--- title: "Request ID and Language" description: "Hono provides specialized middleware and utilities for tracking requests and managing client localization across web applications. The request ID middleware assigns or propagates unique correlation..." last_updated: "2026-10-12T08:14:12.769531+00:00" canonical_url: "https://www.doc0.dev/docs/552ca36e-f67e-41c3-a07a-def9bd9551b0/technical/traffic-middleware/request-id-and-language" ---
Relevant source files The following files were used as context for generating this wiki page: - [src/middleware/request-id/request-id.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/request-id.ts) - [src/middleware/secure-headers/secure-headers.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/secure-headers/secure-headers.ts) - [src/middleware/language/language.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts) - [src/context.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/context.ts) - [src/adapter/aws-lambda/handler.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/adapter/aws-lambda/handler.ts) - [src/middleware/request-id/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/index.ts) - [src/helper/route/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/helper/route/index.ts) - [src/middleware/logger/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/logger/index.ts) - [src/middleware/language/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/index.ts) - [src/request.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/request.ts) - [src/middleware/ip-restriction/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/ip-restriction/index.ts) - [src/middleware/cache/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/cache/index.ts) - [src/middleware/etag/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/etag/index.ts) - [src/middleware/jsx-renderer/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/jsx-renderer/index.ts) - [src/middleware/method-override/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/method-override/index.ts) - [src/helper/accepts/accepts.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/helper/accepts/accepts.ts) - [src/middleware/timing/timing.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/timing/timing.ts) - [src/adapter/cloudflare-pages/handler.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/adapter/cloudflare-pages/handler.ts) - [src/middleware/context-storage/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/context-storage/index.ts) - [src/helper/streaming/text.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/helper/streaming/text.ts) - [src/helper/ssg/middleware.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/helper/ssg/middleware.ts) - [src/hono-base.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/hono-base.ts) - [src/adapter/vercel/conninfo.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/adapter/vercel/conninfo.ts) - [src/adapter/lambda-edge/conninfo.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/adapter/lambda-edge/conninfo.ts) - [src/helper/adapter/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/helper/adapter/index.ts) - [src/utils/headers.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/utils/headers.ts) - [package.json](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/package.json) - [src/helper/accepts/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/helper/accepts/index.ts) - [runtime-tests/workerd/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/runtime-tests/workerd/index.ts) - [src/middleware/trailing-slash/index.ts](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/trailing-slash/index.ts)
## Overview Hono provides specialized middleware and utilities for tracking requests and managing client localization across web applications. The request ID middleware assigns or propagates unique correlation identifiers via configurable headers and generator functions, integrating directly with TypeScript type definitions through declaration merging. For localization, language detection strategies parse quality-weighted `Accept-Language` headers, query parameters, cookies, and URL paths, normalizing locale tags against supported options and persisting selections to optimize downstream handling. Sources: [src/middleware/request-id/request-id.ts:9-56](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/request-id.ts#L9-L56), [src/middleware/request-id/index.ts:5-7](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/index.ts#L5-L7), [src/middleware/language/language.ts:13-172](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L13-L172), [src/middleware/language/index.ts:10-12](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/index.ts#L10-L12) ## Request identifier generation and propagation ### Middleware configuration and options The `requestId` middleware factory accepts an optional `RequestIdOptions` configuration object defining constraints for request tracking. If omitted, the middleware defaults to a maximum length of 255 characters, uses `X-Request-Id` as the header name, and generates identifiers using `crypto.randomUUID()`. | Option | Type | Default Value | Purpose | | :--- | :--- | :--- | :--- | | `limitLength` | `number` | `255` | Maximum allowed character length for incoming or generated request IDs. | | `headerName` | `string` | `'X-Request-Id'` | HTTP header name used to read incoming request IDs and inject outgoing response IDs. | | `generator` | `(c: Context) => string` | `() => crypto.randomUUID()` | Custom function invoked to produce a new identifier when validation fails or no header is present. | Sources: [src/middleware/request-id/request-id.ts:13-17](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/request-id.ts#L13-L17), [src/middleware/request-id/request-id.ts:41-45](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/request-id.ts#L41-L45) ### Generation and validation flow When an incoming request hits the middleware, it checks whether `headerName` is configured. If `headerName` is provided, the middleware reads the corresponding header from the request object. If `headerName` is an empty string, `c.req.header()` evaluates to an undefined or unqueried state. ```mermaid flowchart TD Start([Incoming Request]) --> CheckHeader{headerName set?} CheckHeader -- Yes --> ReadHeader[Read c.req.header headerName] CheckHeader -- No --> Gen[Invoke generator function] ReadHeader --> Validate{Valid ID?} Validate -- Missing, > limitLength, or matches /[^\w\-=]/ --> Gen Validate -- Valid format and length --> Assign[Store reqId in Context] Gen --> Assign Assign --> Inject{headerName set?} Inject -- Yes --> SetHeader[Inject header into Response] Inject -- No --> Next["Call await next()"] SetHeader --> Next Next --> End([End Middleware]) ``` Sources: [src/middleware/request-id/request-id.ts:46-58](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/request-id.ts#L46-L58) > [!WARNING] > Incoming request identifiers must pass strict validation checks before being accepted. If an incoming header value exceeds `limitLength` or contains characters outside alphanumeric values, hyphens, and equals signs (`/[^\w\-=]/`), the middleware discards the header value and invokes the `generator` function instead. Sources: [src/middleware/request-id/request-id.ts:49-51](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/request-id.ts#L49-L51) ## Context variable typing for request identifiers ### Type definition and declaration merging The request ID middleware exposes the `RequestIdVariables` type definition, which defines the variable map shape for [context storage](https://www.doc0.dev/docs/552ca36e-f67e-41c3-a07a-def9bd9551b0/technical/traffic-middleware/context-storage). To provide seamless type safety when accessing request identifiers via `c.get('requestId')`, the module extends Hono's global `ContextVariableMap` interface through declaration merging. ```typescript export type RequestIdVariables = { requestId: string } ``` Sources: [src/middleware/request-id/request-id.ts:9-11](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/request-id.ts#L9-L11) ```typescript import type { RequestIdVariables } from './request-id' export type { RequestIdVariables } export { requestId } from './request-id' declare module '../..' { interface ContextVariableMap extends RequestIdVariables {} } ``` Sources: [src/middleware/request-id/index.ts:1-7](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/index.ts#L1-L7) | Exported Member | Type / Signature | Target Interface | Purpose | | :--- | :--- | :--- | :--- | | `RequestIdVariables` | `{ requestId: string }` | `ContextVariableMap` | Defines the mapping from the `'requestId'` key to its string value type within application instances. | | `requestId` | `(options?: RequestIdOptions) => MiddlewareHandler` | N/A | Middleware factory that assigns the generated ID to `requestId` via `c.set()`. | Sources: [src/middleware/request-id/request-id.ts:9-11](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/request-id.ts#L9-L11), [src/middleware/request-id/request-id.ts:41-45](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/request-id.ts#L41-L45), [src/middleware/request-id/index.ts:1-7](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/index.ts#L1-L7) ### Context retrieval and instantiation Developers integrate the typed variables by importing `RequestIdVariables` and passing it to the generic `Hono` application constructor. Once registered, handlers can retrieve the identifier using `c.get('requestId')` with full type inference. ```ts type Variables = RequestIdVariables const app = new Hono<{ Variables: Variables }>() app.use(requestId()) app.get('/', (c) => { console.log(c.get('requestId')) return c.text('Hello World!') }) ``` Sources: [src/middleware/request-id/request-id.ts:31-39](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/request-id.ts#L31-L39) > [!NOTE] > When importing from `hono/request-id`, declaration merging automatically augments the global `ContextVariableMap` so that manual generic binding is optional if utilizing global type environments, while explicit generic parameterization ensures strict scoped typing in modular applications. Sources: [src/middleware/request-id/index.ts:5-7](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/request-id/index.ts#L5-L7) ## Accept-Language header parsing and quality weighting ### Parsing and quality score extraction The `parseAcceptLanguage` function extracts language tags and their associated quality values (`q`) from raw `Accept-Language` headers. It delegates the underlying string decomposition to the utility function `parseAccept`, then maps each returned record to an array of objects containing the language type (`lang`) and quality weighting (`q`). ```typescript export function parseAcceptLanguage(header: string): Array<{ lang: string; q: number }> { return parseAccept(header).map(({ type, q }) => ({ lang: type, q })) } ``` Sources: [src/middleware/language/language.ts:74-76](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L74-L76) When matching headers explicitly via helpers, the `accepts` function retrieves the header specified in configuration options and processes the values. If the header is missing, it falls back to the default configured string. ```typescript export const accepts = (c: Context, options: acceptsOptions): string => { const acceptHeader = c.req.header(options.header) if (!acceptHeader) { return options.default } const accepts = parseAccept(acceptHeader) const match = options.match || defaultMatch return match(accepts, options) } ``` Sources: [src/helper/accepts/accepts.ts:40-49](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/helper/accepts/accepts.ts#L40-L49) ### Quality weighting and default matching The `defaultMatch` function sorts parsed accept objects in descending order by their quality weighting score (`q`) and returns the first language tag that exists within the supported languages array. If no matches are found, it yields the configured default string. ```typescript export const defaultMatch = (accepts: Accept[], config: acceptsConfig): string => { const { supports, default: defaultSupport } = config const accept = accepts.sort((a, b) => b.q - a.q).find((accept) => supports.includes(accept.type)) return accept ? accept.type : defaultSupport } ``` Sources: [src/helper/accepts/accepts.ts:21-25](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/helper/accepts/accepts.ts#L21-L25) | Configuration Property | Type | Default / Scope | Purpose | | :--- | :--- | :--- | :--- | | `header` | `AcceptHeader` | Required | Specifies the HTTP header key to inspect (e.g., `'Accept-Language'`). | | `supports` | `string[]` | Required | Array of supported language codes or media types. | | `default` | `string` | Required | Fallback value returned when no entries match supported options. | | `match` | `(accepts: Accept[], config: acceptsConfig) => string` | Optional | Custom matching strategy function replacing `defaultMatch`. | Sources: [src/helper/accepts/accepts.ts:11-19](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/helper/accepts/accepts.ts#L11-L19) > [!WARNING] > The `defaultMatch` algorithm strictly iterates through sorted quality values from highest to lowest. If a client provides multiple supported languages with identical quality scores, the order in which they appear in the raw header string dictates precedence based on the underlying parser's stability. Sources: [src/helper/accepts/accepts.ts:21-23](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/helper/accepts/accepts.ts#L21-L23) ## Language detector strategy and lookup chain ### Detection strategies and mapping The language module supports four distinct detection strategies encapsulated within the `DetectorType` union: `'path'`, `'querystring'`, `'cookie'`, and `'header'`. Each strategy extracts a raw string candidate from different parts of the incoming HTTP request context, which is then processed through `normalizeLanguage` against the configured `supportedLanguages`. The `detectors` mapping object binds these strategy identifiers to their respective implementation functions. | Strategy Name | Implementation Function | Source Location | Description | | :--- | :--- | :--- | :--- | | `querystring` | `detectFromQuery` | `src/middleware/language/language.ts:128-131` | Inspects URL query parameters using `lookupQueryString`. | | `cookie` | `detectFromCookie` | `src/middleware/language/language.ts:136-139` | Retrieves cookie values using `lookupCookie`. | | `header` | `detectFromHeader` | `src/middleware/language/language.ts:144-162` | Parses `Accept-Language` headers via `lookupFromHeaderKey`. | | `path` | `detectFromPath` | `src/middleware/language/language.ts:167-172` | Extracts path segments from the URL path at `lookupFromPathIndex`. | Sources: [src/middleware/language/language.ts:10-10](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L10-L10), [src/middleware/language/language.ts:128-182](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L128-L182) ### Normalization and RFC 4647 lookup The `normalizeLanguage` function validates and cleanses raw language strings using progressive truncation adhering to RFC 4647 lookup rules. When `ignoreCase` is enabled, candidate strings and supported entries are lowercased for comparison. If an exact match fails, the function splits the language code by hyphens and progressively truncates segments from right to left until a matching prefix is found in `supportedLanguages`. ```typescript export const normalizeLanguage = ( lang: string | null | undefined, options: DetectorOptions ): string | undefined => { if (!lang) { return undefined } try { let normalizedLang = lang.trim() if (options.convertDetectedLanguage) { normalizedLang = options.convertDetectedLanguage(normalizedLang) } const compLang = options.ignoreCase ? normalizedLang.toLowerCase() : normalizedLang const compSupported = options.supportedLanguages.map((l) => options.ignoreCase ? l.toLowerCase() : l ) // Exact match const exactIndex = compSupported.indexOf(compLang) if (exactIndex !== -1) { return options.supportedLanguages[exactIndex] } // Progressive truncation (RFC 4647 Lookup) const parts = compLang.split('-') for (let i = parts.length - 1; i > 0; i--) { const candidate = parts.slice(0, i).join('-') const prefixIndex = compSupported.indexOf(candidate) if (prefixIndex !== -1) { return options.supportedLanguages[prefixIndex] } } return undefined } catch { return undefined } } ``` Sources: [src/middleware/language/language.ts:84-123](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L84-L123) > [!WARNING] > If a custom transformation function is provided via `convertDetectedLanguage`, it executes before normalization and case-folding, allowing pre-processing of non-standard locale tokens. Sources: [src/middleware/language/language.ts:94-96](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L94-L96) ### Validation of detector options Before runtime execution, `validateOptions` inspects the active `DetectorOptions` configuration to ensure consistency. It verifies that `fallbackLanguage` exists within the `supportedLanguages` collection, that `lookupFromPathIndex` is non-negative, and that all entries in the `order` array correspond to valid keys within the `detectors` map. ```typescript export function validateOptions(options: DetectorOptions): void { if (!options.supportedLanguages.includes(options.fallbackLanguage)) { throw new Error('Fallback language must be included in supported languages') } if (options.lookupFromPathIndex < 0) { throw new Error('Path index must be non-negative') } if (!options.order.every((detector) => Object.keys(detectors).includes(detector))) { throw new Error('Invalid detector type in order array') } } ``` Sources: [src/middleware/language/language.ts:195-207](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L195-L207) ## Locale persistence and response caching ### Cookie-based caching strategies The language detection middleware manages detected locale persistence through the `cacheLanguage` function, which serializes resolved language codes into HTTP cookies. Caching behavior is governed by the `caches` option array and the default configuration settings. ```typescript export const DEFAULT_OPTIONS: DetectorOptions = { order: ['querystring', 'cookie', 'header'], lookupQueryString: 'lang', lookupCookie: 'language', lookupFromHeaderKey: 'accept-language', lookupFromPathIndex: 0, caches: ['cookie'], ignoreCase: true, fallbackLanguage: 'en', supportedLanguages: ['en'], cookieOptions: { sameSite: 'Strict', secure: true, maxAge: 365 * 24 * 60 * 60, httpOnly: true, }, debug: false, } ``` Sources: [src/middleware/language/language.ts:51-68](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L51-L68) The `cacheLanguage` utility inspects whether `'cookie'` is present in `options.caches` before invoking `setCookie` with the configured `lookupCookie` identifier and `cookieOptions`. ```typescript function cacheLanguage(c: Context, language: string, options: DetectorOptions): void { if (!Array.isArray(options.caches) || !options.caches.includes('cookie')) { return } try { setCookie(c, options.lookupCookie, language, options.cookieOptions) } catch (error) { if (options.debug) { console.error('Failed to cache language:', error) } } } ``` Sources: [src/middleware/language/language.ts:212-224](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L212-L224) | Option Property | Default Value | Description | | :--- | :--- | :--- | | `sameSite` | `'Strict'` | Restricts cross-site cookie transmission. | | `secure` | `true` | Ensures cookies are sent only over encrypted connections. | | `maxAge` | `31536000` (`365 * 24 * 60 * 60`) | Sets cookie lifetime to one year in seconds. | | `httpOnly` | `true` | Prevents client-side script access to the cookie. | Sources: [src/middleware/language/language.ts:61-66](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L61-L66) > [!CAUTION] > If cookie serialization fails during `cacheLanguage` execution, the error is swallowed unless `options.debug` is enabled, in which case it prints to `console.error`. Sources: [src/middleware/language/language.ts:217-223](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/language/language.ts#L217-L223) ### Response mutation and headers manipulation Response header modification and persistence are handled across various platform adapters and utility layers. Secure headers, timing metrics, and response cookies apply mutations directly to response headers or result objects. The secure headers middleware mutates response headers via `setHeaders`, which assigns security policies directly to `ctx.res.headers`. ```typescript function setHeaders(ctx: Context, headersToSet: [string, string][]) { headersToSet.forEach(([header, value]) => { ctx.res.headers.set(header, value) }) } ``` Sources: [src/middleware/secure-headers/secure-headers.ts:330-334](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/secure-headers/secure-headers.ts#L330-L334) Similarly, the server-timing middleware appends execution metrics and cross-origin timing allowances directly to the response headers collection. ```typescript c.res.headers.append('Server-Timing', headers.join(',')) const crossOrigin = typeof options.crossOrigin === 'function' ? options.crossOrigin(c) : options.crossOrigin if (crossOrigin) { c.res.headers.append( 'Timing-Allow-Origin', typeof crossOrigin === 'string' ? crossOrigin : '*' ) ``` Sources: [src/middleware/timing/timing.ts:113-122](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/middleware/timing/timing.ts#L113-L122) ### Platform-specific result formatting When handling requests under serverless or edge environments, response cookies and headers require explicit mapping to platform result objects. AWS Lambda processors handle cookie persistence via `setCookiesToResult` implementations across v1, v2, and ALB event structures, assigning serialized cookie arrays to `multiValueHeaders['set-cookie']` or `result.cookies`. ```typescript protected setCookiesToResult(result: APIGatewayProxyResult, cookies: string[]): void { result.cookies = cookies } ``` Sources: [src/adapter/aws-lambda/handler.ts:423-425](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/adapter/aws-lambda/handler.ts#L423-L425) Cloudflare Pages middleware constructs a Web Standard `Context` instance wrapping the execution event request and environment bindings, parsing exceptions and HTTP exceptions into finalized `Response` instances. ```typescript return async (executionCtx) => { const context = new Context(executionCtx.request, { env: { ...executionCtx.env, eventContext: executionCtx }, executionCtx, }) let response: Response | void = undefined try { response = await middleware(context, async () => { try { context.res = await executionCtx.next() } catch (error) { if (error instanceof Error) { context.error = error } else { throw error } } }) } catch (error) { if (error instanceof Error) { context.error = error } else { throw error } } if (response) { return response } if (context.error instanceof HTTPException) { return context.error.getResponse() } if (context.error) { throw context.error } return context.res } ``` Sources: [src/adapter/cloudflare-pages/handler.ts:60-101](https://github.com/blade47/hono/blob/e50df01453e71b071c3e6136b161b160b9fdf916/src/adapter/cloudflare-pages/handler.ts#L60-L101) ## Related - [Logger and Timing](https://www.doc0.dev/docs/552ca36e-f67e-41c3-a07a-def9bd9551b0/technical/traffic-middleware/logger-and-timing) ## Sitemap See the full [sitemap](https://www.doc0.dev/docs/552ca36e-f67e-41c3-a07a-def9bd9551b0/llms.txt) for all pages in this wiki.