# Start Node, Global Variables, and System Variables Reference

> Reference guide for workflow start node outputs, 12 global variable types, read-only system variables, and node I/O data types.

Source: https://doc.fastgpt.io/en/guide/build/workflow/variables

In FastGPT workflows, data flows across the canvas from three variable sources: **Start node outputs**, **application-level global variables**, and **read-only runtime system variables**.

## 1. Workflow Start Node (`workflowStart`)

Every main workflow canvas contains a single **Workflow Start** node that serves as the entry point for incoming conversation requests.

| Output Field      | Internal Key    | Value Type      | Description                                                                                                                                |
| ----------------- | --------------- | --------------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
| **User question** | `userChatInput` | `String`        | Text message submitted by the user in the current turn                                                                                     |
| **File URLs**     | `userFiles`     | `Array<string>` | Temporary signed URLs of documents and images uploaded in the current turn when [File Input](/en/guide/build/general/fileInput) is enabled |

## 2. Global Variables

Declare global variables under **System configuration → Global Variable** in the workflow editor or in the **Global Variable** section of a Chat Agent. Global variables can be referenced in any node via the variable picker and updated at runtime by the [Variable Update](/en/guide/build/workflow/nodes/variable_update) node.

### 1. Pre-Chat Form Variables (User-Facing)

When configured, users see the corresponding form controls before starting a new conversation:

| Variable Type                | Enum Key          | Default Value Type                    | Typical Use Case                                             |
| ---------------------------- | ----------------- | ------------------------------------- | ------------------------------------------------------------ |
| **Text Input box**           | `input`           | `String` (or `Object` / typed arrays) | Name, ticket number, background context, or structured input |
| **Number Input Box**         | `numberInput`     | `Number`                              | Result count limit, budget cap, or numeric threshold         |
| **Single Select Box**        | `select`          | `String`                              | Business category, target language, or output tone           |
| **Multiple selection boxes** | `multipleSelect`  | `Array<string>`                       | Multiple review dimensions or delivery channels              |
| **Switch**                   | `switch`          | `Boolean`                             | Toggle web search, deep analysis, or strict review branches  |
| **Password**                 | `password`        | `String`                              | Masked temporary access token or secret                      |
| **Time point**               | `timePointSelect` | `String`                              | Specific deadline or query timestamp                         |
| **Time range**               | `timeRangeSelect` | `Array<string>`                       | Start and end time pair                                      |
| **Chat Model Selection**     | `llmSelect`       | `String`                              | Allow the user to switch the underlying chat model           |
| **File upload**              | `file`            | `Array<string>`                       | Supply pre-chat attachment file URLs                         |

### 2. Hidden and Internal State Variables

| Variable Type                     | Enum Key   | Visibility                                                                        | Initialization and Update                                                                                                                                                |
| --------------------------------- | ---------- | --------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| **External Variable (Custom)**    | `custom`   | Hidden only in share links; the input box is shown in in-app chat and run preview | Supplied via embedded URL query parameters, share-auth callbacks, or OpenAPI `variables`                                                                                 |
| **Internal variables (Internal)** | `internal` | Hidden from end users and external APIs                                           | Initialized with its default value inside the workflow and mutated across nodes or loop iterations via [Variable Update](/en/guide/build/workflow/nodes/variable_update) |

![Configure numeric global variables and comparison operators](https://cdn.jsdelivr.net/gh/labring/fastgpt-img@main/optimized/current/variable-number-operators.png.webp)

## 3. Runtime System Variables

System variables are injected automatically by the workflow engine on each run and are always available in the variable picker:

| System Variable     | Internal Key         | Value Type    | Description                                                                                       |
| ------------------- | -------------------- | ------------- | ------------------------------------------------------------------------------------------------- |
| **User ID**         | `userId`             | `String`      | Authenticated member ID or external `customUid`, often passed to HTTP nodes for permission lookup |
| **App ID**          | `appId`              | `String`      | Unique identifier of the running application                                                      |
| **Current Chat ID** | `chatId`             | `String`      | Unique identifier of the active multi-turn conversation                                           |
| **AI Response ID**  | `responseChatItemId` | `String`      | Unique record ID of the current assistant response item                                           |
| **Chat history**    | `histories`          | `ChatHistory` | Conversation history array formatted as `{ obj: 'System' \| 'Human' \| 'AI', value: string }[]`   |
| **Current time**    | `cTime`              | `String`      | Timestamp string with timezone context when the run started                                       |

## 4. Node I/O Value Types (`WorkflowIOValueTypeEnum`)

Canvas connections and variable pickers validate compatibility using the declared port value types:

| Type Key                                                       | Display Label                   | Structure                                                                                                                                             |
| -------------------------------------------------------------- | ------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- |
| `string` / `number` / `boolean`                                | `String` / `Number` / `Boolean` | Scalar primitive types                                                                                                                                |
| `object`                                                       | `Object`                        | JSON key-value object                                                                                                                                 |
| `arrayString` / `arrayNumber` / `arrayBoolean` / `arrayObject` | `Array<T>`                      | Strongly typed arrays used directly by [Loop](/en/guide/build/workflow/nodes/loop_run) or [Parallel Run](/en/guide/build/workflow/nodes/parallel_run) |
| `arrayAny` / `any`                                             | `Array` / `Any`                 | Untyped array or dynamic value (common in Code Run and HTTP Request outputs)                                                                          |
| `chatHistory`                                                  | History                         | Multi-turn context array consumed by AI Chat and Question Classification                                                                              |
| `datasetQuote`                                                 | Dataset citations               | Retrieved chunk array `{ id, datasetId, collectionId, sourceName, q, a }[]`                                                                           |
| `selectDataset`                                                | Select Dataset                  | Target knowledge base ID list passed into a workflow tool                                                                                             |

Next: Learn how to mutate state with [Variable Update](/en/guide/build/workflow/nodes/variable_update) or check [Workflow Connection Rules](/en/guide/build/workflow/rules).