Workflow API quickstart

import CodeBlock from '@theme/CodeBlock'; import exampleQuickstartSync from '!!raw-loader!@site/docs/API-Reference/curl-examples/workflows-api/example-quickstart-sync.sh'; import examplePythonQuickstartSync from '!!raw-loader!@site/docs/API-Reference/python-examples/workflows-api/example-quickstart-sync.py'; import exampleJavascriptQuickstartSync from '!!raw-loader!@site/docs/API-Reference/javascript-examples/workflows-api/example-quickstart-sync.js'; import exampleQuickstartStreamTokens from '!!raw-loader!@site/docs/API-Reference/curl-examples/workflows-api/example-quickstart-stream-tokens.sh'; import examplePythonQuickstartStreamTokens from '!!raw-loader!@site/docs/API-Reference/python-examples/workflows-api/example-quickstart-stream-tokens.py'; import exampleJavascriptQuickstartStreamTokens from '!!raw-loader!@site/docs/API-Reference/javascript-examples/workflows-api/example-quickstart-stream-tokens.js'; import exampleStreamAguiParse from '!!raw-loader!@site/docs/API-Reference/curl-examples/workflows-api/example-stream-agui-parse.sh'; import examplePythonStreamAguiParse from '!!raw-loader!@site/docs/API-Reference/python-examples/workflows-api/example-stream-agui-parse.py'; import exampleJavascriptStreamAguiParse from '!!raw-loader!@site/docs/API-Reference/javascript-examples/workflows-api/example-stream-agui-parse.js'; import exampleQuickstartBackgroundPoll from '!!raw-loader!@site/docs/API-Reference/curl-examples/workflows-api/example-quickstart-background-poll.sh'; import examplePythonQuickstartBackgroundPoll from '!!raw-loader!@site/docs/API-Reference/python-examples/workflows-api/example-quickstart-background-poll.py'; import exampleJavascriptQuickstartBackgroundPoll from '!!raw-loader!@site/docs/API-Reference/javascript-examples/workflows-api/example-quickstart-background-poll.js';

import Tabs from '@theme/Tabs'; import TabItem from '@theme/TabItem'; import PartialAPISetup from '@site/docs/_partial-api-setup.mdx';

The Workflow API executes Langflow flows over POST /api/v2/workflows in three modes.

Use the default sync mode when you want to wait for the full JSON result in one response. Use stream when you need live Server-Sent Events (SSE) emitted as the flow runs. Use background when you want to queue a job and then poll or re-attach to its event stream.

This quickstart runs the same flow with each mode, so you can use the mode that fits your application.

The examples on this page also expect FLOW_ID to be set to your flow's UUID. Use a chat-style flow (for example Basic Prompting) so output.text contains the assistant reply.

Run a flow synchronously

Omit mode or set "mode": "sync" to run inline. When the flow finishes, the response includes a top-level output.text field with the primary answer.

<CodeBlock language="python">{examplePythonQuickstartSync}</CodeBlock>

<CodeBlock language="javascript">{exampleJavascriptQuickstartSync}</CodeBlock>

<CodeBlock language="bash">{exampleQuickstartSync}</CodeBlock>

{
  "flow_id": "67ccd2be-17f0-8190-81ff-3bb2cf6508e6",
  "session_id": "session-123",
  "object": "response",
  "status": "completed",
  "output": {
    "reason": "single",
    "text": "2 + 2 equals 4.",
    "source": "ChatOutput-xyz"
  },
  "has_errors": false
}

Pass the same session_id on the next request to continue chat history for that conversation.

Stream LLM tokens

Set "mode": "stream" to open an SSE stream. Choose the wire format with stream_protocol:

• langflow (default): Langflow EventManager frames for existing Langflow clients.
• agui: AG-UI lifecycle events for compatible clients.

For request examples, event types, and protocol details, see Execute flow with selected stream mode in the Workflow API reference.

Langflow EventManager (default)

Each data: line is JSON shaped like {"event": "<type>", "data": {...}}. The example below prints only token events (data.chunk) as they arrive.

<CodeBlock language="python">{examplePythonQuickstartStreamTokens}</CodeBlock>

<CodeBlock language="javascript">{exampleJavascriptQuickstartStreamTokens}</CodeBlock>

<CodeBlock language="bash">{exampleQuickstartStreamTokens}</CodeBlock>

AG-UI {#ag-ui}

Send "stream_protocol": "agui". Each data: line contains one AG-UI event as JSON. The example below handles TEXT_MESSAGE_CONTENT, TOOL_CALL_RESULT, and RUN_FINISHED, extracts a number from the first reply, then chains a follow-up prompt in the same session_id.

<CodeBlock language="python">{examplePythonStreamAguiParse}</CodeBlock>

<CodeBlock language="javascript">{exampleJavascriptStreamAguiParse}</CodeBlock>

<CodeBlock language="bash">{exampleStreamAguiParse}</CodeBlock>

Run in the background

Set "mode": "background" to queue a job and receive a job_id immediately. Poll GET /api/v2/workflows?job_id=… until status is completed, then read output.text from the result.

<CodeBlock language="python">{examplePythonQuickstartBackgroundPoll}</CodeBlock>

<CodeBlock language="javascript">{exampleJavascriptQuickstartBackgroundPoll}</CodeBlock>

<CodeBlock language="bash">{exampleQuickstartBackgroundPoll}</CodeBlock>

While a job is still queued or in_progress, the poll endpoint returns a job object (object: "job") with links for status, events, and stop. When the job completes, the same endpoint returns the full execution response.

To connect to a background run, see Re-attach to a background run.

Next steps

• Workflow API reference — request body fields, response schemas, status polling, stop endpoint, tweaks, globals, and error codes.
• Flow trigger endpoints — v1 /run and /webhook endpoints if you are migrating from or comparing with the v1 API.