diff --git a/product-team/roadmap-communicator/scripts/changelog_generator.py b/product-team/roadmap-communicator/scripts/changelog_generator.py
index 6e50535..aa60675 100755
--- a/product-team/roadmap-communicator/scripts/changelog_generator.py
+++ b/product-team/roadmap-communicator/scripts/changelog_generator.py
@@ -1,8 +1,10 @@
 #!/usr/bin/env python3
-"""Generate changelog sections from git log using conventional commit prefixes."""
+"""Generate changelog sections from git log or piped commit messages using conventional commit prefixes."""
 
 import argparse
+import shutil
 import subprocess
+import sys
 from collections import defaultdict
 
 
@@ -20,31 +22,71 @@ SECTIONS = {
     "revert": "Reverts",
 }
 
+DEMO_COMMITS = [
+    "feat: add user dashboard with analytics widgets",
+    "feat: implement dark mode toggle",
+    "fix: resolve crash on empty CSV import",
+    "fix: correct timezone offset in calendar view",
+    "docs: update API reference for v2 endpoints",
+    "refactor: extract shared validation into utils module",
+    "chore: bump dependencies to latest patch versions",
+    "perf: optimize database queries for user listing",
+]
+
 
 def parse_args() -> argparse.Namespace:
-    parser = argparse.ArgumentParser(description="Generate changelog from git commits.")
-    parser.add_argument("--from", dest="from_ref", default="HEAD~50")
-    parser.add_argument("--to", dest="to_ref", default="HEAD")
-    parser.add_argument("--format", choices=["markdown", "text"], default="markdown")
+    parser = argparse.ArgumentParser(
+        description="Generate changelog from git commits or piped input.",
+        epilog="Examples:\n"
+               "  %(prog)s --from v1.0.0 --to HEAD\n"
+               "  git log --pretty=format:%%s v1.0..HEAD | %(prog)s --stdin\n"
+               "  %(prog)s --demo\n",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+    )
+    parser.add_argument("--from", dest="from_ref", default="HEAD~50",
+                        help="Start ref for git log (default: HEAD~50)")
+    parser.add_argument("--to", dest="to_ref", default="HEAD",
+                        help="End ref for git log (default: HEAD)")
+    parser.add_argument("--format", choices=["markdown", "text"], default="markdown",
+                        help="Output format (default: markdown)")
+    parser.add_argument("--stdin", action="store_true",
+                        help="Read commit subjects from stdin instead of git log")
+    parser.add_argument("--demo", action="store_true",
+                        help="Run with sample data (no git required)")
     return parser.parse_args()
 
 
 def get_git_log(from_ref: str, to_ref: str) -> list[str]:
+    """Get commit subjects from git log. Requires git on PATH and a git repo."""
+    if not shutil.which("git"):
+        print("Error: git not found on PATH. Use --stdin or --demo instead.", file=sys.stderr)
+        sys.exit(1)
     commit_range = f"{from_ref}..{to_ref}"
     cmd = ["git", "log", "--pretty=format:%s", commit_range]
-    result = subprocess.run(cmd, check=True, capture_output=True, text=True)
+    try:
+        result = subprocess.run(cmd, capture_output=True, text=True, timeout=30)
+    except subprocess.TimeoutExpired:
+        print("Error: git log timed out.", file=sys.stderr)
+        sys.exit(1)
+    if result.returncode != 0:
+        print(f"Error: git log failed: {result.stderr.strip()}", file=sys.stderr)
+        sys.exit(1)
     lines = [line.strip() for line in result.stdout.splitlines() if line.strip()]
     return lines
 
 
+def read_stdin() -> list[str]:
+    """Read commit subjects from stdin, one per line."""
+    return [line.strip() for line in sys.stdin if line.strip()]
+
+
 def group_commits(subjects: list[str]) -> dict[str, list[str]]:
-    grouped = defaultdict(list)
-    grouped["other"] = []
+    grouped: dict[str, list[str]] = defaultdict(list)
 
     for subject in subjects:
         commit_type = "other"
         for prefix in SECTIONS:
-            if subject.startswith(f"{prefix}:"):
+            if subject.startswith(f"{prefix}:") or subject.startswith(f"{prefix}("):
                 commit_type = prefix
                 break
         grouped[commit_type].append(subject)
@@ -68,7 +110,7 @@ def render_markdown(grouped: dict[str, list[str]]) -> str:
 
 
 def render_text(grouped: dict[str, list[str]]) -> str:
-    out = []
+    out: list[str] = []
     ordered_types = list(SECTIONS.keys()) + ["other"]
     for commit_type in ordered_types:
         commits = grouped.get(commit_type, [])
@@ -84,7 +126,18 @@ def render_text(grouped: dict[str, list[str]]) -> str:
 
 def main() -> int:
     args = parse_args()
-    subjects = get_git_log(args.from_ref, args.to_ref)
+
+    if args.demo:
+        subjects = DEMO_COMMITS
+    elif args.stdin:
+        subjects = read_stdin()
+    else:
+        subjects = get_git_log(args.from_ref, args.to_ref)
+
+    if not subjects:
+        print("No commits found.", file=sys.stderr)
+        return 0
+
     grouped = group_commits(subjects)
 
     if args.format == "markdown":