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next-openapi-gen

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Automatically generate OpenAPI 3.0, 3.1, and 3.2 documentation from Next.js projects, with support for Zod schemas, TypeScript types, and reusable OpenAPI fragments.

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# next-openapi-gen

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Generate OpenAPI `3.0`, `3.1`, and `3.2` from the routes and schemas you already have.

`next-openapi-gen` scans Next.js, TanStack Router, and React Router route handlers, reads JSDoc metadata, and generates an OpenAPI spec plus an optional docs UI. It is built for real codebases that use Zod, TypeScript, drizzle-zod, or reusable OpenAPI fragments, including mixed-schema migrations.

[Quick start](#quick-start) • [Docs index](./docs/README.md) • [Example apps](#example-apps) • [Validation and coverage](#validation-and-coverage)

## Why teams use it

- Keep OpenAPI close to your handlers instead of maintaining a separate manual spec.
- Reuse existing `zod`, `typescript`, `drizzle-zod`, and YAML/JSON OpenAPI fragments in one pipeline.
- Target `3.0`, `3.1`, or `3.2` from the same route metadata with version-aware finalization.
- Ship interactive docs quickly with built-in UI scaffolding for Scalar, Swagger, Redoc, Stoplight Elements, or RapiDoc.
- Fall back on checker-assisted App Router response inference when explicit `@response` tags are missing.
- Keep richer Zod 4 and TypeScript output in modern targets with selective runtime-assisted Zod export and checker fallback for advanced type constructs.

## Quick start

### Requirements

- Node.js `>=24`
- TypeScript `>=5.9 <8` for TypeScript schemas and checker-assisted response inference. The generator prefers your project-installed TypeScript, uses TypeScript 7's native checker API when available, and falls back to its bundled TypeScript 6 compatibility compiler when needed.
- A supported app framework:
  - Next.js using App Router or Pages Router
  - TanStack Router
  - React Router

### Install

```bash
pnpm add -D next-openapi-gen
```

```bash
npm install --save-dev next-openapi-gen
```

```bash
yarn add --dev next-openapi-gen
```

### Initialize and generate

```bash
# Next.js is the default framework
pnpm exec openapi-gen init

# Or choose another supported framework
pnpm exec openapi-gen init --framework tanstack
pnpm exec openapi-gen init --framework react-router

# Scans your routes and writes the spec once
pnpm exec openapi-gen generate

# Keeps the spec fresh during local development
pnpm exec openapi-gen generate --watch
```

> [!TIP]
> Use `--ui none` during `init` if you only want the generated OpenAPI file.
>
> The package name is still `next-openapi-gen` during the transition. Config
> discovery also accepts the new `openapi-gen.config.ts` and
> `openapi-gen.config.json` aliases, while `next-openapi.config.*` and
> `next.openapi.json` continue to work with deprecation warnings. The legacy
> `next-openapi-gen` binary still works too, but `openapi-gen` is the preferred
> CLI name going forward.

Need the full setup flow, config walkthrough, or production notes? See
[docs/getting-started.md](./docs/getting-started.md).

> [!NOTE]
> TypeScript 7 ships a faster native CLI and language server, but its stable
> programmatic API is still in transition. Projects can use TypeScript 7 for
> `tsc`; `next-openapi-gen` will use the native checker API when it is exposed
> by the installed package, otherwise it falls back to the bundled TypeScript 6
> API. TypeScript 5.9 remains the minimum supported compiler for consumers.

### What you get

- `next.openapi.json` in your project root
- `public/openapi.json` by default
- `/api-docs` with your selected UI provider by default

## Framework support

| Framework       | Setup path                                            | Notes                                                          |
| --------------- | ----------------------------------------------------- | -------------------------------------------------------------- |
| Next.js         | `pnpm exec openapi-gen init`                          | Supports App Router and Pages Router                           |
| TanStack Router | `pnpm exec openapi-gen init --framework tanstack`     | Uses the public `next-openapi-gen/vite` plugin surface         |
| React Router    | `pnpm exec openapi-gen init --framework react-router` | Uses the public `next-openapi-gen/react-router` plugin surface |

## Minimal example

```ts
import { NextRequest } from "next/server";
import { z } from "zod";

export const ProductParams = z.object({
  id: z.string().describe("Product ID"),
});

export const ProductResponse = z.object({
  id: z.string(),
  name: z.string(),
  price: z.number().positive(),
});

/**
 * Get product information
 * @description Fetch a product by ID
 * @path ProductParams
 * @response ProductResponse
 * @openapi
 */
export async function GET(request: NextRequest, { params }: { params: { id: string } }) {
  return Response.json({ id: params.id, name: "Keyboard", price: 99 });
}
```

## Why `next-openapi-gen` is different

| Capability                            | Why it matters                                                                                        |
| ------------------------------------- | ----------------------------------------------------------------------------------------------------- |
| Framework-aware route scanning        | Covers Next.js, TanStack Router, and React Router with one generator and shared docs story.           |
| Mixed schema sources                  | Combine `zod`, `typescript`, `schemaFiles`, and drizzle-zod-backed schemas during gradual migrations. |
| OpenAPI `3.0` / `3.1` / `3.2` targets | Keep one authoring flow while emitting version-aware output for newer spec features.                  |
| Response inference                    | Infer typed App Router responses when `@response` is omitted, while still letting explicit tags win.  |
| Docs UI scaffolding                   | Generate a docs page fast instead of stopping at a JSON file.                                         |

## Common workflows

### Start with Zod or TypeScript

Use one schema system if your app is already consistent:

```json
{
  "schemaType": "zod",
  "schemaDir": "src/schemas"
}
```

### Migrate gradually with mixed schema sources

Use multiple schema types in the same project when you are moving from TypeScript to Zod or merging generated and hand-authored schemas:

```json
{
  "schemaType": ["zod", "typescript"],
  "schemaDir": "./src/schemas",
  "schemaFiles": ["./schemas/external-api.yaml"]
}
```

Resolution priority is:

1. `schemaFiles`
2. `zod`
3. `typescript`

See [apps/next-app-mixed-schemas](./apps/next-app-mixed-schemas) for a full working example.
For more adoption patterns, see
[docs/workflows-and-integrations.md](./docs/workflows-and-integrations.md).

When you target modern OpenAPI output, the Zod path can also split request and response component refs when a supported Zod 4 schema emits different input and output JSON Schema shapes, while the TypeScript path can use selective checker fallback for mapped, conditional, template-literal, and import-based named types.

### Add OpenAPI metadata directly in Zod schemas

Use `.describe()` for a quick description, or Zod v4's `.meta()` to attach `description`, `examples`, `example`, `deprecated`, `title`, and custom `x-*` extensions without any JSDoc:

```ts
// .describe() → description field
z.string().describe("ISO 639-1 language code");
// → { type: "string", description: "ISO 639-1 language code" }

// .meta() → description + examples (and any other OpenAPI key)
z.number()
  .int()
  .positive()
  .meta({
    description: "PIM ID of the slider",
    examples: [42, 1337],
  });
// → { type: "integer", exclusiveMinimum: 0, description: "PIM ID of the slider", examples: [42, 1337] }
```

Both work inside `z.object({...})` properties, in drizzle-zod override callbacks, and at the top level of named schemas. See [docs/zod4-support-matrix.md](./docs/zod4-support-matrix.md) for the full supported metadata surface.

### Decouple component names from source identifiers

Use `.meta({ id })` for Zod schemas or `/** @id */` for TypeScript types to set the OpenAPI component name independently of the export name — useful when enforcing PascalCase naming or migrating from another generator without renaming existing exports:

```ts
// Zod: use .meta({ id }) to decouple the component name from the variable name
export const audioSchema = z.object({ ... }).meta({ id: "Audio" });
// → components.schemas.Audio (not: audioSchema)

// TypeScript: use /** @id */ at the declaration level
/** @id Audio */
export interface AudioInterface { ... }
// → components.schemas.Audio (not: AudioInterface)
```

Existing `@requestBody audioSchema` or `@response audioSchema` references in route handlers continue to work — the generator resolves them transparently to the override name. See [docs/jsdoc-reference.md#component-naming](./docs/jsdoc-reference.md#component-naming) for details.

### Generate docs from Drizzle schemas

`next-openapi-gen` works well with `drizzle-zod`, so your database schema, validation, and API docs can share the same source of truth.

```ts
import { createInsertSchema, createSelectSchema } from "drizzle-zod";
import { posts } from "@/db/schema";

export const CreatePostSchema = createInsertSchema(posts, {
  title: (schema) => schema.title.min(5).max(255),
  content: (schema) => schema.content.min(10),
});

export const PostResponseSchema = createSelectSchema(posts);
```

See [apps/next-app-drizzle-zod](./apps/next-app-drizzle-zod) for the full CRUD example.

### Rely on inference when you want less annotation

If you omit `@response`, App Router handlers can infer responses from typed `NextResponse.json(...)` and `Response.json(...)` returns.

```ts
import { NextResponse } from "next/server";

type SearchResponse = {
  total: number;
};

/**
 * Search events
 * @responseDescription Search result
 * @openapi
 */
export async function POST(): Promise<NextResponse<SearchResponse>> {
  return NextResponse.json({ total: 3 });
}
```

Explicit `@response` tags still take precedence when you want stable schema names or exact response codes.

## Configuration

`init` creates a `next.openapi.json` file like this:

```json
{
  "openapi": "3.0.0",
  "info": {
    "title": "Next.js API",
    "version": "1.0.0",
    "description": "API generated by next-openapi-gen"
  },
  "apiDir": "src/app/api",
  "routerType": "app",
  "schemaDir": "src/schemas",
  "schemaType": "zod",
  "schemaFiles": [],
  "outputFile": "openapi.json",
  "outputDir": "./public",
  "docsUrl": "api-docs",
  "includeOpenApiRoutes": false,
  "ignoreRoutes": [],
  "debug": false
}
```

Version guidance:

- Use `3.0.0` when you want the broadest downstream tooling compatibility.
- Use `3.1.0` when you want JSON Schema 2020-12-aligned output such as `jsonSchemaDialect`.
- Use `3.2.0` when you want first-class `querystring`, enhanced tag metadata, sequential media, and richer example objects.

### Important options

| Option                                | Purpose                                                                                 |
| ------------------------------------- | --------------------------------------------------------------------------------------- |
| `openapi`                             | Target `3.0.0`, `3.1.0`, `3.2.0`, or experimental `3.3-preview` output                  |
| `apiDir`                              | Route directory to scan                                                                 |
| `routerType`                          | `"app"` or `"pages"`                                                                    |
| `schemaDir`                           | Directory or directories to search for schemas/types                                    |
| `schemaType`                          | `"zod"`, `"typescript"`, or both                                                        |
| `schemaFiles`                         | YAML/JSON OpenAPI fragments to merge into the generated document                        |
| `includeOpenApiRoutes`                | Only include handlers tagged with `@openapi`                                            |
| `ignoreRoutes`                        | Exclude routes with wildcard support                                                    |
| `excludeSchemas`                      | Exclude internal schemas from `components/schemas` by name or glob (e.g. `["*Params"]`) |
| `defaultResponseSet` / `responseSets` | Reusable error-response groups                                                          |
| `errorConfig`                         | Shared error schema templates                                                           |
| `authPresets`                         | Override or extend the `@auth` keyword → scheme-name mapping                            |
| `diagnostics.failOn`                  | CI gate: `"never"` (default), `"warning"`, or `"error"`                                 |

During generation, the CLI prints diagnostics grouped by severity (`error`, `warning`, `info`) and also writes them to `.openapi-gen/manifest.json` in non-production runs. Common codes include `missing-query-params-type`, `multipart-missing-body-schema`, `schema-not-found`, `schema-dir-empty`, `path-param-schema-conflict`, `unknown-zod-helper`, `unknown-zod-method`, `type-resolution-fallback`, `inferred-path-params`, `inferred-query-params`, and `inferred-body`.

For a fuller setup guide, Pages Router notes, response sets, and route exclusion
patterns, see [docs/getting-started.md](./docs/getting-started.md).

## JSDoc tags you will use most

| Tag                                    | Purpose                                                                                                 |
| -------------------------------------- | ------------------------------------------------------------------------------------------------------- |
| `@path` / `@pathParams`                | Path parameter schema or type                                                                           |
| `@query` / `@params` / `@queryParams`  | Query parameter schema or type                                                                          |
| `@header` / `@cookie`                  | Header / cookie parameter schema or type                                                                |
| `@requestBody` / `@body`               | Request body schema or type; append `required` to set `requestBody.required`                            |
| `@response`                            | Response schema, code, and optional description                                                         |
| `@responseDescription`                 | Response description without redefining the schema                                                      |
| `@responseHeader`                      | Add a response header to a given status code                                                            |
| `@link`                                | Add an OpenAPI link to a response                                                                       |
| `@auth` / `@security`                  | Security requirement(s); built-in presets: `bearer`, `basic`, `apikey` — configurable via `authPresets` |
| `@servers`                             | Operation-level servers                                                                                 |
| `@externalDocs`                        | Operation-level external documentation                                                                  |
| `@callback`                            | OpenAPI operation callback                                                                              |
| `@webhook`                             | Mark the handler as a webhook (`3.1`+ `webhooks` section)                                               |
| `@requestContentType` / `@contentType` | Request content type such as `multipart/form-data`                                                      |
| `@examples`                            | Request, response, querystring, query, header, and cookie examples                                      |
| `@openapi`                             | Explicit inclusion marker when `includeOpenApiRoutes` is enabled                                        |
| `@openapi-override`                    | Deep-merge extra OpenAPI fields onto the operation                                                      |
| `@ignore`                              | Exclude a route from generation                                                                         |
| `@internal`                            | Exclude a schema/type declaration from `components/schemas`                                             |
| `@method`                              | Override or declare the HTTP method; `QUERY` emits the OpenAPI 3.2 Path Item `query` field              |

For the complete tag guide and usage recipes, see
[docs/jsdoc-reference.md](./docs/jsdoc-reference.md).

OpenAPI `3.2`-specific tags such as `@querystring`, `@tagSummary`, `@tagKind`,
`@itemSchema`, and sequential media annotations are documented in the same guide and shown in
[apps/next-app-zod](./apps/next-app-zod).

## Compatibility

| Area            | Support                                                      |
| --------------- | ------------------------------------------------------------ |
| Frameworks      | Next.js, TanStack Router, React Router                       |
| Next.js routers | App Router and Pages Router                                  |
| OpenAPI targets | `3.0`, `3.1`, `3.2`, experimental `3.3-preview`              |
| Schema sources  | `zod`, `typescript`, drizzle-zod output, YAML/JSON fragments |
| Docs UIs        | Scalar, Swagger, Redoc, Stoplight Elements, RapiDoc          |

For Pages Router projects, set `routerType` to `"pages"` and annotate handlers with `@method`. See [apps/next-pages-router](./apps/next-pages-router).

For the supported Zod 4 surface and known gaps, see
[docs/zod4-support-matrix.md](./docs/zod4-support-matrix.md).

## Framework integrations

Use the integration that matches your framework:

- `next-openapi-gen/next`: Next.js adapter helpers such as `createNextOpenApiAdapter`
- `next-openapi-gen/vite`: Vite plugin surface used by the TanStack example app
- `next-openapi-gen/react-router`: React Router plugin surface

The main package export also exposes `generateProject`, `watchProject`, and
config helpers when you want to script generation directly.

## Example apps

Use the checked-in examples to evaluate the tool in realistic setups:

- [apps/next-app-zod](./apps/next-app-zod): Zod-first App Router example
- [apps/next-app-next-config](./apps/next-app-next-config): typed config example targeting OpenAPI `3.1`
- [apps/next-app-typescript](./apps/next-app-typescript): TypeScript-first example
- [apps/next-app-mixed-schemas](./apps/next-app-mixed-schemas): mixed schema migration example
- [apps/next-app-drizzle-zod](./apps/next-app-drizzle-zod): Drizzle + drizzle-zod CRUD example
- [apps/next-app-sandbox](./apps/next-app-sandbox): edge-case route and exclusion playground
- [apps/next-app-ts-config](./apps/next-app-ts-config): typed config loading example
- [apps/next-app-adapter](./apps/next-app-adapter): Next adapter integration smoke example
- [apps/next-pages-router](./apps/next-pages-router): legacy Pages Router support
- [apps/tanstack-app](./apps/tanstack-app): TanStack Router framework parity example
- [apps/react-router-app](./apps/react-router-app): React Router framework parity example
- [apps/next-app-scalar](./apps/next-app-scalar), [apps/next-app-swagger](./apps/next-app-swagger): docs UI variants

### Run an example

```bash
pnpm install
cd apps/next-app-zod
pnpm exec openapi-gen generate
pnpm dev
```

Then open `http://localhost:3000/api-docs`.

## Validation and coverage

This repo is not just a demo. The CI pipeline covers:

- formatting and linting
- workspace builds
- unit tests
- integration tests
- coverage reporting
- Playwright E2E runs across an app matrix

For the detailed version matrix and validation notes, see:

- [docs/openapi-version-coverage.md](./docs/openapi-version-coverage.md)
- [docs/zod4-support-matrix.md](./docs/zod4-support-matrix.md)

The checked-in examples intentionally span different goals: most apps stay on
`3.0` as the conservative default, `apps/next-app-next-config` demonstrates a
typed `3.1` config, and `apps/next-app-zod` showcases richer `3.2` route and
document features.

## Available UI providers

| Scalar                                                                                         | Swagger                                                                                          | Redoc                                                                                        | Stoplight Elements                                                                                            | RapiDoc                                                                                          |
| ---------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------ |
| ![Scalar UI](https://raw.githubusercontent.com/tazo90/next-openapi-gen/main/assets/scalar.png) | ![Swagger UI](https://raw.githubusercontent.com/tazo90/next-openapi-gen/main/assets/swagger.png) | ![Redoc UI](https://raw.githubusercontent.com/tazo90/next-openapi-gen/main/assets/redoc.png) | ![Stoplight Elements UI](https://raw.githubusercontent.com/tazo90/next-openapi-gen/main/assets/stoplight.png) | ![RapiDoc UI](https://raw.githubusercontent.com/tazo90/next-openapi-gen/main/assets/rapidoc.png) |

## Advanced docs

Use these deeper references when you need more than the quick start:

- [docs/README.md](./docs/README.md): docs index
- [docs/getting-started.md](./docs/getting-started.md): setup, config, framework defaults, watch mode, and production notes
- [docs/jsdoc-reference.md](./docs/jsdoc-reference.md): full route tag reference and examples
- [docs/workflows-and-integrations.md](./docs/workflows-and-integrations.md): framework integrations, mixed schemas, drizzle-zod, and downstream workflows
- [docs/faq.md](./docs/faq.md): troubleshooting and common questions
- [docs/openapi-version-coverage.md](./docs/openapi-version-coverage.md): version-specific behavior, validation strategy, and generated vs preserved fields
- [docs/zod4-support-matrix.md](./docs/zod4-support-matrix.md): tested Zod 4 coverage and known boundaries
- [docs/example-app-coverage-plan.md](./docs/example-app-coverage-plan.md): example app roles, coverage goals, and expansion roadmap
- [apps](./apps): complete runnable examples

## CLI

```bash
pnpm exec openapi-gen init
pnpm exec openapi-gen generate
pnpm exec openapi-gen generate --watch
```

### `init` options

| Option        | Choices                                                      | Default             |
| ------------- | ------------------------------------------------------------ | ------------------- |
| `--framework` | `next`, `tanstack`, `react-router`                           | `next`              |
| `--ui`        | `scalar`, `swagger`, `redoc`, `stoplight`, `rapidoc`, `none` | `scalar`            |
| `--schema`    | `zod`, `typescript`                                          | `zod`               |
| `--docs-url`  | any string                                                   | `api-docs`          |
| `--output`    | any path                                                     | `next.openapi.json` |

### `generate` options

| Option       | Purpose                                                                  |
| ------------ | ------------------------------------------------------------------------ |
| `--config`   | Use a specific config file                                               |
| `--template` | Merge a specific OpenAPI template or fragment                            |
| `--watch`    | Regenerate when routes or schema files change                            |
| `--fail-on`  | Exit with an error when diagnostics reach `error`, `warning`, or `never` |

Generated diagnostics are printed after each run and recorded in `.openapi-gen/manifest.json` (development only) for automation and CI review.

## Contributing

Contributions are welcome. See [CONTRIBUTING.md](./CONTRIBUTING.md) for setup, commit conventions, and workflow details.

## Changelog

See [CHANGELOG.md](./CHANGELOG.md) for release history and recent changes.

## License

MIT

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