> ## 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.

# const

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

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

## Meaning and placement

### document

Named constants · `${{ const.X }}` · a fixed value baked into the workflow. Either a bare literal, or a `{ type, value }` typed constant whose `value:` MUST conform to `type:`. The literal half of the dead `vars:` block (R3a · LAW-SURFACE-0201) · everything that is not `required: true` lands here per the E-split total rule.

| Property             | Declaration                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
| -------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Requirement          | Optional in this object                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| Schema location      | `/properties/const`                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| type                 | "object"                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
| additionalProperties | \{"type": \["string", "number", "boolean", "array", "object", "null"], "if": \{"type": "object", "required": \["type", "value"]}, "then": \{"additionalProperties": false, "properties": \{"type": \{"$ref": "#/$defs/typeExpr"}, "value": \{"description": "The constant value · MUST conform to `type:` (NIKA-DEFAULT-001)."}, "description": \{"description": "Free-form prose about this constant · why the value is what it is. Documentation only — the contract is `type` and `value`.", "type": "string"}}, "\$comment": "An object carrying BOTH `type` and `value` is a typed constant · the type speaks the full TypeExpr (R3b) and values\_core checks the value against it (NIKA-DEFAULT-001) · an object missing either key is a bare literal object constant."}} |

**In the same object:** [inputs](/reference/language/words/inputs) · [model](/reference/language/words/model) · [nika](/reference/language/words/nika) · [outputs](/reference/language/words/outputs) · [permits](/reference/language/words/permits) · [run](/reference/language/words/run) · [secrets](/reference/language/words/secrets) · [tasks](/reference/language/words/tasks)

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

## In a source template

Excerpt from `templates/api-upload-and-create.nika.yaml`, source lines 36–45. This is a fragment, not a runnable workflow.

```yaml illustration theme={"system"}
# Run · nika run <file>          # offline rehearsal · no key exported
nika: api-upload-and-create-template       # SLOT: kebab-case workflow id

const:
  api_base: "https://api.example.com"     # SLOT: the product API base
  asset_path: "./out/assets/asset-1.png"  # SLOT: the file to upload

secrets:
  API_KEY:
    source: env
```

### Templates containing this field

| Template                                    | Source                                                                                                                                            |
| ------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------- |
| `templates/api-upload-and-create.nika.yaml` | [Line 39](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/api-upload-and-create.nika.yaml#L39) |
| `templates/chain.nika.yaml`                 | [Line 32](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/chain.nika.yaml#L32)                 |
| `templates/classify-and-route.nika.yaml`    | [Line 20](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/classify-and-route.nika.yaml#L20)    |
| `templates/corpus-qa.nika.yaml`             | [Line 21](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/corpus-qa.nika.yaml#L21)             |
| `templates/document-to-fields.nika.yaml`    | [Line 21](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/document-to-fields.nika.yaml#L21)    |
| `templates/etl-state.nika.yaml`             | [Line 50](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/etl-state.nika.yaml#L50)             |
| `templates/evaluate-and-optimize.nika.yaml` | [Line 33](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/evaluate-and-optimize.nika.yaml#L33) |
| `templates/fanout.nika.yaml`                | [Line 63](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/fanout.nika.yaml#L63)                |
| `templates/gate-and-act.nika.yaml`          | [Line 28](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/gate-and-act.nika.yaml#L28)          |
| `templates/human-gated-ship.nika.yaml`      | [Line 56](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/human-gated-ship.nika.yaml#L56)      |
| `templates/media-asset-pack.nika.yaml`      | [Line 35](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/media-asset-pack.nika.yaml#L35)      |
| `templates/website-brief.nika.yaml`         | [Line 37](https://github.com/supernovae-st/nika-spec/blob/c5ebbb7b862b68bc6cf7235efba61173b844afc6/templates/website-brief.nika.yaml#L37)         |

These are literal key occurrences in the source files, not an execution or conformance claim. [How to instantiate a template](/guides/templates).

## 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:const`. Spec revision: [`c5ebbb7b862b`](https://github.com/supernovae-st/nika-spec/tree/c5ebbb7b862b68bc6cf7235efba61173b844afc6).

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