diff --git a/cache.inc.php b/cache.inc.php
index 27869fe..6fce811 100644
--- a/cache.inc.php
+++ b/cache.inc.php
@@ -268,19 +268,30 @@ class ConfigCacheFileMap
     return array_keys($this->file2deps[$file]);
   }
 
-  function update(array $files)
+  function differs(array $files) : bool
+  {
+    $this_files = array_keys($this->file2deps);
+
+    return count($files) !== count($this_files) || 
+      count(array_intersect($files, $this_files)) != count($this_files);
+  }
+
+  function compare(array $files) : array
   {
     $this_files = array_keys($this->file2deps);
 
     $added = array_diff($files, $this_files);
     $removed = array_diff($this_files, $files);
 
+    return [$added, $removed];
+  }
+
+  function update(array $added, array $removed)
+  {
     foreach($added as $file)
       $this->file2deps[$file] = [];
     foreach($removed as $file)
       unset($this->file2deps[$file]);
-
-    return [$added, $removed];
   }
 
   function updateDepsForEntry(ConfigCacheEntry $entry)
diff --git a/config.inc.php b/config.inc.php
index d754d55..4789c16 100644
--- a/config.inc.php
+++ b/config.inc.php
@@ -15,7 +15,6 @@ class ConfigGlobals
   public ?string $worker_init_fn = null;
   public string $base_class = '\ConfBase';
   public string $build_dir;
-  public ?ConfigCacheFileMap $file_map;
 
   function __construct(array $base_dirs, string $build_dir, ?string $worker_init_fn = null)
   {
@@ -38,9 +37,9 @@ class ConfigGlobals
 
 enum ConfigUpdateMode : int
 {
-  case ChangedOnly      = 1;
+  case Full             = 1;
   case RelativeToBundle = 2;
-  case Full             = 3;
+  case ChangedOnly      = 3;
 }
 
 class ConfigManager
@@ -49,6 +48,7 @@ class ConfigManager
   private int $workers_num;
 
   private ConfigCache $cache;
+  private ?ConfigCacheFileMap $file_map;
 
   function __construct(ConfigGlobals $globals, int $workers_num)
   {
@@ -56,6 +56,7 @@ class ConfigManager
     $this->workers_num = $workers_num;
 
     $this->cache = new ConfigCache($globals);
+    $this->file_map = null;
   }
 
   function getGlobals() : ConfigGlobals
@@ -73,6 +74,18 @@ class ConfigManager
     return [$this->globals->base_dirs, ['.js']];
   }
 
+  function getFileMap() : ConfigCacheFileMap
+  {
+    if($this->file_map === null)
+    {
+      $map = $this->_tryLoadMap();
+      if($map === null)
+        $map = $this->_makeMap($this->scanFiles(extension: '.js'));
+      $this->file_map = $map;
+    }
+    return $this->file_map;
+  }
+
   function updateCache(
     ConfigUpdateMode $update_mode,
     ConfigDirFiles $input_files = null,
@@ -80,6 +93,8 @@ class ConfigManager
     bool $verbose = false
    ) : ConfigCacheUpdateResult
   {
+    config_log("Updating cache, mode {$update_mode->value}...");
+
     if($input_files === null && $update_mode === ConfigUpdateMode::ChangedOnly)
       throw new Exception("input_files argument is required for ChangedOnly mode");
 
@@ -124,32 +139,33 @@ class ConfigManager
     }
 
     if($affected_files->count() > 0 || $added_files || $removed_files)
+    {
+      $fs_cache_map->update($added_files, $removed_files);
       $this->_saveMap($fs_cache_map);
+    }
 
     return $update_result;
   }
 
   private function _checkFileMap(ConfigUpdateMode $update_mode, ConfigDirFiles $input_files, array &$added_files, array &$removed_files) : ConfigCacheFileMap
   {
-    //TODO: do we need to check if cache stale somehow? 
-    $fs_cache_map = $this->_tryLoadMap();
+    $fs_cache_map = $this->file_map;
     //NOTE: if there's no map so far we need to create one
     if($fs_cache_map === null)
     {
-      $fs_cache_map = new ConfigCacheFileMap();
-
       //let's re-use the input files
       if($update_mode === ConfigUpdateMode::Full || $update_mode === ConfigUpdateMode::RelativeToBundle)
         $tmp_files = $input_files;
       else
         $tmp_files = $this->scanFiles(extension: '.js');
 
-      $fs_cache_map->update($tmp_files->getAllFiles());
+      $fs_cache_map = $this->_makeMap($tmp_files);
+      $this->file_map = $fs_cache_map;
     }
 
     if($update_mode === ConfigUpdateMode::Full || $update_mode === ConfigUpdateMode::RelativeToBundle)
     {
-      list($added_files, $removed_files) = $fs_cache_map->update($input_files->getAllFiles());
+      list($added_files, $removed_files) = $fs_cache_map->compare($input_files->getAllFiles());
       config_log("File map added: ".count($added_files).", removed: ".count($removed_files));
     }
 
@@ -193,7 +209,7 @@ class ConfigManager
         {
           $affected_by_file = $fs_cache_map->getAffectedFiles($file);
           foreach($affected_by_file as $dep)
-            $affected_files->add(config_map_base_dir($this->globals->base_dirs, $dep), $dep, unique: true);
+            $affected_files->addFile($dep, unique: true);
         }
         else
         {
@@ -234,6 +250,15 @@ class ConfigManager
     return ConfigCacheFileMap::unserialize(ensure_read($this->_getMapPath()));
   }
 
+  private function _makeMap(ConfigDirFiles $files) : ConfigCacheFileMap
+  {
+    config_log("Creating file map");
+    $map = new ConfigCacheFileMap();
+    $map->update($files->getAllFiles(), []);
+    $this->_saveMap($map);
+    return $map;
+  }
+
   private function _saveMap(ConfigCacheFileMap $map)
   {
     ensure_write($this->_getMapPath(), ConfigCacheFileMap::serialize($map));
diff --git a/pack.inc.php b/pack.inc.php
index bb0278b..fb924a7 100644
--- a/pack.inc.php
+++ b/pack.inc.php
@@ -12,8 +12,8 @@ class ConfigPackParams
   public ?int $version = null;
   public bool $debug = false;
 
-  public const string EXTRA_FMT3_CHUNK_SIZE = "EXTRA_FMT3_CHUNK_SIZE";
-  public const string EXTRA_FMT3_COMPRESSION_LEVEL = "EXTRA_FMT3_COMPRESSION_LEVEL";
+  public const EXTRA_FMT3_CHUNK_SIZE = "EXTRA_FMT3_CHUNK_SIZE";
+  public const EXTRA_FMT3_COMPRESSION_LEVEL = "EXTRA_FMT3_COMPRESSION_LEVEL";
   public array $extras = array();
 
   function __construct(