@kubb/plugin-fetch

@kubb/plugin-fetch turns each OpenAPI operation into a typed async function that calls your API with the global Fetch API. The path, query parameters, request body, response, and error shape all come from the spec, so a call stays in sync with the API it targets.

It builds on @kubb/plugin-ts for the types, so add that to your config. The client uses the runtime's built-in fetch, so there is no extra HTTP dependency to install.

Each generated function takes one grouped options object ({ path, query, headers, body }) and returns a RequestResult of { data, error, request, response }. throwOnError defaults to true, so a resolved call means the request succeeded and data is set. Pass throwOnError: false per call to get the discriminated { data?, error? } form and read error and response.status yourself. The runtime is always bundled into .kubb/client.ts, so there is no bundle option.

See also

• Fetch API
• @kubb/plugin-ts

Installation

bun

bun add -d @kubb/plugin-fetch@beta

pnpm

pnpm add -D @kubb/plugin-fetch@beta

npm

npm install --save-dev @kubb/plugin-fetch@beta

yarn

yarn add -D @kubb/plugin-fetch@beta

Options

output

Where the generated functions are written and how they are exported.

Type:	Output
Required:	false
Default:	{ path: 'clients', barrel: { type: 'named' } }

output.path

Folder where the plugin writes its files. It is resolved against the global output.path on defineConfig. To write everything to one file instead, set output.mode: 'file' and give path a file name with its extension, such as 'clients.ts'.

Type:	string
Required:	true
Default:	'clients'

TIP

output.path sets where files go, output.mode sets how many. Use 'directory' (the default) for one file per operation, optionally grouped into subdirectories with the group option. Use 'file' to write everything into a single file.

kubb.config.ts

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      output: { path: './clients' },
    }),
  ],
})

Resulting tree

src/
└── gen/
    └── clients/
        ├── addPet.ts
        └── getPetById.ts

output.mode

How the plugin consolidates its generated code into files.

• 'directory' (default) writes one file per operation under output.path.
• 'file' writes everything into a single file. The output.path must include the file extension (e.g. 'clients.ts').

Type:	'directory' | 'file'
Required:	false
Default:	'directory'

TIP

Pair 'directory' with the group option to organize output into per-tag or per-path subdirectories. mode: 'file' forbids group. A single-file output has nothing to group, and combining them stops the build with a KUBB_INVALID_PLUGIN_OPTIONS error.

output.barrel

Controls how the generated index.ts (barrel) file re-exports the plugin's output.

• { type: 'named' } re-exports each symbol by name. Best for tree-shaking and explicit imports.
• { type: 'all' } uses export *. Smaller barrel file, but exports everything.
• { nested: true } creates a barrel in every subdirectory, so callers can import from any depth.
• false skips the barrel entirely. The plugin's files are also excluded from the root index.ts.

Type:	{ type: 'named' | 'all', nested?: boolean } | false
Required:	false
Default:	{ type: 'named' }

TIP

Pick 'named' when consumers care about which symbols they import (better tree-shaking, friendlier auto-import). Pick 'all' when the file count is small and you want a one-line barrel.

output.banner

Text added to the top of every generated file. Use it for license headers, lint disables, or a @ts-nocheck directive. Pass a string for a fixed banner, or a function that builds one from each file's RootNode (the AST root with the path, schema, and operation context).

Type:	string | ((node: RootNode) => string)
Required:	false

output.footer

Text added to the bottom of every generated file. It works like banner but for closing comments, such as re-enabling a lint rule. Pass a string or a function that receives the file's RootNode and returns the text.

Type:	string | ((node: RootNode) => string)
Required:	false

group

Splits generated files into subfolders by the operation's first tag or first path segment. Each group gets its own directory under {output.path}/{groupName}/. Without group, every file lands directly in output.path.

Type:	Group
Required:	false
Default:	null

TIP

Use group to mirror your API's domain structure (pet, store, user) in the generated code. Combine it with output.barrel: { type: 'named', nested: true } to get a barrel file per group.

group only applies to output.mode: 'directory' (the default). It is not valid with output.mode: 'file', since a single-file output has no grouping concept.

kubb.config.ts

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      group: { type: 'tag' },
    }),
  ],
})

With the configuration above, the generator emits one folder per tag, named after the camelCased tag:

Resulting tree

src/gen/
├── pet/
│   ├── addPet.ts
│   └── getPetById.ts
└── store/
    ├── getInventory.ts
    └── placeOrder.ts

Pass group.name to customize the folder name. For example, a name function that appends Controller to the group keeps the pre-v5 petController/ layout.

group.type

Property used to assign each operation to a group. Required whenever group is set.

• 'tag' reads the first tag on the operation (operation.getTags().at(0)?.name). Operations without a tag go in a default group.
• 'path' reads the first segment of the operation's URL.

Type:	'tag' | 'path'
Required:	true

NOTE

Required here is conditional. It applies only when the parent group option is set, and group itself stays optional.

group.name

Function that builds the folder name from the group key. The default depends on group.type. A 'tag' group uses the camelCased tag. A 'path' group uses the second path segment (/pet/findByStatus becomes pet). A group.name you pass always wins over the default.

Type:	(context: { group: string }) => string
Required:	false

exclude

Skips any operation that matches at least one entry in the list. It is the opposite of include. Entries use a type (tag, operationId, path, method, contentType, schemaName) and a pattern (string or RegExp). When both are set, exclude wins.

Type:	Array<Exclude>
Required:	false

Type definition

export type Exclude = {
  type: 'tag' | 'operationId' | 'path' | 'method' | 'contentType' | 'schemaName'
  pattern: string | RegExp
}

Skip everything under the store tag

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      exclude: [{ type: 'tag', pattern: 'store' }],
    }),
  ],
})

include

Generates only the operations that match at least one entry in the list. Everything else is skipped. Entries use the same type (tag, operationId, path, method, contentType, schemaName) and pattern (string or RegExp) as exclude.

Type:	Array<Include>
Required:	false

Type definition

export type Include = {
  type: 'tag' | 'operationId' | 'path' | 'method' | 'contentType' | 'schemaName'
  pattern: string | RegExp
}

Only the pet tag

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      include: [{ type: 'tag', pattern: 'pet' }],
    }),
  ],
})

override

Applies different plugin options to operations that match a pattern. Use it for the few endpoints that need special treatment. Each entry takes the same type and pattern as include and exclude, plus an options object. Entries run top to bottom. The first match merges onto the plugin defaults, and later entries do not stack.

Type:	Array<Override>
Required:	false

Type definition

export type Override = {
  type: 'tag' | 'operationId' | 'path' | 'method' | 'contentType' | 'schemaName'
  pattern: string | RegExp
  options: Partial<Options>
}

Send the admin tag to its own folder

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      output: { path: './clients' },
      override: [
        {
          type: 'tag',
          pattern: 'admin',
          options: { output: { path: './clients/admin' } },
        },
      ],
    }),
  ],
})

baseURL

Base URL prepended to every request the functions make. When omitted, the URL comes from the adapter's server URL (servers[0].url in the spec). Set it to point the client at a different environment (staging, production) than the spec.

Type:	string
Required:	false

parser

Runtime validator applied to request and response data using schemas from @kubb/plugin-zod.

• false (default) does no validation. The client returns the response cast to the generated type.
• 'zod' validates response bodies only.
• { request?: 'zod', response?: 'zod' } opts in per direction. request validates the request body before the call. response validates the response body after.

Add @kubb/plugin-zod to the plugins list when either direction is 'zod'.

Type:	false | 'zod' | { request?: 'zod'; response?: 'zod' }
Required:	false
Default:	false

sdk

Generates a class-based SDK instead of standalone functions. Leave sdk unset to keep the per-operation functions, which is what the query plugins consume.

• mode: 'tag' (default) emits one instance class per tag.
• mode: 'tag' with name emits a composed root class that instantiates every tag client from one config.
• mode: 'flat' emits a single class named by name with every operation as a direct method.

Type:	{ mode?: 'tag' | 'flat'; name?: string }
Required:	false

Standalone functions (sdk unset)

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [pluginFetch()],
})

One class per tag

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      sdk: {},
    }),
  ],
})

Composed root class

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      sdk: { name: 'petStore' },
    }),
  ],
})

Single flat class

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      sdk: { name: 'petStore', mode: 'flat' },
    }),
  ],
})

resolver

Changes how the plugin names generated files and functions. Use it to add a prefix or suffix, or to swap the casing, without forking the plugin. Override only the methods you want to change. Anything you omit, or that returns null or undefined, falls back to the default. Inside a method, this is the full resolver, so you can call this.default(name, 'function') to reuse the built-in name.

Type:	Partial<ResolverClient> & ThisType<ResolverClient>
Required:	false

TIP

Use resolver for naming and file-location tweaks. To change the AST nodes themselves (e.g. stripping descriptions), use macros instead.

Prefix every function name with "Api"

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      resolver: {
        resolveName(name) {
          return `Api${this.default(name, 'function')}`
        },
      },
    }),
  ],
})

macros

Rewrites AST nodes before they are printed to source. Use it to rename operation IDs, drop descriptions, or change schema metadata without forking the generator. Each macro callback (such as schema or operation) receives the node and a context object. Return a new node to replace it, or undefined to leave it as is. Callbacks you omit keep their default behavior. Macros run in order, so a later one sees the output of an earlier one.

Type:	Array<Macro>
Required:	false

TIP

Use macros to rewrite node properties before printing. To change the names of generated symbols and files, use resolver instead.

Strip descriptions before printing

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      macros: [
        {
          name: 'strip-descriptions',
          schema(node) {
            return { ...node, description: undefined }
          },
        },
      ],
    }),
  ],
})

Prefix every operationId

import { defineConfig } from 'kubb'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginFetch({
      macros: [
        {
          name: 'prefix-operation-id',
          operation(node) {
            return { ...node, operationId: `api_${node.operationId}` }
          },
        },
      ],
    }),
  ],
})

Authentication

The generated functions carry the security schemes from your spec, so you configure credentials in one place. Set an auth resolver on the client config and the runtime attaches a bearer, basic, or apiKey token to every guarded call.

import { client } from './gen/clients/.kubb/client'

client.setConfig({
  auth: () => localStorage.getItem('token') ?? undefined,
})

See the authentication guide for the full scheme mapping, per-instance clients, and per-call overrides.

Dependencies

This plugin needs @kubb/plugin-ts in your config. Kubb runs it before plugin-fetch so the functions can import the generated types.

• @kubb/plugin-ts

Example

kubb.config.ts

import { defineConfig } from 'kubb'
import { pluginTs } from '@kubb/plugin-ts'
import { pluginFetch } from '@kubb/plugin-fetch'

export default defineConfig({
  input: { path: './petStore.yaml' },
  output: { path: './src/gen' },
  plugins: [
    pluginTs(),
    pluginFetch({
      output: { path: 'clients', barrel: { type: 'named' } },
      baseURL: 'https://petstore.swagger.io/v2',
      group: {
        type: 'tag',
        name: ({ group }) => `${group}Service`,
      },
    }),
  ],
})

See Also

• Fetch API
• Changelog