# Configure the hosted Pi runtime

Select the default model, thinking level, and hosted Pi behavior for new sessions.

`.pi/settings.json` is the standard Pi project settings file. Salambo reads the server-safe settings and reports unsupported local-only behavior before deployment.

## Select the default model

```json
{
  "defaultProvider": "openai",
  "defaultModel": "gpt-5.2",
  "defaultThinkingLevel": "medium"
}
```

| Field                  | Requirement                                                            |
| ---------------------- | ---------------------------------------------------------------------- |
| `defaultProvider`      | Non-empty provider identifier                                          |
| `defaultModel`         | Non-empty model identifier for that provider                           |
| `defaultThinkingLevel` | Optional: `off`, `minimal`, `low`, `medium`, `high`, `xhigh`, or `max` |

Provider credentials remain in `salambo.yaml`. A custom provider is registered by a Pi extension with `pi.registerProvider()`.

## Built-in tools

The hosted runtime supplies four Pi tools:

| Tool    | Use                                                                      |
| ------- | ------------------------------------------------------------------------ |
| `read`  | Read text or supported images, with offsets for large files              |
| `write` | Create or replace a workspace file and create missing parent directories |
| `edit`  | Apply one or more exact, non-overlapping replacements                    |
| `bash`  | Run a sandbox command with progress updates and bounded output           |

Tools registered by discovered `.pi/extensions/` modules also start active. `grep`, `find`, and `ls` are shell commands, not separate hosted tools. Run them through `bash`, or register a typed extension tool.

## Change tools for one turn

An extension may call `pi.setActiveTools()` from `before_agent_start`. The selection must remain within the tools allowed by the deployment. Salambo persists the resulting active set for durable follow-up turns.

The discovered deployment tool set remains the default for new sessions. Next, [build your first extension](/docs/agent-development/extensions).