fix(powershell): ensure UTF-8 templates are written without BOM

scripts/powershell/create-new-feature.ps1

@@ -350,7 +350,10 @@ if (-not $DryRun) {
     if (-not (Test-Path -PathType Leaf $specFile)) {
         $template = Resolve-Template -TemplateName 'spec-template' -RepoRoot $repoRoot
         if ($template -and (Test-Path $template)) {
-            Copy-Item $template $specFile -Force
+            # Read the template content and write it to the spec file with UTF-8 encoding without BOM
+            $content = [System.IO.File]::ReadAllText($template)
+            $utf8NoBom = New-Object System.Text.UTF8Encoding($false)
+            [System.IO.File]::WriteAllText($specFile, $content, $utf8NoBom)
         } else {
             New-Item -ItemType File -Path $specFile -Force | Out-Null
         }

scripts/powershell/setup-plan.ps1

@@ -34,8 +34,10 @@ New-Item -ItemType Directory -Path $paths.FEATURE_DIR -Force | Out-Null
 # Copy plan template if it exists, otherwise note it or create empty file
 $template = Resolve-Template -TemplateName 'plan-template' -RepoRoot $paths.REPO_ROOT
 if ($template -and (Test-Path $template)) { 
-    Copy-Item $template $paths.IMPL_PLAN -Force
-    Write-Output "Copied plan template to $($paths.IMPL_PLAN)"
+    # Read the template content and write it to the implementation plan file with UTF-8 encoding without BOM
+    $content = [System.IO.File]::ReadAllText($template)
+    $utf8NoBom = New-Object System.Text.UTF8Encoding($false)
+    [System.IO.File]::WriteAllText($paths.IMPL_PLAN, $content, $utf8NoBom)
 } else {
     Write-Warning "Plan template not found"
     # Create a basic plan file if template doesn't exist

tests/test_timestamp_branches.py

@@ -649,7 +649,25 @@ def test_powershell_surfaces_checkout_errors(self):
         contents = CREATE_FEATURE_PS.read_text(encoding="utf-8")
         assert "$switchBranchError = git checkout -q $branchName 2>&1 | Out-String" in contents
         assert "exists but could not be checked out.`n$($switchBranchError.Trim())" in contents
+
+    @pytest.mark.skipif(not _has_pwsh(), reason="pwsh not installed")
+    def test_ps_spec_file_written_without_bom(self, ps_git_repo: Path):
+        """spec.md generated by create-new-feature.ps1 must not contain a UTF-8 BOM."""
+        result = run_ps_script(
+            ps_git_repo, "-ShortName", "bom-check", "BOM check feature"
+        )
+        assert result.returncode == 0, result.stderr
+
+        # Find the generated spec.md
+        spec_file = next((ps_git_repo / "specs").rglob("spec.md"), None)
+        assert spec_file is not None, "spec.md was not created"
 
+        # Read the first 3 raw bytes and assert no BOM present
+        with open(spec_file, "rb") as f:
+            raw_bytes = f.read(3)
+        assert raw_bytes != b"\xef\xbb\xbf", (
+            f"spec.md contains a UTF-8 BOM — found {raw_bytes!r} at start of file"
+        )
 
 class TestGitExtensionParity:
     def test_bash_extension_surfaces_checkout_errors(self):