---
title: Stack
---

## Framework

- [Next.js](https://nextjs.org/) 15 (App Router, Turbopack in dev)
- [React](https://react.dev/) 19
- [TypeScript](https://www.typescriptlang.org/)
- [pnpm](https://pnpm.io/) workspaces monorepo

## Containerization and runtime

- [Docker](https://www.docker.com/) (linux/amd64 and linux/arm64)
- Shared entrypoint that runs DB migrations by default and can bootstrap embedded SeaweedFS before app startup

## Next.js client

- UI: [Tailwind CSS](https://tailwindcss.com), [Headless UI](https://headlessui.com), [@tailwindcss/typography](https://tailwindcss.com/docs/typography-plugin)
- Interactions: `react-dnd`, `react-dropzone`
- Server state: [TanStack Query](https://tanstack.com/query) (React Query v5)
- Authentication: [Better Auth](https://www.better-auth.com/) client SDK
- Browser blob performance cache: Cache Storage (evictable; never authoritative)
- Audio playback: [Howler.js](https://howlerjs.com/)
- Notifications: `react-hot-toast`
- Document rendering:
  - PDF: [react-pdf](https://github.com/wojtekmaj/react-pdf), [pdf.js](https://mozilla.github.io/pdf.js/)
  - EPUB: [react-reader](https://github.com/gerhardsletten/react-reader), [epubjs](https://github.com/futurepress/epub.js/)
  - Markdown/Text: [react-markdown](https://github.com/remarkjs/react-markdown), [remark-gfm](https://github.com/remarkjs/remark-gfm)
- Text preprocessing/matching: [compromise](https://github.com/spencermountain/compromise), [cmpstr](https://github.com/remsky/cmpstr)
- Analytics: [Vercel Analytics](https://vercel.com/analytics)

## Next.js server

- APIs: Route Handlers for sync, blob/content access, migrations, audiobook export, TTS/Whisper proxying
- State sync: request-based today (not realtime push updates)
- Authentication: [Better Auth](https://www.better-auth.com/) server handlers/adapters with anonymous session support
- Metadata DB: [Drizzle ORM](https://orm.drizzle.team/) with SQLite (`better-sqlite3`) by default and optional Postgres (`pg`)
  - App tables are manually maintained in Drizzle schema files
  - Auth tables are auto-generated by the [Better Auth](https://www.better-auth.com/) CLI and migrated alongside app tables via Drizzle
- Blob storage: embedded [SeaweedFS](https://github.com/seaweedfs/seaweedfs) (`weed mini`) by default, or external S3-compatible storage via AWS SDK v3
- TTS providers: OpenAI-compatible API (`openai` SDK), [Replicate](https://replicate.com/) (`replicate` client), DeepInfra, and custom OpenAI-compatible endpoints — credentials are encrypted at rest
- Audio pipeline: [ffmpeg](https://ffmpeg.org/) (`ffmpeg-static`) for audiobook assembly, `archiver` for export packaging
- Utilities: `lru-cache` for in-process caching, `fast-xml-parser` for EPUB/XML parsing, `uuid` for identifier generation, `zod` for schema validation

## External compute worker (optional)

Standalone worker package:

- **`@openreader/compute-worker`** — standalone Node.js compute service containing its private inference and queue runtime
  - ONNX runtime: `onnxruntime-node` with `@huggingface/tokenizers`
  - Whisper alignment: `onnx-community/whisper-base_timestamped` (q4) for word-level timestamps
  - PDF layout: `Bei0001/PP-DocLayoutV3-ONNX` for document block detection and layout parsing
  - PDF rendering: `pdfjs-dist`, `@napi-rs/canvas` for server-side page rasterization
  - Utilities: `jszip`, `ffmpeg-static`
- HTTP server: [Fastify](https://fastify.dev/) v5 with a versioned OpenAPI contract
  - Job queue + state: [NATS](https://nats.io/) JetStream WorkQueue pull consumers + NATS KV (`jobs.whisper`, `jobs.layout`)
  - Storage: AWS SDK v3 S3 client for reading/writing blobs
  - Logging: [Pino](https://getpino.io/)
  - Validation: [Zod](https://zod.dev/)
- The Next.js app communicates with the worker only through the versioned HTTP API generated from OpenAPI.

## Tooling and testing

- ESLint
- TypeScript
- [Playwright](https://playwright.dev/) end-to-end tests
- Drizzle migration/generation scripts
- [Docusaurus](https://docusaurus.io/) documentation site (`docs-site/`)