# ClientContext

**Kind:** Interface

**Source:** [`src/adapter/aws-lambda/types.ts`](https://github.com/honojs/hono/blob/main/src/adapter/aws-lambda/types.ts#L8)

**Part of:** [Adapter](subsystem-src-adapter)

`ClientContext` defines the request-scoped context passed through the AWS Lambda adapter. It groups the platform client API, environment values, and an open-ended `Custom` field for application-specific context.

## Properties

| Property | Type |
|---|---|
| `client` | `ClientContextClient` |
| `Custom` | `any` |
| `env` | `ClientContextEnv` |

## Diagram

```mermaid
graph LR
  Context[ClientContext]
  Client[client: ClientContextClient]
  Env[env: ClientContextEnv]
  Custom[Custom: any]

  Context --> Client
  Context --> Env
  Context --> Custom
```

## Usage

```ts
import type { ClientContext } from "./types";

function handleRequest(context: ClientContext) {
  const region = context.env.region;

  context.client.log({
    message: `Handling request in ${region}`,
  });

  const tenantId = context.Custom?.tenantId;

  return {
    tenantId,
    region,
  };
}
```

## AI Coding Instructions

- Pass `ClientContext` through Lambda request handling code instead of separately passing `client`, `env`, and custom values.
- Access AWS adapter APIs through `context.client` and configuration through `context.env`.
- Treat `Custom` as application-defined data; narrow or validate its shape before reading properties.
- Keep custom context values request-scoped to avoid sharing mutable state across Lambda invocations.

## How it works

`ClientContext` is an exported TypeScript interface that describes the `clientContext` value on an AWS Lambda `LambdaContext`. That enclosing property is optional and may be `undefined`. [src/adapter/aws-lambda/types.ts:8-13](src/adapter/aws-lambda/types.ts#L8-L13) [src/adapter/aws-lambda/types.ts:35-47](src/adapter/aws-lambda/types.ts#L35-L47)

Its required members are:

- `client`, a `ClientContextClient` object containing string fields for `installationId`, `appTitle`, `appVersionName`, `appVersionCode`, and `appPackageName`. [src/adapter/aws-lambda/types.ts:9](src/adapter/aws-lambda/types.ts#L9) [src/adapter/aws-lambda/types.ts:15-21](src/adapter/aws-lambda/types.ts#L15-L21)
- `env`, a `ClientContextEnv` object containing string fields for `platformVersion`, `platform`, `make`, `model`, and `locale`. [src/adapter/aws-lambda/types.ts:12](src/adapter/aws-lambda/types.ts#L12) [src/adapter/aws-lambda/types.ts:23-29](src/adapter/aws-lambda/types.ts#L23-L29)

It also declares an optional, capitalized `Custom` member with the `any` type. [src/adapter/aws-lambda/types.ts:11](src/adapter/aws-lambda/types.ts#L11)

The interface declares no methods, runtime validation, thrown errors, or side effects. [src/adapter/aws-lambda/types.ts:8-13](src/adapter/aws-lambda/types.ts#L8-L13) The AWS Lambda adapter passes its received `LambdaContext` onward as `context` in `streamHandle` and as `lambdaContext` in `handle`; neither shown path reads `clientContext` directly. [src/adapter/aws-lambda/handler.ts:147-157](src/adapter/aws-lambda/handler.ts#L147-L157) [src/adapter/aws-lambda/handler.ts:252-272](src/adapter/aws-lambda/handler.ts#L252-L272)