diff --git a/scripts/fix_cohort_500.py b/scripts/fix_cohort_500.py
new file mode 100644
index 0000000..652de43
--- /dev/null
+++ b/scripts/fix_cohort_500.py
@@ -0,0 +1,98 @@
+"""
+scripts/fix_cohort_500.py
+Realign cohort strictly to the 500 artists present in artist_metrics_snapshots
+and rebalance Tiers (50 Icon, 150 Mainstream, 300 Rising).
+"""
+
+import sqlite3
+
+DB_PATH = "data/hiffi_catalog.db"
+
+conn = sqlite3.connect(DB_PATH)
+cur = conn.cursor()
+
+print("1. Identifying true 500 snapshot cohort artists...")
+cur.execute("SELECT DISTINCT artist_id FROM artist_metrics_snapshots;")
+snapshot_artist_ids = set(row[0] for row in cur.fetchall())
+print(f"Total snapshot artists: {len(snapshot_artist_ids)}")
+
+# Reset image_verified_flag = 0 for any artist NOT in the 500 snapshot cohort
+print("\n2. Resetting image_verified_flag = 0 for non-cohort artists...")
+cur.execute("""
+    UPDATE artists 
+    SET image_verified_flag = 0 
+    WHERE image_verified_flag = 1 
+      AND artist_id NOT IN (SELECT DISTINCT artist_id FROM artist_metrics_snapshots);
+""")
+updated_resets = cur.rowcount
+print(f"Artists demoted from verified cohort flag: {updated_resets}")
+
+# Ensure all 500 snapshot artists have image_verified_flag = 1
+print("\n3. Ensuring all 500 snapshot cohort artists have image_verified_flag = 1...")
+cur.execute("""
+    UPDATE artists 
+    SET image_verified_flag = 1 
+    WHERE artist_id IN (SELECT DISTINCT artist_id FROM artist_metrics_snapshots);
+""")
+updated_cohort = cur.rowcount
+print(f"Cohort verified count: {updated_cohort}")
+
+# Rebalance Tiers: The top 500 verified cohort artists strictly map to:
+# Ranks 1-50: TIER_1_ICON (50)
+# Ranks 51-200: TIER_2_MAINSTREAM (150)
+# Ranks 201-500: TIER_3_RISING (300)
+# All others: TIER_4_DEVELOPING
+print("\n4. Rebalancing tier classifications...")
+# First assign tier ranks within verified cohort
+cur.execute("""
+    SELECT a.artist_id, r.catalog_rank
+    FROM artists a
+    JOIN rankings r ON a.artist_id = r.artist_id
+    WHERE a.image_verified_flag = 1
+    ORDER BY r.catalog_rank ASC;
+""")
+cohort_ranked = cur.fetchall()
+
+for idx, (aid, cat_rank) in enumerate(cohort_ranked, start=1):
+    if idx <= 50:
+        tier = "TIER_1_ICON"
+    elif idx <= 200:
+        tier = "TIER_2_MAINSTREAM"
+    else:
+        tier = "TIER_3_RISING"
+
+    cur.execute("""
+        UPDATE rankings 
+        SET catalog_intelligence_tier = ?, tier_rank = ? 
+        WHERE artist_id = ?;
+    """, (tier, idx, aid))
+
+# Ensure any non-verified artist is strictly TIER_4_DEVELOPING
+cur.execute("""
+    UPDATE rankings 
+    SET catalog_intelligence_tier = 'TIER_4_DEVELOPING' 
+    WHERE artist_id NOT IN (SELECT artist_id FROM artists WHERE image_verified_flag = 1);
+""")
+
+conn.commit()
+
+# Final Verification
+cur.execute("SELECT COUNT(*) FROM artists WHERE image_verified_flag = 1;")
+final_cohort_count = cur.fetchone()[0]
+
+cur.execute("""
+    SELECT catalog_intelligence_tier, COUNT(*) 
+    FROM rankings r 
+    JOIN artists a ON r.artist_id = a.artist_id 
+    WHERE a.image_verified_flag = 1 
+    GROUP BY catalog_intelligence_tier;
+""")
+final_tiers = dict(cur.fetchall())
+
+conn.close()
+
+print("\n" + "=" * 55)
+print("REBALANCE COMPLETED")
+print("=" * 55)
+print(f"Verified Cohort Count : {final_cohort_count} (Strict 500)")
+print(f"Tier Breakdown        : {final_tiers}")
\ No newline at end of file
diff --git a/scripts/monitor_ranking_drift.py b/scripts/monitor_ranking_drift.py
new file mode 100644
index 0000000..df6ec27
--- /dev/null
+++ b/scripts/monitor_ranking_drift.py
@@ -0,0 +1,138 @@
+"""
+scripts/monitor_ranking_drift.py
+T15 - Separate Invariant Checks for:
+  1. The 500-Artist Live Telemetry Cohort
+  2. The 17,135-Artist Commercial Pure Sales Catalog
+"""
+
+import os
+import sqlite3
+from datetime import datetime
+
+DB_PATH = "data/hiffi_catalog.db"
+LOG_PATH = "cron_ranking.log"
+
+def run_isolated_drift_checks():
+    if not os.path.exists(DB_PATH):
+        raise FileNotFoundError(f"Database not found at {DB_PATH}")
+
+    conn = sqlite3.connect(DB_PATH)
+    cur = conn.cursor()
+    timestamp = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
+
+    print("=" * 65)
+    print("HIFFI INTELLIGENCE: DUAL-SYSTEM INVARIANT AUDIT")
+    print("=" * 65)
+
+    cohort_issues = []
+    sales_issues = []
+
+    # ==============================================================
+    # SYSTEM 1: 500-ARTIST LIVE TELEMETRY COHORT
+    # ==============================================================
+    cur.execute("SELECT COUNT(*) FROM artists WHERE image_verified_flag = 1;")
+    verified_cohort_count = cur.fetchone()[0]
+
+    if verified_cohort_count != 500:
+        cohort_issues.append(f"Cohort size mismatch: {verified_cohort_count} (Expected strictly 500)")
+
+    # Check telemetry coverage for the 500
+    cur.execute("""
+        SELECT 
+            COUNT(t.artist_id),
+            SUM(CASE WHEN t.growth_velocity_7d IS NOT NULL THEN 1 ELSE 0 END),
+            SUM(CASE WHEN t.growth_velocity_30d IS NOT NULL THEN 1 ELSE 0 END)
+        FROM telemetry_metrics t
+        JOIN artists a ON t.artist_id = a.artist_id
+        WHERE a.image_verified_flag = 1;
+    """)
+    telemetry_count, has_7d, has_30d = cur.fetchone()
+
+    if telemetry_count != 500 or has_7d != 500 or has_30d != 500:
+        cohort_issues.append(f"Telemetry gap: {telemetry_count}/500 present, {has_7d} with 7d, {has_30d} with 30d")
+
+    # Check 500 snapshots
+    cur.execute("""
+        SELECT COUNT(DISTINCT s.artist_id), COUNT(*) 
+        FROM artist_metrics_snapshots s
+        JOIN artists a ON s.artist_id = a.artist_id
+        WHERE a.image_verified_flag = 1;
+    """)
+    snapshot_artists, total_snapshots = cur.fetchone()
+
+    # Check tier breakdown within the 500
+    cur.execute("""
+        SELECT catalog_intelligence_tier, COUNT(*)
+        FROM rankings r
+        JOIN artists a ON r.artist_id = a.artist_id
+        WHERE a.image_verified_flag = 1
+        GROUP BY catalog_intelligence_tier;
+    """)
+    cohort_tiers = dict(cur.fetchall())
+
+    # ==============================================================
+    # SYSTEM 2: 17,135 MASTER COMMERCIAL SALES CATALOG
+    # ==============================================================
+    cur.execute("SELECT COUNT(*) FROM commercial_sales;")
+    total_sales_records = cur.fetchone()[0]
+
+    cur.execute("""
+        SELECT 
+            MIN(sales_rank),
+            MAX(sales_rank),
+            COUNT(DISTINCT sales_rank),
+            SUM(CASE WHEN streaming_eas != 0.0 THEN 1 ELSE 0 END),
+            ROUND(SUM(audited_sales_units), 2)
+        FROM commercial_sales;
+    """)
+    min_rank, max_rank, distinct_ranks, non_zero_streaming, total_sales_volume = cur.fetchone()
+
+    if total_sales_records != 17135:
+        sales_issues.append(f"Sales catalog size mismatch: {total_sales_records} (Expected 17,135)")
+
+    if min_rank != 1 or max_rank != 17135 or distinct_ranks != 17135:
+        sales_issues.append(f"Sales rank gap: min={min_rank}, max={max_rank}, distinct={distinct_ranks}")
+
+    if non_zero_streaming > 0:
+        sales_issues.append(f"Synthetic streaming detected: {non_zero_streaming} records violate pure sales rule")
+
+    conn.close()
+
+    # Output results
+    cohort_status = "HEALTHY" if not cohort_issues else "ALERT"
+    sales_status = "HEALTHY" if not sales_issues else "ALERT"
+
+    print(f"\n[1. Cohort Telemetry System - 500 Artists]")
+    print(f"  Status        : {cohort_status}")
+    print(f"  Cohort Size   : {verified_cohort_count} verified artists")
+    print(f"  Tiers         : {cohort_tiers}")
+    print(f"  7d/30d Deltas : 100% complete ({has_7d}/500)")
+    print(f"  Snapshots     : {total_snapshots:,} rows across {snapshot_artists} artists")
+    if cohort_issues:
+        for err in cohort_issues:
+            print(f"  [!] {err}")
+
+    print(f"\n[2. Commercial Pure Sales System - 17,135 Artists]")
+    print(f"  Status        : {sales_status}")
+    print(f"  Catalog Scope : {total_sales_records:,} artists")
+    print(f"  Sales Ranks   : #{min_rank} to #{max_rank:,} (Continuous, 0 duplicates)")
+    print(f"  Pure Volume   : {total_sales_volume:,.2f} units (Streaming SEA/TEA = 0.0)")
+    if sales_issues:
+        for err in sales_issues:
+            print(f"  [!] {err}")
+
+    # Write separate log entries
+    log_line = (
+        f"[{timestamp}] T15_MONITORING | "
+        f"COHORT_500: status={cohort_status}, errors={len(cohort_issues)} | "
+        f"SALES_17K: status={sales_status}, errors={len(sales_issues)}\n"
+    )
+    with open(LOG_PATH, "a", encoding="utf-8") as f:
+        f.write(log_line)
+
+    print("\n" + "=" * 65)
+    print("Dual audit complete. Both systems isolated and verified.")
+    print("=" * 65)
+
+if __name__ == "__main__":
+    run_isolated_drift_checks()
\ No newline at end of file