diff --git a/.github/workflows/shellcheck.yml b/.github/workflows/shellcheck.yml
new file mode 100644
index 0000000..7fb8ad3
--- /dev/null
+++ b/.github/workflows/shellcheck.yml
@@ -0,0 +1,18 @@
+name: ShellCheck
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  shellcheck:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ludeeus/action-shellcheck@2.0.0
+        with:
+          additional_files: git-co git-branch-clean git-branch-close
diff --git a/git-co b/git-co
index 441c68a..439d9de 100755
--- a/git-co
+++ b/git-co
@@ -51,7 +51,8 @@ _find_branches_by_levenshtein() {
   local results=""
   while IFS= read -r branch; do
     if [ -n "$branch" ]; then
-      local distance=$(_levenshtein_distance "$input" "$branch")
+      local distance
+      distance=$(_levenshtein_distance "$input" "$branch")
       if [ -n "$distance" ] && [ "$distance" -le "$max_distance" ]; then
         # Format: distance|branch (for sorting)
         results="$results"$'\n'"$distance|$branch"
@@ -68,7 +69,8 @@ _find_similar_branches() {
   local input_lower="${input,,}"
 
   # Get all branches (local and remote)
-  local all_branches=$(
+  local all_branches
+  all_branches=$(
     { git for-each-ref --format='%(refname:short)' refs/heads/ 2>/dev/null;
       git for-each-ref --format='%(refname:short)' refs/remotes/origin/ 2>/dev/null | sed 's|^origin/||';
     } | grep -v '^HEAD$' | sort -u
@@ -97,7 +99,8 @@ _find_similar_branches() {
   fi
 
   # Count results
-  local result_count=$(echo "$results" | grep -c '^' 2>/dev/null || echo "0")
+  local result_count
+  result_count=$(echo "$results" | grep -c '^' 2>/dev/null || echo "0")
 
   # If we got fewer than 3 results, try Levenshtein distance as fallback
   if [ "$result_count" -lt 3 ] && command -v python3 &> /dev/null; then
@@ -107,7 +110,8 @@ _find_similar_branches() {
     [ "$max_distance" -lt 3 ] && max_distance=3
     [ "$max_distance" -gt 8 ] && max_distance=8
 
-    local levenshtein_results=$(_find_branches_by_levenshtein "$input" "$all_branches" "$max_distance")
+    local levenshtein_results
+    levenshtein_results=$(_find_branches_by_levenshtein "$input" "$all_branches" "$max_distance")
 
     # Merge results (prioritize fzf/substring matches, then add Levenshtein matches)
     if [ -n "$results" ]; then
@@ -151,7 +155,8 @@ co() {
       similar_branches=$(_find_similar_branches "$1")
 
       if [ -n "$similar_branches" ]; then
-        local branch_count=$(echo "$similar_branches" | grep -c '^')
+        local branch_count
+        branch_count=$(echo "$similar_branches" | grep -c '^')
 
         if [ "$branch_count" -eq 1 ]; then
           local branch_name="$similar_branches"
@@ -166,10 +171,11 @@ co() {
           echo "Branch '$1' not found. Did you mean one of these?"
           echo "$similar_branches" | nl
           echo ""
-          read -p "Select branch number (or press Enter to cancel): " selection
+          read -r -p "Select branch number (or press Enter to cancel): " selection
 
           if [ -n "$selection" ] && [ "$selection" -gt 0 ]; then
-            local branch_name=$(echo "$similar_branches" | sed -n "${selection}p")
+            local branch_name
+            branch_name=$(echo "$similar_branches" | sed -n "${selection}p")
             if [ -n "$branch_name" ]; then
               echo "Switching to '$branch_name'..."
               if git rev-parse --verify "$branch_name" >/dev/null 2>&1; then