diff --git a/playground/app/types/auth.d.ts b/playground/app/types/auth.d.ts
deleted file mode 100644
index 7cf40ce..0000000
--- a/playground/app/types/auth.d.ts
+++ /dev/null
@@ -1,9 +0,0 @@
-// Augment AuthUser with plugin fields (admin, twoFactor)
-declare module '#nuxt-better-auth' {
-  interface AuthUser {
-    role?: 'user' | 'admin'
-    twoFactorEnabled?: boolean
-  }
-}
-
-export {}
diff --git a/src/module/type-templates.ts b/src/module/type-templates.ts
index 8192fd2..3b01bc3 100644
--- a/src/module/type-templates.ts
+++ b/src/module/type-templates.ts
@@ -37,31 +37,57 @@ declare module '#auth/database' {
   addTypeTemplate({
     filename: 'types/nuxt-better-auth-infer.d.ts',
     getContents: () => `
-import type { InferUser, InferSession, InferPluginTypes } from 'better-auth'
+import type { BetterAuthOptions, BetterAuthPlugin, InferPluginTypes, UnionToIntersection } from 'better-auth'
+import type { InferFieldsOutput } from 'better-auth/db'
 import type { RuntimeConfig } from 'nuxt/schema'
 import type createServerAuth from '${serverConfigPath}'
 
-type _Config = ReturnType<typeof createServerAuth>
+type _RawConfig = ReturnType<typeof createServerAuth>
+type _RawPlugins = _RawConfig extends { plugins: infer P } ? P : _RawConfig extends { plugins?: infer P } ? P : []
+type _NormalizedPlugins = _RawPlugins extends readonly (infer T)[]
+  ? Array<T & BetterAuthPlugin>
+  : _RawPlugins extends (infer T)[]
+      ? Array<T & BetterAuthPlugin>
+      : BetterAuthPlugin[]
+type _Config = Omit<BetterAuthOptions, 'plugins'> & Omit<_RawConfig, 'plugins'> & {
+  plugins?: _NormalizedPlugins
+}
+
+type _InferModelFieldsFromPlugins<P, M extends string> = P extends readonly (infer Plugin)[]
+  ? UnionToIntersection<Plugin extends { schema: { [K in M]: { fields: infer F } } } ? InferFieldsOutput<F> : {}>
+  : P extends (infer Plugin)[]
+      ? UnionToIntersection<Plugin extends { schema: { [K in M]: { fields: infer F } } } ? InferFieldsOutput<F> : {}>
+      : {}
+
+type _InferModelFieldsFromOptions<C, M extends 'user' | 'session'> = C extends { [K in M]: { additionalFields: infer F } }
+  ? InferFieldsOutput<F>
+  : {}
+
+type _UserFallback = _InferModelFieldsFromPlugins<_RawPlugins, 'user'> & _InferModelFieldsFromOptions<_RawConfig, 'user'>
+type _SessionFallback = _InferModelFieldsFromPlugins<_RawPlugins, 'session'> & _InferModelFieldsFromOptions<_RawConfig, 'session'>
 
 declare module '#nuxt-better-auth' {
-  interface AuthUser extends InferUser<_Config> {}
-  interface AuthSession extends InferSession<_Config> {}
+  interface AuthUser extends _UserFallback {}
+  interface AuthSession extends _SessionFallback {}
   interface ServerAuthContext {
     runtimeConfig: RuntimeConfig
-    ${hasHubDb ? `db: typeof import('@nuxthub/db')['db']` : ''}
+    db: ${hasHubDb ? `typeof import('@nuxthub/db')['db']` : 'unknown'}
   }
   type PluginTypes = InferPluginTypes<_Config>
 }
 
 interface _AugmentedServerAuthContext {
   runtimeConfig: RuntimeConfig
-  ${hasHubDb ? `db: typeof import('@nuxthub/db')['db']` : 'db: unknown'}
+  db: ${hasHubDb ? `typeof import('@nuxthub/db')['db']` : 'unknown'}
 }
 
 declare module '@onmax/nuxt-better-auth/config' {
-  import type { BetterAuthOptions } from 'better-auth'
-  type ServerAuthConfig = Omit<BetterAuthOptions, 'database' | 'secret' | 'baseURL'>
-  export function defineServerAuth<T extends ServerAuthConfig>(config: T | ((ctx: _AugmentedServerAuthContext) => T)): (ctx: _AugmentedServerAuthContext) => T
+  import type { BetterAuthOptions, BetterAuthPlugin } from 'better-auth'
+  type ServerAuthConfig = Omit<BetterAuthOptions, 'database' | 'secret' | 'baseURL'> & {
+    plugins?: readonly BetterAuthPlugin[]
+  }
+  export function defineServerAuth<const R extends ServerAuthConfig>(config: R): (ctx: _AugmentedServerAuthContext) => R
+  export function defineServerAuth<const R extends ServerAuthConfig>(config: (ctx: _AugmentedServerAuthContext) => R): (ctx: _AugmentedServerAuthContext) => R
 }
 `,
   }, { nuxt: true, nitro: true, node: true })
diff --git a/src/runtime/config.ts b/src/runtime/config.ts
index 26d6e3e..67ca804 100644
--- a/src/runtime/config.ts
+++ b/src/runtime/config.ts
@@ -1,4 +1,4 @@
-import type { BetterAuthOptions } from 'better-auth'
+import type { BetterAuthOptions, BetterAuthPlugin } from 'better-auth'
 import type { BetterAuthClientOptions } from 'better-auth/client'
 import type { DatabaseProvider } from '../database-provider'
 import type { CasingOption } from '../schema-generator'
@@ -12,7 +12,9 @@ export interface ClientAuthContext {
   siteUrl: string
 }
 
-export type ServerAuthConfig = Omit<BetterAuthOptions, 'database' | 'secret' | 'baseURL'>
+export type ServerAuthConfig = Omit<BetterAuthOptions, 'database' | 'secret' | 'baseURL'> & {
+  plugins?: readonly BetterAuthPlugin[]
+}
 export type ClientAuthConfig = Omit<BetterAuthClientOptions, 'baseURL'> & { baseURL?: string }
 
 export type ServerAuthConfigFn = (ctx: ServerAuthContext) => ServerAuthConfig
@@ -72,6 +74,8 @@ export interface AuthPrivateRuntimeConfig {
   secondaryStorage: boolean
 }
 
+export function defineServerAuth<const R extends ServerAuthConfig>(config: R): (ctx: ServerAuthContext) => R
+export function defineServerAuth<const R extends ServerAuthConfig>(config: (ctx: ServerAuthContext) => R): (ctx: ServerAuthContext) => R
 export function defineServerAuth<T extends ServerAuthConfig>(config: T | ((ctx: ServerAuthContext) => T)): (ctx: ServerAuthContext) => T {
   return typeof config === 'function' ? config : () => config
 }
diff --git a/test/fixtures/basic/.nuxtrc b/test/cases/core-auth/.nuxtrc
similarity index 100%
rename from test/fixtures/basic/.nuxtrc
rename to test/cases/core-auth/.nuxtrc
diff --git a/test/fixtures/basic/app/app.vue b/test/cases/core-auth/app/app.vue
similarity index 100%
rename from test/fixtures/basic/app/app.vue
rename to test/cases/core-auth/app/app.vue
diff --git a/test/fixtures/basic/app/auth.config.ts b/test/cases/core-auth/app/auth.config.ts
similarity index 100%
rename from test/fixtures/basic/app/auth.config.ts
rename to test/cases/core-auth/app/auth.config.ts
diff --git a/test/fixtures/basic/app/pages/custom-protected.vue b/test/cases/core-auth/app/pages/custom-protected.vue
similarity index 100%
rename from test/fixtures/basic/app/pages/custom-protected.vue
rename to test/cases/core-auth/app/pages/custom-protected.vue
diff --git a/test/fixtures/basic/app/pages/dynamic/[...slug].vue b/test/cases/core-auth/app/pages/dynamic/[...slug].vue
similarity index 100%
rename from test/fixtures/basic/app/pages/dynamic/[...slug].vue
rename to test/cases/core-auth/app/pages/dynamic/[...slug].vue
diff --git a/test/fixtures/basic/app/pages/index.vue b/test/cases/core-auth/app/pages/index.vue
similarity index 100%
rename from test/fixtures/basic/app/pages/index.vue
rename to test/cases/core-auth/app/pages/index.vue
diff --git a/test/fixtures/basic/app/pages/login.vue b/test/cases/core-auth/app/pages/login.vue
similarity index 100%
rename from test/fixtures/basic/app/pages/login.vue
rename to test/cases/core-auth/app/pages/login.vue
diff --git a/test/fixtures/basic/app/pages/protected.vue b/test/cases/core-auth/app/pages/protected.vue
similarity index 100%
rename from test/fixtures/basic/app/pages/protected.vue
rename to test/cases/core-auth/app/pages/protected.vue
diff --git a/test/fixtures/basic/nuxt.config.ts b/test/cases/core-auth/nuxt.config.ts
similarity index 100%
rename from test/fixtures/basic/nuxt.config.ts
rename to test/cases/core-auth/nuxt.config.ts
diff --git a/test/fixtures/basic/server/api/test/config.get.ts b/test/cases/core-auth/server/api/test/config.get.ts
similarity index 100%
rename from test/fixtures/basic/server/api/test/config.get.ts
rename to test/cases/core-auth/server/api/test/config.get.ts
diff --git a/test/fixtures/basic/server/api/test/me.get.ts b/test/cases/core-auth/server/api/test/me.get.ts
similarity index 100%
rename from test/fixtures/basic/server/api/test/me.get.ts
rename to test/cases/core-auth/server/api/test/me.get.ts
diff --git a/test/fixtures/basic/server/auth.config.ts b/test/cases/core-auth/server/auth.config.ts
similarity index 100%
rename from test/fixtures/basic/server/auth.config.ts
rename to test/cases/core-auth/server/auth.config.ts
diff --git a/test/fixtures/basic/server/plugins/init-db.ts b/test/cases/core-auth/server/plugins/init-db.ts
similarity index 100%
rename from test/fixtures/basic/server/plugins/init-db.ts
rename to test/cases/core-auth/server/plugins/init-db.ts
diff --git a/test/fixtures/no-db/.nuxtrc b/test/cases/database-less/.nuxtrc
similarity index 100%
rename from test/fixtures/no-db/.nuxtrc
rename to test/cases/database-less/.nuxtrc
diff --git a/test/fixtures/no-db/app/app.vue b/test/cases/database-less/app/app.vue
similarity index 100%
rename from test/fixtures/no-db/app/app.vue
rename to test/cases/database-less/app/app.vue
diff --git a/test/fixtures/no-db/app/auth.config.ts b/test/cases/database-less/app/auth.config.ts
similarity index 100%
rename from test/fixtures/no-db/app/auth.config.ts
rename to test/cases/database-less/app/auth.config.ts
diff --git a/test/fixtures/no-db/app/pages/index.vue b/test/cases/database-less/app/pages/index.vue
similarity index 100%
rename from test/fixtures/no-db/app/pages/index.vue
rename to test/cases/database-less/app/pages/index.vue
diff --git a/test/fixtures/no-db/nuxt.config.ts b/test/cases/database-less/nuxt.config.ts
similarity index 100%
rename from test/fixtures/no-db/nuxt.config.ts
rename to test/cases/database-less/nuxt.config.ts
diff --git a/test/fixtures/no-db/server/api/test/config.get.ts b/test/cases/database-less/server/api/test/config.get.ts
similarity index 100%
rename from test/fixtures/no-db/server/api/test/config.get.ts
rename to test/cases/database-less/server/api/test/config.get.ts
diff --git a/test/fixtures/no-db/server/auth.config.ts b/test/cases/database-less/server/auth.config.ts
similarity index 100%
rename from test/fixtures/no-db/server/auth.config.ts
rename to test/cases/database-less/server/auth.config.ts
diff --git a/test/fixtures/no-hub/.nuxtrc b/test/cases/plugins-type-inference/.nuxtrc
similarity index 100%
rename from test/fixtures/no-hub/.nuxtrc
rename to test/cases/plugins-type-inference/.nuxtrc
diff --git a/test/cases/plugins-type-inference/app/app.vue b/test/cases/plugins-type-inference/app/app.vue
new file mode 100644
index 0000000..2bb142d
--- /dev/null
+++ b/test/cases/plugins-type-inference/app/app.vue
@@ -0,0 +1,3 @@
+<template>
+  <div>type infer 107</div>
+</template>
diff --git a/test/cases/plugins-type-inference/app/auth.config.ts b/test/cases/plugins-type-inference/app/auth.config.ts
new file mode 100644
index 0000000..ce985ee
--- /dev/null
+++ b/test/cases/plugins-type-inference/app/auth.config.ts
@@ -0,0 +1,3 @@
+import { defineClientAuth } from '../../../../src/runtime/config'
+
+export default defineClientAuth({})
diff --git a/test/cases/plugins-type-inference/nuxt.config.ts b/test/cases/plugins-type-inference/nuxt.config.ts
new file mode 100644
index 0000000..4d5379e
--- /dev/null
+++ b/test/cases/plugins-type-inference/nuxt.config.ts
@@ -0,0 +1,10 @@
+export default defineNuxtConfig({
+  modules: ['../../../src/module'],
+  runtimeConfig: {
+    betterAuthSecret: 'test-secret-for-testing-only-32chars!',
+    public: { siteUrl: 'http://localhost:3000' },
+  },
+  routeRules: {
+    '/admin/**': { auth: { user: { role: 'admin', internalCode: 'x' } } },
+  },
+})
diff --git a/test/cases/plugins-type-inference/server/auth.config.ts b/test/cases/plugins-type-inference/server/auth.config.ts
new file mode 100644
index 0000000..c55110d
--- /dev/null
+++ b/test/cases/plugins-type-inference/server/auth.config.ts
@@ -0,0 +1,37 @@
+import { defineServerAuth } from '../../../../src/runtime/config'
+
+function customAdminLikePlugin() {
+  return {
+    id: 'custom-admin-like',
+    $ERROR_CODES: {
+      BROKEN: {
+        code: 'BROKEN',
+        message: 'Broken',
+      },
+    },
+    schema: {
+      user: {
+        fields: {
+          role: {
+            type: 'string',
+            required: false,
+            input: false,
+          },
+        },
+      },
+    },
+  } as const
+}
+
+export default defineServerAuth({
+  emailAndPassword: { enabled: true },
+  plugins: [customAdminLikePlugin()],
+  user: {
+    additionalFields: {
+      internalCode: {
+        type: 'string',
+        required: false,
+      },
+    },
+  },
+})
diff --git a/test/cases/plugins-type-inference/tsconfig.json b/test/cases/plugins-type-inference/tsconfig.json
new file mode 100644
index 0000000..4b34df1
--- /dev/null
+++ b/test/cases/plugins-type-inference/tsconfig.json
@@ -0,0 +1,3 @@
+{
+  "extends": "./.nuxt/tsconfig.json"
+}
diff --git a/test/cases/plugins-type-inference/tsconfig.type-check.json b/test/cases/plugins-type-inference/tsconfig.type-check.json
new file mode 100644
index 0000000..04e57dc
--- /dev/null
+++ b/test/cases/plugins-type-inference/tsconfig.type-check.json
@@ -0,0 +1,25 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "lib": [
+      "ESNext",
+      "DOM"
+    ],
+    "baseUrl": ".",
+    "module": "preserve",
+    "moduleResolution": "bundler",
+    "paths": {
+      "#auth/client": ["./app/auth.config"],
+      "#auth/server": ["./server/auth.config"],
+      "#nuxt-better-auth": ["../../../src/runtime/types/augment"]
+    },
+    "types": [],
+    "strict": true,
+    "noEmit": true,
+    "skipLibCheck": true
+  },
+  "files": [
+    "./.nuxt/types/nuxt-better-auth-infer.d.ts",
+    "./typecheck-target.ts"
+  ]
+}
diff --git a/test/cases/plugins-type-inference/typecheck-target.ts b/test/cases/plugins-type-inference/typecheck-target.ts
new file mode 100644
index 0000000..1937fad
--- /dev/null
+++ b/test/cases/plugins-type-inference/typecheck-target.ts
@@ -0,0 +1,14 @@
+import type { AuthUser } from '#nuxt-better-auth'
+
+const user: AuthUser = {
+  id: '1',
+  createdAt: new Date(),
+  updatedAt: new Date(),
+  email: 'a@b.c',
+  emailVerified: false,
+  name: 'n',
+  role: 'admin',
+  internalCode: 'x',
+}
+
+void user
diff --git a/test/cases/without-nuxthub/.nuxtrc b/test/cases/without-nuxthub/.nuxtrc
new file mode 100644
index 0000000..c85c9d1
--- /dev/null
+++ b/test/cases/without-nuxthub/.nuxtrc
@@ -0,0 +1 @@
+setups.@onmax/nuxt-better-auth="0.0.2-alpha.21"
\ No newline at end of file
diff --git a/test/fixtures/no-hub/app/app.vue b/test/cases/without-nuxthub/app/app.vue
similarity index 100%
rename from test/fixtures/no-hub/app/app.vue
rename to test/cases/without-nuxthub/app/app.vue
diff --git a/test/fixtures/no-hub/app/auth.config.ts b/test/cases/without-nuxthub/app/auth.config.ts
similarity index 100%
rename from test/fixtures/no-hub/app/auth.config.ts
rename to test/cases/without-nuxthub/app/auth.config.ts
diff --git a/test/fixtures/no-hub/app/pages/index.vue b/test/cases/without-nuxthub/app/pages/index.vue
similarity index 100%
rename from test/fixtures/no-hub/app/pages/index.vue
rename to test/cases/without-nuxthub/app/pages/index.vue
diff --git a/test/fixtures/no-hub/nuxt.config.ts b/test/cases/without-nuxthub/nuxt.config.ts
similarity index 100%
rename from test/fixtures/no-hub/nuxt.config.ts
rename to test/cases/without-nuxthub/nuxt.config.ts
diff --git a/test/fixtures/no-hub/server/auth.config.ts b/test/cases/without-nuxthub/server/auth.config.ts
similarity index 100%
rename from test/fixtures/no-hub/server/auth.config.ts
rename to test/cases/without-nuxthub/server/auth.config.ts
diff --git a/test/infer-plugins-types.test.ts b/test/infer-plugins-types.test.ts
new file mode 100644
index 0000000..03ab556
--- /dev/null
+++ b/test/infer-plugins-types.test.ts
@@ -0,0 +1,32 @@
+import { spawnSync } from 'node:child_process'
+import { fileURLToPath } from 'node:url'
+import { describe, expect, it } from 'vitest'
+
+const fixtureDir = fileURLToPath(new URL('./cases/plugins-type-inference', import.meta.url))
+const env = {
+  ...process.env,
+  BETTER_AUTH_SECRET: 'test-secret-for-testing-only-32chars',
+}
+
+describe('type inference regression #107', () => {
+  it('typechecks routeRules user fields inferred from plugins/additionalFields', () => {
+    const prepare = spawnSync('npx', ['nuxi', 'prepare'], {
+      cwd: fixtureDir,
+      env,
+      encoding: 'utf8',
+    })
+    expect(prepare.status, `nuxi prepare failed:\n${prepare.stdout}\n${prepare.stderr}`).toBe(0)
+
+    const typecheck = spawnSync('npx', ['vue-tsc', '--noEmit', '--pretty', 'false', '-p', 'tsconfig.type-check.json'], {
+      cwd: fixtureDir,
+      env,
+      encoding: 'utf8',
+    })
+    expect(typecheck.status, `vue-tsc failed:\n${typecheck.stdout}\n${typecheck.stderr}`).toBe(0)
+    const output = `${typecheck.stdout}\n${typecheck.stderr}`
+
+    expect(output).not.toContain(`is not assignable to type 'BetterAuthPlugin'`)
+    expect(output).not.toContain(`'role' does not exist in type`)
+    expect(output).not.toContain(`'internalCode' does not exist in type`)
+  }, 60_000)
+})
diff --git a/test/module.test.ts b/test/module.test.ts
index 28d5a50..52ed6f8 100644
--- a/test/module.test.ts
+++ b/test/module.test.ts
@@ -4,7 +4,7 @@ import { describe, expect, it } from 'vitest'
 
 describe('nuxt-better-auth module', async () => {
   await setup({
-    rootDir: fileURLToPath(new URL('./fixtures/basic', import.meta.url)),
+    rootDir: fileURLToPath(new URL('./cases/core-auth', import.meta.url)),
   })
 
   describe('page rendering', () => {
diff --git a/test/no-db.test.ts b/test/no-db.test.ts
index 59176b2..b65774d 100644
--- a/test/no-db.test.ts
+++ b/test/no-db.test.ts
@@ -4,7 +4,7 @@ import { describe, expect, it } from 'vitest'
 
 describe('no-db mode (NuxtHub without database)', async () => {
   await setup({
-    rootDir: fileURLToPath(new URL('./fixtures/no-db', import.meta.url)),
+    rootDir: fileURLToPath(new URL('./cases/database-less', import.meta.url)),
   })
 
   it('renders home page without database', async () => {
diff --git a/test/no-hub.test.ts b/test/no-hub.test.ts
index 21c57e9..c670cd9 100644
--- a/test/no-hub.test.ts
+++ b/test/no-hub.test.ts
@@ -4,7 +4,7 @@ import { describe, expect, it } from 'vitest'
 
 describe('no-hub mode (without NuxtHub)', async () => {
   await setup({
-    rootDir: fileURLToPath(new URL('./fixtures/no-hub', import.meta.url)),
+    rootDir: fileURLToPath(new URL('./cases/without-nuxthub', import.meta.url)),
   })
 
   it('renders home page without NuxtHub', async () => {
diff --git a/test/schema-generator.test.ts b/test/schema-generator.test.ts
index eba7521..bc6e456 100644
--- a/test/schema-generator.test.ts
+++ b/test/schema-generator.test.ts
@@ -140,6 +140,13 @@ describe('loadUserAuthConfig', () => {
     const result = await loadUserAuthConfig(configPath, false)
     expect(result).toEqual({ appName: 'Test', plugins: [] })
   })
+
+  it('accepts readonly plugin tuples in object syntax defineServerAuth', async () => {
+    const configPath = join(TEST_DIR, 'readonly-object-config.ts')
+    writeFileSync(configPath, `const plugin = { id: 'test-plugin', schema: { user: { fields: {} } } } as const\nexport default defineServerAuth({ appName: 'Readonly', plugins: [plugin] as const })`)
+    const result = await loadUserAuthConfig(configPath, false)
+    expect(result).toEqual({ appName: 'Readonly', plugins: [{ id: 'test-plugin', schema: { user: { fields: {} } } }] })
+  })
 })
 
 describe('defineServerAuth', () => {