diff --git a/lib/domain-discovery.sh b/lib/domain-discovery.sh
index 9b47b7f..43a2ebf 100644
--- a/lib/domain-discovery.sh
+++ b/lib/domain-discovery.sh
@@ -8,8 +8,9 @@
 # Source dependencies
 if [ -z "$TOOLKIT_BASE_DIR" ]; then
     SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-    source "$SCRIPT_DIR/common-functions.sh"
-    source "$SCRIPT_DIR/system-detect.sh"
+
+    [ -f "$SCRIPT_DIR/common-functions.sh" ] && source "$SCRIPT_DIR/common-functions.sh" || { echo "ERROR: common-functions.sh not found" >&2; return 1; }
+    [ -f "$SCRIPT_DIR/system-detect.sh" ] && source "$SCRIPT_DIR/system-detect.sh" || { echo "ERROR: system-detect.sh not found" >&2; return 1; }
 fi
 
 # Source control panel helpers if available
diff --git a/lib/mysql-analyzer.sh b/lib/mysql-analyzer.sh
index 87733c5..60fb4e6 100755
--- a/lib/mysql-analyzer.sh
+++ b/lib/mysql-analyzer.sh
@@ -8,9 +8,10 @@
 # Source dependencies
 if [ -z "$TOOLKIT_BASE_DIR" ]; then
     SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-    source "$SCRIPT_DIR/common-functions.sh"
-    source "$SCRIPT_DIR/system-detect.sh"
-    source "$SCRIPT_DIR/user-manager.sh"
+
+    [ -f "$SCRIPT_DIR/common-functions.sh" ] && source "$SCRIPT_DIR/common-functions.sh" || { echo "ERROR: common-functions.sh not found" >&2; return 1; }
+    [ -f "$SCRIPT_DIR/system-detect.sh" ] && source "$SCRIPT_DIR/system-detect.sh" || { echo "ERROR: system-detect.sh not found" >&2; return 1; }
+    [ -f "$SCRIPT_DIR/user-manager.sh" ] && source "$SCRIPT_DIR/user-manager.sh" || { echo "ERROR: user-manager.sh not found" >&2; return 1; }
 fi
 
 #############################################################################
diff --git a/lib/plesk-helpers.sh b/lib/plesk-helpers.sh
index 3c70c45..e0f84b2 100644
--- a/lib/plesk-helpers.sh
+++ b/lib/plesk-helpers.sh
@@ -8,7 +8,7 @@
 # Source common functions if not already loaded
 if [ -z "$TOOLKIT_BASE_DIR" ]; then
     SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-    source "$SCRIPT_DIR/common-functions.sh"
+    [ -f "$SCRIPT_DIR/common-functions.sh" ] && source "$SCRIPT_DIR/common-functions.sh" || { echo "ERROR: common-functions.sh not found" >&2; return 1; }
 fi
 
 #############################################################################
diff --git a/lib/reference-db.sh b/lib/reference-db.sh
index 38a252f..4c576f6 100755
--- a/lib/reference-db.sh
+++ b/lib/reference-db.sh
@@ -9,9 +9,10 @@
 # Source dependencies
 if [ -z "$TOOLKIT_BASE_DIR" ]; then
     SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-    source "$SCRIPT_DIR/common-functions.sh"
-    source "$SCRIPT_DIR/system-detect.sh"
-    source "$SCRIPT_DIR/user-manager.sh"
+
+    [ -f "$SCRIPT_DIR/common-functions.sh" ] && source "$SCRIPT_DIR/common-functions.sh" || { echo "ERROR: common-functions.sh not found" >&2; return 1; }
+    [ -f "$SCRIPT_DIR/system-detect.sh" ] && source "$SCRIPT_DIR/system-detect.sh" || { echo "ERROR: system-detect.sh not found" >&2; return 1; }
+    [ -f "$SCRIPT_DIR/user-manager.sh" ] && source "$SCRIPT_DIR/user-manager.sh" || { echo "ERROR: user-manager.sh not found" >&2; return 1; }
 fi
 
 # Reference database location
diff --git a/lib/system-detect.sh b/lib/system-detect.sh
index 88d6b19..745b606 100755
--- a/lib/system-detect.sh
+++ b/lib/system-detect.sh
@@ -9,7 +9,7 @@
 # Source common functions if not already loaded
 if [ -z "$TOOLKIT_BASE_DIR" ]; then
     SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-    source "$SCRIPT_DIR/common-functions.sh"
+    [ -f "$SCRIPT_DIR/common-functions.sh" ] && source "$SCRIPT_DIR/common-functions.sh" || { echo "ERROR: common-functions.sh not found" >&2; return 1; }
 fi
 
 # Global variables (session-only) - only initialize if not already set
diff --git a/lib/user-manager.sh b/lib/user-manager.sh
index 96b7de6..22d73e4 100755
--- a/lib/user-manager.sh
+++ b/lib/user-manager.sh
@@ -8,8 +8,9 @@
 # Source dependencies
 if [ -z "$TOOLKIT_BASE_DIR" ]; then
     _LIB_SRCDIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
-    source "$_LIB_SRCDIR/common-functions.sh"
-    source "$_LIB_SRCDIR/system-detect.sh"
+
+    [ -f "$_LIB_SRCDIR/common-functions.sh" ] && source "$_LIB_SRCDIR/common-functions.sh" || { echo "ERROR: common-functions.sh not found" >&2; return 1; }
+    [ -f "$_LIB_SRCDIR/system-detect.sh" ] && source "$_LIB_SRCDIR/system-detect.sh" || { echo "ERROR: system-detect.sh not found" >&2; return 1; }
 fi
 
 # Initialize temp session directory if not set
diff --git a/modules/website/website-error-analyzer.sh b/modules/website/website-error-analyzer.sh
index ba08956..382bfe8 100755
--- a/modules/website/website-error-analyzer.sh
+++ b/modules/website/website-error-analyzer.sh
@@ -9,10 +9,11 @@
 ################################################################################
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
-source "$SCRIPT_DIR/lib/common-functions.sh"
-source "$SCRIPT_DIR/lib/system-detect.sh"
-source "$SCRIPT_DIR/lib/user-manager.sh"
-source "$SCRIPT_DIR/lib/ip-reputation.sh"
+
+[ -f "$SCRIPT_DIR/lib/common-functions.sh" ] && source "$SCRIPT_DIR/lib/common-functions.sh" || { echo "ERROR: common-functions.sh not found" >&2; exit 1; }
+[ -f "$SCRIPT_DIR/lib/system-detect.sh" ] && source "$SCRIPT_DIR/lib/system-detect.sh" || { echo "ERROR: system-detect.sh not found" >&2; exit 1; }
+[ -f "$SCRIPT_DIR/lib/user-manager.sh" ] && source "$SCRIPT_DIR/lib/user-manager.sh" || { echo "ERROR: user-manager.sh not found" >&2; exit 1; }
+[ -f "$SCRIPT_DIR/lib/ip-reputation.sh" ] && source "$SCRIPT_DIR/lib/ip-reputation.sh" || { echo "ERROR: ip-reputation.sh not found" >&2; exit 1; }
 
 # Configuration - Use system-detected paths
 APACHE_ERROR_LOG="/var/log/apache2/error_log"  # Will be auto-detected
diff --git a/modules/website/wordpress/wordpress-cron-manager.sh b/modules/website/wordpress/wordpress-cron-manager.sh
index 2b476ab..55186f3 100755
--- a/modules/website/wordpress/wordpress-cron-manager.sh
+++ b/modules/website/wordpress/wordpress-cron-manager.sh
@@ -12,8 +12,9 @@
 ################################################################################
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/../../.." && pwd)"
-source "$SCRIPT_DIR/lib/common-functions.sh"
-source "$SCRIPT_DIR/lib/system-detect.sh"
+
+[ -f "$SCRIPT_DIR/lib/common-functions.sh" ] && source "$SCRIPT_DIR/lib/common-functions.sh" || { echo "ERROR: common-functions.sh not found" >&2; exit 1; }
+[ -f "$SCRIPT_DIR/lib/system-detect.sh" ] && source "$SCRIPT_DIR/lib/system-detect.sh" || { echo "ERROR: system-detect.sh not found" >&2; exit 1; }
 
 if [ "$EUID" -ne 0 ]; then
     print_error "This script must be run as root"