fix(scripts): reject whitespace-only plans

scripts/bash/check-prerequisites.sh

@@ -148,7 +148,14 @@ if [[ ! -f "$IMPL_PLAN" ]]; then
     exit 1
 fi
 
-if [[ ! -s "$IMPL_PLAN" ]]; then
+# Read the file because opening it alone can succeed before a read error.
+if ! cat -- "$IMPL_PLAN" >/dev/null 2>&1; then
+    echo "ERROR: plan.md is not readable in $FEATURE_DIR" >&2
+    echo "Check its file permissions and rerun the prerequisite check." >&2
+    exit 1
+fi
+
+if ! file_has_non_whitespace_content "$IMPL_PLAN"; then
     echo "ERROR: plan.md is empty in $FEATURE_DIR" >&2
     echo "Populate it, or remove the empty file and rerun $(format_speckit_command plan "$REPO_ROOT") with a valid plan template." >&2
     exit 1

scripts/bash/common.sh

@@ -1,6 +1,13 @@
 #!/usr/bin/env bash
 # Common functions and variables for all scripts
 
+# Match Unicode White_Space, as PowerShell does, even under LC_ALL=C.
+# Remove only a file-leading UTF-8 BOM for the check; never rewrite the file.
+file_has_non_whitespace_content() {
+    LC_ALL=C sed $'1s/^\357\273\277//' "$1" |
+        LC_ALL=C grep -aEv $'^([[:space:]]|\302[\205\240]|\341\232\200|\342\200[\200-\212\250\251\257]|\342\201\237|\343\200\200)*$' >/dev/null
+}
+
 # Find repository root by searching upward for .specify directory
 # This is the primary marker for spec-kit projects
 find_specify_root() {

scripts/bash/setup-plan.sh

@@ -46,7 +46,7 @@ else
     template_file=$(mktemp)
     trap 'rm -f "$template_file"' EXIT
     if resolve_template_content "plan-template" "$REPO_ROOT" > "$template_file"; then
-        if [[ ! -s "$template_file" ]]; then
+        if ! file_has_non_whitespace_content "$template_file"; then
             echo "ERROR: Plan template is empty; no new plan.md was created." >&2
             echo "Restore a valid plan template and rerun plan setup." >&2
             exit 1

scripts/powershell/check-prerequisites.ps1

@@ -108,7 +108,15 @@ if (-not (Test-Path -LiteralPath $paths.IMPL_PLAN -PathType Leaf)) {
     exit 1
 }
 
-if ((Get-Item -LiteralPath $paths.IMPL_PLAN).Length -eq 0) {
+try {
+    $planContent = [System.IO.File]::ReadAllText($paths.IMPL_PLAN)
+} catch {
+    [Console]::Error.WriteLine("ERROR: plan.md is not readable in $($paths.FEATURE_DIR)")
+    [Console]::Error.WriteLine("Check its file permissions and rerun the prerequisite check.")
+    exit 1
+}
+
+if ([string]::IsNullOrWhiteSpace($planContent)) {
     [Console]::Error.WriteLine("ERROR: plan.md is empty in $($paths.FEATURE_DIR)")
     $planCommand = Format-SpecKitCommand -CommandName 'plan' -RepoRoot $paths.REPO_ROOT
     [Console]::Error.WriteLine(

scripts/powershell/setup-plan.ps1

@@ -48,7 +48,7 @@ if (Test-Path -LiteralPath $paths.IMPL_PLAN -PathType Leaf) {
 } else {
     $content = Resolve-TemplateContent -TemplateName 'plan-template' -RepoRoot $paths.REPO_ROOT
     if ($null -ne $content) {
-        if ($content.Length -eq 0) {
+        if ([string]::IsNullOrWhiteSpace($content)) {
             [Console]::Error.WriteLine(
                 "ERROR: Plan template is empty; no new plan.md was created."
             )

scripts/python/check_prerequisites.py

@@ -14,6 +14,7 @@
         TemplateResolutionError,
         format_speckit_command,
         get_feature_paths,
+        has_non_whitespace_content,
         resolve_template_content,
     )
 except ImportError:  # pragma: no cover - direct execution from unusual cwd
@@ -23,6 +24,7 @@
         TemplateResolutionError,
         format_speckit_command,
         get_feature_paths,
+        has_non_whitespace_content,
         resolve_template_content,
     )
 
@@ -236,7 +238,17 @@ def main(argv: list[str] | None = None) -> int:
         )
         return 1
 
-    if paths.impl_plan.stat().st_size == 0:
+    try:
+        plan_content = paths.impl_plan.read_text(encoding="utf-8", errors="replace")
+    except OSError:
+        print(f"ERROR: plan.md is not readable in {paths.feature_dir}", file=sys.stderr)
+        print(
+            "Check its file permissions and rerun the prerequisite check.",
+            file=sys.stderr,
+        )
+        return 1
+
+    if not has_non_whitespace_content(plan_content):
         print(f"ERROR: plan.md is empty in {paths.feature_dir}", file=sys.stderr)
         print(
             "Populate it, or remove the empty file and rerun "

scripts/python/common.py

@@ -11,6 +11,15 @@
 from pathlib import Path
 
 
+def has_non_whitespace_content(content: str) -> bool:
+    """Check Unicode White_Space like PowerShell, ignoring one leading BOM."""
+    whitespace = (
+        "\t\n\v\f\r \u0085\u00a0\u1680\u2000\u2001\u2002\u2003\u2004\u2005"
+        "\u2006\u2007\u2008\u2009\u200a\u2028\u2029\u202f\u205f\u3000"
+    )
+    return bool(content.removeprefix("\ufeff").strip(whitespace))
+
+
 def _trim_trailing_separators(value: Path) -> str:
     text = str(value)
     while len(text) > 1 and text.endswith((os.sep, "/")):

scripts/python/setup_plan.py

@@ -11,13 +11,15 @@
     from common import (
         TemplateResolutionError,
         get_feature_paths,
+        has_non_whitespace_content,
         resolve_template_content,
     )
 except ImportError:  # pragma: no cover - direct execution from unusual cwd
     sys.path.insert(0, str(Path(__file__).resolve().parent))
     from common import (
         TemplateResolutionError,
         get_feature_paths,
+        has_non_whitespace_content,
         resolve_template_content,
     )
 
@@ -70,7 +72,7 @@ def main(argv: list[str] | None = None) -> int:
             print(f"Error: {exc}", file=sys.stderr)
             return 1
         if template_content is not None:
-            if template_content == "":
+            if not has_non_whitespace_content(template_content):
                 print(
                     "ERROR: Plan template is empty; no new plan.md was created.",
                     file=sys.stderr,