diff --git a/packages/next-swc/crates/next-build/src/next_app/app_entries.rs b/packages/next-swc/crates/next-build/src/next_app/app_entries.rs
index 8b8f75b289b36..973b30ea7d548 100644
--- a/packages/next-swc/crates/next-build/src/next_app/app_entries.rs
+++ b/packages/next-swc/crates/next-build/src/next_app/app_entries.rs
@@ -61,7 +61,7 @@ pub async fn get_app_entries(
     server_compile_time_info: Vc<CompileTimeInfo>,
     next_config: Vc<NextConfig>,
 ) -> Result<Vc<AppEntries>> {
-    let app_dir = find_app_dir_if_enabled(project_root, next_config);
+    let app_dir = find_app_dir_if_enabled(project_root);
 
     let Some(&app_dir) = app_dir.await?.as_ref() else {
         return Ok(AppEntries::cell(AppEntries {
diff --git a/packages/next-swc/crates/next-core/src/app_structure.rs b/packages/next-swc/crates/next-core/src/app_structure.rs
index 3967fc89d8d3a..c09ccdc644c98 100644
--- a/packages/next-swc/crates/next-core/src/app_structure.rs
+++ b/packages/next-swc/crates/next-core/src/app_structure.rs
@@ -243,13 +243,7 @@ pub async fn find_app_dir(project_path: Vc<FileSystemPath>) -> Result<Vc<OptionA
 /// Finds and returns the [DirectoryTree] of the app directory if enabled and
 /// existing.
 #[turbo_tasks::function]
-pub async fn find_app_dir_if_enabled(
-    project_path: Vc<FileSystemPath>,
-    next_config: Vc<NextConfig>,
-) -> Result<Vc<OptionAppDir>> {
-    if !*next_config.app_dir().await? {
-        return Ok(Vc::cell(None));
-    }
+pub async fn find_app_dir_if_enabled(project_path: Vc<FileSystemPath>) -> Result<Vc<OptionAppDir>> {
     Ok(find_app_dir(project_path))
 }
 
diff --git a/packages/next-swc/crates/next-core/src/next_config.rs b/packages/next-swc/crates/next-core/src/next_config.rs
index 4c61e995c3a16..443f07f6bf3f5 100644
--- a/packages/next-swc/crates/next-core/src/next_config.rs
+++ b/packages/next-swc/crates/next-core/src/next_config.rs
@@ -403,7 +403,6 @@ pub enum LoaderItem {
 #[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize, TraceRawVcs)]
 #[serde(rename_all = "camelCase")]
 pub struct ExperimentalConfig {
-    pub app_dir: Option<bool>,
     pub server_components_external_packages: Option<Vec<String>>,
     pub turbo: Option<ExperimentalTurboConfig>,
     pub allowed_revalidate_header_keys: Option<Vec<String>>,
@@ -527,18 +526,6 @@ impl NextConfig {
         ))
     }
 
-    #[turbo_tasks::function]
-    pub async fn app_dir(self: Vc<Self>) -> Result<Vc<bool>> {
-        Ok(Vc::cell(
-            self.await?
-                .experimental
-                .app_dir
-                .as_ref()
-                .cloned()
-                .unwrap_or_default(),
-        ))
-    }
-
     #[turbo_tasks::function]
     pub async fn env(self: Vc<Self>) -> Result<Vc<EnvMap>> {
         // The value expected for env is Record<String, String>, but config itself
diff --git a/packages/next-swc/crates/next-dev/src/lib.rs b/packages/next-swc/crates/next-dev/src/lib.rs
index 902ab2c13bc90..85810cde65812 100644
--- a/packages/next-swc/crates/next-dev/src/lib.rs
+++ b/packages/next-swc/crates/next-dev/src/lib.rs
@@ -388,7 +388,7 @@ async fn source(
         next_config,
         server_addr,
     );
-    let app_dir = find_app_dir_if_enabled(project_path, next_config);
+    let app_dir = find_app_dir_if_enabled(project_path);
     let app_source = create_app_source(
         app_dir,
         project_path,
diff --git a/packages/next/src/build/utils.ts b/packages/next/src/build/utils.ts
index 8ca734be0f830..35a3b907a53bc 100644
--- a/packages/next/src/build/utils.ts
+++ b/packages/next/src/build/utils.ts
@@ -1987,7 +1987,7 @@ startServer({
   port: currentPort,
   allowRetry: false,
   keepAliveTimeout,
-  useWorkers: !!nextConfig.experimental?.appDir,
+  useWorkers: true,
 }).catch((err) => {
   console.error(err);
   process.exit(1);
diff --git a/packages/next/src/cli/next-dev.ts b/packages/next/src/cli/next-dev.ts
index 765bdf051d1f7..969712a27492d 100644
--- a/packages/next/src/cli/next-dev.ts
+++ b/packages/next/src/cli/next-dev.ts
@@ -11,7 +11,7 @@ import { CliCommand } from '../lib/commands'
 import { getProjectDir } from '../lib/get-project-dir'
 import { CONFIG_FILES, PHASE_DEVELOPMENT_SERVER } from '../shared/lib/constants'
 import path from 'path'
-import { defaultConfig, NextConfigComplete } from '../server/config-shared'
+import { NextConfigComplete } from '../server/config-shared'
 import { traceGlobals } from '../trace/shared'
 import { Telemetry } from '../telemetry/storage'
 import loadConfig from '../server/config'
@@ -352,12 +352,7 @@ const nextDev: CliCommand = async (argv) => {
     })
 
     const distDir = path.join(dir, rawNextConfig.distDir || '.next')
-    const { pagesDir, appDir } = findPagesDir(
-      dir,
-      typeof rawNextConfig?.experimental?.appDir === 'undefined'
-        ? !!defaultConfig.experimental?.appDir
-        : !!rawNextConfig.experimental?.appDir
-    )
+    const { pagesDir, appDir } = findPagesDir(dir, true)
     const telemetry = new Telemetry({
       distDir,
     })
diff --git a/packages/next/src/server/config-schema.ts b/packages/next/src/server/config-schema.ts
index 50d91ae00d8a6..935b5814b8f98 100644
--- a/packages/next/src/server/config-schema.ts
+++ b/packages/next/src/server/config-schema.ts
@@ -298,9 +298,6 @@ const configSchema = {
             },
           ] as any,
         },
-        appDir: {
-          type: 'boolean',
-        },
         serverActions: {
           type: 'boolean',
         },
diff --git a/packages/next/src/server/config-shared.ts b/packages/next/src/server/config-shared.ts
index 4ef7751f618e3..6d8b4762e219d 100644
--- a/packages/next/src/server/config-shared.ts
+++ b/packages/next/src/server/config-shared.ts
@@ -183,11 +183,6 @@ export interface ExperimentalConfig {
   nextScriptWorkers?: boolean
   scrollRestoration?: boolean
   externalDir?: boolean
-  /**
-   * The App Router (app directory) enables support for layouts, Server Components, streaming, and colocated data fetching.
-   * @see https://nextjs.org/docs/app/api-reference/next-config-js/appDir
-   */
-  appDir?: boolean
   amp?: {
     optimizer?: any
     validator?: string
@@ -702,7 +697,7 @@ export const defaultConfig: NextConfig = {
     deploymentId: undefined,
     useDeploymentIdServerActions: false,
     appDocumentPreloading: undefined,
-    clientRouterFilter: false,
+    clientRouterFilter: true,
     clientRouterFilterRedirects: false,
     fetchCacheKeyPrefix: '',
     middlewarePrefetch: 'flexible',
@@ -727,7 +722,6 @@ export const defaultConfig: NextConfig = {
     gzipSize: true,
     craCompat: false,
     esmExternals: true,
-    appDir: true,
     // default to 50MB limit
     isrMemoryCacheSize: 50 * 1024 * 1024,
     incrementalCacheHandlerPath: undefined,
diff --git a/packages/next/src/server/config.ts b/packages/next/src/server/config.ts
index 49c8ecd87df2a..cfdf251330d82 100644
--- a/packages/next/src/server/config.ts
+++ b/packages/next/src/server/config.ts
@@ -425,13 +425,6 @@ function assignDefaults(
     silent
   )
 
-  if (
-    typeof userConfig.experimental?.clientRouterFilter === 'undefined' &&
-    result.experimental?.appDir
-  ) {
-    result.experimental.clientRouterFilter = true
-  }
-
   if (
     result.experimental?.outputFileTracingRoot &&
     !isAbsolute(result.experimental.outputFileTracingRoot)