> For the complete documentation index, see [llms.txt](https://vibemx.gitbook.io/neuronai-studio/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://vibemx.gitbook.io/neuronai-studio/workflows/flow-nodes.md).

# Flow Nodes

Flow nodes control workflow execution structure — entry points, termination, pauses, and timing.

## Start

**Purpose:** Entry point for every workflow. Exactly one Start node is required.

| Config | Description                               |
| ------ | ----------------------------------------- |
| (none) | Passes through to the next connected node |

All runs begin at the Start node. Initial state is merged from the test harness message and optional "Initial state JSON".

## Stop

**Purpose:** Terminates the workflow run successfully.

| Config | Description            |
| ------ | ---------------------- |
| (none) | Marks run as completed |

At least one Stop node is required. A workflow may have multiple Stop nodes for different exit paths.

## Delay

**Purpose:** Pause execution for a specified duration.

| Config    | Description              |
| --------- | ------------------------ |
| `seconds` | Delay duration (integer) |

Useful for rate limiting, waiting on external systems, or demo pacing.

```mermaid
flowchart LR
    Start[Start] --> Agent[Agent] --> Delay[Delay 5s] --> LLM[LLM summary] --> Stop[Stop]
```

## Human

**Purpose:** Pause execution and wait for user input (Human-in-the-Loop).

| Config       | Description                                         |
| ------------ | --------------------------------------------------- |
| `prompt`     | Message shown to the user                           |
| `output_key` | State key for the reply (default: `human_response`) |

When the Human node executes, the workflow pauses and saves a checkpoint. The user replies via the test harness, and execution resumes from the checkpoint.

See [Human-in-the-Loop](/neuronai-studio/workflows/human-in-the-loop.md) for the full resume flow.

## Flow node summary

| Node  | Category | Handles           |
| ----- | -------- | ----------------- |
| Start | flow     | 1 output          |
| Stop  | flow     | 1 input           |
| Delay | flow     | 1 input, 1 output |
| Human | flow     | 1 input, 1 output |

## Related code

* `StartNodeExecutor`, `StopNodeExecutor`, `DelayNodeExecutor`, `HumanNodeExecutor`

## See also

* [AI Nodes](/neuronai-studio/workflows/ai-nodes.md)
* [Logic Nodes](/neuronai-studio/workflows/logic-nodes.md)


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