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

# Task Errors

> Error classes for the task-augmented tool invocation lifecycle

These errors surface from the task-augmented tool invocation system (per the MCP 2025-11-25 task-support protocol). All inherit from `PublicMcpError` (safe to surface to clients) except `TaskStoreNotInitializedError`.

## Reference

| Class                               | Inherits           | JSON-RPC Code | When                                                                         |
| ----------------------------------- | ------------------ | ------------- | ---------------------------------------------------------------------------- |
| `TaskNotFoundError`                 | `PublicMcpError`   | `-32602`      | `tasks/get`, `tasks/cancel`, or `tasks/result` referenced an unknown task ID |
| `TaskAlreadyTerminalError`          | `PublicMcpError`   | `-32602`      | `tasks/cancel` invoked on a task already in `succeeded`/`failed`/`cancelled` |
| `TaskAugmentationNotSupportedError` | `PublicMcpError`   | `-32601`      | Client invoked `tools/call` with task augmentation on a tool that opts out   |
| `TaskAugmentationRequiredError`     | `PublicMcpError`   | `-32601`      | Tool declared `taskSupport: 'required'` but client did not request a task    |
| `TaskStoreNotInitializedError`      | `InternalMcpError` | —             | Internal: task store provider not registered when task subsystem is required |

## Usage

```typescript theme={"theme":{"light":"snazzy-light","dark":"dark-plus"}}
import { TaskNotFoundError, TaskAlreadyTerminalError } from '@frontmcp/sdk';

if (!task) {
  throw new TaskNotFoundError(taskId);
}

if (isTerminal(task.status)) {
  throw new TaskAlreadyTerminalError(task.status);
}
```

## Related

* [Tasks](/frontmcp/servers/tools#task-augmented-tools) — opt a tool into task augmentation
* [Errors Overview](/frontmcp/sdk-reference/errors/overview)