fix: prepend YAML frontmatter to Cursor .mdc files

scripts/bash/update-agent-context.sh

@@ -351,10 +351,19 @@ create_new_agent_file() {
     # Convert \n sequences to actual newlines
     newline=$(printf '\n')
     sed -i.bak2 "s/\\\\n/${newline}/g" "$temp_file"
-    
+
     # Clean up backup files
     rm -f "$temp_file.bak" "$temp_file.bak2"
-
+
+    # Prepend Cursor frontmatter for .mdc files so rules are auto-included
+    if [[ "$target_file" == *.mdc ]]; then
+        local frontmatter_file
+        frontmatter_file=$(mktemp) || return 1
+        printf '%s\n' "---" "description: Project Development Guidelines" "globs: [\"**/*\"]" "alwaysApply: true" "---" "" > "$frontmatter_file"
+        cat "$temp_file" >> "$frontmatter_file"
+        mv "$frontmatter_file" "$temp_file"
+    fi
+
     return 0
 }
 
@@ -492,13 +501,24 @@ update_existing_agent_file() {
         changes_entries_added=true
     fi
 
+    # Ensure Cursor .mdc files have YAML frontmatter for auto-inclusion
+    if [[ "$target_file" == *.mdc ]]; then
+        if ! head -1 "$temp_file" | grep -q '^---$'; then
+            local frontmatter_file
+            frontmatter_file=$(mktemp) || { rm -f "$temp_file"; return 1; }
+            printf '%s\n' "---" "description: Project Development Guidelines" "globs: [\"**/*\"]" "alwaysApply: true" "---" "" > "$frontmatter_file"
+            cat "$temp_file" >> "$frontmatter_file"
+            mv "$frontmatter_file" "$temp_file"
+        fi
+    fi
+
     # Move temp file to target atomically
     if ! mv "$temp_file" "$target_file"; then
         log_error "Failed to update target file"
         rm -f "$temp_file"
         return 1
     fi
-    
+
     return 0
 }
 #==============================================================================

scripts/powershell/update-agent-context.ps1

@@ -258,6 +258,12 @@ function New-AgentFile {
     # Convert literal \n sequences introduced by Escape to real newlines
     $content = $content -replace '\\n',[Environment]::NewLine
 
+    # Prepend Cursor frontmatter for .mdc files so rules are auto-included
+    if ($TargetFile -match '\.mdc$') {
+        $frontmatter = @('---','description: Project Development Guidelines','globs: ["**/*"]','alwaysApply: true','---','') -join [Environment]::NewLine
+        $content = $frontmatter + [Environment]::NewLine + $content
+    }
+
     $parent = Split-Path -Parent $TargetFile
     if (-not (Test-Path $parent)) { New-Item -ItemType Directory -Path $parent | Out-Null }
     Set-Content -LiteralPath $TargetFile -Value $content -NoNewline -Encoding utf8
@@ -334,6 +340,12 @@ function Update-ExistingAgentFile {
         $newTechEntries | ForEach-Object { $output.Add($_) }
     }
 
+    # Ensure Cursor .mdc files have YAML frontmatter for auto-inclusion
+    if ($TargetFile -match '\.mdc$' -and $output.Count -gt 0 -and $output[0] -ne '---') {
+        $frontmatter = @('---','description: Project Development Guidelines','globs: ["**/*"]','alwaysApply: true','---','')
+        $output.InsertRange(0, $frontmatter)
+    }
+
     Set-Content -LiteralPath $TargetFile -Value ($output -join [Environment]::NewLine) -Encoding utf8
     return $true
 }

tests/test_cursor_frontmatter.py

@@ -0,0 +1,264 @@
+"""
+Tests for Cursor .mdc frontmatter generation (issue #669).
+
+Verifies that update-agent-context.sh properly prepends YAML frontmatter
+to .mdc files so that Cursor IDE auto-includes the rules.
+"""
+
+import os
+import shutil
+import subprocess
+import tempfile
+import textwrap
+
+import pytest
+
+SCRIPT_PATH = os.path.join(
+    os.path.dirname(__file__),
+    os.pardir,
+    "scripts",
+    "bash",
+    "update-agent-context.sh",
+)
+
+EXPECTED_FRONTMATTER_LINES = [
+    "---",
+    "description: Project Development Guidelines",
+    'globs: ["**/*"]',
+    "alwaysApply: true",
+    "---",
+]
+
+requires_git = pytest.mark.skipif(
+    shutil.which("git") is None,
+    reason="git is not installed",
+)
+
+
+class TestScriptFrontmatterPattern:
+    """Static analysis — no git required."""
+
+    def test_create_new_has_mdc_frontmatter_logic(self):
+        """create_new_agent_file() must contain .mdc frontmatter logic."""
+        with open(SCRIPT_PATH) as f:
+            content = f.read()
+        assert 'if [[ "$target_file" == *.mdc ]]' in content
+        assert "alwaysApply: true" in content
+
+    def test_update_existing_has_mdc_frontmatter_logic(self):
+        """update_existing_agent_file() must also handle .mdc frontmatter."""
+        with open(SCRIPT_PATH) as f:
+            content = f.read()
+        # There should be two occurrences of the .mdc check — one per function
+        occurrences = content.count('if [[ "$target_file" == *.mdc ]]')
+        assert occurrences >= 2, (
+            f"Expected at least 2 .mdc frontmatter checks, found {occurrences}"
+        )
+
+    def test_powershell_script_has_mdc_frontmatter_logic(self):
+        """PowerShell script must also handle .mdc frontmatter."""
+        ps_path = os.path.join(
+            os.path.dirname(__file__),
+            os.pardir,
+            "scripts",
+            "powershell",
+            "update-agent-context.ps1",
+        )
+        with open(ps_path) as f:
+            content = f.read()
+        assert "alwaysApply: true" in content
+        occurrences = content.count(r"\.mdc$")
+        assert occurrences >= 2, (
+            f"Expected at least 2 .mdc frontmatter checks in PS script, found {occurrences}"
+        )
+
+
+@requires_git
+class TestCursorFrontmatterIntegration:
+    """Integration tests using a real git repo."""
+
+    @pytest.fixture
+    def git_repo(self, tmp_path):
+        """Create a minimal git repo with the spec-kit structure."""
+        repo = tmp_path / "repo"
+        repo.mkdir()
+
+        # Init git repo
+        subprocess.run(
+            ["git", "init"], cwd=str(repo), capture_output=True, check=True
+        )
+        subprocess.run(
+            ["git", "config", "user.email", "test@test.com"],
+            cwd=str(repo),
+            capture_output=True,
+            check=True,
+        )
+        subprocess.run(
+            ["git", "config", "user.name", "Test"],
+            cwd=str(repo),
+            capture_output=True,
+            check=True,
+        )
+
+        # Create .specify dir with config
+        specify_dir = repo / ".specify"
+        specify_dir.mkdir()
+        (specify_dir / "config.yaml").write_text(
+            textwrap.dedent("""\
+                project_type: webapp
+                language: python
+                framework: fastapi
+                database: N/A
+            """)
+        )
+
+        # Create template
+        templates_dir = specify_dir / "templates"
+        templates_dir.mkdir()
+        (templates_dir / "agent-file-template.md").write_text(
+            "# [PROJECT NAME] Development Guidelines\n\n"
+            "Auto-generated from all feature plans. Last updated: [DATE]\n\n"
+            "## Active Technologies\n\n"
+            "[EXTRACTED FROM ALL PLAN.MD FILES]\n\n"
+            "## Project Structure\n\n"
+            "[ACTUAL STRUCTURE FROM PLANS]\n\n"
+            "## Development Commands\n\n"
+            "[ONLY COMMANDS FOR ACTIVE TECHNOLOGIES]\n\n"
+            "## Coding Conventions\n\n"
+            "[LANGUAGE-SPECIFIC, ONLY FOR LANGUAGES IN USE]\n\n"
+            "## Recent Changes\n\n"
+            "[LAST 3 FEATURES AND WHAT THEY ADDED]\n"
+        )
+
+        # Create initial commit
+        subprocess.run(
+            ["git", "add", "-A"], cwd=str(repo), capture_output=True, check=True
+        )
+        subprocess.run(
+            ["git", "commit", "-m", "init"],
+            cwd=str(repo),
+            capture_output=True,
+            check=True,
+        )
+
+        # Create a feature branch so CURRENT_BRANCH detection works
+        subprocess.run(
+            ["git", "checkout", "-b", "001-test-feature"],
+            cwd=str(repo),
+            capture_output=True,
+            check=True,
+        )
+
+        # Create a spec so the script detects the feature
+        spec_dir = repo / "specs" / "001-test-feature"
+        spec_dir.mkdir(parents=True)
+        (spec_dir / "plan.md").write_text(
+            "# Test Feature Plan\n\n"
+            "## Technology Stack\n\n"
+            "- Language: Python\n"
+            "- Framework: FastAPI\n"
+        )
+
+        return repo
+
+    def _run_update(self, repo, agent_type="cursor-agent"):
+        """Run update-agent-context.sh for a specific agent type."""
+        script = os.path.abspath(SCRIPT_PATH)
+        result = subprocess.run(
+            ["bash", script, agent_type],
+            cwd=str(repo),
+            capture_output=True,
+            text=True,
+            timeout=30,
+        )
+        return result
+
+    def test_new_mdc_file_has_frontmatter(self, git_repo):
+        """Creating a new .mdc file must include YAML frontmatter."""
+        result = self._run_update(git_repo)
+        assert result.returncode == 0, f"Script failed: {result.stderr}"
+
+        mdc_file = git_repo / ".cursor" / "rules" / "specify-rules.mdc"
+        assert mdc_file.exists(), "Cursor .mdc file was not created"
+
+        content = mdc_file.read_text()
+        lines = content.splitlines()
+
+        # First line must be the opening ---
+        assert lines[0] == "---", f"Expected frontmatter start, got: {lines[0]}"
+
+        # Check all frontmatter lines are present
+        for expected in EXPECTED_FRONTMATTER_LINES:
+            assert expected in content, f"Missing frontmatter line: {expected}"
+
+        # Content after frontmatter should be the template content
+        assert "Development Guidelines" in content
+
+    def test_existing_mdc_without_frontmatter_gets_it_added(self, git_repo):
+        """Updating an existing .mdc file that lacks frontmatter must add it."""
+        # First, create the file WITHOUT frontmatter (simulating pre-fix state)
+        cursor_dir = git_repo / ".cursor" / "rules"
+        cursor_dir.mkdir(parents=True, exist_ok=True)
+        mdc_file = cursor_dir / "specify-rules.mdc"
+        mdc_file.write_text(
+            "# repo Development Guidelines\n\n"
+            "Auto-generated from all feature plans. Last updated: 2025-01-01\n\n"
+            "## Active Technologies\n\n"
+            "- Python + FastAPI (main)\n\n"
+            "## Recent Changes\n\n"
+            "- main: Added Python + FastAPI\n"
+        )
+
+        result = self._run_update(git_repo)
+        assert result.returncode == 0, f"Script failed: {result.stderr}"
+
+        content = mdc_file.read_text()
+        lines = content.splitlines()
+
+        assert lines[0] == "---", f"Expected frontmatter start, got: {lines[0]}"
+        for expected in EXPECTED_FRONTMATTER_LINES:
+            assert expected in content, f"Missing frontmatter line: {expected}"
+
+    def test_existing_mdc_with_frontmatter_not_duplicated(self, git_repo):
+        """Updating an .mdc file that already has frontmatter must not duplicate it."""
+        cursor_dir = git_repo / ".cursor" / "rules"
+        cursor_dir.mkdir(parents=True, exist_ok=True)
+        mdc_file = cursor_dir / "specify-rules.mdc"
+
+        frontmatter = (
+            "---\n"
+            "description: Project Development Guidelines\n"
+            'globs: ["**/*"]\n'
+            "alwaysApply: true\n"
+            "---\n\n"
+        )
+        body = (
+            "# repo Development Guidelines\n\n"
+            "Auto-generated from all feature plans. Last updated: 2025-01-01\n\n"
+            "## Active Technologies\n\n"
+            "- Python + FastAPI (main)\n\n"
+            "## Recent Changes\n\n"
+            "- main: Added Python + FastAPI\n"
+        )
+        mdc_file.write_text(frontmatter + body)
+
+        result = self._run_update(git_repo)
+        assert result.returncode == 0, f"Script failed: {result.stderr}"
+
+        content = mdc_file.read_text()
+        # Count occurrences of the frontmatter delimiter
+        assert content.count("alwaysApply: true") == 1, (
+            "Frontmatter was duplicated"
+        )
+
+    def test_non_mdc_file_has_no_frontmatter(self, git_repo):
+        """Non-.mdc agent files (e.g., Claude) must NOT get frontmatter."""
+        result = self._run_update(git_repo, agent_type="claude")
+        assert result.returncode == 0, f"Script failed: {result.stderr}"
+
+        claude_file = git_repo / ".claude" / "CLAUDE.md"
+        if claude_file.exists():
+            content = claude_file.read_text()
+            assert not content.startswith("---"), (
+                "Non-mdc file should not have frontmatter"
+            )