Bundler Setup

formulon-cell reuses the pthread-enabled @libraz/formulon WASM module. The same browser bundling constraints apply to the UI package.

Vite

import { defineConfig } from 'vite'

export default defineConfig({
  server: {
    headers: {
      'Cross-Origin-Opener-Policy': 'same-origin',
      'Cross-Origin-Embedder-Policy': 'require-corp'
    }
  },
  preview: {
    headers: {
      'Cross-Origin-Opener-Policy': 'same-origin',
      'Cross-Origin-Embedder-Policy': 'require-corp'
    }
  },
  optimizeDeps: {
    exclude: ['@libraz/formulon-cell', '@libraz/formulon']
  },
  build: {
    target: 'es2022'
  },
  worker: {
    format: 'es'
  }
})

Why These Settings Matter

The server and preview headers above only cover local Vite serving. Your production host must send the same COOP/COEP headers for pages that run the spreadsheet engine.

Workers must be emitted as ES modules because the Formulon scheduler is spawned through Emscripten with module workers.

The main and worker builds need an ES2022 target because the engine wrapper uses top-level await and conditional dynamic imports.

Dependency pre-bundling should skip both packages so the Emscripten wrapper can keep control of worker and WASM asset resolution.

The COOP/COEP headers are required for SharedArrayBuffer. Without them, WorkbookHandle.createDefault() falls back to the stub engine.