@zenstackhq/better-auth bundles @zenstackhq/language at runtime, crashing Cloudflare Workers (createRequire(import.meta.url))

[Azzerty23]

Summary

When using @zenstackhq/better-auth in a Cloudflare Workers environment, the Worker crashes on startup with:

Uncaught TypeError: The argument 'path' must be a file URL object, a file URL string, or an absolute path string. Received 'undefined'
  at node:module:34:15 in createRequire

The crash happens at module initialisation — before any request is served.

---

Root cause

@zenstackhq/better-auth/dist/index.mjs has top-level imports from @zenstackhq/language:

// @zenstackhq/better-auth/dist/index.mjs (top of file)
import { ZModelCodeGenerator, formatDocument, loadDocument } from "@zenstackhq/language";
import { isDataModel } from "@zenstackhq/language/ast";
import { hasAttribute } from "@zenstackhq/language/utils";

These imports are used inside generateSchema(), which is wired as the createSchema callback of the adapter (for the better-auth CLI migration tool). Because the reference is live inside the exported zenstackAdapter, esbuild cannot tree-shake the imports away.

@zenstackhq/language is the Langium / VS Code grammar-tooling package. Its dist/index.mjs contains:

// @zenstackhq/language/dist/index.mjs line 16
var __require = /* @__PURE__ */ createRequire(import.meta.url);

In Cloudflare Workers, import.meta.url is undefined, so createRequire(undefined) throws immediately when the module is evaluated, killing the Worker before it can handle any request.

---

Import chain

apps/server/src/index.ts
  → @my-better-t-app/auth (workspace package)
    → @zenstackhq/better-auth  ← zenstackAdapter
      → @zenstackhq/language   ← createRequire(import.meta.url) 💥

---

Context / reproduction

The project was generated with better-t-stack targeting Cloudflare Workers and then migrated from Prisma to ZenStack:

bun create better-t-stack@latest my-better-t-app \
  --frontend tanstack-router \
  --backend hono \
  --runtime workers \
  --api trpc \
  --auth better-auth \
  --payments none \
  --database postgres \
  --orm prisma \
  --db-setup neon \
  --package-manager bun \
  --git \
  --web-deploy cloudflare \
  --server-deploy cloudflare \
  --no-install \
  --addons oxlint pwa skills turborepo wxt \
  --examples ai todo

The infrastructure is managed by Alchemy (Cloudflare Workers / Miniflare). The server bundle is built by Alchemy's internal esbuild pipeline.

Versions:

• @zenstackhq/better-auth: 3.6.2
• @zenstackhq/language: 3.6.2
• better-auth: ~1.4
• Alchemy: 0.91.2
• Miniflare: 4.20260310.0

---

Workaround

We stub out @zenstackhq/language via an esbuild alias so the grammar package is never bundled into the Worker. Since generateSchema() is only called by the better-auth CLI (schema migrations) and never during request handling, replacing it with no-op exports is safe at runtime.

packages/infra/stubs/zenstack-language-stub.js

// Stub replacing @zenstackhq/language, /ast, /utils in CF Workers.
// Only needed by the better-auth CLI for schema migration — never at request time.
export const ZModelCodeGenerator = class {};
export const formatDocument = async (s) => s;
export const loadDocument = async () => null;
export const isDataModel = () => false;
export const hasAttribute = () => false;

alchemy.run.ts (Alchemy Worker config)

// ...
const __dirname = dirname(fileURLToPath(import.meta.url));
const zenstackLanguageStub = join(__dirname, "stubs/zenstack-language-stub.js");
// ...

export const server = await Worker("server", {
  // ...
  bundle: {
    alias: {
      "@zenstackhq/language": zenstackLanguageStub,
      "@zenstackhq/language/ast": zenstackLanguageStub,
      "@zenstackhq/language/utils": zenstackLanguageStub,
    },
  },
});

The same alias approach applies to any bundler (esbuild, Rollup, Vite, tsdown) targeting Cloudflare Workers or any other runtime where import.meta.url is unavailable.

---

Suggested fix

@zenstackhq/language is a development / CLI tool dependency — it is only needed when running zenstack generate or better-auth migrate. It should never be part of the runtime adapter bundle.

Two possible approaches:

Option A — Lazy / dynamic import (preferred)

In schema-generator.ts, replace the static top-level imports with dynamic import() calls:

// Before (crashes CF Workers on load)
import { ZModelCodeGenerator, formatDocument, loadDocument } from "@zenstackhq/language";

// After (only evaluated when generateSchema() is actually called)
const { ZModelCodeGenerator, formatDocument, loadDocument } = await import("@zenstackhq/language");

This way the import is never evaluated during request handling, and bundlers can safely exclude it or mark it external without breaking runtime behaviour.

Option B — Separate entrypoint / sub-path export

Split @zenstackhq/better-auth into two sub-path exports:

"exports": {
  ".":          "./dist/adapter.mjs",        // runtime only — no language dep
  "./cli":      "./dist/schema-generator.mjs" // CLI only — requires @zenstackhq/language
}

Users import zenstackAdapter from "@zenstackhq/better-auth" (runtime) and the CLI tool imports generateSchema from "@zenstackhq/better-auth/cli".

---

Additional notes

• The tsdown.config.ts in the generated project already had external: ["@zenstackhq/language"] as a workaround — indicating this problem was previously known at the build level, but it doesn't solve the runtime crash when using Alchemy's bundler directly.
• This issue affects any edge/serverless runtime where import.meta.url is undefined (Cloudflare Workers, Deno Deploy, etc.).

[Azzerty23]

Simply importing zenstackAdapter causes the development server to crash.

Minimal repro:

1. clone https://github.com/Azzerty23/repro-2610
2. bun install
3. cp apps/server/.env.example apps/server/.env && cp apps/web/.env.example apps/ web/.env + update DATABASE_URL path
4. bun run db:migrate -- --name init
5. bun run dev -> should work
6. uncomment import { zenstackAdapter } from "@zenstackhq/better-auth"; -> no longer works

[ymc9]

Hi @Azzerty23 , thanks for filing this. I believe the issue can be resolved by dynamically importing the generateSchema method. I can't seem to open your repro project. Do you mind checking it? Thanks!

[Azzerty23]

My bad, I’ve made it public.

The project still uses Prisma — I only imported @zenstackhq/better-auth for demonstration:

bun create better-t-stack@latest repro-2610 --frontend tanstack-router --backend hono --runtime workers --api trpc --auth better-auth --payments none --database sqlite --orm prisma --db-setup d1 --package-manager bun --git --web-deploy cloudflare --server-deploy cloudflare --no-install --addons none --examples todo

[Azzerty23]

Just to confirm the issue, lazy loading "@zenstackhq/better-auth" fixes it: Azzerty23/repro-2610#1.