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

# Otto extensions

<Info>
  **Labs**

  This feature is in [Labs](/docs/astro/feature-previews).
</Info>

Extensions are opt-in capabilities that ship inside the Otto binary and add tools, slash commands, or background behaviors to a session. Some are on by default because they catch common mistakes or add useful slash commands; others are off by default because they spawn subprocesses, consume credits, or materially change behavior.

## Bundled extensions

| Name             | Default | What it does                                                                                                                                                                                                                    |
| ---------------- | ------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `ask-user`       | on      | Registers the `ask_user` tool so Otto can ask 1-4 focused questions in a single batch rather than many one-at-a-time prompts.                                                                                                   |
| `dag-validation` | on      | After any edit or write to `dags/*.py`, runs `af dags errors` and surfaces import errors so Otto self-corrects in the same turn. Only fires when a local Airflow is reachable.                                                  |
| `memory`         | on      | Registers `/bootstrap` (seed memories from git and GitHub history) and `/remember` (save learnings from the current conversation).                                                                                              |
| `skills`         | on      | Provides the hosted-skill surface: the `skill` tool, the `/skills` picker, and `/skill:<name>` commands for hosted skills. Disabling removes hosted skills entirely; local skills still work. See [Skills](/docs/astro/otto-skills). |
| `spinner-verbs`  | on      | Replaces the default loader with space-themed verbs and an elapsed-time counter. Cosmetic only.                                                                                                                                 |
| `subagent`       | off     | Registers a `subagent` tool that delegates tasks to isolated `otto` subprocesses. Supports single (`task`) or parallel (`tasks: [...]`) delegation, with `fast` and `deep` model tiers.                                         |

## Enable or disable an extension

Four layers control whether an extension is on, merged in order (highest priority first):

| Layer                | Where                                                           | Example                                              |
| -------------------- | --------------------------------------------------------------- | ---------------------------------------------------- |
| CLI flag             | `--extension <name>`, `--no-extension <name>` (repeatable)      | `astro otto --no-extension dag-validation`           |
| Environment variable | `OTTO_EXTENSIONS`, `OTTO_DISABLED_EXTENSIONS` (comma-separated) | `OTTO_DISABLED_EXTENSIONS=dag-validation astro otto` |
| Project settings     | `.astro/otto/extensions.json`                                   | `{ "dag-validation": false }`                        |
| User settings        | `~/.astro/otto/extensions.json`                                 | `{ "memory": false }`                                |

Within a layer, an explicit disable beats an explicit enable. For example, `--extension foo --no-extension foo` disables `foo`.

## Manage extensions interactively

Run `/extensions` inside an Otto session to open an interactive editor.

The main picker shows each bundled extension with its current state and a `*` marker when a CLI flag or environment variable is overriding the settings files. Select an extension to open a per-extension editor with two rows: a User scope row and a Project scope row. Each row has a three-state checkbox:

* `[x]` on — writes `enabled: true` to that settings file.
* `[ ]` off — writes `enabled: false` to that settings file.
* `[~]` unset — removes the `enabled` field so lower layers win.

Press `Enter` or `Space` to cycle the focused row. The title bar updates to show the predicted next-session state and which layer is winning. Press `Escape` to save and close.

To apply the change:

* Run `/reload` to re-run the extension list against the fresh settings while keeping your conversation history.
* Run `/new` to start a fresh session.
* Restart Otto for a full reset.

## Configure an extension

The settings file accepts either a boolean shorthand or an object with `enabled` plus any extension-specific config. Both forms can coexist in the same file:

```json title="extensions.json" wrap theme={null}
{
  "memory": false,
  "dag-validation": {
    "enabled": true,
    "timeout": 60000
  },
  "subagent": {
    "enabled": true,
    "tiers": { "fast": "gpt-5.4-nano", "deep": "gpt-5.4" }
  }
}
```

Project settings shadow user settings per extension (whole-entry replace, not a deep merge).

### Configurable fields

| Extension        | Field        | Type   | Default        | Description                                                                                         |
| ---------------- | ------------ | ------ | -------------- | --------------------------------------------------------------------------------------------------- |
| `dag-validation` | `timeout`    | number | `30000`        | Timeout in milliseconds for `af dags errors`.                                                       |
| `subagent`       | `tiers.fast` | string | `gpt-5.4-nano` | Model used when a subagent call uses `tier: "fast"`.                                                |
| `subagent`       | `tiers.deep` | string | parent's model | Model used when a subagent call uses `tier: "deep"`. Omit to inherit the main conversation's model. |

Extensions that don't appear in the table take no configuration — they're either on or off.