event. Carries system-role content that is appended to the sessi… Messages Claude Developer Platform · in the page api/messages …- `content: MessageContentParam` - `role: "assistant"` - `SystemMessageParam object` - `content: string or array of TextBlockParam` - `string` - `Blocks = array of TextB… Batches Claude Developer Platform · in the page api/messages/batches …ontent: MessageContentParam` - `role: "assistant"` - `SystemMessageParam object` - `content: string or array of TextBlockParam` - `string` - `Blocks = ar… Create a Message Batch Claude Developer Platform · in the page api/messages/batches/create …ontent: MessageContentParam` - `role: "assistant"` - `SystemMessageParam object` - `content: string or array of TextBlockParam` - `string` - `Blocks = ar… Count tokens in a Message Claude Developer Platform · in the page api/messages/count_tokens …- `content: MessageContentParam` - `role: "assistant"` - `SystemMessageParam object` - `content: string or array of TextBlockParam` - `string` - `Blocks = array of TextB… Create a Message Claude Developer Platform · in the page api/messages/create …- `content: MessageContentParam` - `role: "assistant"` - `SystemMessageParam object` - `content: string or array of TextBlockParam` - `string` - `Blocks = array of TextB… effort Claude Developer Platform · in the page build-with-claude/effort …the new level takes effect from the next user turn. new BetaSystemMessageParam { Content = new([]), OutputConfig = new() { Effort = BetaSystemMessageOut… mid-conversation-effort-example Claude Developer Platform · in the page build-with-claude/mid-conversation-effort-example …one-line refresher every TURNS_BETWEEN_REFRESHERS user turns. #dueSystemMessages(): Anthropic.MessageParam[] { const due: Anthropic.MessageParam[] = []; if (this.#exitPending) {… mid-conversation-system-messages Claude Developer Platform · in the page build-with-claude/mid-conversation-system-messages …// byte-identical and the cache still hits. new BetaSystemMessageParam { Content = new( [ new BetaRequestToolRemovalBlock… Delivering work Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-fable-5-1 …erMessageParam { Content = toolResults }); messages.Add(new BetaSystemMessageParam { Content = BatchNudge, ClearAt = ClearAt.NextUserMessage, }); } foreach (… openai-sdk Claude Developer Platform · in the page cli-sdks-libraries/libraries/openai-sdk …e Messages: []openai.ChatCompletionMessageParamUnion{ openai.SystemMessage("You are a helpful assistant."), openai.UserMessage("Who are you?"), }, }) if err != nil { panic(… events-and-streaming Claude Developer Platform · in the page managed-agents/events-and-streaming …n.ID, new() { Events = [ new BetaManagedAgentsSystemMessageEventParams { Content = [ new BetaManagedAgentsSystemContentB… Or, for Claude Mythos 5.1, which offers the same capabilities to verified organizations: Claude Developer Platform · in the page models/fable-5-1/migration-guide …leaves the // earlier turns unchanged. new SystemMessageParam { Content = "Tool-use requirement for the current turn: the application requires… whats-new-fable-5-1 Claude Developer Platform · in the page models/fable-5-1/whats-new-fable-5-1 …the new level takes effect from the next user turn. new BetaSystemMessageParam { Content = new([]), OutputConfig = new() { Effort = BetaSystemMessageOut… How the agent loop works Claude Code CLI · in the page agent-sdk/agent-loop …rompt, tool definitions, and conversation history. The SDK yields a [`SystemMessage`](#message-types) with subtype `"init"` containing session metadata. 2. **Evaluate and respond.** Claude evaluates t… Intercept and control agent behavior with hooks Claude Code CLI · in the page agent-sdk/hooks …ries of fields: * **Top-level fields** are accepted on every event: `systemMessage` shows a message to the user, and `continue` (`continue_` in Python) determines whether the agent keeps running afte… Connect to external tools with MCP Claude Code CLI · in the page agent-sdk/mcp …mport asyncio from claude_agent_sdk import query, ClaudeAgentOptions, SystemMessage async def main(): options = ClaudeAgentOptions( mcp_servers={ # your servers },… Plugins in the SDK Claude Code CLI · in the page agent-sdk/plugins …mport asyncio from claude_agent_sdk import query, ClaudeAgentOptions, SystemMessage async def main(): async for message in query( prompt="Hello", options=ClaudeAgentOptions(… Agent SDK reference - Python Claude Code CLI · in the page agent-sdk/python …theme={null} Message = ( UserMessage | AssistantMessage | SystemMessage | ResultMessage | StreamEvent | RateLimitEvent | ConversationResetMessage ) ``` ### `UserMessage`… Work with sessions Claude Code CLI · in the page agent-sdk/sessions …cript the ID is also available earlier as a direct field on the init `SystemMessage`; in Python it's nested inside `SystemMessage.data`. ```python Python theme={null} import asyncio from claude_agent… Extend agents with skills Claude Code CLI · in the page agent-sdk/skills …mport asyncio from claude_agent_sdk import query, ClaudeAgentOptions, SystemMessage async def main(): async for message in query(prompt="Hello Claude", options=ClaudeAgentOptions(max_turns=1)):… Stream responses in real-time Claude Code CLI · in the page agent-sdk/streaming-output …receive all message types except `StreamEvent`. Common types include `SystemMessage` (session initialization), `AssistantMessage` (complete content blocks), `ResultMessage` (final result), and a compa… Get structured output from agents Claude Code CLI · in the page agent-sdk/structured-outputs …answer. The [system init message](/docs/en/agent-sdk/typescript.md#sdksystemmessage) lists it in the `tools` array, and each call arrives as two blocks: * A `tool_use` block named `StructuredOutput`,… Troubleshoot the Agent SDK Claude Code CLI · in the page agent-sdk/troubleshooting …permission prompts multiplying, recursive hook loops with subagents, `systemMessage` not appearing in output | [Fix common issues](/docs/en/agent-sdk/hooks.md#fix-common-issues) on the hooks page | |… Agent SDK reference - TypeScript Claude Code CLI · in the page agent-sdk/typescript …When the CLI advertises the `interrupt_receipt_v1` capability in [`SDKSystemMessage.capabilities`](#sdksystemmessage), resolves with an [`SDKControlInterruptResponse`](#sdkcontrolinterruptresponse) li… Run Claude Code programmatically Claude Code CLI · in the page headless …ring version strings, and ignore values you don't recognize. See [`SDKSystemMessage`](/docs/en/agent-sdk/typescript#sdksystemmessage) for the capability list. #### Fail CI when a plugin or MCP server… Hooks reference Claude Code CLI · in the page hooks …dev/tty`. To surface a message to the user on any platform, return [`systemMessage`](#json-output) in JSON output. Some events discard it or deliver it elsewhere, and each [event's section](#hook-eve… Automate actions with hooks Claude Code CLI · in the page hooks-guide …you see nothing, unless the hook's JSON surfaces something, such as `systemMessage` or Stop hook feedback. * To confirm the hook ran, check for its effect, like a reformatted file * **Blocking erro… Monitoring Claude Code CLI · in the page monitoring-usage …Code v2.1.280 or later * `system_message_chars`: Total characters of `systemMessage` returned by the matching hooks. Requires Claude Code v2.1.280 or later * `initial_user_message_chars`: Total charac…