Hono Skill

Build Hono web applications. This skill provides inline API knowledge for AI. Use Hono CLI to inspect and test the app.

Latest Documentation

For details beyond this inline reference, fetch the latest documentation from https://hono.dev. Get the index of doc pages from https://hono.dev/llms.txt, then fetch a page with the Accept: text/markdown header to receive it as Markdown:

curl -H "Accept: text/markdown" https://hono.dev/docs/helpers/cookie

Hono CLI

Verify with Hono CLI, not with throwaway scripts or a dev server. It is a dev dependency (projects from create-hono already have it), loads the app in-process with app.request(), and prints JSON. Install it if missing, then read its help:

npm install -D @hono/cli@next
npx hono --help

Follow the note at the top. It explains the JSON output contract and the workflow. npx hono <command> --help has examples and notes for each command (routes, request, batch, snapshot, benchmark, ssg, init).

Notes:

• npx hono routes lists the routes; npx hono request /path sends one request — no server needed. If the app is not at the default path (src/index.ts), pass the file to every command: npx hono request / src/app.ts. Do not pass credentials directly in CLI arguments; use environment variables for sensitive values.
• Cloudflare bindings (KV, D1, R2, vars) reach c.env automatically — no server, no flag. In a project with cloudflare.config.ts (the cf CLI) and a Vite config, request, batch, and snapshot run through the Vite dev server by default, and c.env has the local bindings; request and batch default to Vite as well in a Vite project with no src/index.* (an app built by a Vite plugin; snapshot still needs the file), and --runtime vite selects it explicitly. In a project with a wrangler config, the app runs on Node.js with the real local bindings loaded; for the full Workers runtime there, add --runtime workerd (pass no file argument; the entry is main in the wrangler config). --trace, --watch, and a file argument run the app on Node.js, where c.env is empty in a cf project.
• routes and snapshot also load apps that import cloudflare:workers (Durable Objects); the import is stubbed while the routes are read.
• To add a Hono app to an existing directory, run npx hono init --template cloudflare-workers (or nodejs, bun, deno, ...; without --template it is detected from the files in the directory), then install the dependencies. It copies the create-hono template and never overwrites an existing file. For an empty directory, npm create hono@next does the same with prompts.

• For several requests, or a flow that keeps state (POST, then use the returned id), run them in one hono batch - call. One JSON object per line; save a value and use it as {{id}} in later steps. The steps share one app instance. Declare the expected status/body per step with expect (body is a deep partial match) and iterate until the summary shows "failed": 0:

  npx hono batch - <<'EOF'
  {"method":"POST","path":"/users","body":{"name":"Alice"},"save":{"id":".id"},"expect":{"status":201}}
  {"path":"/users/{{id}}","expect":{"status":200,"body":{"name":"Alice"}}}
  EOF

• Before changing existing routes, capture the current behavior: npx hono snapshot prints it as batch JSONL lines (real responses become the expect). Keep the lines, make the change, then rerun them with npx hono batch - until "failed": 0.
• On a large API, use npx hono snapshot --status-only and npx hono batch - --compact — same loop, much smaller output. A failed step carries diff: fix what it names.

Hono API Reference

App Constructor

import { Hono } from 'hono'

const app = new Hono()

// With TypeScript generics
type AppEnv = {
  Bindings: Env // generated from the bindings config — see "Environment (Cloudflare Workers)"
  Variables: { user: User }
}
const app = new Hono<AppEnv>()

Routing Methods

app.get('/path', handler)
app.post('/path', handler)
app.put('/path', handler)
app.delete('/path', handler)
app.patch('/path', handler)
app.options('/path', handler)
app.all('/path', handler) // all HTTP methods
app.on('PURGE', '/path', handler) // custom method
app.on(['PUT', 'DELETE'], '/path', handler) // multiple methods

Routing Patterns

// Path parameters
app.get('/user/:name', (c) => {
  const name = c.req.param('name')
  return c.json({ name })
})

// Multiple params
app.get('/posts/:id/comments/:commentId', (c) => {
  const { id, commentId } = c.req.param()
})

// Optional parameters
app.get('/api/animal/:type?', (c) => c.text('Animal!'))

// Wildcards
app.get('/wild/*/card', (c) => c.text('Wildcard'))

// Regexp constraints
app.get('/post/:date{[0-9]+}/:title{[a-z]+}', (c) => {
  const { date, title } = c.req.param()
})

// Chained routes
app
  .get('/endpoint', (c) => c.text('GET'))
  .post((c) => c.text('POST'))
  .delete((c) => c.text('DELETE'))

Route Grouping

// Using route()
const api = new Hono()
api.get('/users', (c) => c.json([]))

const app = new Hono()
app.route('/api', api) // mounts at /api/users

// Using basePath()
const app = new Hono().basePath('/api')
app.get('/users', (c) => c.json([])) // GET /api/users

Error Handling

app.notFound((c) => c.json({ message: 'Not Found' }, 404))

app.onError((err, c) => {
  console.error(err)
  return c.json({ message: 'Internal Server Error' }, 500)
})

Context (c)

Response Methods

c.text('Hello') // text/plain
c.json({ message: 'Hello' }) // application/json
c.html('<h1>Hello</h1>') // text/html
c.redirect('/new-path') // 302 redirect
c.redirect('/new-path', 301) // 301 redirect
c.body('raw body', 200, headers) // raw response
c.notFound() // 404 response

Headers & Status

c.status(201)
c.header('X-Custom', 'value')
c.header('Cache-Control', 'no-store')

Variables (request-scoped data)

// In middleware
c.set('user', { id: 1, name: 'Alice' })

// In handler
const user = c.get('user')
// or
const user = c.var.user

Environment (Cloudflare Workers)

Never write the Bindings type by hand: generate it, and rerun after every change to the bindings. Which tool a project uses is visible from its files.

cf CLI projects (cloudflare.config.ts; this is what create-hono generates for cloudflare-workers now): bindings are declared in cloudflare.config.ts with the bindings helpers from cf/config. Local bindings need no IDs; do not create Cloudflare resources (KV, D1, R2) or set IDs unless the user asks. Then run npm run typecheck (= cf workers types && tsc; it writes .cloudflare/types) and use the generated Env:

// cloudflare.config.ts
import { bindings, defineConfig } from 'cf/config'
import * as entrypoint from './src/index.ts' with { type: 'cf-worker' }

export default defineConfig({
  worker: {
    name: 'my-app',
    compatibilityDate: '2026-10-06',
    entrypoint,
    env: {
      MY_KV: bindings.kv(),
      MY_VAR: bindings.text('my-variable'),
    },
  },
})

const app = new Hono<{ Bindings: Env }>()

Scripts are cf dev, cf build, and cf deploy. Such a project has no wrangler config; do not add one, and do not run cf init in a Hono project (its autoconfig stops on Hono).

wrangler projects (wrangler.jsonc or wrangler.toml): bindings are in the wrangler config. npm run cf-typegen (= wrangler types --env-interface CloudflareBindings) writes worker-configuration.d.ts, which declares CloudflareBindings together with the Workers runtime types. If there is no cf-typegen script, run npx wrangler types and use the interface it declares instead (Env, also available as Cloudflare.Env). @cloudflare/workers-types is superseded by either: do not install it.

const app = new Hono<{ Bindings: CloudflareBindings }>()

app.get('/', async (c) => {
  const value = await c.env.MY_KV.get('key')
  const db = c.env.MY_DB
  c.executionCtx.waitUntil(promise)
})

Renderer

app.use(async (c, next) => {
  c.setRenderer((content) =>
    c.html(
      <html><body>{content}</body></html>
    )
  )
  await next()
})

app.get('/', (c) => c.render(<h1>Hello</h1>))

HonoRequest (c.req)

c.req.param('id') // path parameter
c.req.param() // all path params as object
c.req.query('page') // query string parameter
c.req.query() // all query params; values are string | undefined
c.req.queries('tags') // multiple values: ?tags=A&tags=B → ['A', 'B']
c.req.header('Authorization') // request header
c.req.header() // all headers (keys are lowercase)

// Body parsing
await c.req.json<{ title: string }>() // parse JSON body (unknown without the type argument)
await c.req.text() // parse text body
await c.req.formData() // parse as FormData
await c.req.parseBody() // parse multipart/form-data or urlencoded
await c.req.arrayBuffer() // parse as ArrayBuffer
await c.req.blob() // parse as Blob

// Validated data (used with validator middleware)
c.req.valid('json')
c.req.valid('query')
c.req.valid('form')
c.req.valid('param')

// Properties
c.req.url // full URL string
c.req.path // pathname
c.req.method // HTTP method
c.req.raw // underlying Request object

Middleware

Using Built-in Middleware

import { cors } from 'hono/cors'
import { logger } from 'hono/logger'
import { basicAuth } from 'hono/basic-auth'
import { prettyJSON } from 'hono/pretty-json'
import { secureHeaders } from 'hono/secure-headers'
import { etag } from 'hono/etag'
import { compress } from 'hono/compress'
import { poweredBy } from 'hono/powered-by'
import { timing } from 'hono/timing'
import { cache } from 'hono/cache'
import { bearerAuth } from 'hono/bearer-auth'
import { jwt } from 'hono/jwt'
import { jwk } from 'hono/jwk'
import { csrf } from 'hono/csrf'
import { ipRestriction } from 'hono/ip-restriction'
import { bodyLimit } from 'hono/body-limit'
import { timeout } from 'hono/timeout'
import { requestId } from 'hono/request-id'
import { methodOverride } from 'hono/method-override'
import { methodNotAllowed } from 'hono/method-not-allowed'
import { languageDetector } from 'hono/language'
import { some, every, except } from 'hono/combine'
import { contextStorage, getContext } from 'hono/context-storage'
import { trailingSlash, trimTrailingSlash } from 'hono/trailing-slash'

// Registration
app.use(logger()) // all routes
app.use('/api/*', cors()) // specific path
app.post('/api/*', basicAuth({ username: 'admin', password: 'secret' }))

Custom Middleware

// Inline
app.use(async (c, next) => {
  const start = Date.now()
  await next()
  const elapsed = Date.now() - start
  c.res.headers.set('X-Response-Time', `${elapsed}ms`)
})

// Reusable with createMiddleware
import { createMiddleware } from 'hono/factory'

const auth = createMiddleware(async (c, next) => {
  const token = c.req.header('Authorization')
  if (!token) return c.json({ error: 'Unauthorized' }, 401)
  await next()
})

app.use('/api/*', auth)

Middleware Execution Order

Middleware executes in registration order. await next() calls the next middleware/handler, and code after next() runs on the way back:

Request → mw1 before → mw2 before → handler → mw2 after → mw1 after → Response

app.use(async (c, next) => {
  // before handler
  await next()
  // after handler
})

Validation

Validation targets: json, form, query, header, param, cookie.

Zod Validator

import { zValidator } from '@hono/zod-validator'
import { z } from 'zod'

const schema = z.object({
  title: z.string().min(1),
  body: z.string()
})

app.post('/posts', zValidator('json', schema), (c) => {
  const data = c.req.valid('json') // fully typed
  return c.json(data, 201)
})

Valibot / Standard Schema Validator

import { sValidator } from '@hono/standard-validator'
import * as v from 'valibot'

const schema = v.object({ name: v.string(), age: v.number() })

app.post('/users', sValidator('json', schema), (c) => {
  const data = c.req.valid('json')
  return c.json(data, 201)
})

JSX

To build UI with it (layouts with jsxRenderer, Vite, client-side code), use the hono-jsx skill. This section covers the syntax only.

Setup

In tsconfig.json:

{
  "compilerOptions": {
    "jsx": "react-jsx",
    "jsxImportSource": "hono/jsx"
  }
}

Or use pragma: /** @jsxImportSource hono/jsx */

Important: Files using JSX must have a .tsx extension. Rename .ts to .tsx or the compiler will fail.

Components

import type { PropsWithChildren } from 'hono/jsx'

const Layout = (props: PropsWithChildren) => (
  <html>
    <head>
      <title>My App</title>
    </head>
    <body>{props.children}</body>
  </html>
)

const UserCard = ({ name }: { name: string }) => (
  <div class="card">
    <h2>{name}</h2>
  </div>
)

app.get('/', (c) => {
  return c.html(
    <Layout>
      <UserCard name="Alice" />
    </Layout>
  )
})

jsxRenderer Middleware

Use jsxRenderer middleware for layouts. For details, see https://hono.dev/docs/middleware/builtin/jsx-renderer

Async Components

const UserList = async () => {
  const users = await fetchUsers()
  return (
    <ul>
      {users.map((u) => (
        <li>{u.name}</li>
      ))}
    </ul>
  )
}

Fragments

const Items = () => (
  <>
    <li>Item 1</li>
    <li>Item 2</li>
  </>
)

Streaming

import { stream, streamText, streamSSE } from 'hono/streaming'

// Basic stream
app.get('/stream', (c) => {
  return stream(c, async (stream) => {
    stream.onAbort(() => console.log('Aborted'))
    await stream.write(new Uint8Array([0x48, 0x65]))
    await stream.pipe(readableStream)
  })
})

// Text stream
app.get('/stream-text', (c) => {
  return streamText(c, async (stream) => {
    await stream.writeln('Hello')
    await stream.sleep(1000)
    await stream.write('World')
  })
})

// Server-Sent Events
app.get('/sse', (c) => {
  return streamSSE(c, async (stream) => {
    let id = 0
    while (true) {
      await stream.writeSSE({
        data: JSON.stringify({ time: new Date().toISOString() }),
        event: 'time-update',
        id: String(id++)
      })
      await stream.sleep(1000)
    }
  })
})

Testing with app.request()

Test endpoints without starting an HTTP server:

// GET
const res = await app.request('/posts')
expect(res.status).toBe(200)
expect(await res.json()).toEqual({ posts: [] })

// POST with JSON
const res = await app.request('/posts', {
  method: 'POST',
  body: JSON.stringify({ title: 'Hello' }),
  headers: { 'Content-Type': 'application/json' }
})

// POST with FormData
const formData = new FormData()
formData.append('name', 'Alice')
const res = await app.request('/users', { method: 'POST', body: formData })

// With mock env (Cloudflare Workers bindings)
const res = await app.request('/api/data', {}, { KV: mockKV, DATABASE: mockDB })

// Using Request object
const req = new Request('http://localhost/api', { method: 'DELETE' })
const res = await app.request(req)

Hono Client (RPC)

Type-safe API client using shared types between server and client.

IMPORTANT: Routes MUST be chained for type inference to work. Without chaining, the client cannot infer route types.

// Server: routes MUST be chained to preserve types
const route = app
  .post('/posts', zValidator('json', schema), (c) => {
    return c.json({ ok: true }, 201)
  })
  .get('/posts', (c) => {
    return c.json({ posts: [] })
  })
export type AppType = typeof route

// Client: use hc() with the exported type
import { hc } from 'hono/client'
import type { AppType } from './server'

const client = hc<AppType>('http://localhost:8787/')
const res = await client.posts.$post({ json: { title: 'Hello' } })
const data = await res.json() // fully typed

Type utilities:

import type { InferRequestType, InferResponseType } from 'hono/client'

type ReqType = InferRequestType<typeof client.posts.$post>
type ResType = InferResponseType<typeof client.posts.$post, 200>

Helpers

Helpers are utility functions imported from hono/<helper-name>:

import { getConnInfo } from 'hono/conninfo'
import { getCookie, setCookie, deleteCookie } from 'hono/cookie'
import { css, Style } from 'hono/css'
import { createFactory } from 'hono/factory'
import { html, raw } from 'hono/html'
import { stream, streamText, streamSSE } from 'hono/streaming'
import { testClient } from 'hono/testing'
import { upgradeWebSocket } from '@hono/cloudflare-workers' // or another @hono/<runtime> adapter package

Available helpers: Accepts, Adapter, ConnInfo, Cookie, css, Dev, Factory, html, JWT, Proxy, Route, SSG, Streaming, Testing, WebSocket.

For details, see https://hono.dev/docs/helpers/<helper-name> (fetch with Accept: text/markdown).

Factory

Use createFactory to define the app's Env type (AppEnv above) once and share it across app, middleware, and handlers:

import { createFactory } from 'hono/factory'

const factory = createFactory<AppEnv>()

// Create app (AppEnv is inherited)
const app = factory.createApp()

// Create middleware (AppEnv is inherited, no need to pass generics)
const mw = factory.createMiddleware(async (c, next) => {
  await next()
})

// Create handlers separately (preserves type inference)
const handlers = factory.createHandlers(logger(), (c) => c.json({ message: 'Hello' }))
app.get('/api', ...handlers)

Best Practices

• Write handlers inline in route definitions for proper type inference of path params.
• Use app.route() to organize large apps by feature, not Rails-style controllers.
• Use createFactory() to share Env type across app, middleware, and handlers.
• Use c.set()/c.get() to pass data between middleware and handlers.
• Chain validators for multiple request parts (param + query + json).
• Export app type for RPC: export type AppType = typeof routes
• Use app.request() for testing — no server startup needed.

Adapters

Hono runs on multiple runtimes. The default export works for Cloudflare Workers, Deno, and Bun. For Node.js, use the Node adapter:

// Cloudflare Workers / Deno / Bun
export default app

// Node.js
import { serve } from '@hono/node-server'
serve(app)

Runtime-specific helpers (serveStatic, upgradeWebSocket, getConnInfo, Lambda handlers) live in separate packages since Hono v5: @hono/cloudflare-workers, @hono/bun, @hono/deno, @hono/aws-lambda, @hono/lambda-edge, @hono/netlify, @hono/vercel, @hono/service-worker. Install the one for the runtime and import from it; hono/<runtime> only exists on v4. hono/adapter (env(), getRuntimeKey()) stays in hono. Hono v5 is ESM only and needs Node.js 22.12 or later.