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

# Project Config (defineConfig)

> Configure Theo for a project with typed settings.

<Note>
  This page is the SDK helper. For the full schema, merge semantics, and JSON-only sandbox rationale, see [MCP / Project Config](/mcp/project-config).
</Note>

## `defineConfig(config)`

Creates a typed `TheoProjectConfig` for use in `theo.config.ts`. The MCP server reads this automatically.

```typescript theme={null}
// theo.config.ts
import { defineConfig } from "@hitheo/sdk";

export default defineConfig({
  persona: "You are Nova, an operations assistant for WarehouseOS.",
  skills: ["inventory-check", "data-extraction"],
  defaultMode: "auto",
  tools: [
    {
      name: "check_stock",
      description: "Look up current stock levels for a SKU",
      input_schema: {
        type: "object",
        properties: { sku: { type: "string" } },
        required: ["sku"],
      },
    },
  ],
  temperature: 0.7,
  metadata: { team: "warehouse-ops" },
});
```

## TheoProjectConfig

| Field         | Type                      | Description                               |
| ------------- | ------------------------- | ----------------------------------------- |
| `persona`     | `string`                  | Custom system prompt for every completion |
| `skills`      | `string[]`                | Skill slugs activated on every request    |
| `defaultMode` | `ChatMode`                | Default execution mode                    |
| `tools`       | `ToolDef[]`               | Inline tool definitions                   |
| `temperature` | `number`                  | Default temperature                       |
| `metadata`    | `Record<string, unknown>` | Metadata attached to every request        |

## File Formats

The MCP server prefers **JSON** config by default:

1. `theo.config.json` — always loaded when present (safe: parsed with `JSON.parse`).
2. `theo.config.js` / `theo.config.ts` — **ignored by default.** Loading them executes arbitrary code from the current working directory, which is unsafe when an IDE launches the MCP server in a project you don't fully trust.

To opt back into JS/TS config loading, set an environment variable before launching the MCP server:

```bash theme={null}
export THEO_ALLOW_JS_CONFIG=1
```

With that flag set, the server loads `theo.config.js` first, then `theo.config.ts`, falling back to `theo.config.json`. If a JS/TS config is found without the flag, the MCP server logs a warning and skips it.

<Warning>
  Only enable `THEO_ALLOW_JS_CONFIG=1` in directories you authored or trust. Any repo with a malicious `theo.config.js` can run arbitrary code in your shell session when the MCP server launches.
</Warning>

## How It's Used

When the `@hitheo/mcp` server starts, it:

1. Reads `THEO_API_KEY` from the environment
2. Loads `theo.config.json` (or JS/TS if opted in)
3. Injects `persona`, `skills`, and `tools` into every MCP tool call
4. Uses `defaultMode` as the fallback mode