diff --git a/src/Internal/CacheManager.php b/src/Internal/CacheManager.php
index 21735b34..8d48d750 100644
--- a/src/Internal/CacheManager.php
+++ b/src/Internal/CacheManager.php
@@ -27,7 +27,7 @@ public static function reset(): void
     }
 
     /**
-     * Returns the absolute path to the cache directory, isolating by system user if using temp dir.
+     * Returns the absolute path to the cache directory, isolating by system user and parallel test worker if using temp dir.
      */
     public static function getCacheDir(): string
     {
@@ -55,7 +55,20 @@ public static function getCacheDir(): string
             $user = (string) getmyuid();
         }
 
-        $userHash = hash('xxh128', 'typephp_' . $user);
+        $testToken = getenv('TEST_TOKEN');
+        $uniqueToken = getenv('UNIQUE_TEST_TOKEN');
+        $pestWorkerId = getenv('PEST_PARALLEL_WORKER_ID');
+
+        $workerToken = '0';
+        if (\is_string($testToken) && $testToken !== '') {
+            $workerToken = $testToken;
+        } elseif (\is_string($uniqueToken) && $uniqueToken !== '') {
+            $workerToken = $uniqueToken;
+        } elseif (\is_string($pestWorkerId) && $pestWorkerId !== '') {
+            $workerToken = $pestWorkerId;
+        }
+
+        $userHash = hash('xxh128', 'typephp_' . $user . '_w' . $workerToken);
 
         return self::$resolvedCacheDir = sys_get_temp_dir() . '/typephp-cache-' . $userHash;
     }
@@ -135,26 +148,59 @@ public static function writeCachedFileSafely(string $cachedFile, string $transfo
     }
 
     /**
-     * Clears all cached transformed files from the cache directory.
+     * Clears all cached transformed files from the cache directory,
+     * including all parallel worker directories (_w1, _w2, etc.).
      */
     public static function clear(): int
     {
-        $cacheDir = self::getCacheDir();
+        $config = Config::get();
+        $customDir = $config['cache_dir'] ?? null;
 
-        if (! is_dir($cacheDir) || is_link($cacheDir)) {
-            return 0;
-        }
+        $dirsToClear = [];
 
-        $files = glob($cacheDir . '/*.php');
-        if ($files === false || \count($files) === 0) {
-            return 0;
+        if (\is_string($customDir) && $customDir !== '') {
+            if (is_dir($customDir) && ! is_link($customDir)) {
+                $dirsToClear[] = $customDir;
+            }
+        } else {
+            $tempBase = sys_get_temp_dir();
+            $matchedDirs = glob($tempBase . '/typephp-cache-*');
+
+            if ($matchedDirs !== false) {
+                foreach ($matchedDirs as $d) {
+                    if (is_dir($d) && ! is_link($d)) {
+                        if (\function_exists('posix_geteuid')) {
+                            $owner = @fileowner($d);
+                            if ($owner !== false && $owner !== posix_geteuid()) {
+                                continue;
+                            }
+                        }
+                        $dirsToClear[] = $d;
+                    }
+                }
+            }
         }
 
         $count = 0;
-        foreach ($files as $file) {
-            if (is_file($file) && ! is_link($file)) {
-                @unlink($file);
-                $count++;
+        foreach ($dirsToClear as $dir) {
+            $files = glob($dir . '/*.php');
+            if ($files !== false) {
+                foreach ($files as $file) {
+                    if (is_file($file) && ! is_link($file)) {
+                        @unlink($file);
+                        $count++;
+                    }
+                }
+            }
+
+            // Also clean up any lingering temporary swap files
+            $tmpFiles = glob($dir . '/.tmp_*');
+            if ($tmpFiles !== false) {
+                foreach ($tmpFiles as $tFile) {
+                    if (is_file($tFile) && ! is_link($tFile)) {
+                        @unlink($tFile);
+                    }
+                }
             }
         }
 
diff --git a/src/bootstrap.php b/src/bootstrap.php
index 10f6491a..93e0060d 100644
--- a/src/bootstrap.php
+++ b/src/bootstrap.php
@@ -11,6 +11,7 @@
     $isDisabledConst = \defined('TYPEPHP_DISABLE') && TYPEPHP_DISABLE;
 
     $isTooling = false;
+    $binary = '';
 
     if (isset($_SERVER['argv']) && \is_array($_SERVER['argv']) && \count($_SERVER['argv']) > 0) {
         $candidate = $_SERVER['argv'][0];
@@ -36,13 +37,32 @@
                 'composer' => true,
                 'deptrac' => true,
                 'phan' => true,
+                'paratest' => true,
             ];
 
             $isTooling = isset($toolingBinaries[$binary]);
         }
     }
 
-    if (! $isDisabledEnv && ! $isDisabledConst && ! $isTooling) {
+    $isParallelParent = false;
+    if (isset($_SERVER['argv']) && \is_array($_SERVER['argv'])) {
+        $hasParallelArg = false;
+        foreach ($_SERVER['argv'] as $arg) {
+            if (\is_string($arg) && (str_starts_with($arg, '--parallel') || $arg === '-p' || str_starts_with($arg, '--processes'))) {
+                $hasParallelArg = true;
+
+                break;
+            }
+        }
+
+        $isParallelParent = ($binary === 'paratest') || ($binary === 'pest' && $hasParallelArg);
+
+        if (getenv('TEST_TOKEN') !== false || getenv('PARATEST') !== false || getenv('PEST_PARALLEL_WORKER_ID') !== false) {
+            $isParallelParent = false;
+        }
+    }
+
+    if (! $isDisabledEnv && ! $isDisabledConst && ! $isTooling && ! $isParallelParent) {
         TypePHP::boot();
     }
 }
diff --git a/tests/TypeChecking/ArraysAndShapes/KeyOfValueOfTest.php b/tests/TypeChecking/ArraysAndShapes/KeyOfValueOfTest.php
index e784c436..c14a2dcd 100644
--- a/tests/TypeChecking/ArraysAndShapes/KeyOfValueOfTest.php
+++ b/tests/TypeChecking/ArraysAndShapes/KeyOfValueOfTest.php
@@ -167,7 +167,8 @@ function testKeylessTupleKeyOf(int $index): int
             expect($conn->localAction(['action' => 'start']))->toBeTrue();
 
             expect(fn () => $conn->localAction(['action' => 'pause']))
-                ->toThrow(TypeError::class, "['action'] must be a key of TypePHP\Tests\Fixtures\Types\DoctrineLikeConnection::LOCAL_ACTIONS");
+                ->toThrow(TypeError::class, "['action'] must be a key of TypePHP\Tests\Fixtures\Types\DoctrineLikeConnection::LOCAL_ACTIONS")
+            ;
         });
     });
 });
diff --git a/tests/TypeChecking/Boundaries/MultiBranchConditionalReturnsTest.php b/tests/TypeChecking/Boundaries/MultiBranchConditionalReturnsTest.php
index 80a3b659..9d5fb481 100644
--- a/tests/TypeChecking/Boundaries/MultiBranchConditionalReturnsTest.php
+++ b/tests/TypeChecking/Boundaries/MultiBranchConditionalReturnsTest.php
@@ -136,7 +136,8 @@ public function formatValue(bool $asInt, mixed $value): mixed
             expect($service->formatByNegation(true, 100))->toBe(100);
 
             expect(fn () => $service->formatByNegation(true, -50))
-                ->toThrow(TypeError::class, 'Return value must be of type positive-int');
+                ->toThrow(TypeError::class, 'Return value must be of type positive-int')
+            ;
         });
     });
 });
diff --git a/tests/TypeChecking/Scalars/ClassStringInterfaceTest.php b/tests/TypeChecking/Scalars/ClassStringInterfaceTest.php
index ccb9097e..8e63d393 100644
--- a/tests/TypeChecking/Scalars/ClassStringInterfaceTest.php
+++ b/tests/TypeChecking/Scalars/ClassStringInterfaceTest.php
@@ -100,6 +100,7 @@ public function count(): int
         expect(testTemplateWithIntersectionBoundClassString(ArrayObject::class))->toBe(ArrayObject::class);
 
         expect(fn () => testTemplateWithIntersectionBoundClassString(stdClass::class))
-            ->toThrow(TypeError::class, 'must be a class-string of');
+            ->toThrow(TypeError::class, 'must be a class-string of')
+        ;
     });
 });