HTTP Interactive Execution

February 18, 2026 ยท View on GitHub

NeMo Agent Toolkit supports interactive workflows (Human-in-the-Loop and OAuth) over plain HTTP, without requiring a WebSocket connection. This is useful in deployment environments where WebSocket support is limited.

When enabled, the interactive extensions allow HTTP clients to:

  • Start a workflow execution and receive an execution ID
  • Poll for execution status (running, interaction required, OAuth required, completed, or failed)
  • Submit interaction responses (text, binary choice, radio, checkbox, dropdown, or notification acknowledgment)
  • Handle OAuth2 authorization code flows through status polling

Two client integration patterns are supported:

  • Polling mode: The server returns 202 Accepted with an execution ID. The client polls GET /executions/{execution_id} until the workflow completes or requires interaction.
  • Streaming mode (SSE): The server streams workflow output as Server-Sent Events. When an interaction or OAuth flow is needed, a typed SSE event is emitted. The client submits its response, and the stream resumes.

Configuration

HTTP interactive extensions are enabled by default on all workflow endpoints except for OpenAI-compatible endpoints (/v1/chat/completions). To force the interactive extension to work with OpenAI-compatible endpoints, set enable_interactive_extensions to true in the FastAPI front-end configuration:

general:
  front_end:
    _type: fastapi
    enable_interactive_extensions: true

The following table describes the relevant configuration parameters:

ParameterTypeDefaultDescription
enable_interactive_extensionsbooleanfalseEnable HTTP interactive execution on OpenAI-compatible endpoints. When true, POST requests to chat and OpenAI-compatible endpoints (/v1/chat/completions) return 202 Accepted if the workflow pauses for interaction or OAuth
disable_legacy_routesbooleanfalseDisable legacy endpoint paths (/generate, /chat). When true, only versioned paths with interactive support (/v1/workflow, /v1/chat) are registered
oauth2_callback_pathstring/auth/redirectPath for the OAuth2 authorization code grant callback endpoint

:::{note} Interactive extensions are enabled for versioned workflow and chat endpoints (for example, /v1/workflow and /v1/chat).

OpenAI-compatible endpoints (/v1/chat/completions) are opt-in only (defaulting to disabled). :::

Execution Lifecycle

An interactive HTTP execution moves through the following states:

flowchart TD
    Start(["Start workflow"])
    Running(["Running"])
    Interaction(["Interaction Required"])
    OAuth(["OAuth Required"])
    Completed(["Completed"])
    Failed(["Failed"])

    Start --> Running
    Running -->|Workflow has interaction| Interaction
    Running -->|Workflow needs authentication| OAuth
    Running -->|Workflow execution completes| Completed
    Running -->|Workflow execution failed| Failed
    Interaction -->|Client submits response to execution endpoint| Running
    Interaction -->|Timeout| Failed
    OAuth -->|OAuth redirect resolves token| Running
    OAuth -->|Timeout| Failed

    style Completed fill:#2e7d32,color:#fff,stroke:#1b5e20
    style Failed fill:#c62828,color:#fff,stroke:#b71c1c
    style Running fill:#006699,color:#fff,stroke:#003366

Endpoints

Starting an Execution (Polling Mode)

POST requests to versioned endpoints such as /v1/chat return a 202 Accepted response if the workflow requires interaction or OAuth before it can complete. Interactive support is enabled by default on these endpoints; the enable_interactive_extensions flag only gates OpenAI-compatible endpoints (see Configuration).

Request:

curl -X POST http://localhost:8000/v1/chat \
  -H "Content-Type: application/json" \
  -d '{
    "messages": [
      {"role": "user", "content": "Analyze the sales data"}
    ]
  }'

Response (202 Accepted, interaction required):

{
  "status": "interaction_required",
  "status_url": "/executions/550e8400-e29b-41d4-a716-446655440000",
  "interaction_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "prompt": {
    "input_type": "text",
    "text": "Should I include Q4 projections?",
    "placeholder": "Type your response...",
    "required": true,
    "timeout": null,
    "error": null
  },
  "response_url": "/executions/550e8400-e29b-41d4-a716-446655440000/interactions/a1b2c3d4-e5f6-7890-abcd-ef1234567890/response"
}

The error field inside the prompt object is only populated when the prompt times out or becomes unavailable. Under normal operation it is null.

Response (202 Accepted, OAuth required):

{
  "status": "oauth_required",
  "status_url": "/executions/550e8400-e29b-41d4-a716-446655440000",
  "auth_url": "https://provider.example.com/authorize?client_id=...&state=abc123",
  "oauth_state": "abc123"
}

If the workflow completes without requiring interaction, a standard 200 OK response with the workflow result is returned, identical to the non-interactive behavior.

Getting Execution Status

Poll the execution status endpoint to check progress or retrieve the final result.

  • Route: GET /executions/{execution_id}
  • Description: Returns the current status of an execution.

Request:

curl http://localhost:8000/executions/550e8400-e29b-41d4-a716-446655440000

Response (running):

{
  "status": "running"
}

Response (interaction required):

{
  "status": "interaction_required",
  "interaction_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "prompt": {
    "input_type": "text",
    "text": "Should I include Q4 projections?",
    "placeholder": "Type your response...",
    "required": true,
    "timeout": null,
    "error": null
  },
  "response_url": "/executions/550e8400-e29b-41d4-a716-446655440000/interactions/a1b2c3d4-e5f6-7890-abcd-ef1234567890/response"
}

The error field inside the prompt object is only populated when the prompt times out or becomes unavailable. Under normal operation it is null.

Response (OAuth required):

{
  "status": "oauth_required",
  "auth_url": "https://provider.example.com/authorize?client_id=...&state=abc123",
  "oauth_state": "abc123"
}

Response (completed):

{
  "status": "completed",
  "result": {
    "id": "chatcmpl-abc123",
    "object": "chat.completion",
    "choices": [
      {
        "message": {
          "content": "The analysis is complete. Q4 projections have been included.",
          "role": "assistant"
        },
        "finish_reason": "stop",
        "index": 0
      }
    ]
  }
}

Response (failed):

{
  "status": "failed",
  "error": "Workflow execution timed out after 300 seconds"
}

The following table lists all possible status values:

StatusDescription
runningThe workflow is actively executing
interaction_requiredThe workflow is paused waiting for a human response
oauth_requiredThe workflow is paused waiting for OAuth2 authorization
completedThe workflow finished successfully; the result field contains the output
failedThe workflow failed; the error field contains the error message

Submitting an Interaction Response

When an execution has status interaction_required, submit a response to resume the workflow.

  • Route: POST /executions/{execution_id}/interactions/{interaction_id}/response
  • Description: Submit a human response to a pending interaction prompt.

Request (text response):

curl -X POST http://localhost:8000/executions/550e8400-e29b-41d4-a716-446655440000/interactions/a1b2c3d4-e5f6-7890-abcd-ef1234567890/response \
  -H "Content-Type: application/json" \
  -d '{
    "response": {
      "input_type": "text",
      "text": "Yes, include Q4 projections"
    }
  }'

Response: 204 No Content

After submitting a response, the execution transitions back to running. Continue polling GET /executions/{execution_id} to track progress.

Supported Response Types

The response field in the request body is a discriminated union based on input_type. All prompt types supported by Interactive Workflows are available:

input_typeFieldsDescription
texttext (string)Free-text response
binary_choiceselected_option (object)One of two options (for example, Continue or Cancel)
radioselected_option (object)Single selection from multiple options
checkboxselected_options (array of objects)Multiple selections from a list
dropdownselected_option (object)Single selection from a dropdown
notification(none)Acknowledgment of a notification prompt

Request (radio response):

curl -X POST http://localhost:8000/executions/550e8400-e29b-41d4-a716-446655440000/interactions/a1b2c3d4-e5f6-7890-abcd-ef1234567890/response \
  -H "Content-Type: application/json" \
  -d '{
    "response": {
      "input_type": "radio",
      "selected_option": {"id": "email", "label": "Email", "value": "email"}
    }
  }'

Request (checkbox response):

curl -X POST http://localhost:8000/executions/550e8400-e29b-41d4-a716-446655440000/interactions/a1b2c3d4-e5f6-7890-abcd-ef1234567890/response \
  -H "Content-Type: application/json" \
  -d '{
    "response": {
      "input_type": "checkbox",
      "selected_options": [
        {"id": "email", "label": "Email", "value": "email"},
        {"id": "sms", "label": "SMS", "value": "sms"}
      ]
    }
  }'

Success Responses

Status CodeCondition
204Response accepted successfully

Error Responses

Status CodeCondition
400Interaction has already been resolved
404Execution or interaction not found

Streaming Mode with SSE Events

When using streaming endpoints (/v1/chat/stream or /v1/chat/completions with stream: true), interactive events are delivered as typed Server-Sent Events within the stream.

Interaction Required Event

When the workflow pauses for human interaction, the following SSE event is emitted:

event: interaction_required
data: {"event_type": "interaction_required", "execution_id": "550e8400-...", "interaction_id": "a1b2c3d4-...", "prompt": {"input_type": "text", "text": "Should I proceed?", ...}, "response_url": "/executions/550e8400-.../interactions/a1b2c3d4-.../response"}

After receiving this event, submit the interaction response through the POST /executions/{execution_id}/interactions/{interaction_id}/response endpoint. The SSE stream remains open and resumes sending workflow output once the response is submitted.

OAuth Required Event

When the workflow requires OAuth2 authorization, the following SSE event is emitted:

event: oauth_required
data: {"event_type": "oauth_required", "execution_id": "550e8400-...", "auth_url": "https://provider.example.com/authorize?...", "oauth_state": "abc123"}

Direct the user to the auth_url to complete authorization. After the OAuth redirect callback is processed, the stream resumes automatically.

Client Integration Example

The following Python example demonstrates how to consume the SSE stream and handle interactive events:

import httpx
import json


def stream_with_interactions(base_url: str, messages: list[dict]) -> str:
    """Stream a chat request and handle any interactive events."""
    with httpx.Client(base_url=base_url, timeout=300) as client:
        with client.stream(
            "POST",
            "/v1/chat/stream",
            json={"messages": messages},
        ) as response:
            lines_iter = response.iter_lines()
            for line in lines_iter:
                if not line:
                    continue

                # Check for typed SSE events
                if line.startswith("event: interaction_required"):
                    # Next line is the data payload
                    data_line = next(lines_iter)
                    event = json.loads(data_line.removeprefix("data: "))

                    # Prompt the user
                    print(f"Workflow asks: {event['prompt']['text']}")
                    user_input = input("> ")

                    # Submit the response
                    client.post(
                        event["response_url"],
                        json={
                            "response": {
                                "input_type": "text",
                                "text": user_input,
                            }
                        },
                    )
                    continue

                if line.startswith("event: oauth_required"):
                    data_line = next(lines_iter)
                    event = json.loads(data_line.removeprefix("data: "))
                    print(f"Please authorize at: {event['auth_url']}")
                    input("Press Enter after completing authorization...")
                    continue

                # Regular data chunk
                if line.startswith("data: "):
                    chunk = json.loads(line.removeprefix("data: "))
                    if "value" in chunk:
                        return chunk["value"]

    return ""

OpenAI Chat Completions API Compatibility

The OpenAI-compatible endpoint (/v1/chat/completions) also supports interactive extensions when enable_interactive_extensions is true. The behavior is the same as for the chat endpoints:

  • Non-streaming (stream: false): Returns 202 Accepted with execution details when interaction or OAuth is required
  • Streaming (stream: true): Emits interaction_required or oauth_required SSE events within the stream
curl -X POST http://localhost:8000/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "nvidia/llama-3.1-8b-instruct",
    "messages": [
      {"role": "user", "content": "Summarize my documents"}
    ],
    "stream": false
  }'

If the workflow needs human input, the response is 202 Accepted with the same structure as the polling mode responses described above.

OAuth2 Flow over HTTP

When a workflow requires OAuth2 authentication (for example, to access a third-party API), the execution pauses and the authorization URL is surfaced through the execution status or SSE event.

The flow works as follows:

  1. The workflow calls an authenticated tool that requires OAuth2
  2. The execution status changes to oauth_required with the auth_url
  3. The client directs the user to the auth_url to complete authorization
  4. The OAuth provider redirects the user to the configured callback path (default: /auth/redirect)
  5. The callback endpoint exchanges the authorization code for a token and resolves the execution
  6. The execution transitions back to running and the workflow continues

:::{note} The OAuth2 callback endpoint must be reachable by the user's browser. Ensure oauth2_callback_path is configured correctly for your deployment environment. :::