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HomeDocsClaude Code CLI 27 Aug 2026
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Subagents in the SDK changedagent-sdk/subagents

Nearest release: v2.1.248, published under an hour before this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.

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140140 
141141### AgentDefinition configuration
142142 
143| Field | Type | Required | Description |
144| :---------------- | :---------------------------------------------------------- | :------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
145| `description` | `string` | Yes | Natural language description of when to use this agent |
146| `prompt` | `string` | Yes | The agent's system prompt defining its role and behavior |
147| `tools` | `string[]` | No | Array of allowed tool names. If omitted, inherits every [tool available to subagents](/docs/en/sub-agents#available-tools) |
148| `disallowedTools` | `string[]` | No | Array of tool names to remove from the agent's tool set. MCP server-level patterns are also accepted: `mcp__server` or `mcp__server__*` removes every tool from that server, and `mcp__*` removes every MCP tool from any server |
149| `model` | `string` | No | Model override for this agent. Accepts an alias such as `'fable'`, `'opus'`, `'sonnet'`, `'haiku'`, `'inherit'`, or a full model ID. Defaults to main model if omitted |
150| `skills` | `string[]` | No | List of skill names to preload into the agent's context at startup. Unlisted skills remain invocable through the Skill tool |
151| `memory` | `'user' \| 'project' \| 'local'` | No | Memory source for this agent |
152| `mcpServers` | `(string \| object)[]` | No | MCP servers available to this agent, by name or inline config |
153| `initialPrompt` | `string` | No | Auto-submitted as the first user turn when this agent runs as the main thread agent. Ignored when the agent is invoked as a subagent |
154| `maxTurns` | `number` | No | Maximum number of agentic turns before the agent stops |
155| `background` | `boolean` | No | Run this agent as a non-blocking background task when invoked |
156| `effort` | `'low' \| 'medium' \| 'high' \| 'xhigh' \| 'max' \| number` | No | Reasoning effort level for this agent |
157| `permissionMode` | `PermissionMode` | No | Permission mode for tool execution within this agent |
143| Field | Type | Required | Description |
144| :---------------- | :---------------------------------------------------------- | :------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
145| `description` | `string` | Yes | Natural language description of when to use this agent |
146| `prompt` | `string` | Yes | The agent's system prompt defining its role and behavior |
147| `tools` | `string[]` | No | Array of allowed tool names. If omitted, inherits every [tool available to subagents](/docs/en/sub-agents#available-tools) |
148| `disallowedTools` | `string[]` | No | Array of tool names to remove from the agent's tool set. MCP server-level patterns are also accepted: `mcp__server` or `mcp__server__*` removes every tool from that server, and `mcp__*` removes every MCP tool from any server |
149| `model` | `string` | No | Model override for this agent. Accepts an alias such as `'fable'`, `'opus'`, `'sonnet'`, `'haiku'`, `'inherit'`, or a full model ID. Defaults to main model if omitted |
150| `skills` | `string[]` | No | List of skill names to preload into the agent's context at startup. Unlisted skills remain invocable through the Skill tool |
151| `memory` | `'user' \| 'project' \| 'local'` | No | Memory source for this agent |
152| `mcpServers` | `(string \| object)[]` | No | MCP servers available to this agent, by name or inline config |
153| `initialPrompt` | `string` | No | Auto-submitted as the first user turn when this agent runs as the main thread agent. Ignored when the agent is invoked as a subagent |
154| `maxTurns` | `number` | No | Maximum number of agentic turns before the agent stops. When the agent reaches the limit, Claude Code returns its output marked as partial, and you can [resume the agent](#resume-subagents) to continue. The partial marking requires Claude Code v2.1.246 or later |
155| `background` | `boolean` | No | Run this agent as a non-blocking background task when invoked |
156| `effort` | `'low' \| 'medium' \| 'high' \| 'xhigh' \| 'max' \| number` | No | Reasoning effort level for this agent |
157| `permissionMode` | `PermissionMode` | No | Permission mode for tool execution within this agent |
158158 
159159In the Python SDK, multi-word field names such as `disallowedTools` and `mcpServers` keep their camelCase spelling to match the wire format rather than following Python's snake\_case convention. See the [`AgentDefinition` reference](/docs/en/agent-sdk/python#agentdefinition) for details.
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391391## Resume subagents
392392 
393393You can resume a subagent to continue where it left off rather than starting fresh. A resumed subagent retains its full conversation history, including all previous tool calls, results, and reasoning.
394 
395When a subagent stops at its [`maxTurns`](#agentdefinition-configuration) limit, Claude Code marks the output in the Agent tool result as partial, so Claude knows the run is unfinished.
394396 
395397When a subagent completes, the Agent tool result includes a text block containing `agentId: <id>`. The built-in [`Explore` and `Plan` agents](/docs/en/sub-agents#built-in-subagents) are one-shot and don't return an `agentId`, so use a custom agent or `general-purpose` when you need to resume. To resume a subagent programmatically:
396398 
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