diff --git a/scripts/freshness.py b/scripts/freshness.py
new file mode 100644
index 0000000..3cbcceb
--- /dev/null
+++ b/scripts/freshness.py
@@ -0,0 +1,387 @@
+#!/usr/bin/env python3
+"""
+Knowledge Freshness Cron — Detect stale entries from code changes (Issue #200)
+
+Automatically detects when knowledge entries become stale due to code changes.
+
+Detection Method:
+1. Track source file hash alongside knowledge entry
+2. Compare current file hashes vs stored
+3. Mismatch → flag entry as potentially stale
+4. Report stale entries and optionally re-extract
+
+Usage:
+    python3 scripts/freshness.py --knowledge-dir knowledge/
+    python3 scripts/freshness.py --knowledge-dir knowledge/ --json
+    python3 scripts/freshness.py --knowledge-dir knowledge/ --repo /path/to/repo
+    python3 scripts/freshness.py --knowledge-dir knowledge/ --auto-reextract
+"""
+
+import argparse
+import hashlib
+import json
+import os
+import subprocess
+import sys
+import yaml
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Dict, List, Any, Optional, Tuple
+
+
+def compute_file_hash(filepath: str) -> Optional[str]:
+    """Compute SHA-256 hash of a file. Returns None if file doesn't exist."""
+    try:
+        with open(filepath, "rb") as f:
+            return "sha256:" + hashlib.sha256(f.read()).hexdigest()
+    except (FileNotFoundError, IsADirectoryError, PermissionError):
+        return None
+
+
+def get_git_file_changes(repo_path: str, days: int = 1) -> Dict[str, List[str]]:
+    """
+    Get files changed in git in the last N days.
+    
+    Returns dict with 'modified', 'added', 'deleted' lists of file paths.
+    """
+    changes = {"modified": [], "added": [], "deleted": []}
+    
+    try:
+        # Get commits from last N days
+        cmd = [
+            "git", "-C", repo_path, "log",
+            f"--since={days} days ago",
+            "--name-status",
+            "--pretty=format:",
+            "--diff-filter=MAD"
+        ]
+        result = subprocess.run(cmd, capture_output=True, text=True, timeout=30)
+        
+        if result.returncode != 0:
+            return changes
+        
+        for line in result.stdout.splitlines():
+            line = line.strip()
+            if not line:
+                continue
+            
+            parts = line.split('\t', 1)
+            if len(parts) != 2:
+                continue
+            
+            status, filepath = parts
+            if status == 'M':
+                changes["modified"].append(filepath)
+            elif status == 'A':
+                changes["added"].append(filepath)
+            elif status == 'D':
+                changes["deleted"].append(filepath)
+    
+    except (subprocess.TimeoutExpired, FileNotFoundError):
+        pass
+    
+    # Deduplicate
+    for key in changes:
+        changes[key] = list(set(changes[key]))
+    
+    return changes
+
+
+def load_knowledge_entries(knowledge_dir: str) -> List[Dict[str, Any]]:
+    """
+    Load knowledge entries from YAML files in the knowledge directory.
+    
+    Supports:
+    - knowledge/index.json (legacy format)
+    - knowledge/global/*.yaml
+    - knowledge/repos/*.yaml
+    - knowledge/agents/*.yaml
+    """
+    entries = []
+    
+    # Load from index.json if exists
+    index_path = os.path.join(knowledge_dir, "index.json")
+    if os.path.exists(index_path):
+        try:
+            with open(index_path) as f:
+                data = json.load(f)
+            for fact in data.get("facts", []):
+                entries.append({
+                    "source": "index.json",
+                    "fact": fact.get("fact", ""),
+                    "source_file": fact.get("source_file"),
+                    "source_hash": fact.get("source_hash"),
+                    "category": fact.get("category", "unknown"),
+                    "confidence": fact.get("confidence", 0.5)
+                })
+        except (json.JSONDecodeError, KeyError):
+            pass
+    
+    # Load from YAML files
+    for subdir in ["global", "repos", "agents"]:
+        subdir_path = os.path.join(knowledge_dir, subdir)
+        if not os.path.isdir(subdir_path):
+            continue
+        
+        for filename in os.listdir(subdir_path):
+            if not filename.endswith((".yaml", ".yml")):
+                continue
+            
+            filepath = os.path.join(subdir_path, filename)
+            try:
+                with open(filepath) as f:
+                    data = yaml.safe_load(f)
+                
+                if not data or not isinstance(data, dict):
+                    continue
+                
+                # Extract entries from YAML structure
+                for key, value in data.items():
+                    if isinstance(value, list):
+                        for item in value:
+                            if isinstance(item, dict):
+                                entries.append({
+                                    "source": f"{subdir}/{filename}",
+                                    "fact": item.get("description", item.get("fact", "")),
+                                    "source_file": item.get("source_file"),
+                                    "source_hash": item.get("source_hash"),
+                                    "category": item.get("category", "unknown"),
+                                    "confidence": item.get("confidence", 0.5)
+                                })
+                    elif isinstance(value, dict):
+                        entries.append({
+                            "source": f"{subdir}/{filename}",
+                            "fact": value.get("description", value.get("fact", "")),
+                            "source_file": value.get("source_file"),
+                            "source_hash": value.get("source_hash"),
+                            "category": value.get("category", "unknown"),
+                            "confidence": value.get("confidence", 0.5)
+                        })
+            except (yaml.YAMLError, IOError):
+                pass
+    
+    return entries
+
+
+def check_freshness(knowledge_dir: str, repo_root: str = ".", 
+                   days: int = 1) -> Dict[str, Any]:
+    """
+    Check freshness of knowledge entries against recent code changes.
+    
+    Returns:
+        {
+            "timestamp": ISO timestamp,
+            "total_entries": int,
+            "stale_entries": [...],
+            "fresh_entries": [...],
+            "git_changes": {...},
+            "summary": {...}
+        }
+    """
+    entries = load_knowledge_entries(knowledge_dir)
+    git_changes = get_git_file_changes(repo_root, days)
+    
+    stale_entries = []
+    fresh_entries = []
+    
+    for entry in entries:
+        source_file = entry.get("source_file")
+        if not source_file:
+            # Entry without source file reference
+            fresh_entries.append({**entry, "status": "no_source"})
+            continue
+        
+        # Check if source file was recently modified
+        is_stale = False
+        reason = ""
+        
+        if source_file in git_changes["modified"]:
+            is_stale = True
+            reason = "source_modified"
+        elif source_file in git_changes["deleted"]:
+            is_stale = True
+            reason = "source_deleted"
+        elif source_file in git_changes["added"]:
+            is_stale = True
+            reason = "source_added"
+        
+        # Also check hash if available
+        stored_hash = entry.get("source_hash")
+        if stored_hash:
+            full_path = os.path.join(repo_root, source_file)
+            current_hash = compute_file_hash(full_path)
+            
+            if current_hash is None:
+                is_stale = True
+                reason = "source_missing"
+            elif current_hash != stored_hash:
+                is_stale = True
+                reason = "hash_mismatch"
+        
+        if is_stale:
+            stale_entries.append({
+                **entry,
+                "status": "stale",
+                "reason": reason
+            })
+        else:
+            fresh_entries.append({**entry, "status": "fresh"})
+    
+    # Compute summary
+    total = len(entries)
+    stale_count = len(stale_entries)
+    fresh_count = len(fresh_entries)
+    
+    # Group stale entries by reason
+    stale_by_reason = {}
+    for entry in stale_entries:
+        reason = entry.get("reason", "unknown")
+        if reason not in stale_by_reason:
+            stale_by_reason[reason] = 0
+        stale_by_reason[reason] += 1
+    
+    return {
+        "timestamp": datetime.now(timezone.utc).isoformat(),
+        "total_entries": total,
+        "stale_entries": stale_entries,
+        "fresh_entries": fresh_entries,
+        "git_changes": git_changes,
+        "summary": {
+            "total": total,
+            "stale": stale_count,
+            "fresh": fresh_count,
+            "stale_percentage": round(stale_count / total * 100, 1) if total > 0 else 0,
+            "stale_by_reason": stale_by_reason,
+            "git_changes_summary": {
+                "modified": len(git_changes["modified"]),
+                "added": len(git_changes["added"]),
+                "deleted": len(git_changes["deleted"])
+            }
+        }
+    }
+
+
+def update_stale_hashes(knowledge_dir: str, repo_root: str = ".") -> int:
+    """
+    Update hashes for stale entries. Returns count of updated entries.
+    """
+    entries = load_knowledge_entries(knowledge_dir)
+    updated = 0
+    
+    # This is a simplified version - in practice, you'd need to
+    # write back to the specific YAML files
+    for entry in entries:
+        source_file = entry.get("source_file")
+        if not source_file:
+            continue
+        
+        full_path = os.path.join(repo_root, source_file)
+        current_hash = compute_file_hash(full_path)
+        
+        if current_hash and entry.get("source_hash") != current_hash:
+            # Mark for update (in practice, you'd write back to the file)
+            updated += 1
+    
+    return updated
+
+
+def format_report(result: Dict[str, Any], max_items: int = 20) -> str:
+    """Format freshness check results as a human-readable report."""
+    timestamp = result["timestamp"]
+    summary = result["summary"]
+    stale_entries = result["stale_entries"]
+    git_changes = result["git_changes"]
+    
+    lines = [
+        "Knowledge Freshness Report",
+        "=" * 50,
+        f"Generated: {timestamp}",
+        f"Total entries: {summary['total']}",
+        f"Stale entries: {summary['stale']} ({summary['stale_percentage']}%)",
+        f"Fresh entries: {summary['fresh']}",
+        ""
+    ]
+    
+    # Git changes summary
+    lines.extend([
+        "Git Changes (last 24h):",
+        f"  Modified: {len(git_changes['modified'])} files",
+        f"  Added: {len(git_changes['added'])} files",
+        f"  Deleted: {len(git_changes['deleted'])} files",
+        ""
+    ])
+    
+    # Stale entries by reason
+    if summary.get("stale_by_reason"):
+        lines.extend([
+            "Stale Entries by Reason:",
+            ""
+        ])
+        for reason, count in summary["stale_by_reason"].items():
+            lines.append(f"  {reason}: {count}")
+        lines.append("")
+    
+    # List stale entries
+    if stale_entries:
+        lines.extend([
+            "Stale Entries:",
+            ""
+        ])
+        for i, entry in enumerate(stale_entries[:max_items], 1):
+            source = entry.get("source_file", "?")
+            reason = entry.get("reason", "unknown")
+            fact = entry.get("fact", "")[:60]
+            lines.append(f"{i:2d}. [{reason}] {source}")
+            if fact:
+                lines.append(f"    {fact}")
+        
+        if len(stale_entries) > max_items:
+            lines.append(f"\n... and {len(stale_entries) - max_items} more")
+    else:
+        lines.append("No stale entries found. All knowledge is fresh!")
+    
+    return "\n".join(lines)
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Knowledge Freshness Cron — detect stale entries from code changes")
+    parser.add_argument("--knowledge-dir", required=True,
+                       help="Path to knowledge directory")
+    parser.add_argument("--repo", default=".",
+                       help="Path to repository for git change detection")
+    parser.add_argument("--days", type=int, default=1,
+                       help="Number of days to check for git changes (default: 1)")
+    parser.add_argument("--json", action="store_true",
+                       help="Output as JSON instead of human-readable")
+    parser.add_argument("--max", type=int, default=20,
+                       help="Maximum stale entries to show (default: 20)")
+    parser.add_argument("--auto-reextract", action="store_true",
+                       help="Auto-re-extract knowledge for stale entries")
+    
+    args = parser.parse_args()
+    
+    if not os.path.isdir(args.knowledge_dir):
+        print(f"Error: {args.knowledge_dir} is not a directory", file=sys.stderr)
+        sys.exit(1)
+    
+    if not os.path.isdir(args.repo):
+        print(f"Error: {args.repo} is not a directory", file=sys.stderr)
+        sys.exit(1)
+    
+    result = check_freshness(args.knowledge_dir, args.repo, args.days)
+    
+    if args.json:
+        print(json.dumps(result, indent=2))
+    else:
+        print(format_report(result, args.max))
+    
+    # Auto-re-extract if requested
+    if args.auto_reextract and result["stale_entries"]:
+        print(f"\nAuto-re-extracting {len(result['stale_entries'])} stale entries...")
+        # In a real implementation, this would call the harvester
+        print("(Auto-re-extraction not yet implemented)")
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file