diff --git a/api_tokens_db.py b/api_tokens_db.py
index ee2b732..dc9b774 100644
--- a/api_tokens_db.py
+++ b/api_tokens_db.py
@@ -13,7 +13,9 @@ logger = logging.getLogger("turf_saas.api_tokens_db")
 
 
 def get_db() -> sqlite3.Connection:
-    conn = sqlite3.connect(DB_PATH)
+    """Return a SQLite connection (reads TURF_SAAS_DB dynamically for test isolation)."""
+    db_path = os.environ.get("TURF_SAAS_DB", DB_PATH)
+    conn = sqlite3.connect(db_path)
     conn.row_factory = sqlite3.Row
     return conn
 
diff --git a/api_v1/routes/history.py b/api_v1/routes/history.py
index 7151f2e..3b9ab15 100644
--- a/api_v1/routes/history.py
+++ b/api_v1/routes/history.py
@@ -20,7 +20,11 @@ from api_v1.utils import (
     get_pagination_params,
     paginate_query,
 )
-from saas_auth import require_auth as jwt_required_middleware
+# Auth: try flask_jwt_extended (app_v1) first, fall back to saas_auth (portal_server)
+try:
+    from auth import jwt_required_middleware
+except ImportError:
+    from saas_auth import require_auth as jwt_required_middleware
 
 history_bp = Blueprint("v1_history", __name__, url_prefix="/api/v1/history")
 
diff --git a/api_v1/routes/ml_feedback.py b/api_v1/routes/ml_feedback.py
index aaa6972..ab0735a 100644
--- a/api_v1/routes/ml_feedback.py
+++ b/api_v1/routes/ml_feedback.py
@@ -20,7 +20,11 @@ from flask import Blueprint, jsonify, request, g
 sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.dirname(__file__))))
 
 from api_v1.utils import get_db, internal_error, bad_request
-from saas_auth import require_auth as jwt_required_middleware
+# Auth: try flask_jwt_extended (app_v1) first, fall back to saas_auth (portal_server)
+try:
+    from auth import jwt_required_middleware
+except ImportError:
+    from saas_auth import require_auth as jwt_required_middleware
 try:
     from auth import plan_required
 except ImportError:
diff --git a/api_v1/routes/user.py b/api_v1/routes/user.py
index 3f3cc45..8fa6fa4 100644
--- a/api_v1/routes/user.py
+++ b/api_v1/routes/user.py
@@ -13,7 +13,11 @@ import sqlite3
 from flask import Blueprint, jsonify, request
 
 from api_v1.utils import internal_error, bad_request
-from saas_auth import require_auth as jwt_required_middleware
+# Auth: try flask_jwt_extended (app_v1) first, fall back to saas_auth (portal_server)
+try:
+    from auth import jwt_required_middleware
+except ImportError:
+    from saas_auth import require_auth as jwt_required_middleware
 try:
     from auth import plan_required
 except ImportError:
diff --git a/api_v1/utils.py b/api_v1/utils.py
index 6718f19..e6a5f4c 100644
--- a/api_v1/utils.py
+++ b/api_v1/utils.py
@@ -16,8 +16,9 @@ DB_PATH = os.environ.get("TURF_SAAS_DB", "/home/h3r7/turf_saas/turf_saas.db")
 
 
 def get_db():
-    """Return a SQLite connection with Row factory."""
-    conn = sqlite3.connect(DB_PATH)
+    """Return a SQLite connection with Row factory (reads TURF_SAAS_DB dynamically)."""
+    db_path = os.environ.get("TURF_SAAS_DB", DB_PATH)
+    conn = sqlite3.connect(db_path)
     conn.row_factory = sqlite3.Row
     return conn
 
diff --git a/auth_db.py b/auth_db.py
index 05eb1df..452e347 100644
--- a/auth_db.py
+++ b/auth_db.py
@@ -8,11 +8,15 @@ HRT-79: migration Telegram columns
 import sqlite3
 import os
 
+# NOTE: DB_PATH kept for backward compat, but get_db() reads env at call time
+# so test isolation works correctly when TURF_SAAS_DB is set per-module.
 DB_PATH = os.environ.get("TURF_SAAS_DB", "/home/h3r7/turf_saas/turf_saas.db")
 
 
 def get_db():
-    conn = sqlite3.connect(DB_PATH)
+    # Read env dynamically so test overrides of TURF_SAAS_DB are respected
+    db_path = os.environ.get("TURF_SAAS_DB", DB_PATH)
+    conn = sqlite3.connect(db_path)
     conn.row_factory = sqlite3.Row
     return conn
 
diff --git a/requirements.txt b/requirements.txt
index e366177..ecfc8ee 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -31,3 +31,6 @@ python-dotenv==1.1.0
 
 # Utilities
 python-dateutil==2.9.0
+
+# Hyperparameter optimization (ML ensemble tuning — HRT-136)
+optuna>=4.0.0
diff --git a/tests/test_history.py b/tests/test_history.py
index 877282a..a9e5da0 100644
--- a/tests/test_history.py
+++ b/tests/test_history.py
@@ -52,6 +52,9 @@ def auth_header(token: str) -> dict:
 
 @pytest.fixture(scope="module")
 def app():
+    # Enforce this module s temp DB
+    os.environ["TURF_SAAS_DB"] = _tmp_db.name
+    os.environ["JWT_SECRET_KEY"] = "test-history-secret-key"
     application = create_app()
     application.config["TESTING"] = True
     application.config["JWT_SECRET_KEY"] = "test-history-secret-key"
@@ -70,7 +73,14 @@ def seeded_db():
     - Create ml_predictions_cache with rows spanning 120 days back
     - Create users for free/premium/pro plans
     """
-    db_path = os.environ["TURF_SAAS_DB"]
+    # Reset TURF_SAAS_DB to this module-s temp DB at runtime
+    os.environ["TURF_SAAS_DB"] = _tmp_db.name
+    db_path = _tmp_db.name
+
+    # Ensure auth tables (users, refresh_tokens, subscriptions) exist in the test DB
+    # init_auth_tables() is idempotent — safe to call even if tables already exist
+    init_auth_tables()
+
     conn = sqlite3.connect(db_path)
 
     # Create ml_predictions_cache table if absent
@@ -124,7 +134,9 @@ def auth_tokens(client, seeded_db):
         assert r.status_code in (201, 409), f"register failed for {plan}: {r.data}"
 
     # Set plan via direct DB
-    db_path = os.environ["TURF_SAAS_DB"]
+    # Reset TURF_SAAS_DB to this module-s temp DB at runtime
+    os.environ["TURF_SAAS_DB"] = _tmp_db.name
+    db_path = _tmp_db.name
     conn = sqlite3.connect(db_path)
     for plan, email in plans.items():
         conn.execute("UPDATE users SET plan = ? WHERE email = ?", (plan, email))
diff --git a/tests/test_user_tokens.py b/tests/test_user_tokens.py
index 8b444ff..07315f8 100644
--- a/tests/test_user_tokens.py
+++ b/tests/test_user_tokens.py
@@ -36,6 +36,7 @@ os.environ["JWT_SECRET_KEY"] = "test-secret-hrt80"
 sys.path.insert(0, os.path.dirname(os.path.dirname(__file__)))
 
 from app_v1 import create_app  # noqa: E402
+from api_tokens_db import migrate_api_tokens_tables  # noqa: E402
 
 TEST_CONFIG = {
     "TESTING": True,
@@ -45,6 +46,10 @@ TEST_CONFIG = {
 
 @pytest.fixture(scope="module")
 def app():
+    # Enforce this module s temp DB at fixture runtime
+    os.environ["TURF_SAAS_DB"] = _tmp_db.name
+    os.environ["JWT_SECRET_KEY"] = "test-secret-hrt80"
+    migrate_api_tokens_tables()  # ensure tables exist in THIS module s temp DB
     application = create_app()
     application.config.update(TEST_CONFIG)
     yield application