Enable the filesystem cache for dev in canary builds

Author: lukesandberg

packages/next/src/server/config-shared.ts

@@ -409,6 +409,8 @@ export interface ExperimentalConfig {
 
   /**
    * Enable filesystem cache for the turbopack dev server.
+   *
+   * Defaults to `true` in canary releases.
    */
   turbopackFileSystemCacheForDev?: boolean
 
@@ -1525,6 +1527,8 @@ export const defaultConfig = Object.freeze({
     proxyClientMaxBodySize: 10_485_760, // 10MB
     hideLogsAfterAbort: false,
     mcpServer: true,
+    turbopackFileSystemCacheForDev: !isStableBuild(),
+    turbopackFileSystemCacheForBuild: false,
   },
   htmlLimitedBots: undefined,
   bundlePagesRouterDependencies: false,

packages/next/src/server/config.ts

@@ -400,7 +400,7 @@ function assignDefaultsAndValidate(
 
   if (isStableBuild()) {
     // Prevents usage of certain experimental features outside of canary
-    if (result.experimental?.turbopackFileSystemCacheForBuild) {
+    if (result.experimental.turbopackFileSystemCacheForBuild) {
       throw new CanaryOnlyConfigError({
         feature: 'experimental.turbopackFileSystemCacheForBuild',
       })