> For the complete documentation index, see [llms.txt](https://docs.lingoql.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lingoql.com/sub0/apis-abi/action-chaining.md).

# Action Chaining

Action chaining lets one actionable reuse the output of another.

That is how Sub0 handles multi-step workflows without controllers or service classes.

### Use `depends_on`

Add `depends_on` inside the actionable that needs previous output.

```json
"depends_on": [ ... ]
```

You can depend on:

* another actionable in the same resource
* an actionable in another resource

### Same-resource example

Action `2` reuses the result from action `1`.

```json
{
  "id": 2,
  "mode": "QUERY",
  "depends_on": [
    {
      "resource_id": "self",
      "action_ids": [1],
      "extract_response_for": [
        {
          "extract": "id",
          "for": "user_id"
        }
      ]
    }
  ],
  "sql_query": {
    "query": "SELECT * FROM users WHERE id = $1",
    "parameters": ["user_id"]
  }
}
```

`self` refers to the current resource.

### Cross-resource example

Reuse an actionable from another endpoint:

```json
{
  "depends_on": [
    {
      "resource_id": "transactions-fetch-01",
      "action_ids": [1],
      "extract_response_for": [
        {
          "extract": "transaction_id",
          "for": "txn_id"
        }
      ]
    }
  ]
}
```

This is useful when the same workflow step should serve multiple endpoints.

### Extract values with `extract_response_for`

Each rule maps a value from the dependency result into a new field.

```json
{
  "extract": "transactionNo",
  "for": "txn_id"
}
```

Special extractor:

* `self_` returns the full response body

Nested paths also work:

* `user.profile.email`
* `items.0.id`

### HTTP request example

Fetch data first, then reuse it in another request:

```json
{
  "id": 4,
  "mode": "HTTPREQUEST",
  "depends_on": [
    {
      "resource_id": "self",
      "action_ids": [3],
      "extract_response_for": [
        {
          "extract": "self_",
          "for": "message"
        }
      ]
    }
  ],
  "http": {
    "url": "https://api.sendgrid.com/send",
    "method": "POST"
  }
}
```

### Upload chaining

Upload results automatically flow into the next actionable.

```json
{
  "id": 1,
  "mode": "UPLOAD"
}
```

```json
{
  "id": 2,
  "mode": "QUERY",
  "sql_query": {
    "query": "INSERT INTO gallery (url, file_size) VALUES ($1, $2)",
    "parameters": ["url", "file_size"]
  }
}
```

### Guardrails

* Actionables run sequentially by default.
* Use `parallel: true` only for independent actions.
* Use `no_op: true` when an action should run only through `depends_on`.

### Why this matters

Action chaining is where Sub0 starts to feel different.

You stop writing orchestration code and start declaring the flow directly.


---

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