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Agent SDK reference - Python changedagent-sdk/python

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Upstream edited this page at 25 Sep 2026 22:47 UTC, give or take a minute or two: the time comes from Anthropic’s own sitemap rather than from a commit. This site recorded the change at 25 Sep 2026 23:07 UTC.

Upstream edited 25 Sep 2026 22:47 UTC

Recorded here 25 Sep 2026 23:07 UTC

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First seen 14 Aug 2026 this site's first read of the page

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from line 779

779779 include_partial_messages: bool = False

780780 include_hook_events: bool = False

781781 forward_subagent_text: bool = False

782 verbatim_prompts: bool = False

782783 fork_session: bool = False

783784 resume_session_at: str | None = None

784785 resume_drops_turn: str | None = None

from line 798

797798 task_budget: TaskBudget | None = None

798799```

799800

801| :---------------------------- | :------------------------------------------------------------------------------------ | :--------------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |

802| `tools` | `list[str] \| ToolsPreset \| None` | `None` | Tools configuration. Use `{"type": "preset", "preset": "claude_code"}` for Claude Code's default tools |

803| `allowed_tools` | `list[str]` | `[]` | Tools to auto-approve without prompting. This does not restrict Claude to only these tools. If you name one of the [task-tracking tools](/docs/en/agent-sdk/todo-tracking#model-availability) here, Claude Code also opts the session in. Other unlisted tools fall through to `permission_mode` and `can_use_tool`. Use `disallowed_tools` to block tools. See [Permissions](/docs/en/agent-sdk/permissions#allow-and-deny-rules) |

804| `system_prompt` | `str \| SystemPromptPreset \| SystemPromptCustom \| SystemPromptFile \| None` | `None` | System prompt configuration. Pass a string for a custom prompt, `{"type": "preset", "preset": "claude_code"}` for Claude Code's system prompt with optional `"append"`, `{"type": "custom", "prompt": "..."}` for a custom prompt that can also set `"snapshot"`, or `{"type": "file", "path": "..."}` to load a large prompt from disk. See [`SystemPromptPreset`](#systempromptpreset), [`SystemPromptCustom`](#systempromptcustom), and [`SystemPromptFile`](#systempromptfile) |

805| `mcp_servers` | `dict[str, McpServerConfig] \| str \| Path` | `{}` | MCP server configurations or path to config file |

806| `strict_mcp_config` | `bool` | `False` | When `True`, use only the servers passed in `mcp_servers` and ignore project `.mcp.json`, user settings, plugin-provided MCP servers, and [claude.ai connectors](/docs/en/mcp#use-mcp-servers-from-claude-ai). Maps to the CLI `--strict-mcp-config` flag |

812| `max_budget_usd` | `float \| None` | `None` | Stop the query when the client-side cost estimate reaches this USD value. Counts only the call's own spend; totals restored from a resumed session don't count. For accuracy caveats and reset behavior, see [Track cost and usage](/docs/en/agent-sdk/cost-tracking) |

813| `disallowed_tools` | `list[str]` | `[]` | Tools to deny. A bare name such as `"Bash"` removes the tool from Claude's context. A scoped rule such as `"Bash(rm *)"` leaves the tool available and denies matching calls in every permission mode, including `bypassPermissions`, for the command [as written](/docs/en/permissions#bash-rule-limits). See [Permissions](/docs/en/agent-sdk/permissions#allow-and-deny-rules) |

818| `output_format` | `dict[str, Any] \| None` | `None` | Output format for structured responses (e.g., `{"type": "json_schema", "schema": {...}}`). See [Structured outputs](/docs/en/agent-sdk/structured-outputs) for details |

820| `cwd` | `str \| Path \| None` | `None` | Current working directory |

823| `add_dirs` | `list[str \| Path]` | `[]` | Additional directories Claude can access. The SDK passes each entry to Claude Code as `--add-dir`, so with the `project` setting source Claude Code also [loads the directory's skills, commands, and subagents](/docs/en/permissions#additional-directories-grant-file-access-not-configuration) |

824| `env` | `dict[str, str]` | `{}` | Environment variables merged on top of the inherited process environment. See [Environment variables](/docs/en/env-vars) for variables the underlying CLI reads, and [Handle slow or stalled API responses](#handle-slow-or-stalled-api-responses) for timeout-related variables. Set `CLAUDE_AGENT_SDK_CLIENT_APP` to identify your app in the User-Agent header |

825| `extra_args` | `dict[str, str \| None]` | `{}` | Additional CLI arguments to pass directly to the CLI |

829| `can_use_tool` | [`CanUseTool`](#canusetool) ` \| None` | `None` | Tool permission callback, invoked only when the [permission flow](/docs/en/agent-sdk/permissions#how-permissions-are-evaluated) falls through to a prompt. Not invoked for calls auto-approved by `allowed_tools`, allow rules, or `permission_mode`. An allow rule doesn't pre-approve the [actions no mode auto-approves](/docs/en/permission-modes#actions-no-mode-auto-approves). See [`CanUseTool`](#canusetool) for details |

834| `forward_subagent_text` | `bool` | `False` | Forward subagent text and thinking blocks in the message stream. Without this option, Claude Code emits subagent `tool_use` and `tool_result` blocks but not text or thinking. Requires Python Agent SDK 0.2.140 or later |

836| `resume_session_at` | `str \| None` | `None` | When resuming, load the conversation only up to and including the message with this UUID. Use with `resume`, and usually `fork_session`, to branch from an earlier point. Requires Python Agent SDK 0.2.137 or later |

837| `resume_drops_turn` | `str \| None` | `None` | UUID of the user prompt whose turn a `resume_session_at` truncation discards. When set, the CLI refuses the resume if the discarded range holds entries not attributable to that turn. Requires Python Agent SDK 0.2.137 or later and Claude Code v2.1.223 or later; the CLI bundled with those SDK versions satisfies the Claude Code requirement |

841| `setting_sources` | `list[SettingSource] \| None` | `None` (CLI defaults: all sources) | Control which filesystem settings to load. Pass `[]` to disable user, project, and local settings. With `skills` set and this field unset, only user and project sources load. Set `setting_sources` explicitly to keep local settings. Endpoint-managed policy loads regardless; server-managed settings are fetched when the session authenticates with an organization credential on an [eligible configuration](/docs/en/server-managed-settings#platform-availability). For inputs read regardless of this option, see [What settingSources does not control](/docs/en/agent-sdk/claude-code-features#what-settingsources-does-not-control) |

842| `skills` | `list[str] \| Literal["all"] \| None` | `None` | Skills available to the session. Pass `"all"` to enable every discovered skill, or a list of skill names. Pass exact names only. The SDK rejects malformed and wildcard-form names with a `ValueError` before starting the Claude Code process; this check requires Python Agent SDK 0.2.129 or later. When set, the SDK adds the Skill tool to `allowed_tools` automatically. If you also pass `tools`, include `"Skill"` in that list. See [Skills](/docs/en/agent-sdk/skills) |

846| `session_store` | [`SessionStore`](/docs/en/agent-sdk/session-storage#the-sessionstore-interface) ` \| None` | `None` | Mirror session transcripts to an external backend so another host can resume them. See [Persist sessions to external storage](/docs/en/agent-sdk/session-storage) |

847| `session_store_flush` | `Literal["batched", "eager"]` | `"batched"` | When to flush mirrored transcript entries to `session_store`. `"batched"` flushes once per turn or when the buffer fills; `"eager"` triggers a background flush after every frame. Ignored when `session_store` is `None` |

848| `load_timeout_ms` | `int` | `60000` | Per-call timeout for `session_store.load()` and `list_subkeys()` during resume materialization, in milliseconds |

849| `task_budget` | `TaskBudget \| None` | `None` | API-side token budget. Sent as `output_config.task_budget` with the `task-budgets-2026-03-13` beta header. Pass `{"total": <int>}`. |

802| :---------------------------- | :------------------------------------------------------------------------------------ | :--------------------------------- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |

803| `tools` | `list[str] \| ToolsPreset \| None` | `None` | Tools configuration. Use `{"type": "preset", "preset": "claude_code"}` for Claude Code's default tools |

804| `allowed_tools` | `list[str]` | `[]` | Tools to auto-approve without prompting. This does not restrict Claude to only these tools. If you name one of the [task-tracking tools](/docs/en/agent-sdk/todo-tracking#model-availability) here, Claude Code also opts the session in. Other unlisted tools fall through to `permission_mode` and `can_use_tool`. Use `disallowed_tools` to block tools. See [Permissions](/docs/en/agent-sdk/permissions#allow-and-deny-rules) |

805| `system_prompt` | `str \| SystemPromptPreset \| SystemPromptCustom \| SystemPromptFile \| None` | `None` | System prompt configuration. Pass a string for a custom prompt, `{"type": "preset", "preset": "claude_code"}` for Claude Code's system prompt with optional `"append"`, `{"type": "custom", "prompt": "..."}` for a custom prompt that can also set `"snapshot"`, or `{"type": "file", "path": "..."}` to load a large prompt from disk. See [`SystemPromptPreset`](#systempromptpreset), [`SystemPromptCustom`](#systempromptcustom), and [`SystemPromptFile`](#systempromptfile) |

806| `mcp_servers` | `dict[str, McpServerConfig] \| str \| Path` | `{}` | MCP server configurations or path to config file |

807| `strict_mcp_config` | `bool` | `False` | When `True`, use only the servers passed in `mcp_servers` and ignore project `.mcp.json`, user settings, plugin-provided MCP servers, and [claude.ai connectors](/docs/en/mcp#use-mcp-servers-from-claude-ai). Maps to the CLI `--strict-mcp-config` flag |

813| `max_budget_usd` | `float \| None` | `None` | Stop the query when the client-side cost estimate reaches this USD value. Counts only the call's own spend; totals restored from a resumed session don't count. For accuracy caveats and reset behavior, see [Track cost and usage](/docs/en/agent-sdk/cost-tracking) |

814| `disallowed_tools` | `list[str]` | `[]` | Tools to deny. A bare name such as `"Bash"` removes the tool from Claude's context. A scoped rule such as `"Bash(rm *)"` leaves the tool available and denies matching calls in every permission mode, including `bypassPermissions`, for the command [as written](/docs/en/permissions#bash-rule-limits). See [Permissions](/docs/en/agent-sdk/permissions#allow-and-deny-rules) |

819| `output_format` | `dict[str, Any] \| None` | `None` | Output format for structured responses (e.g., `{"type": "json_schema", "schema": {...}}`). See [Structured outputs](/docs/en/agent-sdk/structured-outputs) for details |

821| `cwd` | `str \| Path \| None` | `None` | Current working directory |

824| `add_dirs` | `list[str \| Path]` | `[]` | Additional directories Claude can access. The SDK passes each entry to Claude Code as `--add-dir`, so with the `project` setting source Claude Code also [loads the directory's skills, commands, and subagents](/docs/en/permissions#additional-directories-grant-file-access-not-configuration) |

825| `env` | `dict[str, str]` | `{}` | Environment variables merged on top of the inherited process environment. See [Environment variables](/docs/en/env-vars) for variables the underlying CLI reads, and [Handle slow or stalled API responses](#handle-slow-or-stalled-api-responses) for timeout-related variables. Set `CLAUDE_AGENT_SDK_CLIENT_APP` to identify your app in the User-Agent header |

826| `extra_args` | `dict[str, str \| None]` | `{}` | Additional CLI arguments to pass directly to the CLI |

830| `can_use_tool` | [`CanUseTool`](#canusetool) ` \| None` | `None` | Tool permission callback, invoked only when the [permission flow](/docs/en/agent-sdk/permissions#how-permissions-are-evaluated) falls through to a prompt. Not invoked for calls auto-approved by `allowed_tools`, allow rules, or `permission_mode`. An allow rule doesn't pre-approve the [actions no mode auto-approves](/docs/en/permission-modes#actions-no-mode-auto-approves). See [`CanUseTool`](#canusetool) for details |

835| `forward_subagent_text` | `bool` | `False` | Forward subagent text and thinking blocks in the message stream. Without this option, Claude Code emits subagent `tool_use` and `tool_result` blocks but not text or thinking. Requires Python Agent SDK 0.2.140 or later |

836| `verbatim_prompts` | `bool` | `False` | Deliver every prompt as written. The SDK sends each user message with `client_composed` set to `True`. See [`client_composed`](/docs/en/agent-sdk/typescript#sdkusermessage) for what Claude Code skips on those messages. Use this option when your prompt text includes content the end user didn't type. For per-turn control, leave it off and set `"client_composed": True` on individual streamed messages instead. While the option is on, the SDK overwrites any `client_composed` value you set. Requires Python Agent SDK 0.2.158 or later and Claude Code v2.1.248 or later; the CLI bundled with those SDK versions satisfies the Claude Code requirement |

838| `resume_session_at` | `str \| None` | `None` | When resuming, load the conversation only up to and including the message with this UUID. Use with `resume`, and usually `fork_session`, to branch from an earlier point. Requires Python Agent SDK 0.2.137 or later |

839| `resume_drops_turn` | `str \| None` | `None` | UUID of the user prompt whose turn a `resume_session_at` truncation discards. When set, the CLI refuses the resume if the discarded range holds entries not attributable to that turn. Requires Python Agent SDK 0.2.137 or later and Claude Code v2.1.223 or later; the CLI bundled with those SDK versions satisfies the Claude Code requirement |

843| `setting_sources` | `list[SettingSource] \| None` | `None` (CLI defaults: all sources) | Control which filesystem settings to load. Pass `[]` to disable user, project, and local settings. With `skills` set and this field unset, only user and project sources load. Set `setting_sources` explicitly to keep local settings. Endpoint-managed policy loads regardless; server-managed settings are fetched when the session authenticates with an organization credential on an [eligible configuration](/docs/en/server-managed-settings#platform-availability). For inputs read regardless of this option, see [What settingSources does not control](/docs/en/agent-sdk/claude-code-features#what-settingsources-does-not-control) |

844| `skills` | `list[str] \| Literal["all"] \| None` | `None` | Skills available to the session. Pass `"all"` to enable every discovered skill, or a list of skill names. Pass exact names only. The SDK rejects malformed and wildcard-form names with a `ValueError` before starting the Claude Code process; this check requires Python Agent SDK 0.2.129 or later. When set, the SDK adds the Skill tool to `allowed_tools` automatically. If you also pass `tools`, include `"Skill"` in that list. See [Skills](/docs/en/agent-sdk/skills) |

848| `session_store` | [`SessionStore`](/docs/en/agent-sdk/session-storage#the-sessionstore-interface) ` \| None` | `None` | Mirror session transcripts to an external backend so another host can resume them. See [Persist sessions to external storage](/docs/en/agent-sdk/session-storage) |

849| `session_store_flush` | `Literal["batched", "eager"]` | `"batched"` | When to flush mirrored transcript entries to `session_store`. `"batched"` flushes once per turn or when the buffer fills; `"eager"` triggers a background flush after every frame. Ignored when `session_store` is `None` |

850| `load_timeout_ms` | `int` | `60000` | Per-call timeout for `session_store.load()` and `list_subkeys()` during resume materialization, in milliseconds |

851| `task_budget` | `TaskBudget \| None` | `None` | API-side token budget. Sent as `output_config.task_budget` with the `task-budgets-2026-03-13` beta header. Pass `{"total": <int>}`. |

850852

851853#### Handle slow or stalled API responses

852854

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