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Stream responses in real-time changedagent-sdk/streaming-output

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Upstream edited this page at 21 Oct 2026 02:01 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 22 Oct 2026 18:07 UTC.

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9> This page covers output streaming (receiving tokens in real-time). For input modes (how you send messages), see [Send messages to agents](/docs/en/agent-sdk/streaming-vs-single-mode). You can also [stream responses using the Agent SDK via the CLI](/docs/en/headless).
9> This page covers output streaming (receiving tokens in real-time). For input modes (how you send messages), see [Send messages to agents](/docs/en/agent-sdk/streaming-vs-single-mode.md). You can also [stream responses using the Agent SDK via the CLI](/docs/en/headless.md).
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1111## Enable streaming output
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7575Both contain raw Claude API events, not accumulated text. You need to extract and accumulate text deltas yourself.
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77The `parent_tool_use_id` field is always `None` in Python and `null` in TypeScript. Stream events are emitted for the main session only; token-level deltas from subagents aren't forwarded. To attribute output to a subagent, use complete messages, which carry `parent_tool_use_id`. See [Detect subagent invocation](/docs/en/agent-sdk/subagents#detect-subagent-invocation).
77The `parent_tool_use_id` field is always `None` in Python and `null` in TypeScript. Stream events are emitted for the main session only; token-level deltas from subagents aren't forwarded. To attribute output to a subagent, use complete messages, which carry `parent_tool_use_id`. See [Detect subagent invocation](/docs/en/agent-sdk/subagents.md#detect-subagent-invocation).
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7979Claude Code sets `user_message_uuid` on the turn's first non-ping stream event, and again when the message the turn is answering changes, under the conditions in [`user_message_uuid`](/docs/en/agent-sdk/typescript#user_message_uuid). The Python `StreamEvent` doesn't expose this field.
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315315## Known limitations
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317* **Structured output**: with partial messages enabled, the JSON streams as a tool call's unvalidated `input_json_delta` chunks, and only the validated result reaches the final `ResultMessage.structured_output`. [Recognize the StructuredOutput tool call](/docs/en/agent-sdk/structured-outputs#recognize-the-structuredoutput-tool-call) covers how that call appears in your stream.
317* **Structured output**: with partial messages enabled, the JSON streams as a tool call's unvalidated `input_json_delta` chunks, and only the validated result reaches the final `ResultMessage.structured_output`. [Recognize the StructuredOutput tool call](/docs/en/agent-sdk/structured-outputs.md#recognize-the-structuredoutput-tool-call) covers how that call appears in your stream.
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319319## Next steps
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321321Now that you can stream text and tool calls in real-time, explore these related topics:
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323* [Interactive vs one-shot queries](/docs/en/agent-sdk/streaming-vs-single-mode): choose between input modes for your use case
324* [Structured outputs](/docs/en/agent-sdk/structured-outputs): get typed JSON responses from the agent
325* [Permissions](/docs/en/agent-sdk/permissions): control which tools the agent can use
323* [Interactive vs one-shot queries](/docs/en/agent-sdk/streaming-vs-single-mode.md): choose between input modes for your use case
324* [Structured outputs](/docs/en/agent-sdk/structured-outputs.md): get typed JSON responses from the agent
325* [Permissions](/docs/en/agent-sdk/permissions.md): control which tools the agent can use
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