From 26447d5a99302cf018103ea02da699762d19fe2b Mon Sep 17 00:00:00 2001
From: Zack Jackson <25274700+ScriptedAlchemy@users.noreply.github.com>
Date: Sun, 28 Jun 2026 23:48:02 +0000
Subject: [PATCH] perf: enable lazy compilation by default

---
 .changeset/default-lazy-compilation.md |  5 +++++
 src/index.ts                           | 11 +++++++----
 src/types.ts                           |  3 ++-
 tests/index.test.ts                    | 10 +++++++++-
 4 files changed, 23 insertions(+), 6 deletions(-)
 create mode 100644 .changeset/default-lazy-compilation.md

diff --git a/.changeset/default-lazy-compilation.md b/.changeset/default-lazy-compilation.md
new file mode 100644
index 00000000..08b07216
--- /dev/null
+++ b/.changeset/default-lazy-compilation.md
@@ -0,0 +1,5 @@
+---
+"rsbuild-plugin-react-router": patch
+---
+
+Enable guarded Rsbuild lazy compilation by default during development. Pass `lazyCompilation: false` to keep the previous eager compilation behavior.
diff --git a/src/index.ts b/src/index.ts
index 105a405e..f157388b 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -143,6 +143,7 @@ export const pluginReactRouter = (
   async setup(api) {
     const defaultOptions = {
       customServer: false,
+      lazyCompilation: true,
       serverOutput: 'module' as const,
     };
 
@@ -767,10 +768,12 @@ export const pluginReactRouter = (
         serverBundleEntries,
       });
 
-      const configuredLazyCompilation =
-        pluginOptions.lazyCompilation === undefined
-          ? config.dev?.lazyCompilation
-          : pluginOptions.lazyCompilation;
+      const configuredLazyCompilation = Object.prototype.hasOwnProperty.call(
+        options,
+        'lazyCompilation'
+      )
+        ? pluginOptions.lazyCompilation
+        : (config.dev?.lazyCompilation ?? pluginOptions.lazyCompilation);
       const guardedLazyCompilation = guardReactRouterLazyCompilation({
         lazyCompilation: configuredLazyCompilation,
         entryClientPath: finalEntryClientPath,
diff --git a/src/types.ts b/src/types.ts
index 5d2fe1c6..727ad33f 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -32,7 +32,8 @@ export type PluginOptions = {
 
   /**
    * Rsbuild dev-only lazy compilation behavior.
-   * @default false
+   * Pass `false` to disable.
+   * @default true
    */
   lazyCompilation?: NonNullable<RsbuildConfig['dev']>['lazyCompilation'];
 
diff --git a/tests/index.test.ts b/tests/index.test.ts
index c8cfe4b9..4e3ed92d 100644
--- a/tests/index.test.ts
+++ b/tests/index.test.ts
@@ -31,7 +31,15 @@ describe('pluginReactRouter', () => {
     expect(config.dev.hmr).toBe(true);
     expect(config.dev.liveReload).toBe(true);
     expect(config.dev.writeToDisk).toBe(true);
-    expect(config.dev.lazyCompilation).toBeUndefined();
+    expect(config.dev.lazyCompilation).toMatchObject({
+      entries: true,
+      imports: true,
+    });
+    expect(
+      config.dev.lazyCompilation.test({
+        resource: `${process.cwd()}/app/entry.client.tsx`,
+      })
+    ).toBe(false);
   });
 
   it('adds the committed custom-server build entry only in development', async () => {