---
title: "Start a Process When a Human Task Becomes Available — Spiff Arena 0.1 documentation"
description: "Spiff Arena can start another process model when a human task becomes available. This works for User Tasks and Manual Tasks."
source_url: https://spiff.works/docs/spiff-arena/how_to_guides/building_diagrams/start_process_when_task_available.html
---

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# Start a Process When a Human Task Becomes Available[](#start-a-process-when-a-human-task-becomes-available "Link to this heading")

Spiff Arena can start another process model when a human task becomes available.
This works for User Tasks and Manual Tasks.

Use this when task availability should trigger related workflow, such as assigning follow-up work, creating an audit record, sending a message, or starting a task-specific integration process.

## How It Works[](#how-it-works "Link to this heading")

When Arena creates a new waiting human task, it checks the task for the `spiffworkflow:processModelToStartOnTaskAvailable` BPMN extension.
If the extension has a value, Arena starts that process model as a separate process instance.

The started process receives only one injected data value:

| Variable | Description |
| --- | --- |
| `task_guid` | The runtime task GUID for the newly available User Task or Manual Task. This is the identifier used in Arena task URLs and task helper scripts; it is not the BPMN task id or the human task database row id. |

The started process can use script helpers to look up any other information it needs from that task GUID.

## Configure the Task Hook[](#configure-the-task-hook "Link to this heading")

1. Create the process model that should be started when the task becomes available.
   The process should use a none start event that can be started by Arena.
2. In the source process model, select the User Task or Manual Task.
3. In the properties panel, open **Task Hooks**.
4. Set **Process Model to Start on Task Available** to the target process model identifier.
   This is the process model path, such as `task-hooks/task-available`.
5. Save the source process model and start a new process instance.

Adding the hook to a task that is already waiting will not retrigger the hook.
Start a new source process instance to test a new configuration.

## BPMN XML[](#bpmn-xml "Link to this heading")

The modeler writes the hook as a SpiffWorkflow extension element:

```
<bpmn:userTask id="ReviewRequest" name="Review request">
  <bpmn:extensionElements>
    <spiffworkflow:processModelToStartOnTaskAvailable>task-hooks/task-available</spiffworkflow:processModelToStartOnTaskAvailable>
  </bpmn:extensionElements>
</bpmn:userTask>
```

Manual Tasks use the same extension inside the task’s `<bpmn:extensionElements>`.
For the full extension naming reference, see [Spiff-Flavored BPMN](../../reference/spiff_flavored_bpmn.html).

## Get Task Details in the Started Process[](#get-task-details-in-the-started-process "Link to this heading")

Because only the runtime task GUID is injected, use scripts in the started process to derive the details needed for that workflow.

For example:

```
task_url = get_url_for_task(task_guid)
public_task_url = get_url_for_task(task_guid, public=True)
potential_owners = get_task_potential_owners(task_guid)
usernames = potential_owners["users"]
groups = potential_owners["groups"]
```

`get_url_for_task(task_guid)` returns the full Arena URL for the task, which is appropriate to include in a user notification so the user can go directly to the exact piece of work they need to complete.
Use the `public=True` option only when the task is configured for public completion.
`get_task_potential_owners(task_guid)` returns the usernames and group identifiers that can complete the task.