diff --git a/phpunit/src/Build/AtomicFileTest.php b/phpunit/src/Build/AtomicFileTest.php
new file mode 100644
index 00000000..dcadf708
--- /dev/null
+++ b/phpunit/src/Build/AtomicFileTest.php
@@ -0,0 +1,67 @@
+<?php
+/**
+ * This file is part of TypePHP(AOT).
+ *
+ * @link     https://www.swoole.com/aot/
+ * @contact  service@swoole.com
+ */
+
+namespace TypePhp\Tests\Build;
+
+use PHPUnit\Framework\TestCase;
+use TypePhp\Build\AtomicFile;
+
+/**
+ * @internal
+ * @coversNothing
+ */
+final class AtomicFileTest extends TestCase
+{
+    private string $directory;
+
+    protected function setUp(): void
+    {
+        $this->directory = sys_get_temp_dir() . '/typephp-atomic-file-' . bin2hex(random_bytes(6));
+    }
+
+    protected function tearDown(): void
+    {
+        if (!is_dir($this->directory)) {
+            return;
+        }
+        $iterator = new \RecursiveIteratorIterator(
+            new \RecursiveDirectoryIterator($this->directory, \FilesystemIterator::SKIP_DOTS),
+            \RecursiveIteratorIterator::CHILD_FIRST,
+        );
+        foreach ($iterator as $entry) {
+            $entry->isDir() ? rmdir($entry->getPathname()) : unlink($entry->getPathname());
+        }
+        rmdir($this->directory);
+    }
+
+    public function testWriteCreatesDirectoriesAndReplacesExistingContents(): void
+    {
+        $path = $this->directory . '/nested/state.json';
+
+        AtomicFile::write($path, 'first', '.state-');
+        AtomicFile::write($path, 'second', '.state-');
+
+        self::assertSame('second', file_get_contents($path));
+        self::assertSame([$path], glob($this->directory . '/nested/*'));
+    }
+
+    public function testMissingReplacementDoesNotRemoveExistingTarget(): void
+    {
+        $target = $this->directory . '/state.json';
+        AtomicFile::write($target, 'stable');
+
+        try {
+            AtomicFile::replace($this->directory . '/missing.tmp', $target);
+            self::fail('Missing replacement must be rejected');
+        } catch (\RuntimeException $error) {
+            self::assertStringContainsString('does not exist', $error->getMessage());
+        }
+
+        self::assertSame('stable', file_get_contents($target));
+    }
+}
diff --git a/src/Build/AstCache.php b/src/Build/AstCache.php
index 637d9b0d..81fe3f8d 100644
--- a/src/Build/AstCache.php
+++ b/src/Build/AstCache.php
@@ -100,13 +100,6 @@ final class AstCache
     private function store(string $cacheFile, string $source, string $sourceHash, array $ast): void
     {
         try {
-            if (!is_dir($this->cacheDirectory)
-                && !mkdir($this->cacheDirectory, 0777, true)
-                && !is_dir($this->cacheDirectory)
-            ) {
-                return;
-            }
-
             $contents = serialize([
                 'schema' => self::SCHEMA_VERSION,
                 'phpVersion' => $this->phpVersion,
@@ -115,26 +108,7 @@ final class AstCache
                 'sourceHash' => $sourceHash,
                 'ast' => $ast,
             ]);
-            $temporary = tempnam($this->cacheDirectory, '.ast-');
-            if ($temporary === false) {
-                return;
-            }
-            try {
-                if (file_put_contents($temporary, $contents, LOCK_EX) === false) {
-                    return;
-                }
-                if (!@rename($temporary, $cacheFile)) {
-                    // Windows cannot atomically replace an existing file. A
-                    // concurrent reader may safely treat the short gap as a
-                    // cache miss and rebuild the disposable snapshot.
-                    @unlink($cacheFile);
-                    @rename($temporary, $cacheFile);
-                }
-            } finally {
-                if (is_file($temporary)) {
-                    @unlink($temporary);
-                }
-            }
+            AtomicFile::write($cacheFile, $contents, '.ast-');
         } catch (\Throwable) {
             // AST caching is an optimization. Serialization or filesystem
             // failures must never prevent an otherwise valid compilation.
diff --git a/src/Build/AtomicFile.php b/src/Build/AtomicFile.php
new file mode 100644
index 00000000..61ede1de
--- /dev/null
+++ b/src/Build/AtomicFile.php
@@ -0,0 +1,64 @@
+<?php
+/**
+ * This file is part of TypePHP(AOT).
+ *
+ * @link     https://www.swoole.com/aot/
+ * @contact  service@swoole.com
+ */
+
+namespace TypePhp\Build;
+
+final class AtomicFile
+{
+    public static function write(string $path, string $contents, string $temporaryPrefix = '.tmp-'): void
+    {
+        $directory = dirname($path);
+        self::ensureDirectory($directory);
+        $temporary = tempnam($directory, $temporaryPrefix);
+        if ($temporary === false) {
+            throw new \RuntimeException("Cannot create temporary file for: {$path}");
+        }
+
+        try {
+            if (file_put_contents($temporary, $contents, LOCK_EX) === false) {
+                throw new \RuntimeException("Cannot write temporary file for: {$path}");
+            }
+            self::replace($temporary, $path);
+        } finally {
+            if (is_file($temporary)) {
+                @unlink($temporary);
+            }
+        }
+    }
+
+    /** Replace a target with a temporary file created in the same directory. */
+    public static function replace(string $temporary, string $target): void
+    {
+        if (!is_file($temporary)) {
+            throw new \RuntimeException("Replacement file does not exist: {$temporary}");
+        }
+        if (@rename($temporary, $target)) {
+            return;
+        }
+
+        // Windows cannot rename over an existing file. A concurrent reader may
+        // safely treat this short gap as a cache miss and rebuild the snapshot.
+        if (PHP_OS_FAMILY === 'Windows' && is_file($target)) {
+            if (!@unlink($target)) {
+                throw new \RuntimeException("Cannot remove file before replacement: {$target}");
+            }
+            if (@rename($temporary, $target)) {
+                return;
+            }
+        }
+
+        throw new \RuntimeException("Cannot replace file: {$target}");
+    }
+
+    private static function ensureDirectory(string $directory): void
+    {
+        if (!is_dir($directory) && !mkdir($directory, 0777, true) && !is_dir($directory)) {
+            throw new \RuntimeException("Cannot create directory: {$directory}");
+        }
+    }
+}
diff --git a/src/Build/EmbeddedArchiveBuilder.php b/src/Build/EmbeddedArchiveBuilder.php
index 5204ca0a..6617a7d9 100644
--- a/src/Build/EmbeddedArchiveBuilder.php
+++ b/src/Build/EmbeddedArchiveBuilder.php
@@ -60,13 +60,12 @@ final class EmbeddedArchiveBuilder
                 throw new \RuntimeException("Cannot remove unchanged embedded archive: {$temporaryPath}");
             }
         } else {
-            if (is_file($archivePath) && !unlink($archivePath)) {
-                @unlink($temporaryPath);
-                throw new \RuntimeException("Cannot replace embedded file archive: {$archivePath}");
-            }
-            if (!rename($temporaryPath, $archivePath)) {
-                @unlink($temporaryPath);
-                throw new \RuntimeException("Cannot install embedded file archive: {$archivePath}");
+            try {
+                AtomicFile::replace($temporaryPath, $archivePath);
+            } finally {
+                if (is_file($temporaryPath)) {
+                    @unlink($temporaryPath);
+                }
             }
         }
 
diff --git a/src/Build/IncrementalBuildState.php b/src/Build/IncrementalBuildState.php
index 0f77b55f..60125eb5 100644
--- a/src/Build/IncrementalBuildState.php
+++ b/src/Build/IncrementalBuildState.php
@@ -115,29 +115,7 @@ final class IncrementalBuildState
             'generatorFingerprint' => $generatorFingerprint,
             'files' => $files,
         ], JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_THROW_ON_ERROR) . PHP_EOL;
-        $directory = dirname($this->file);
-        if (!is_dir($directory) && !mkdir($directory, 0777, true) && !is_dir($directory)) {
-            throw new \RuntimeException('Cannot create incremental build state directory: ' . $directory);
-        }
-        $temporary = tempnam($directory, '.graph-');
-        if ($temporary === false) {
-            throw new \RuntimeException('Cannot create incremental build state temporary file');
-        }
-        try {
-            if (file_put_contents($temporary, $contents, LOCK_EX) === false) {
-                throw new \RuntimeException('Cannot write incremental build state: ' . $this->file);
-            }
-            if (!@rename($temporary, $this->file)) {
-                @unlink($this->file);
-                if (!@rename($temporary, $this->file)) {
-                    throw new \RuntimeException('Cannot write incremental build state: ' . $this->file);
-                }
-            }
-        } finally {
-            if (is_file($temporary)) {
-                @unlink($temporary);
-            }
-        }
+        AtomicFile::write($this->file, $contents, '.graph-');
         $this->generatorFingerprint = $generatorFingerprint;
         $this->files = $files;
     }
diff --git a/src/Build/PrecompiledHeaderManager.php b/src/Build/PrecompiledHeaderManager.php
index d415ac51..a1344f69 100644
--- a/src/Build/PrecompiledHeaderManager.php
+++ b/src/Build/PrecompiledHeaderManager.php
@@ -183,15 +183,14 @@ final readonly class PrecompiledHeaderManager
         }
 
         if ($digests !== $saved && is_dir($cacheDirectory)) {
-            $temporary = tempnam($cacheDirectory, '.pch-digests-');
-            if ($temporary !== false) {
-                try {
-                    if (file_put_contents($temporary, json_encode($digests, JSON_THROW_ON_ERROR)) !== false) {
-                        @rename($temporary, $digestFile);
-                    }
-                } finally {
-                    @unlink($temporary);
-                }
+            try {
+                AtomicFile::write(
+                    $digestFile,
+                    json_encode($digests, JSON_THROW_ON_ERROR),
+                    '.pch-digests-',
+                );
+            } catch (\Throwable) {
+                // Digest reuse is optional; hashing every dependency remains correct.
             }
         }
 
diff --git a/src/Build/PreparedProjectCacheTrait.php b/src/Build/PreparedProjectCacheTrait.php
index 0f31de65..ade0d097 100644
--- a/src/Build/PreparedProjectCacheTrait.php
+++ b/src/Build/PreparedProjectCacheTrait.php
@@ -98,7 +98,6 @@ trait PreparedProjectCacheTrait
         if ($this->externalImportStubFiles !== []) {
             return;
         }
-        $temporary = '';
         $bodies = [];
         try {
             // Conversion always loads a fresh pristine AST. The prepared tree
@@ -133,24 +132,13 @@ trait PreparedProjectCacheTrait
                 $state[$field] = $this->{$field};
             }
             $file = $this->preparedProjectCacheFile();
-            if (!is_dir(dirname($file)) && !mkdir(dirname($file), 0777, true) && !is_dir(dirname($file))) {
-                return;
-            }
-            $candidate = tempnam(dirname($file), '.prepared-');
-            if (is_string($candidate)) {
-                $temporary = $candidate;
-                $this->writeFile($temporary, $key . "\n" . serialize($state));
-                @rename($temporary, $file);
-            }
+            AtomicFile::write($file, $key . "\n" . serialize($state), '.prepared-');
         } catch (\Throwable) {
             // Optional cache failures must not fail a valid compilation.
         } finally {
             foreach ($bodies as [$node, $statements]) {
                 $node->stmts = $statements;
             }
-            if (is_string($temporary) && is_file($temporary)) {
-                @unlink($temporary);
-            }
         }
     }
 }
diff --git a/src/Build/StableIdRegistry.php b/src/Build/StableIdRegistry.php
index d5f7ff2a..25893d9c 100644
--- a/src/Build/StableIdRegistry.php
+++ b/src/Build/StableIdRegistry.php
@@ -65,34 +65,12 @@ final class StableIdRegistry
         if (!$this->dirty || $this->file === '') {
             return;
         }
-        $directory = dirname($this->file);
-        if (!is_dir($directory) && !mkdir($directory, 0777, true) && !is_dir($directory)) {
-            throw new \RuntimeException('Cannot create stable ID cache directory: ' . $directory);
-        }
         $contents = json_encode([
             'schema' => self::SCHEMA_VERSION,
             'domains' => $this->domains,
             'nextIds' => $this->nextIds,
         ], JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_THROW_ON_ERROR) . PHP_EOL;
-        $temporary = tempnam($directory, '.ids-');
-        if ($temporary === false) {
-            throw new \RuntimeException('Cannot create stable ID cache temporary file');
-        }
-        try {
-            if (file_put_contents($temporary, $contents, LOCK_EX) === false) {
-                throw new \RuntimeException('Cannot write stable ID cache: ' . $this->file);
-            }
-            if (!@rename($temporary, $this->file)) {
-                @unlink($this->file);
-                if (!@rename($temporary, $this->file)) {
-                    throw new \RuntimeException('Cannot replace stable ID cache: ' . $this->file);
-                }
-            }
-        } finally {
-            if (is_file($temporary)) {
-                @unlink($temporary);
-            }
-        }
+        AtomicFile::write($this->file, $contents, '.ids-');
         $this->dirty = false;
     }