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

# group

> Contract, placement, related fields and source examples for this Nika YAML field.

[Language reference](/reference/language/overview) / `group`

## Meaning and placement

### task

Fan-in MEMBERSHIP · this task joins the named group, and a consumer folds the whole group with one `${{ group.<name> }}` binding in its `with:` (spec/03-dag.md §group). Membership is DECLARED, never matched: a renamed member leaves its group loudly (NIKA-DAG-008 on the reference), where a glob would shrink the fold in silence. A group exists iff at least one task declares it. An `unwind` task may not join one (NIKA-DAG-009 · cleanup never schedules).

| Property        | Declaration                    |
| --------------- | ------------------------------ |
| Requirement     | Optional in this object        |
| Schema location | `/$defs/task/properties/group` |
| type            | "string"                       |
| pattern         | "^\[a-z]\[a-z0-9\_]\*\$"       |

**In the same object:** [after](/reference/language/words/after) · [agent](/reference/language/words/agent) · [exec](/reference/language/words/exec) · [extract](/reference/language/words/extract) · [for\_each](/reference/language/words/for_each) · [infer](/reference/language/words/infer) · [invoke](/reference/language/words/invoke) · [lift](/reference/language/words/lift) · [on\_error](/reference/language/words/on_error) · [retry](/reference/language/words/retry) · [returns](/reference/language/words/returns) · [timeout](/reference/language/words/timeout) · [when](/reference/language/words/when) · [with](/reference/language/words/with)

[Schema source (use the pointer above)](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/schemas/workflow.schema.json)

## Examples

No matching source-template occurrence is recorded in this projection. [Write a workflow](/guides/templates) or consult the schema declaration above.

## Contract and implementation

This page projects the named specification revision. Check [released engine status](/reference/status) and [the validation workflow](/guides/agent-authoring) before running a file. An optional field is not evidence that every engine supports every value.

Canonical identity: `language:word:group`. Spec revision: [`c5ebbb7b862b`](https://github.com/supernovae-st/nika-spec/tree/c5ebbb7b862b68bc6cf7235efba61173b844afc6).

[How documentation stays connected](/reference/knowledge-system).