[BUG] Windows: empty requireChunk() switch in patched Turbopack runtime → every route 500s with "ComponentMod.handler is not a function"

[fmseitai-coder]

Describe the bug

Building on Windows with @opennextjs/cloudflare@1.20.1 and Next.js 16.2.10 (Turbopack) produces a worker where every route returns 500 with:

⨯ TypeError: components.ComponentMod.handler is not a function

(Symptom looks like #1258 / the 1.19 boot issue, but this one is Windows-specific and still present on 1.20.1.)

Root cause

In dist/cli/build/patches/plugins/turbopack.js, the traced file paths use Windows backslashes (...\.next\server\chunks\...), but the filters compare against forward-slash literals:

• getInlinableChunks: file.includes(".next/server/chunks/") → matches nothing on Windows
• discoverBareExternalImports: f.includes(".next/server/chunks/") → same
• the case path rewrite chunk.replace(/.*\/\.next\//, "") also assumes /

As a result the generated requireChunk() switch is empty:

function requireChunk(chunkPath) {
  switch(chunkPath) {

    default:
      throw new Error(`Not found ${chunkPath}`);
  }
}

so loading any page module throws ChunkLoadError: Failed to load chunk server/chunks/ssr/..., which surfaces as the ComponentMod.handler TypeError at request time.

Workaround / suggested fix

Normalizing the paths at the top of patchTurbopackRuntime.patchCode fixes it (verified — the switch then contains all 58 chunks and the deployed worker serves all routes):

patchCode: async ({ code, tracedFiles, filePath }) => {
    tracedFiles = tracedFiles.map((f) => f.replace(/\/g, "/"));
    filePath = filePath.replace(/\/g, "/");
    // ...unchanged

A more general fix would be to normalize separators wherever tracedFiles are filtered/rewritten in this plugin.

Steps to reproduce

1. On Windows, create-next-app (App Router, Next 16.x, default Turbopack build) with any page + route handler
2. opennextjs-cloudflare build && opennextjs-cloudflare deploy
3. Open any route → 500; wrangler tail shows the TypeError above
4. Inspect .open-next/server-functions/default/.next/server/chunks/ssr/[turbopack]_runtime.js → requireChunk switch has zero cases

Environment

• OS: Windows 11 (build run in PowerShell/Git Bash, not WSL)
• @opennextjs/cloudflare: 1.20.1 (@opennextjs/aws 4.0.2)
• Next.js: 16.2.10 (Turbopack build)
• wrangler: 4.97.0, Node.js: 24.15.0