diff --git a/control-pipeline/api/__init__.py b/control-pipeline/api/__init__.py
index 5d23aae..c3087c9 100644
--- a/control-pipeline/api/__init__.py
+++ b/control-pipeline/api/__init__.py
@@ -4,9 +4,11 @@ from api.control_generator_routes import router as generator_router
 from api.canonical_control_routes import router as canonical_router
 from api.document_compliance_routes import router as document_router
 from api.dependency_routes import router as dependency_router
+from api.master_control_routes import router as master_control_router
 
 router = APIRouter()
 router.include_router(generator_router)
 router.include_router(canonical_router)
 router.include_router(document_router)
 router.include_router(dependency_router)
+router.include_router(master_control_router)
diff --git a/control-pipeline/api/master_control_routes.py b/control-pipeline/api/master_control_routes.py
new file mode 100644
index 0000000..70ffa04
--- /dev/null
+++ b/control-pipeline/api/master_control_routes.py
@@ -0,0 +1,178 @@
+"""Master Control API — G-pre3.
+
+Provides read access to Master Controls (lifecycle-grouped atomic controls).
+"""
+
+import json
+import logging
+from typing import Optional
+
+from fastapi import APIRouter, HTTPException, Query
+from sqlalchemy import text
+
+from db.session import SessionLocal
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(prefix="/v1/master-controls", tags=["master-controls"])
+
+
+@router.get("")
+async def list_master_controls(
+    limit: int = Query(50, ge=1, le=500),
+    offset: int = Query(0, ge=0),
+    search: Optional[str] = None,
+    min_phases: Optional[int] = None,
+    min_controls: Optional[int] = None,
+    sort: str = Query("total_controls", regex="^(total_controls|phases|name|created_at)$"),
+):
+    """List Master Controls with optional filtering."""
+    db = SessionLocal()
+    try:
+        where_clauses = []
+        params: dict = {"limit": limit, "offset": offset}
+
+        if search:
+            where_clauses.append("mc.canonical_name ILIKE :search")
+            params["search"] = f"%{search}%"
+        if min_phases:
+            where_clauses.append("jsonb_array_length(mc.phases_covered) >= :min_phases")
+            params["min_phases"] = min_phases
+        if min_controls:
+            where_clauses.append("mc.total_controls >= :min_controls")
+            params["min_controls"] = min_controls
+
+        where = "WHERE " + " AND ".join(where_clauses) if where_clauses else ""
+
+        sort_map = {
+            "total_controls": "mc.total_controls DESC",
+            "phases": "jsonb_array_length(mc.phases_covered) DESC",
+            "name": "mc.canonical_name ASC",
+            "created_at": "mc.created_at DESC",
+        }
+        order = sort_map.get(sort, "mc.total_controls DESC")
+
+        rows = db.execute(text(f"""
+            SELECT mc.id, mc.master_control_id, mc.object_group_id,
+                   mc.canonical_name, mc.phases_covered,
+                   mc.phase_control_count, mc.total_controls,
+                   mc.created_at
+            FROM master_controls mc
+            {where}
+            ORDER BY {order}
+            LIMIT :limit OFFSET :offset
+        """), params).fetchall()
+
+        total = db.execute(text(f"""
+            SELECT count(*) FROM master_controls mc {where}
+        """), params).scalar()
+
+        return {
+            "total": total,
+            "limit": limit,
+            "offset": offset,
+            "master_controls": [
+                {
+                    "id": str(r[0]),
+                    "master_control_id": r[1],
+                    "object_group_id": r[2],
+                    "canonical_name": r[3],
+                    "phases_covered": r[4],
+                    "phase_control_count": r[5],
+                    "total_controls": r[6],
+                    "created_at": str(r[7]),
+                }
+                for r in rows
+            ],
+        }
+    finally:
+        db.close()
+
+
+@router.get("/stats")
+async def master_control_stats():
+    """Aggregate statistics about Master Controls."""
+    db = SessionLocal()
+    try:
+        stats = db.execute(text("""
+            SELECT
+                count(*) AS total_master_controls,
+                sum(total_controls) AS total_member_controls,
+                avg(total_controls)::int AS avg_controls_per_mc,
+                max(total_controls) AS max_controls,
+                avg(jsonb_array_length(phases_covered))::numeric(3,1) AS avg_phases,
+                max(jsonb_array_length(phases_covered)) AS max_phases
+            FROM master_controls
+        """)).fetchone()
+
+        phase_dist = db.execute(text("""
+            SELECT phase, count(*) AS control_count
+            FROM master_control_members
+            GROUP BY phase
+            ORDER BY control_count DESC
+        """)).fetchall()
+
+        return {
+            "total_master_controls": stats[0],
+            "total_member_controls": stats[1],
+            "avg_controls_per_mc": stats[2],
+            "max_controls": stats[3],
+            "avg_phases": float(stats[4]) if stats[4] else 0,
+            "max_phases": stats[5],
+            "phase_distribution": {r[0]: r[1] for r in phase_dist},
+        }
+    finally:
+        db.close()
+
+
+@router.get("/{mc_id}")
+async def get_master_control(mc_id: str):
+    """Get a single Master Control with all phase-controls."""
+    db = SessionLocal()
+    try:
+        mc = db.execute(text("""
+            SELECT mc.id, mc.master_control_id, mc.object_group_id,
+                   mc.canonical_name, mc.phases_covered,
+                   mc.phase_control_count, mc.total_controls
+            FROM master_controls mc
+            WHERE mc.master_control_id = :mc_id
+        """), {"mc_id": mc_id}).fetchone()
+
+        if not mc:
+            raise HTTPException(status_code=404, detail="Master Control not found")
+
+        members = db.execute(text("""
+            SELECT mcm.phase, mcm.action,
+                   cc.control_id, cc.title, cc.severity,
+                   cc.source_citation->>'source' AS source
+            FROM master_control_members mcm
+            JOIN canonical_controls cc ON cc.id = mcm.control_uuid
+            WHERE mcm.master_control_uuid = CAST(:mc_uuid AS uuid)
+            ORDER BY mcm.phase, cc.control_id
+        """), {"mc_uuid": str(mc[0])}).fetchall()
+
+        # Group by phase
+        phases = {}
+        for phase, action, ctrl_id, title, severity, source in members:
+            if phase not in phases:
+                phases[phase] = []
+            phases[phase].append({
+                "control_id": ctrl_id,
+                "title": title,
+                "action": action,
+                "severity": severity,
+                "source": source,
+            })
+
+        return {
+            "id": str(mc[0]),
+            "master_control_id": mc[1],
+            "object_group_id": mc[2],
+            "canonical_name": mc[3],
+            "phases_covered": mc[4],
+            "phase_control_count": mc[5],
+            "total_controls": mc[6],
+            "phases": phases,
+        }
+    finally:
+        db.close()
diff --git a/control-pipeline/migrations/004_object_groups.sql b/control-pipeline/migrations/004_object_groups.sql
new file mode 100644
index 0000000..33486a5
--- /dev/null
+++ b/control-pipeline/migrations/004_object_groups.sql
@@ -0,0 +1,18 @@
+-- Migration 004: Object Groups (G-pre1)
+-- Schema: compliance
+-- Run: ssh macmini "docker exec -i bp-core-postgres psql -U breakpilot -d breakpilot_db" < control-pipeline/migrations/004_object_groups.sql
+
+SET search_path TO compliance, public;
+
+CREATE TABLE IF NOT EXISTS object_groups (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    group_id INTEGER NOT NULL,
+    canonical_name VARCHAR(200) NOT NULL,
+    member_count INTEGER DEFAULT 0,
+    members JSONB DEFAULT '[]',
+    top_controls_count INTEGER DEFAULT 0,
+    created_at TIMESTAMPTZ DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_object_groups_group_id ON object_groups(group_id);
+CREATE INDEX IF NOT EXISTS idx_object_groups_canonical ON object_groups(canonical_name);
diff --git a/control-pipeline/migrations/005_master_controls.sql b/control-pipeline/migrations/005_master_controls.sql
new file mode 100644
index 0000000..1aed287
--- /dev/null
+++ b/control-pipeline/migrations/005_master_controls.sql
@@ -0,0 +1,30 @@
+-- Migration 005: Master Controls (G-pre2)
+-- Schema: compliance
+-- Run: ssh macmini "docker exec -i bp-core-postgres psql -U breakpilot -d breakpilot_db" < control-pipeline/migrations/005_master_controls.sql
+
+SET search_path TO compliance, public;
+
+CREATE TABLE IF NOT EXISTS master_controls (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    master_control_id VARCHAR(50) UNIQUE NOT NULL,
+    object_group_id INTEGER NOT NULL,
+    canonical_name VARCHAR(200) NOT NULL,
+    phases_covered JSONB NOT NULL DEFAULT '[]',
+    phase_control_count JSONB NOT NULL DEFAULT '{}',
+    total_controls INTEGER DEFAULT 0,
+    created_at TIMESTAMPTZ DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_master_controls_group ON master_controls(object_group_id);
+
+CREATE TABLE IF NOT EXISTS master_control_members (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    master_control_uuid UUID NOT NULL REFERENCES master_controls(id) ON DELETE CASCADE,
+    control_uuid UUID NOT NULL,
+    phase VARCHAR(50) NOT NULL,
+    action VARCHAR(50) NOT NULL,
+    created_at TIMESTAMPTZ DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_mc_members_master ON master_control_members(master_control_uuid);
+CREATE INDEX IF NOT EXISTS idx_mc_members_control ON master_control_members(control_uuid);
diff --git a/control-pipeline/scripts/gpre1_object_clustering.py b/control-pipeline/scripts/gpre1_object_clustering.py
new file mode 100644
index 0000000..7205def
--- /dev/null
+++ b/control-pipeline/scripts/gpre1_object_clustering.py
@@ -0,0 +1,219 @@
+#!/usr/bin/env python3
+"""
+G-pre1: Object Clustering via Mini-Batch K-Means on Embeddings.
+
+Clusters ~144k unique normalized objects into ~15-25k semantic groups
+using bge-m3 embeddings and Mini-Batch K-Means.
+
+Usage (inside control-pipeline container):
+  python3 /app/scripts/gpre1_object_clustering.py --k 20000
+  python3 /app/scripts/gpre1_object_clustering.py --k 20000 --dry-run
+"""
+
+import argparse
+import json
+import logging
+import sys
+import time
+from collections import Counter
+
+import httpx
+import numpy as np
+from sklearn.cluster import MiniBatchKMeans
+from sqlalchemy import create_engine, text
+
+logging.basicConfig(level=logging.INFO, format="%(asctime)s [%(levelname)s] %(message)s")
+logger = logging.getLogger("gpre1")
+
+import os
+DB_URL = os.getenv("DATABASE_URL", "postgresql://breakpilot:breakpilot123@postgres:5432/breakpilot_db")
+EMBEDDING_URL = "http://embedding-service:8087"
+BATCH_SIZE = 64  # Embeddings per API call
+
+
+def extract_objects(engine) -> tuple[list[str], dict[str, int]]:
+    """Extract unique normalized objects and their frequencies."""
+    from services.control_dedup import normalize_object
+
+    logger.info("Extracting objects from canonical_controls...")
+    with engine.connect() as c:
+        rows = c.execute(text("""
+            SELECT split_part(generation_metadata->>'merge_group_hint', ':', 2) AS obj,
+                   count(*) AS freq
+            FROM canonical_controls
+            WHERE generation_metadata->>'merge_group_hint' IS NOT NULL
+              AND generation_metadata->>'merge_group_hint' != ''
+            GROUP BY 1
+        """)).fetchall()
+
+    # Normalize and aggregate
+    norm_freq: Counter = Counter()
+    norm_to_raw: dict[str, list[str]] = {}
+    for raw_obj, freq in rows:
+        if not raw_obj or not raw_obj.strip():
+            continue
+        normed = normalize_object(raw_obj)
+        norm_freq[normed] += freq
+        norm_to_raw.setdefault(normed, []).append(raw_obj)
+
+    objects = list(norm_freq.keys())
+    freqs = {obj: norm_freq[obj] for obj in objects}
+    logger.info("Extracted %d unique normalized objects (from %d raw)", len(objects), len(rows))
+    return objects, freqs
+
+
+def generate_embeddings(objects: list[str]) -> np.ndarray:
+    """Generate embeddings via embedding-service in batches.
+
+    Uses pre-allocated numpy array to avoid Python list memory overhead
+    (Python float = 28 bytes vs numpy float32 = 4 bytes).
+    """
+    total = len(objects)
+    # Pre-allocate: 144k × 1024 × 4 bytes = ~590 MB (vs ~4 GB with Python lists)
+    result = np.zeros((total, 1024), dtype=np.float32)
+    logger.info("Generating embeddings for %d objects (pre-allocated %.0f MB)...",
+                total, result.nbytes / 1024 / 1024)
+
+    failed_batches = []
+    for i in range(0, total, BATCH_SIZE):
+        batch = objects[i:i + BATCH_SIZE]
+        success = False
+        for attempt in range(3):  # Max 3 retries per batch
+            try:
+                with httpx.Client(timeout=httpx.Timeout(60.0, connect=10.0)) as client:
+                    resp = client.post(
+                        f"{EMBEDDING_URL}/embed",
+                        json={"texts": batch},
+                    )
+                    resp.raise_for_status()
+                    embeddings = resp.json().get("embeddings", [])
+                    end = min(i + len(embeddings), total)
+                    result[i:end] = np.array(embeddings, dtype=np.float32)
+                    success = True
+                    break
+            except Exception as e:
+                if attempt < 2:
+                    logger.warning("Batch %d attempt %d failed: %s — retrying", i, attempt + 1, e)
+                    import time
+                    time.sleep(2)
+                else:
+                    logger.error("Batch %d failed after 3 attempts: %s", i, e)
+                    failed_batches.append(i)
+
+        if (i + BATCH_SIZE) % 5000 == 0 or i + BATCH_SIZE >= total:
+            logger.info("  Embedded %d/%d (%.1f%%) [%d failed]",
+                        min(i + BATCH_SIZE, total), total,
+                        min(i + BATCH_SIZE, total) / total * 100,
+                        len(failed_batches))
+
+    return result
+
+
+def cluster_objects(embeddings: np.ndarray, k: int) -> np.ndarray:
+    """Run Mini-Batch K-Means clustering."""
+    logger.info("Clustering %d objects into %d groups (Mini-Batch K-Means)...", len(embeddings), k)
+
+    # Normalize embeddings for cosine-like clustering
+    norms = np.linalg.norm(embeddings, axis=1, keepdims=True)
+    norms[norms == 0] = 1
+    normalized = embeddings / norms
+
+    kmeans = MiniBatchKMeans(
+        n_clusters=k,
+        batch_size=1000,
+        max_iter=100,
+        random_state=42,
+        verbose=0,
+    )
+    labels = kmeans.fit_predict(normalized)
+    logger.info("Clustering done. Inertia: %.2f", kmeans.inertia_)
+    return labels
+
+
+def store_results(engine, objects: list[str], freqs: dict[str, int],
+                  labels: np.ndarray, dry_run: bool):
+    """Store clustering results in object_groups table."""
+    # Build groups
+    groups: dict[int, list[tuple[str, int]]] = {}
+    for i, obj in enumerate(objects):
+        gid = int(labels[i])
+        groups.setdefault(gid, []).append((obj, freqs.get(obj, 0)))
+
+    # Pick canonical name (highest frequency in group)
+    results = []
+    for gid, members in groups.items():
+        members_sorted = sorted(members, key=lambda x: -x[1])
+        canonical = members_sorted[0][0]
+        results.append({
+            "group_id": gid,
+            "canonical_name": canonical,
+            "member_count": len(members),
+            "members": json.dumps([m[0] for m in members_sorted]),
+            "top_controls_count": members_sorted[0][1],
+        })
+
+    # Stats
+    sizes = [r["member_count"] for r in results]
+    logger.info("Groups: %d total", len(results))
+    logger.info("  Singletons: %d", sum(1 for s in sizes if s == 1))
+    logger.info("  Groups 2-5: %d", sum(1 for s in sizes if 2 <= s <= 5))
+    logger.info("  Groups 6-20: %d", sum(1 for s in sizes if 6 <= s <= 20))
+    logger.info("  Groups 21-100: %d", sum(1 for s in sizes if 21 <= s <= 100))
+    logger.info("  Groups >100: %d", sum(1 for s in sizes if s > 100))
+    logger.info("  Max group size: %d", max(sizes))
+    logger.info("  Avg group size: %.1f", sum(sizes) / len(sizes))
+
+    # Top 10 largest groups
+    top10 = sorted(results, key=lambda x: -x["member_count"])[:10]
+    logger.info("\nTop 10 largest groups:")
+    for g in top10:
+        members_list = json.loads(g["members"])
+        logger.info("  [%d] %s (%d members): %s",
+                     g["group_id"], g["canonical_name"], g["member_count"],
+                     ", ".join(members_list[:5]))
+
+    if dry_run:
+        logger.info("DRY RUN — not writing to DB")
+        return
+
+    # Write to DB
+    with engine.begin() as conn:
+        conn.execute(text("SET search_path TO compliance, public"))
+        conn.execute(text("DELETE FROM object_groups"))  # Clear old results
+        for r in results:
+            conn.execute(text("""
+                INSERT INTO object_groups (group_id, canonical_name, member_count, members, top_controls_count)
+                VALUES (:group_id, :canonical_name, :member_count, CAST(:members AS jsonb), :top_controls_count)
+            """), r)
+    logger.info("Wrote %d groups to object_groups table", len(results))
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--k", type=int, default=20000, help="Number of clusters")
+    parser.add_argument("--dry-run", action="store_true")
+    args = parser.parse_args()
+
+    engine = create_engine(DB_URL, connect_args={"options": "-c search_path=compliance,public"})
+
+    # Step 1: Extract
+    objects, freqs = extract_objects(engine)
+
+    # Step 2: Embed
+    embeddings = generate_embeddings(objects)
+    logger.info("Embedding matrix: %s (%.1f MB)", embeddings.shape,
+                embeddings.nbytes / 1024 / 1024)
+
+    # Adjust k if we have fewer objects
+    k = min(args.k, len(objects) // 2)
+    logger.info("Using k=%d (requested %d, objects=%d)", k, args.k, len(objects))
+
+    # Step 3: Cluster
+    labels = cluster_objects(embeddings, k)
+
+    # Step 4: Store
+    store_results(engine, objects, freqs, labels, args.dry_run)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/control-pipeline/scripts/gpre1_subcluster.py b/control-pipeline/scripts/gpre1_subcluster.py
new file mode 100644
index 0000000..31ab266
--- /dev/null
+++ b/control-pipeline/scripts/gpre1_subcluster.py
@@ -0,0 +1,164 @@
+#!/usr/bin/env python3
+"""
+G-pre1 Step 2: Sub-cluster large object groups (>50 members) into k=4 sub-groups.
+
+Reads existing object_groups, re-embeds members of large groups,
+applies K-Means with k=4 per group, and writes sub-groups back.
+
+Usage (inside container or with PYTHONPATH):
+  python3 /app/scripts/gpre1_subcluster.py
+  python3 /app/scripts/gpre1_subcluster.py --min-size 100  # only groups >100
+  python3 /app/scripts/gpre1_subcluster.py --sub-k 6       # 6 sub-clusters
+"""
+
+import argparse
+import json
+import logging
+import os
+
+import httpx
+import numpy as np
+from sklearn.cluster import MiniBatchKMeans
+from sqlalchemy import create_engine, text
+
+logging.basicConfig(level=logging.INFO, format="%(asctime)s [%(levelname)s] %(message)s")
+logger = logging.getLogger("gpre1-sub")
+
+DB_URL = os.getenv("DATABASE_URL", "postgresql://breakpilot:breakpilot123@postgres:5432/breakpilot_db")
+EMBEDDING_URL = "http://embedding-service:8087"
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--min-size", type=int, default=50, help="Min group size to sub-cluster")
+    parser.add_argument("--sub-k", type=int, default=4, help="Sub-clusters per group")
+    parser.add_argument("--dry-run", action="store_true")
+    args = parser.parse_args()
+
+    engine = create_engine(DB_URL, connect_args={"options": "-c search_path=compliance,public"})
+
+    # Load large groups
+    with engine.connect() as c:
+        groups = c.execute(text(
+            "SELECT group_id, canonical_name, member_count, members "
+            "FROM object_groups WHERE member_count > :min ORDER BY member_count DESC"
+        ), {"min": args.min_size}).fetchall()
+
+    logger.info("Found %d groups with >%d members to sub-cluster", len(groups), args.min_size)
+
+    # Find next available group_id
+    with engine.connect() as c:
+        max_gid = c.execute(text("SELECT COALESCE(MAX(group_id), 0) FROM object_groups")).scalar()
+    next_gid = max_gid + 1
+
+    total_sub_groups = 0
+    all_new_rows = []
+    groups_to_delete = []
+
+    for group_id, canonical_name, member_count, members_json in groups:
+        members = json.loads(members_json) if isinstance(members_json, str) else members_json
+
+        if len(members) < args.sub_k * 2:
+            logger.info("  Skip group %d (%s, %d members) — too small for k=%d",
+                        group_id, canonical_name, len(members), args.sub_k)
+            continue
+
+        # Embed members
+        embeddings = _embed_batch(members)
+        if embeddings is None:
+            logger.error("  Failed to embed group %d (%s)", group_id, canonical_name)
+            continue
+
+        # Normalize for cosine
+        norms = np.linalg.norm(embeddings, axis=1, keepdims=True)
+        norms[norms == 0] = 1
+        normalized = embeddings / norms
+
+        # Sub-cluster
+        k = min(args.sub_k, len(members) // 2)
+        kmeans = MiniBatchKMeans(n_clusters=k, batch_size=min(100, len(members)),
+                                max_iter=50, random_state=42)
+        labels = kmeans.fit_predict(normalized)
+
+        # Build sub-groups
+        sub_groups: dict[int, list[str]] = {}
+        for i, member in enumerate(members):
+            sub_groups.setdefault(int(labels[i]), []).append(member)
+
+        # Create new rows
+        for sub_id, sub_members in sub_groups.items():
+            sub_canonical = sub_members[0]  # Most frequent would be better but we don't have freq here
+            all_new_rows.append({
+                "group_id": next_gid,
+                "canonical_name": sub_canonical,
+                "member_count": len(sub_members),
+                "members": json.dumps(sub_members),
+                "top_controls_count": 0,
+                "parent_group_id": group_id,
+            })
+            next_gid += 1
+
+        groups_to_delete.append(group_id)
+        total_sub_groups += len(sub_groups)
+
+        if len(groups_to_delete) % 50 == 0:
+            logger.info("  Processed %d/%d groups, %d sub-groups created",
+                        len(groups_to_delete), len(groups), total_sub_groups)
+
+    logger.info("Sub-clustering complete: %d groups → %d sub-groups",
+                len(groups_to_delete), total_sub_groups)
+
+    # Stats
+    sub_sizes = [r["member_count"] for r in all_new_rows]
+    if sub_sizes:
+        logger.info("  Sub-group sizes: avg=%.1f, max=%d, min=%d",
+                    sum(sub_sizes) / len(sub_sizes), max(sub_sizes), min(sub_sizes))
+
+    if args.dry_run:
+        logger.info("DRY RUN — not writing to DB")
+        for r in all_new_rows[:10]:
+            logger.info("  [%d] %s (%d members)", r["group_id"], r["canonical_name"], r["member_count"])
+        return
+
+    # Write to DB: delete old large groups, insert sub-groups
+    with engine.begin() as c:
+        c.execute(text("SET search_path TO compliance, public"))
+        # Delete old large groups
+        for gid in groups_to_delete:
+            c.execute(text("DELETE FROM object_groups WHERE group_id = :gid"), {"gid": gid})
+        # Insert sub-groups
+        for r in all_new_rows:
+            c.execute(text("""
+                INSERT INTO object_groups (group_id, canonical_name, member_count, members, top_controls_count)
+                VALUES (:group_id, :canonical_name, :member_count, CAST(:members AS jsonb), :top_controls_count)
+            """), r)
+
+    logger.info("Wrote %d sub-groups to DB (replaced %d large groups)", len(all_new_rows), len(groups_to_delete))
+
+    # Final stats
+    with engine.connect() as c:
+        total = c.execute(text("SELECT count(*) FROM object_groups")).scalar()
+        logger.info("Total groups in DB: %d", total)
+
+
+def _embed_batch(texts: list[str]) -> np.ndarray | None:
+    """Embed a list of texts, return numpy array."""
+    try:
+        all_emb = np.zeros((len(texts), 1024), dtype=np.float32)
+        batch_size = 64
+        for i in range(0, len(texts), batch_size):
+            batch = texts[i:i + batch_size]
+            with httpx.Client(timeout=httpx.Timeout(60.0, connect=10.0)) as client:
+                resp = client.post(f"{EMBEDDING_URL}/embed", json={"texts": batch})
+                resp.raise_for_status()
+                embs = resp.json().get("embeddings", [])
+                end = min(i + len(embs), len(texts))
+                all_emb[i:end] = np.array(embs, dtype=np.float32)
+        return all_emb
+    except Exception as e:
+        logger.error("Embedding failed: %s", e)
+        return None
+
+
+if __name__ == "__main__":
+    main()
diff --git a/control-pipeline/scripts/gpre2_master_controls.py b/control-pipeline/scripts/gpre2_master_controls.py
new file mode 100644
index 0000000..43fcfb7
--- /dev/null
+++ b/control-pipeline/scripts/gpre2_master_controls.py
@@ -0,0 +1,213 @@
+#!/usr/bin/env python3
+"""
+G-pre2: Build Master Controls from Object Groups + Lifecycle Phases.
+
+Groups atomic controls by (object_group_id, phase) and creates
+Master Controls for groups with >=2 distinct phases.
+
+Usage:
+  python3 /app/scripts/gpre2_master_controls.py
+  python3 /app/scripts/gpre2_master_controls.py --min-phases 3
+  python3 /app/scripts/gpre2_master_controls.py --dry-run
+"""
+
+import argparse
+import json
+import logging
+import os
+from collections import defaultdict
+
+from sqlalchemy import create_engine, text
+
+logging.basicConfig(level=logging.INFO, format="%(asctime)s [%(levelname)s] %(message)s")
+logger = logging.getLogger("gpre2")
+
+DB_URL = os.getenv("DATABASE_URL", "postgresql://breakpilot:breakpilot123@postgres:5432/breakpilot_db")
+
+# Canonical phase ordering for lifecycle chains
+PHASE_ORDER = {
+    "scope": 0,
+    "definition": 1, "governance": 1,
+    "design": 2,
+    "implementation": 3, "configuration": 3,
+    "operation": 4, "training": 4,
+    "monitoring": 5,
+    "testing": 6,
+    "review": 7,
+    "assessment": 8, "remediation": 8,
+    "validation": 9,
+    "reporting": 10,
+    "evidence": 11,
+}
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--min-phases", type=int, default=2, help="Min distinct phases for Master Control")
+    parser.add_argument("--dry-run", action="store_true")
+    args = parser.parse_args()
+
+    engine = create_engine(DB_URL, connect_args={"options": "-c search_path=compliance,public"})
+
+    # Step 1: Build reverse index (object_token → group_id)
+    logger.info("Building object → group_id reverse index...")
+    object_to_group = {}
+    with engine.connect() as c:
+        groups = c.execute(text("SELECT group_id, canonical_name, members FROM object_groups")).fetchall()
+
+    for gid, canonical, members_json in groups:
+        members = json.loads(members_json) if isinstance(members_json, str) else members_json
+        for member in members:
+            object_to_group[member] = (gid, canonical)
+
+    logger.info("Reverse index: %d objects → %d groups", len(object_to_group), len(groups))
+
+    # Step 2: Load all controls with merge_group_hint
+    logger.info("Loading controls with merge_group_hint...")
+    with engine.connect() as c:
+        rows = c.execute(text("""
+            SELECT id, control_id,
+                   generation_metadata->>'merge_group_hint' AS hint,
+                   title
+            FROM canonical_controls
+            WHERE generation_metadata->>'merge_group_hint' IS NOT NULL
+              AND generation_metadata->>'merge_group_hint' != ''
+              AND release_state NOT IN ('deprecated', 'rejected')
+        """)).fetchall()
+
+    logger.info("Loaded %d controls with merge_group_hint", len(rows))
+
+    # Step 3: Parse and group by (group_id, phase)
+    # Structure: group_id → {phase → [(control_uuid, control_id, action, title)]}
+    group_phases: dict[int, dict[str, list]] = defaultdict(lambda: defaultdict(list))
+    group_names: dict[int, str] = {}
+    unmatched = 0
+
+    for uuid, control_id, hint, title in rows:
+        parts = hint.split(":", 2)
+        if len(parts) < 2:
+            continue
+        action = parts[0]
+        obj = parts[1]
+        phase = parts[2] if len(parts) > 2 else "implementation"
+
+        # Normalize object and find group
+        from services.control_dedup import normalize_object
+        normed = normalize_object(obj)
+
+        if normed in object_to_group:
+            gid, canonical = object_to_group[normed]
+        elif obj in object_to_group:
+            gid, canonical = object_to_group[obj]
+        else:
+            unmatched += 1
+            continue
+
+        group_phases[gid][phase].append((str(uuid), control_id, action, title))
+        group_names[gid] = canonical
+
+    logger.info("Grouped into %d object groups (%d controls unmatched to any group)",
+                len(group_phases), unmatched)
+
+    # Step 4: Create Master Controls (groups with >= min_phases distinct phases)
+    master_controls = []
+    master_members = []
+    mc_counter = 0
+
+    for gid, phases in group_phases.items():
+        if len(phases) < args.min_phases:
+            continue
+
+        mc_counter += 1
+        mc_id = "MC-%d" % gid
+        canonical = group_names.get(gid, "unknown")
+
+        # Sort phases by lifecycle order
+        sorted_phases = sorted(phases.keys(), key=lambda p: PHASE_ORDER.get(p, 99))
+        phase_counts = {p: len(ctrls) for p, ctrls in phases.items()}
+        total = sum(phase_counts.values())
+
+        master_controls.append({
+            "master_control_id": mc_id,
+            "object_group_id": gid,
+            "canonical_name": canonical,
+            "phases_covered": json.dumps(sorted_phases),
+            "phase_control_count": json.dumps(phase_counts),
+            "total_controls": total,
+        })
+
+        for phase, controls in phases.items():
+            for ctrl_uuid, ctrl_id, action, title in controls:
+                master_members.append({
+                    "mc_id": mc_id,
+                    "control_uuid": ctrl_uuid,
+                    "phase": phase,
+                    "action": action,
+                })
+
+    logger.info("Created %d Master Controls with %d members (min %d phases)",
+                len(master_controls), len(master_members), args.min_phases)
+
+    # Stats
+    if master_controls:
+        phase_counts = [mc["total_controls"] for mc in master_controls]
+        phases_per_mc = [len(json.loads(mc["phases_covered"])) for mc in master_controls]
+        logger.info("  Avg controls per MC: %.1f", sum(phase_counts) / len(phase_counts))
+        logger.info("  Avg phases per MC: %.1f", sum(phases_per_mc) / len(phases_per_mc))
+        logger.info("  Max controls in MC: %d", max(phase_counts))
+        logger.info("  Max phases in MC: %d", max(phases_per_mc))
+
+        # Top 10
+        top10 = sorted(master_controls, key=lambda x: -x["total_controls"])[:10]
+        logger.info("\nTop 10 Master Controls:")
+        for mc in top10:
+            logger.info("  %s: %s (%d controls, phases: %s)",
+                        mc["master_control_id"], mc["canonical_name"],
+                        mc["total_controls"], mc["phases_covered"])
+
+    if args.dry_run:
+        logger.info("DRY RUN — not writing to DB")
+        return
+
+    # Step 5: Write to DB
+    with engine.begin() as c:
+        c.execute(text("SET search_path TO compliance, public"))
+        c.execute(text("DELETE FROM master_control_members"))
+        c.execute(text("DELETE FROM master_controls"))
+
+        for mc in master_controls:
+            c.execute(text("""
+                INSERT INTO master_controls
+                    (master_control_id, object_group_id, canonical_name,
+                     phases_covered, phase_control_count, total_controls)
+                VALUES (:master_control_id, :object_group_id, :canonical_name,
+                        CAST(:phases_covered AS jsonb), CAST(:phase_control_count AS jsonb),
+                        :total_controls)
+            """), mc)
+
+        # Get MC UUIDs for member inserts
+        mc_uuids = {}
+        for row in c.execute(text("SELECT id, master_control_id FROM master_controls")).fetchall():
+            mc_uuids[row[1]] = str(row[0])
+
+        for mem in master_members:
+            mc_uuid = mc_uuids.get(mem["mc_id"])
+            if not mc_uuid:
+                continue
+            c.execute(text("""
+                INSERT INTO master_control_members
+                    (master_control_uuid, control_uuid, phase, action)
+                VALUES (CAST(:mc_uuid AS uuid), CAST(:control_uuid AS uuid), :phase, :action)
+            """), {
+                "mc_uuid": mc_uuid,
+                "control_uuid": mem["control_uuid"],
+                "phase": mem["phase"],
+                "action": mem["action"],
+            })
+
+    logger.info("Wrote %d Master Controls + %d members to DB",
+                len(master_controls), len(master_members))
+
+
+if __name__ == "__main__":
+    main()