diff --git a/examples/3_buyer_seller_agents/buyer_agent.py b/examples/3_buyer_seller_agents/buyer_agent.py
index b98e38c..f8b74b7 100644
--- a/examples/3_buyer_seller_agents/buyer_agent.py
+++ b/examples/3_buyer_seller_agents/buyer_agent.py
@@ -3,7 +3,7 @@
 import uuid
 from pathlib import Path
 from summoner.client import SummonerClient
-from db_files.db_sdk import (
+from db_sdk import (
     configure_db_path,
     init_db,
     create_or_reset_state,
diff --git a/examples/3_buyer_seller_agents/db_sdk.py b/examples/3_buyer_seller_agents/db_sdk.py
new file mode 100644
index 0000000..78fe3d8
--- /dev/null
+++ b/examples/3_buyer_seller_agents/db_sdk.py
@@ -0,0 +1,224 @@
+import aiosqlite
+from pathlib import Path
+from datetime import datetime
+import random
+import uuid
+
+# Module-level database path; set via configure_db_path()
+_DB_PATH: Path = None
+
+def configure_db_path(path: Path):
+    """
+    Configure the SQLite file path for this agent.
+    """
+    global _DB_PATH
+    _DB_PATH = path
+
+
+def get_db_path() -> Path:
+    """
+    Return the configured DB path, or default under this module.
+    """
+    if _DB_PATH:
+        base = Path(_DB_PATH)
+        base.parent.mkdir(parents=True, exist_ok=True)
+        return base
+    base = Path(__file__).resolve().parent
+    base.mkdir(parents=True, exist_ok=True)
+    return base / "negotiation_history.db"
+
+async def init_db():
+    """
+    Create 'state' and 'history' tables if they do not exist,
+    and ensure history(agent_id, txid) is unique.
+    """
+    db_file = get_db_path()
+    async with aiosqlite.connect(str(db_file)) as db:
+        # state table
+        await db.execute("""
+            CREATE TABLE IF NOT EXISTS state (
+                agent_id TEXT PRIMARY KEY,
+                transaction_id TEXT,
+                current_offer REAL,
+                agreement TEXT,
+                negotiation_active INTEGER,
+                limit_acceptable_price REAL,
+                price_shift REAL
+            )
+        """)
+        
+        # history table (without uniqueness on agent_id+txid)
+        await db.execute("""
+            CREATE TABLE IF NOT EXISTS history (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                agent_id TEXT,
+                success INTEGER CHECK(success IN (0,1)),
+                txid TEXT,
+                timestamp TEXT
+            )
+        """)
+        
+        # now enforce one row per (agent_id, txid)
+        await db.execute("""
+            CREATE UNIQUE INDEX IF NOT EXISTS
+                idx_history_agent_tx
+            ON history(agent_id, txid)
+        """)
+        
+        await db.commit()
+
+async def create_or_reset_state(agent_id: str):
+    """
+    Ensure a 'state' row exists for this agent; do not overwrite existing negotiations.
+    """
+    db_file = get_db_path()
+    async with aiosqlite.connect(str(db_file)) as db:
+        # only insert default row if none exists
+        await db.execute(
+            """
+            INSERT OR IGNORE INTO state (
+                agent_id, transaction_id, current_offer,
+                agreement, negotiation_active,
+                limit_acceptable_price, price_shift
+            ) VALUES (?, NULL, 0, 'none', 0, 0, 0)
+            """,
+            (agent_id,)
+        )
+        await db.commit()
+
+async def set_state_fields(agent_id: str, **fields):
+    """
+    Update arbitrary fields for a agent_id in 'state'.
+    """
+    if not fields:
+        return
+    columns = ", ".join(f"{col} = ?" for col in fields.keys())
+    params = list(fields.values()) + [agent_id]
+    db_file = get_db_path()
+    async with aiosqlite.connect(str(db_file)) as db:
+        await db.execute(f"UPDATE state SET {columns} WHERE agent_id = ?", params)
+        await db.commit()
+
+async def get_state(agent_id: str) -> dict:
+    """
+    Return the state row as a dict, or None if missing.
+    """
+    db_file = get_db_path()
+    async with aiosqlite.connect(str(db_file)) as db:
+        cur = await db.execute(
+            "SELECT transaction_id, current_offer, agreement, negotiation_active,"
+            " limit_acceptable_price, price_shift"
+            " FROM state WHERE agent_id = ?",
+            (agent_id,)
+        )
+        row = await cur.fetchone()
+    if not row:
+        return None
+    return {
+        "transaction_id": row[0],
+        "current_offer": row[1],
+        "agreement": row[2],
+        "negotiation_active": bool(row[3]),
+        "limit_acceptable_price": row[4],
+        "price_shift": row[5],
+    }
+
+async def get_active_agents() -> list[str]:
+    """
+    Return list of agent_ids with an active negotiation.
+    """
+    db_file = get_db_path()
+    async with aiosqlite.connect(str(db_file)) as db:
+        cur = await db.execute(
+            "SELECT agent_id FROM state WHERE negotiation_active = 1"
+        )
+        rows = await cur.fetchall()
+    return [r[0] for r in rows]
+
+async def add_history(agent_id: str, success: int, txid: str) -> bool:
+    """
+    Insert one record into 'history' unless (agent_id,txid) already exists.
+    Returns False if this insertion was skipped (duplicate), False if a new row was inserted.
+    """
+    timestamp = datetime.now().isoformat()
+    db_file = get_db_path()
+
+    async with aiosqlite.connect(str(db_file)) as db:
+        cur = await db.execute(
+            """
+            INSERT INTO history (agent_id, success, txid, timestamp)
+            VALUES (?, ?, ?, ?)
+            ON CONFLICT(agent_id, txid) DO NOTHING
+            """,
+            (agent_id, success, txid, timestamp)
+        )
+        await db.commit()
+
+        # rowcount == 1 → inserted; rowcount == 0 → skipped
+        added = (cur.rowcount != 0)
+        return added
+
+async def get_history(agent_id: str) -> list:
+    """
+    Return list of (success, txid) for this agent.
+    """
+    db_file = get_db_path()
+    async with aiosqlite.connect(str(db_file)) as db:
+        cur = await db.execute(
+            "SELECT success, txid FROM history WHERE agent_id = ? ORDER BY id",
+            (agent_id,)
+        )
+        return await cur.fetchall()
+
+async def show_statistics(agent_id: str):
+    """
+    Print success rate and last txid for agent.
+    """
+    history = await get_history(agent_id)
+    total = len(history)
+    successes = sum(s for s,_ in history)
+    last_txid = history[-1][1] if total else None
+    rate = (successes/total*100) if total else 0
+    return {
+        "agent_id": agent_id,
+        "rate": rate, 
+        "successes": successes, 
+        "total": total, 
+        "last_txid": last_txid
+        }
+
+async def start_negotiation_seller(agent_id: str) -> str:
+    """
+    Initialize a fresh negotiation for agent_id, randomize terms, return txid.
+    """
+    min_p = random.randint(60, 90)
+    dec   = random.randint(1, 5)
+    curr  = random.randint(min_p, 100)
+    txid  = str(uuid.uuid4())
+    await set_state_fields(
+        agent_id,
+        limit_acceptable_price=min_p,
+        price_shift=dec,
+        current_offer=curr,
+        agreement="none",
+        negotiation_active=1,
+        transaction_id=txid,
+    )
+    return txid
+
+async def start_negotiation_buyer(agent_id: str, txid: str) -> str:
+    """
+    Initialize a fresh negotiation for agent_id, randomize terms, return txid.
+    """
+    max_p = random.randint(65, 80)
+    inc   = random.randint(1, 5)
+    curr  = random.randint(1, max_p)
+    await set_state_fields(
+        agent_id,
+        limit_acceptable_price=max_p,
+        price_shift=inc,
+        current_offer=curr,
+        agreement="none",
+        negotiation_active=1,
+        transaction_id=txid
+    )
\ No newline at end of file
diff --git a/examples/3_buyer_seller_agents/seller_agent.py b/examples/3_buyer_seller_agents/seller_agent.py
index 396a283..7da8046 100644
--- a/examples/3_buyer_seller_agents/seller_agent.py
+++ b/examples/3_buyer_seller_agents/seller_agent.py
@@ -3,7 +3,7 @@
 import uuid
 from pathlib import Path
 from summoner.client import SummonerClient
-from db_files.db_sdk import (
+from db_sdk import (
     configure_db_path,
     init_db,
     create_or_reset_state,