> ## Documentation Index
> Fetch the complete documentation index at: https://help.statisfy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Milestones & Task Hierarchy

> Structure your projects with milestones, subtasks, and multi-level task hierarchies.

Projects in Statisfy organize tasks in a tree structure — root-level tasks can have subtasks, and milestones unlock an extra level of nesting. This page explains how the hierarchy works and what limits apply.

## Prerequisites

* An existing project open in the **Manage > Projects** section
* Familiarity with adding tasks via the **Add Task/Milestone** button in the project task grid
* To reparent tasks via drag and drop, the project must be a Statisfy-native project (see [Reorder & Reparent Tasks](/projects/drag_drop_task_ordering))

***

## Task Hierarchy

Every project task exists at a specific level in the tree:

* **Root tasks** sit at the top level of the project
* **Subtasks** are children of a root task
* **Sub-subtasks** are children of a subtask (only available under milestones)

You can add a subtask by clicking the **Add Subtask** action on any task, or by dragging a task onto another task's middle drop zone (see [Reorder & Reparent Tasks](/projects/drag_drop_task_ordering)).

![Project task grid showing a milestone with subtasks and a sub-subtask nested underneath](https://cdn.statisfy.com/help-artifacts/projects/task-hierarchy-overview.png)

***

## Milestones

Milestones are a special task type that represent significant project checkpoints. They differ from regular tasks in one key way: **milestones allow one extra level of nesting**.

To create a milestone, select **Milestone** as the task type when adding a new root-level task.

![Add Milestone dialog showing Task Type set to Milestone with the Milestone Name field](https://cdn.statisfy.com/help-artifacts/projects/milestone-creation-dialog.png)

<Note>
  Milestones must be created at the root level of a project. You cannot convert an existing subtask into a milestone.
</Note>

***

## Depth Limits

The maximum nesting depth depends on the root task type:

| Root Task Type | Max Levels | Structure                         |
| -------------- | ---------- | --------------------------------- |
| Regular task   | 2          | Task → Subtask                    |
| Milestone      | 3          | Milestone → Subtask → Sub-subtask |

<Warning>
  You cannot nest tasks beyond these limits. If you try to add a subtask or drag a task to a level that would exceed the maximum depth, the operation is blocked.
</Warning>

These depth limits also apply when reparenting tasks via drag and drop — the system checks the full subtree depth of the task being moved to ensure the target location doesn't exceed the limit.

***

## How Hierarchy Interacts with Dependencies

Task dependencies can only be created between **sibling tasks** — tasks that share the same parent. This means:

* Two root-level tasks can depend on each other
* Two subtasks under the same parent can depend on each other
* A root-level task and a subtask **cannot** depend on each other

If you reparent a task (move it to a different parent), **all dependencies on that task will be removed** — both where it is a blocker and where it is a dependent.

For full details on how dependencies and auto-cascade work with the task hierarchy, see [Task Dependencies & Auto-Cascade Dates](/projects/task_dependencies_and_cascading).

***

## Related Pages

<CardGroup cols={2}>
  <Card title="Task Dependencies & Auto-Cascade" icon="link" href="/projects/task_dependencies_and_cascading">
    Manage blocking relationships and automatic date cascading
  </Card>

  <Card title="Reorder & Reparent Tasks" icon="arrows-up-down" href="/projects/drag_drop_task_ordering">
    Use drag and drop to restructure your task hierarchy
  </Card>
</CardGroup>