diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 84074b4791..e85802a53d 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -54,3 +54,15 @@ jobs:
       # (notably SC2155). Tighten in a follow-up after cleanup.
       - name: Run shellcheck on shell scripts
         run: git ls-files -z -- '*.sh' | xargs -0 shellcheck --severity=error
+
+      # macOS ships bash 3.2, where ${var^^} / ${var,,} error with "bad
+      # substitution". shellcheck assumes bash 4+ from the shebang and cannot
+      # flag these, so guard explicitly; use tr for portable case conversion.
+      - name: Reject bash 4+ case-modification expansions
+        run: |
+          matches=$(git ls-files -z -- '*.sh' | xargs -0 grep -nE '\$\{[A-Za-z_][A-Za-z0-9_]*(\[[^]]*\])?(\^|,)' || true)
+          if [ -n "$matches" ]; then
+            echo "Found bash 4+ case-modification expansion(s); use tr for portability (macOS ships bash 3.2):"
+            echo "$matches"
+            exit 1
+          fi
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3c036a1884..9695b5f669 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 <!-- insert new changelog below this comment -->
 
+- fix(scripts): make branch-name acronym retention portable (uppercase via `tr` instead of bash-4-only `${word^^}`, whole-word match via `grep -w` instead of GNU/BSD-only `\b`), fixing acronym/short-word retention on macOS's default bash 3.2
+
 ## [0.11.9] - 2026-06-26
 
 ### Changed
diff --git a/extensions/git/scripts/bash/create-new-feature-branch.sh b/extensions/git/scripts/bash/create-new-feature-branch.sh
index d638b048c9..ba1c4a7220 100755
--- a/extensions/git/scripts/bash/create-new-feature-branch.sh
+++ b/extensions/git/scripts/bash/create-new-feature-branch.sh
@@ -288,7 +288,9 @@ generate_branch_name() {
         if ! echo "$word" | grep -qiE "$stop_words"; then
             if [ ${#word} -ge 3 ]; then
                 meaningful_words+=("$word")
-            elif echo "$description" | grep -qw -- "${word^^}"; then
+            # Uppercase via tr (portable) rather than bash's 4+ "^^" case
+            # expansion, which breaks on macOS's default bash 3.2 (bad substitution).
+            elif echo "$description" | grep -qw -- "$(printf '%s' "$word" | tr '[:lower:]' '[:upper:]')"; then
                 meaningful_words+=("$word")
             fi
         fi
diff --git a/extensions/git/scripts/powershell/create-new-feature-branch.ps1 b/extensions/git/scripts/powershell/create-new-feature-branch.ps1
index 6a4417f8b9..cd41232e3b 100644
--- a/extensions/git/scripts/powershell/create-new-feature-branch.ps1
+++ b/extensions/git/scripts/powershell/create-new-feature-branch.ps1
@@ -253,9 +253,10 @@ function Get-BranchName {
         if ($word.Length -ge 3) {
             $meaningfulWords += $word
         } elseif ($Description -cmatch "\b$($word.ToUpper())\b") {
-            # Case-sensitive (-cmatch) to mirror the bash twin's `grep -qw -- "${word^^}"`:
-            # keep a short word only when its UPPERCASE form appears in the original
-            # (an acronym). -match is case-insensitive and would keep every short word.
+            # Case-sensitive (-cmatch) to mirror the bash twin's case-sensitive
+            # whole-word acronym match: keep a short word only when its UPPERCASE
+            # form appears in the original (an acronym). -match is case-insensitive
+            # and would keep every short word.
             $meaningfulWords += $word
         }
     }
diff --git a/scripts/bash/create-new-feature.sh b/scripts/bash/create-new-feature.sh
index c9609764f7..8887f39399 100644
--- a/scripts/bash/create-new-feature.sh
+++ b/scripts/bash/create-new-feature.sh
@@ -152,8 +152,10 @@ generate_branch_name() {
         if ! echo "$word" | grep -qiE "$stop_words"; then
             if [ ${#word} -ge 3 ]; then
                 meaningful_words+=("$word")
-            elif echo "$description" | grep -q "\b${word^^}\b"; then
-                # Keep short words if they appear as uppercase in original (likely acronyms)
+            # Keep short words that appear as an uppercase acronym in the original.
+            # Uppercase via tr and match with grep -w (both portable) rather than
+            # bash's 4+ "^^" case expansion (breaks on macOS bash 3.2) and \b (non-POSIX).
+            elif echo "$description" | grep -qw -- "$(printf '%s' "$word" | tr '[:lower:]' '[:upper:]')"; then
                 meaningful_words+=("$word")
             fi
         fi