diff --git a/lib/clean/project.sh b/lib/clean/project.sh
index cea5504..9e5b013 100644
--- a/lib/clean/project.sh
+++ b/lib/clean/project.sh
@@ -220,6 +220,36 @@ is_safe_project_artifact() {
     fi
     return 0
 }
+
+is_rails_project_root() {
+    local dir="$1"
+    [[ -f "$dir/config/application.rb" ]] || return 1
+    [[ -f "$dir/Gemfile" ]] || return 1
+    [[ -f "$dir/bin/rails" || -f "$dir/config/environment.rb" ]]
+}
+
+is_rails_vendor_dir() {
+    local path="$1"
+    local base
+    base=$(basename "$path")
+    [[ "$base" == "vendor" ]] || return 1
+    is_rails_project_root "$(dirname "$path")"
+}
+
+is_protected_purge_artifact() {
+    local path="$1"
+    local base
+    base=$(basename "$path")
+    case "$base" in
+        vendor)
+            if is_rails_vendor_dir "$path"; then
+                return 0
+            fi
+            ;;
+    esac
+    return 1
+}
+
 # Scan purge targets using fd (fast) or pruned find.
 scan_purge_targets() {
     local search_path="$1"
@@ -259,7 +289,7 @@ scan_purge_targets() {
             if is_safe_project_artifact "$item" "$search_path"; then
                 echo "$item"
             fi
-        done | filter_nested_artifacts > "$output_file"
+        done | filter_nested_artifacts | filter_protected_artifacts > "$output_file"
     else
         # Pruned find avoids descending into heavy directories.
         local prune_args=()
@@ -287,7 +317,7 @@ scan_purge_targets() {
             if is_safe_project_artifact "$item" "$search_path"; then
                 echo "$item"
             fi
-        done | filter_nested_artifacts > "$output_file"
+        done | filter_nested_artifacts | filter_protected_artifacts > "$output_file"
     fi
 }
 # Filter out nested artifacts (e.g. node_modules inside node_modules).
@@ -306,6 +336,14 @@ filter_nested_artifacts() {
         fi
     done
 }
+
+filter_protected_artifacts() {
+    while IFS= read -r item; do
+        if ! is_protected_purge_artifact "$item"; then
+            echo "$item"
+        fi
+    done
+}
 # Args: $1 - path
 # Check if a path was modified recently (safety check).
 is_recently_modified() {
diff --git a/tests/purge.bats b/tests/purge.bats
index 805188b..b092148 100644
--- a/tests/purge.bats
+++ b/tests/purge.bats
@@ -101,6 +101,54 @@ setup() {
     [[ "$result" == "2" ]]
 }
 
+@test "scan_purge_targets: skips Rails vendor directory" {
+    mkdir -p "$HOME/www/rails-app/vendor/javascript"
+    mkdir -p "$HOME/www/rails-app/config"
+    touch "$HOME/www/rails-app/config/application.rb"
+    touch "$HOME/www/rails-app/Gemfile"
+    mkdir -p "$HOME/www/rails-app/bin"
+    touch "$HOME/www/rails-app/bin/rails"
+
+    local scan_output
+    scan_output="$(mktemp)"
+
+    result=$(bash -c "
+        source '$PROJECT_ROOT/lib/clean/project.sh'
+        scan_purge_targets '$HOME/www' '$scan_output'
+        if grep -q '$HOME/www/rails-app/vendor' '$scan_output'; then
+            echo 'FOUND'
+        else
+            echo 'SKIPPED'
+        fi
+    ")
+
+    rm -f "$scan_output"
+
+    [[ "$result" == "SKIPPED" ]]
+}
+
+@test "scan_purge_targets: keeps non-Rails vendor directory" {
+    mkdir -p "$HOME/www/php-app/vendor"
+    touch "$HOME/www/php-app/composer.json"
+
+    local scan_output
+    scan_output="$(mktemp)"
+
+    result=$(bash -c "
+        source '$PROJECT_ROOT/lib/clean/project.sh'
+        scan_purge_targets '$HOME/www' '$scan_output'
+        if grep -q '$HOME/www/php-app/vendor' '$scan_output'; then
+            echo 'FOUND'
+        else
+            echo 'MISSING'
+        fi
+    ")
+
+    rm -f "$scan_output"
+
+    [[ "$result" == "FOUND" ]]
+}
+
 @test "is_recently_modified: detects recent projects" {
     mkdir -p "$HOME/www/project/node_modules"
     touch "$HOME/www/project/package.json"