# Custom Context Helpers
URL: /concepts/additional-context/custom-helpers

Custom context helpers let you automatically include application-specific data with every message. A helper is just a function that returns a value (or null/undefined to skip). The object key you provide becomes the context name in messages.

## Defining Helpers

You can define helpers as simple functions:

```tsx
// Reusable helpers
const sessionHelper = async () => ({
  sessionId: getSessionId(),
  startTime: getSessionStartTime(),
  user: await getCurrentUser(),
});

const environmentHelper = async () => ({
  env: process.env.NODE_ENV,
  version: process.env.NEXT_PUBLIC_APP_VERSION,
  feature_flags: await getFeatureFlags(),
});

// Use in TamboProvider
<TamboProvider
  contextHelpers={{
    session: sessionHelper, // Key becomes context name
    environment: environmentHelper,
  }}
/>;
```

## Inline Custom Helpers

Define helpers inline where you configure the provider:

```tsx
<TamboProvider
  contextHelpers={{
    deviceInfo: async () => ({
      userAgent: navigator.userAgent,
      platform: navigator.platform,
      screenResolution: {
        width: window.screen.width,
        height: window.screen.height,
      },
    }),
  }}
/>
```

## Overriding Prebuilt Helpers

Replace a prebuilt helper by using the same key:

```tsx
<TamboProvider
  contextHelpers={{
    // Override the built-in userTime helper
    userTime: async () => ({
      formattedTime: new Date().toLocaleString("en-US", {
        weekday: "long",
        year: "numeric",
        month: "long",
        day: "numeric",
      }),
      timezone: Intl.DateTimeFormat().resolvedOptions().timeZone,
    }),
  }}
/>
```

## Async vs Sync

Helpers can be synchronous or asynchronous:

```tsx
// Synchronous
const syncHelper = () => ({
  theme: getTheme(),
  language: getLanguage(),
});

// Asynchronous
const asyncHelper = async () => ({
  user: await fetchUser(),
  permissions: await fetchPermissions(),
});
```

Tip: Return null/undefined from a helper to skip including it in a particular environment or condition (e.g., return null for browser-only helpers on the server).