diff --git a/CHANGELOG.md b/CHANGELOG.md
index e8e33d6..c6dcdef 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - feat!: require Bun `^1.4.0`, npm `>=10.9.8`, pnpm `^11.23.0`, or Yarn `^4.18.0` and remove legacy manager support.
 - fix: run manager commands in the configured root directory without changing the PHP working directory, and prevent manager probes and npm dependency cleanup when manager execution is disabled.
 - feat!: add secure frontend audits with CVE reporting, CI formats, and strict npm, pnpm, Yarn, and Bun validation.
+- perf: write generated Composer asset manifests directly without first copying their source files.
 
 ## 0.2.0 January 24, 2026
 
diff --git a/src/Solver/Solver.php b/src/Solver/Solver.php
index 8850642..0330468 100644
--- a/src/Solver/Solver.php
+++ b/src/Solver/Solver.php
@@ -27,6 +27,7 @@
 use function is_dir;
 use function is_file;
 use function is_string;
+use function json_decode;
 use function realpath;
 use function rtrim;
 use function sprintf;
@@ -173,7 +174,7 @@ private function getAssets(Composer $composer, string $assetDir, array $packages
      * @param string $assetDir The asset directory.
      * @param string $filename The filename of asset package.
      *
-     * @throws Exception if the asset package cannot be copied or written.
+     * @throws Exception if the asset package cannot be read or written.
      *
      * @return array{0: string, 1: string} The package name and absolute generated manifest path.
      */
@@ -194,17 +195,23 @@ private function getMockPackagePath(PackageInterface $package, string $assetDir,
             );
         }
 
-        if (!$this->fs->copy($filename, $newFilename)) {
+        $sourceContent = file_get_contents($filename);
+
+        if (false === $sourceContent) {
             throw new RuntimeException(
-                sprintf('Unable to copy asset manifest "%s".', $filename),
+                sprintf('Unable to read asset manifest "%s".', $filename),
             );
         }
 
-        $jsonFile = new JsonFile($newFilename);
+        $packageValue = AssetUtil::formatPackage(
+            $package,
+            $packageName,
+            (array) json_decode($sourceContent, false, flags: JSON_THROW_ON_ERROR),
+        );
 
-        $packageValue = AssetUtil::formatPackage($package, $packageName, (array) $jsonFile->read());
+        $targetJsonFile = new JsonFile($newFilename);
 
-        $jsonFile->write($packageValue);
+        $targetJsonFile->write($packageValue);
 
         return [$packageName, $newFilename];
     }
diff --git a/tests/Solver/SolverTest.php b/tests/Solver/SolverTest.php
index a4318ff..c26b2f3 100644
--- a/tests/Solver/SolverTest.php
+++ b/tests/Solver/SolverTest.php
@@ -84,23 +84,74 @@ public function testCanonicalizePathStopsAtFilesystemRootWhenExistenceCheckFails
         );
     }
 
-    public function testGetMockPackagePathRejectsCopyFailure(): void
+    public function testGetMockPackagePathDoesNotCopySourceBeforeWritingFormattedManifest(): void
     {
-        $assetDir = $this->cwd . '/copy-failure-assets';
-        $source = $this->cwd . '/source-package.json';
-        $target = $assetDir . '/foo/bar/source-package.json';
+        $assetDir = "{$this->cwd}/direct-write-assets";
+        $source = "{$this->cwd}/source-package.json";
+
+        $target = "{$assetDir}/foo/bar/source-package.json";
+
+        $sourceContent = <<<JSON
+            {
+                "name": "source-package",
+                "version": "1.2.3",
+                "engines": {},
+                "bundleDependencies": [],
+                "scripts": {
+                    "build": "ignored"
+                },
+                "dependencies": {}
+            }
+            JSON;
+
         $package = $this->createMock(PackageInterface::class);
         $package->method('getName')->willReturn('foo/bar');
-        file_put_contents($source, '{}');
+
+        file_put_contents($source, $sourceContent);
 
         $fs = $this->getMockBuilder(Filesystem::class)->onlyMethods(['copy'])->getMock();
-        $fs->expects(self::once())->method('copy')->with($source, $target)->willReturn(false);
+        $fs->expects(self::never())->method('copy');
         $solver = new Solver($this->manager, $this->config, $fs, $this->composerFallback);
 
+        $result = $this->invokeSolverMethodOn($solver, 'getMockPackagePath', $package, $assetDir, $source);
+
+        self::assertSame(['@composer-asset/foo--bar', $target], $result);
+        self::assertSame($sourceContent, file_get_contents($source));
+        self::assertFileExists($target);
+        self::assertSame(
+            <<<'JSON'
+                {
+                    "name": "@composer-asset/foo--bar",
+                    "version": "1.2.3",
+                    "engines": {},
+                    "bundleDependencies": [],
+                    "dependencies": {}
+                }
+
+                JSON,
+            file_get_contents($target),
+        );
+    }
+
+    public function testGetMockPackagePathRejectsUnreadableSourceManifest(): void
+    {
+        $assetDir = "{$this->cwd}/unreadable-source-assets";
+        $source = "{$this->cwd}/source-package.json";
+
+        $package = $this->createMock(PackageInterface::class);
+        $package->method('getName')->willReturn('foo/bar');
+
+        MockerState::addCondition(
+            'Foxy\\Solver',
+            'file_get_contents',
+            [$source, false, null, 0, null],
+            false,
+        );
+
         $this->expectException(RuntimeException::class);
-        $this->expectExceptionMessage(sprintf('Unable to copy asset manifest "%s".', $source));
+        $this->expectExceptionMessage(sprintf('Unable to read asset manifest "%s".', $source));
 
-        $this->invokeSolverMethodOn($solver, 'getMockPackagePath', $package, $assetDir, $source);
+        $this->invokeSolverMethod('getMockPackagePath', $package, $assetDir, $source);
     }
 
     public function testGetMockPackagePathWrapsDirectoryCreationFailure(): void
diff --git a/tests/Support/InternalMockerExtension.php b/tests/Support/InternalMockerExtension.php
index d61775f..137023e 100644
--- a/tests/Support/InternalMockerExtension.php
+++ b/tests/Support/InternalMockerExtension.php
@@ -60,6 +60,10 @@ public static function load(): void
                 'namespace' => 'Foxy\\Solver',
                 'name' => 'file_exists',
             ],
+            [
+                'namespace' => 'Foxy\\Solver',
+                'name' => 'file_get_contents',
+            ],
             [
                 'namespace' => 'Foxy\\Solver',
                 'name' => 'file_put_contents',