The Task tool has been renamed to Agent across the entire Agent SDK (introduced in Claude Code v2.1.63); Task remains accepted as an alias for backwards compatibility
Python SDK gains list_sessions() and get_session_messages() functions, plus new add_mcp_server() / remove_mcp_server() methods on ClaudeSDKClient
New task lifecycle message types added to Python SDK: TaskStartedMessage, TaskProgressMessage, and TaskNotificationMessage for tracking background task progress
Hook inputs (PreToolUseHookInput, PostToolUseHookInput, PostToolUseFailureHookInput) now include agent_id and agent_type fields when firing inside a subagent
TypeScript SDK adds getSessionMessages() function and a new toolConfig.askUserQuestion.previewFormat option enabling rich HTML/Markdown previews in AskUserQuestion options
List of available remote MCP servers reordered and updated with new entries (Vibe Prospecting, Magic Patterns, Midpage Legal Research, Clerk, Postman added; listing order of existing servers changed).
Reference to allowedTools: ["Task"] updated to allowedTools: ["Agent"] in the subagent delegation row of the feature configuration table. [line 165] [Source]
Matcher description updated: built-in tool list now shows Agent instead of Task. [line 148] [Source]
Guidance for discovering tool names updated to point to the TypeScript SDK reference for the full list. [line 154] [Source]
Hook callback arguments reformatted to bullet list; new agent_id and agent_type fields documented on all hook inputs — these are populated when the hook fires inside a subagent. [lines 161-172] [Source]
New list_sessions() function documented with parameters (directory, limit, include_worktrees), SDKSessionInfo return type, and example. [lines 199-260] [Source]
New get_session_messages() function documented with parameters (session_id, directory, limit, offset), SessionMessage return type, and example. [lines 262-292] [Source]
ClaudeSDKClient.get_mcp_status() return type changed from dict to list[McpServerStatus]. [line 314] [Source]
New add_mcp_server(name, config) and remove_mcp_server(name) methods added to ClaudeSDKClient. [lines 315-316] [Source]
New McpServerStatus type documented (returned by get_mcp_status()), with fields for name, status, serverInfo, error, config, scope, and tools. [lines 1048-1079] [Source]
New TaskStartedMessage, TaskUsage, TaskProgressMessage, and TaskNotificationMessage types documented for tracking background task lifecycle events (subagents, backgrounded Bash commands, remote agents). [lines 1224-1318] [Source]
agent_id and agent_type optional fields added to PreToolUseHookInput, PostToolUseHookInput, and PostToolUseFailureHookInput — populated when the hook fires inside a subagent. [lines 1551-1615] [Source]
Task tool section renamed to Agent (with note that Task is still accepted as an alias). [line 1884] [Source]
Several MCP servers reordered in the listing; new servers added: Airtable, Vibe Prospecting, Magic Patterns, Gusto, SignNow, PagerDuty, Clerk, Postman, Base44, and lastminute.com.
Updated to mention both SDKs now expose session listing and message retrieval: list_sessions() / get_session_messages() in Python, and listSessions() / getSessionMessages() in TypeScript (previously only TypeScript was mentioned). [line 233] [Source]
Compatibility note added: the rename from Task to Agent happened in v2.1.63; current SDK emits "Agent" in tool_use blocks but still uses "Task" in system:init and permission_denials. Checking both values is recommended. [lines 197-200] [Source]
Detection example updated to match on both "Task" and "Agent" in tool_use blocks for cross-version compatibility. [lines 221-228] [Source]
listSessions() updated: options.dir description clarified; new options.includeWorktrees parameter documented (default true, controls whether worktree sessions are included when dir is inside a git repo). [lines 93-112] [Source]
New getSessionMessages() function documented with parameters (sessionId, dir, limit, offset), SessionMessage return type, and example. [lines 130-176] [Source]
New toolConfig option added to ClaudeAgentOptions — see ToolConfig type. [line 226] [Source]
New ToolConfig type documented: askUserQuestion.previewFormat ("markdown" or "html") enables a preview field on AskUserQuestion options for visual mockups. [lines 498-512] [Source]
AskUserQuestionInput and AskUserQuestionOutput updated: each option now has an optional preview field (string). [lines 1241-1583] [Source]
BaseHookInput updated with optional agent_id and agent_type fields (present when hook fires inside a subagent). [lines 893-894] [Source]
ModelInfo updated with new supportsFastMode boolean field. [line 2056] [Source]
Task tool sections renamed to Agent (with note that Task is still accepted as an alias).
New "Option previews (TypeScript)" section documents the toolConfig.askUserQuestion.previewFormat option, explaining "markdown" and "html" modes, how Claude decides when to include previews, and SDK-side sanitization of HTML. [lines 325-371] [Source]
Limitation note updated to reference Agent tool instead of Task. [line 488] [Source]