[BUG] ZenStack V3: better-auth integration leads to startup errors

[SashSpnglr]

Description and expected behavior
After migrating Zenstack in my NestJS app from V2 to V3 the app fails on startup with an error regarding a dependency used in the better-auth integration package. I created a new fresh project with the NestJS CLI and can reproduce the error after I installed better-auth and initialized it using Zenstack's better-auth integration package.

Screenshots

node:internal/modules/cjs/loader:692
throw e;
^

Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: No "exports" main defined in /Users/sash/Documents/projects/test/zenstack-nest/node_modules/langium/package.json
at exportsNotFound (node:internal/modules/esm/resolve:310:10)
at packageExportsResolve (node:internal/modules/esm/resolve:601:13)
at resolveExports (node:internal/modules/cjs/loader:685:36)
at Module._findPath (node:internal/modules/cjs/loader:752:31)
at Module._resolveFilename (node:internal/modules/cjs/loader:1461:27)
at wrapResolveFilename (node:internal/modules/cjs/loader:1049:27)
at defaultResolveImplForCJSLoading (node:internal/modules/cjs/loader:1073:10)
at resolveForCJSWithHooks (node:internal/modules/cjs/loader:1094:12)
at Module._load (node:internal/modules/cjs/loader:1262:25)
at wrapModuleLoad (node:internal/modules/cjs/loader:255:19) {
code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}

Environment:

• ZenStack version: 3.6.4
• Database type: PostgreSQL / Sqlite
• Node.js version: 24.15.0
• Package manager: npm

Additional context
App running on NestJS v11 with better-auth v1.6.9.

auth.ts:

const db = new ZenStackClient(schema, {
  dialect: new SqliteDialect({
    database: new SQLite('../../zenstack/dev.db'),
  }),
});

export const auth = betterAuth({
  database: zenstackAdapter(db, {
    provider: 'sqlite',
  }),
  // other better-auth options...
});

tsconfig:

{
  "compilerOptions": {
    "module": "nodenext",
    "moduleResolution": "nodenext",
    "resolvePackageJsonExports": true,
    "esModuleInterop": true,
    "isolatedModules": true,
    "declaration": true,
    "removeComments": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "allowSyntheticDefaultImports": true,
    "target": "es2025",
    "sourceMap": true,
    "outDir": "./dist",
    "baseUrl": "./",
    "incremental": true,
    "skipLibCheck": true,
    "strictNullChecks": true,
    "forceConsistentCasingInFileNames": true,
    "noImplicitAny": false,
    "strictBindCallApply": false,
    "noFallthroughCasesInSwitch": false
  }
}

[ymc9]

Thanks for filing this @SashSpnglr . Is is possible to push the repro to a public repo? It'll same me some time creating one :D.

[SashSpnglr]

Sure :D You can find it here: https://github.com/SashSpnglr/zenstack-v3-nest-example