diff --git a/sast-engine/tools/generate_stdlib_registry.py b/sast-engine/tools/generate_stdlib_registry.py
index f50d25b0..08fe2758 100755
--- a/sast-engine/tools/generate_stdlib_registry.py
+++ b/sast-engine/tools/generate_stdlib_registry.py
@@ -6,6 +6,8 @@
 JSON registries containing functions, classes, constants, and attributes
 with type information for static analysis.
 
+Minimum Python version: 3.9
+
 Usage:
     # Generate ALL stdlib modules for Python 3.14
     python3.14 generate_stdlib_registry.py --all --output-dir ./registries/python3.14/stdlib/v1/
@@ -23,7 +25,9 @@
 import inspect
 import json
 import os
+import pkgutil
 import sys
+import sysconfig
 from datetime import datetime, timezone
 from pathlib import Path
 from typing import Any, Dict, List, Optional
@@ -357,12 +361,58 @@ def generate_manifest(output_dir: Path, python_version: tuple, modules: List[str
 
 
 def get_all_stdlib_modules() -> List[str]:
-    """Get list of all public stdlib modules."""
-    if not hasattr(sys, "stdlib_module_names"):
-        raise RuntimeError("sys.stdlib_module_names not available (Python 3.10+ required)")
+    """Get list of all public stdlib modules.
+
+    For Python 3.10+, uses sys.stdlib_module_names (PEP 585).
+    For Python 3.9, uses pkgutil and sysconfig to discover modules from:
+    - Built-in modules (C-level)
+    - Standard library path (pure Python modules)
+    - lib-dynload / DLLs (compiled extension modules)
+    - Platform-specific stdlib path
+    """
+    # Python 3.10+ has sys.stdlib_module_names
+    if hasattr(sys, "stdlib_module_names"):
+        # Filter out private modules
+        return sorted([m for m in sys.stdlib_module_names if not m.startswith("_")])
+
+    # Fallback for Python 3.9: Use pkgutil to discover stdlib modules
+    stdlib_modules = set()
+
+    # Add built-in modules
+    stdlib_modules.update(sys.builtin_module_names)
+
+    # Get stdlib path
+    stdlib_path = sysconfig.get_path('stdlib')
+    if stdlib_path:
+        # Discover modules in stdlib path
+        try:
+            for importer, modname, ispkg in pkgutil.iter_modules([stdlib_path]):
+                stdlib_modules.add(modname)
+        except Exception as e:
+            print(f"Warning: Error discovering modules from {stdlib_path}: {e}", file=sys.stderr)
+
+        # Also check lib-dynload subdirectory for compiled extension modules (Unix/Linux)
+        # and DLLs directory (Windows)
+        for dynload_dir_name in ['lib-dynload', 'DLLs']:
+            dynload_path = os.path.join(stdlib_path, dynload_dir_name)
+            if os.path.exists(dynload_path):
+                try:
+                    for importer, modname, ispkg in pkgutil.iter_modules([dynload_path]):
+                        stdlib_modules.add(modname)
+                except Exception as e:
+                    print(f"Warning: Error discovering modules from {dynload_path}: {e}", file=sys.stderr)
+
+    # Get platstdlib path (platform-specific stdlib modules)
+    platstdlib_path = sysconfig.get_path('platstdlib')
+    if platstdlib_path and platstdlib_path != stdlib_path:
+        try:
+            for importer, modname, ispkg in pkgutil.iter_modules([platstdlib_path]):
+                stdlib_modules.add(modname)
+        except Exception as e:
+            print(f"Warning: Error discovering modules from {platstdlib_path}: {e}", file=sys.stderr)
 
-    # Filter out private modules
-    return sorted([m for m in sys.stdlib_module_names if not m.startswith("_")])
+    # Filter out private modules and return sorted list
+    return sorted([m for m in stdlib_modules if not m.startswith("_")])
 
 
 def main():
@@ -400,9 +450,17 @@ def main():
 
     args = parser.parse_args()
 
+    # Check Python version
+    if sys.version_info < (3, 9):
+        print(f"Error: Python 3.9 or higher is required. Current version: {sys.version_info.major}.{sys.version_info.minor}.{sys.version_info.micro}", file=sys.stderr)
+        return 1
+
     # Determine which modules to generate
     if args.all:
         modules = get_all_stdlib_modules()
+        detection_method = "sys.stdlib_module_names" if hasattr(sys, "stdlib_module_names") else "pkgutil fallback"
+        if args.verbose:
+            print(f"Using {detection_method} to discover stdlib modules")
         print(f"Generating registries for ALL {len(modules)} stdlib modules...")
     elif args.modules:
         modules = [m.strip() for m in args.modules.split(",")]
@@ -474,8 +532,11 @@ def main():
 
     # Platform-specific modules that are expected to fail on certain platforms
     WINDOWS_ONLY_MODULES = {'msvcrt', 'nt', 'winreg', 'winsound', '_winapi', 'msilib'}
-    UNIX_SPECIFIC_MODULES = {'nis'}  # Network Information Service (may not be available on all systems)
-    PLATFORM_SPECIFIC_MODULES = WINDOWS_ONLY_MODULES | UNIX_SPECIFIC_MODULES
+    UNIX_SPECIFIC_MODULES = {'nis', 'grp', 'pwd', 'resource', 'syslog', 'termios', 'tty'}
+    MACOS_SPECIFIC_MODULES = {'_scproxy'}
+    # Modules that may not be available in all builds
+    OPTIONAL_MODULES = {'readline', 'dbm', 'gdbm', 'ossaudiodev', 'spwd'}
+    PLATFORM_SPECIFIC_MODULES = WINDOWS_ONLY_MODULES | UNIX_SPECIFIC_MODULES | MACOS_SPECIFIC_MODULES | OPTIONAL_MODULES
 
     # Check if any non-platform-specific modules failed
     unexpected_failures = [m for m in failed if m not in PLATFORM_SPECIFIC_MODULES]