diff --git a/backend/ee/onyx/db/license.py b/backend/ee/onyx/db/license.py
index 03fe523d00..e569aea527 100644
--- a/backend/ee/onyx/db/license.py
+++ b/backend/ee/onyx/db/license.py
@@ -156,7 +156,7 @@ def get_used_seats(tenant_id: str | None = None) -> int:
     Per-user predicate ``user_counts_toward_seats`` mirrors this filter.
     """
     if MULTI_TENANT:
-        from ee.onyx.server.tenants.user_mapping import get_tenant_count
+        from ee.onyx.db.user_tenant_mapping import get_tenant_count
 
         return get_tenant_count(tenant_id or get_current_tenant_id())
     else:
diff --git a/backend/ee/onyx/server/tenants/user_mapping.py b/backend/ee/onyx/db/user_tenant_mapping.py
similarity index 82%
rename from backend/ee/onyx/server/tenants/user_mapping.py
rename to backend/ee/onyx/db/user_tenant_mapping.py
index 11722bb6db..2deffdb120 100644
--- a/backend/ee/onyx/server/tenants/user_mapping.py
+++ b/backend/ee/onyx/db/user_tenant_mapping.py
@@ -1,5 +1,6 @@
 from fastapi_users import exceptions
 from sqlalchemy import select
+from sqlalchemy.dialects.postgresql import insert as pg_insert
 
 from onyx.auth.invited_users import (
     get_invited_users,
@@ -8,10 +9,10 @@ from onyx.auth.invited_users import (
     write_pending_users,
 )
 from onyx.db.engine.sql_engine import (
-    get_session_with_shared_schema,
+    get_catalog_session,
     get_session_with_tenant,
 )
-from onyx.db.models import UserTenantMapping
+from onyx.db.models import UserTenantMapping, UserTenantMappingOAuthAccount
 from onyx.server.manage.models import TenantSnapshot
 from onyx.utils.logger import setup_logger
 from shared_configs.configs import MULTI_TENANT, POSTGRES_DEFAULT_SCHEMA
@@ -25,7 +26,7 @@ def get_tenant_id_for_email(email: str) -> str:
         return POSTGRES_DEFAULT_SCHEMA
     # Implement logic to get tenant_id from the mapping table
     try:
-        with get_session_with_shared_schema() as db_session:
+        with get_catalog_session() as db_session:
             # First try to get an active tenant
             result = db_session.execute(
                 select(UserTenantMapping).where(
@@ -60,7 +61,8 @@ def get_tenant_id_for_email(email: str) -> str:
 
 
 def user_owns_a_tenant(email: str) -> bool:
-    with get_session_with_tenant(tenant_id=POSTGRES_DEFAULT_SCHEMA) as db_session:
+    email = email.lower()
+    with get_catalog_session() as db_session:
         result = (
             db_session.query(UserTenantMapping)
             .filter(UserTenantMapping.email == email)
@@ -69,6 +71,64 @@ def user_owns_a_tenant(email: str) -> bool:
         return result is not None
 
 
+def record_oauth_identity(
+    email: str, tenant_id: str, oauth_name: str, account_id: str
+) -> None:
+    """Link the IdP subject to this user's mapping row so resolution survives
+    an address change at the provider.
+
+    A subject links to one mapping, and the first linked row wins: a later
+    login whose address maps elsewhere never re-links it, so address
+    reassignment cannot steal a linked identity.
+
+    No-op outside multi-tenant, where the mapping tables are not provisioned.
+    """
+    if not MULTI_TENANT:
+        return
+
+    normalized_email = email.lower()
+    with get_catalog_session() as db_session:
+        if db_session.get(UserTenantMapping, (normalized_email, tenant_id)) is None:
+            logger.info("No mapping row to link in tenant %s", tenant_id)
+            return
+
+        inserted = db_session.execute(
+            pg_insert(UserTenantMappingOAuthAccount)
+            .values(
+                oauth_name=oauth_name,
+                account_id=account_id,
+                email=normalized_email,
+                tenant_id=tenant_id,
+            )
+            .on_conflict_do_nothing(
+                index_elements=[
+                    UserTenantMappingOAuthAccount.oauth_name,
+                    UserTenantMappingOAuthAccount.account_id,
+                ]
+            )
+            .returning(
+                UserTenantMappingOAuthAccount.email,
+                UserTenantMappingOAuthAccount.tenant_id,
+            )
+        ).one_or_none()
+        if inserted is None:
+            owner = db_session.execute(
+                select(
+                    UserTenantMappingOAuthAccount.email,
+                    UserTenantMappingOAuthAccount.tenant_id,
+                ).where(
+                    UserTenantMappingOAuthAccount.oauth_name == oauth_name,
+                    UserTenantMappingOAuthAccount.account_id == account_id,
+                )
+            ).one_or_none()
+            if owner is None or tuple(owner) != (normalized_email, tenant_id):
+                logger.warning(
+                    "OAuth identity is already linked to another tenant mapping"
+                )
+                return
+        db_session.commit()
+
+
 def add_users_to_tenant(emails: list[str], tenant_id: str) -> None:
     """
     Add users to a tenant. If a user has an active mapping elsewhere,
@@ -81,7 +141,7 @@ def add_users_to_tenant(emails: list[str], tenant_id: str) -> None:
     if not unique_emails:
         return
 
-    with get_session_with_tenant(tenant_id=POSTGRES_DEFAULT_SCHEMA) as db_session:
+    with get_catalog_session() as db_session:
         try:
             # Start a transaction
             db_session.begin()
@@ -122,7 +182,7 @@ def add_users_to_tenant(emails: list[str], tenant_id: str) -> None:
             if new_active_seat_emails:
                 from ee.onyx.server.tenants.billing import enforce_cloud_seat_limit
 
-                # Lock + bill held across the inserts below; rolled back
+                # Lock + bill held across the inserts below. Rolled back
                 # on Stripe decline by the outer ``except Exception``.
                 enforce_cloud_seat_limit(
                     seats_needed=len(new_active_seat_emails),
@@ -156,7 +216,7 @@ def add_users_to_tenant(emails: list[str], tenant_id: str) -> None:
 
 
 def remove_users_from_tenant(emails: list[str], tenant_id: str) -> None:
-    with get_session_with_tenant(tenant_id=POSTGRES_DEFAULT_SCHEMA) as db_session:
+    with get_catalog_session() as db_session:
         try:
             mappings_to_delete = (
                 db_session.query(UserTenantMapping)
@@ -179,30 +239,19 @@ def remove_users_from_tenant(emails: list[str], tenant_id: str) -> None:
 
 
 def remove_all_users_from_tenant(tenant_id: str) -> None:
-    with get_session_with_tenant(tenant_id=POSTGRES_DEFAULT_SCHEMA) as db_session:
+    with get_catalog_session() as db_session:
         db_session.query(UserTenantMapping).filter(
             UserTenantMapping.tenant_id == tenant_id
         ).delete()
         db_session.commit()
 
 
-def invite_self_to_tenant(email: str, tenant_id: str) -> None:
-    token = CURRENT_TENANT_ID_CONTEXTVAR.set(tenant_id)
-    try:
-        pending_users = get_pending_users()
-        if email in pending_users:
-            return
-        write_pending_users(pending_users + [email])
-    finally:
-        CURRENT_TENANT_ID_CONTEXTVAR.reset(token)
-
-
 def approve_user_invite(email: str, tenant_id: str) -> None:
     """
     Approve a user invite to a tenant.
     This will delete all existing records for this email and create a new mapping entry for the user in this tenant.
     """
-    with get_session_with_shared_schema() as db_session:
+    with get_catalog_session() as db_session:
         # Delete all existing records for this email
         db_session.query(UserTenantMapping).filter(
             UserTenantMapping.email == email
@@ -232,7 +281,7 @@ def accept_user_invite(email: str, tenant_id: str) -> None:
     Accept an invitation to join a tenant.
     This activates the user's mapping to the tenant.
     """
-    with get_session_with_shared_schema() as db_session:
+    with get_catalog_session() as db_session:
         try:
             # Lock the user's mappings first to prevent race conditions.
             # This ensures no concurrent request can modify this user's mappings.
@@ -311,7 +360,7 @@ def deny_user_invite(email: str, tenant_id: str) -> None:
     Deny an invitation to join a tenant.
     This removes the user's mapping to the tenant.
     """
-    with get_session_with_shared_schema() as db_session:
+    with get_catalog_session() as db_session:
         # Delete the mapping for this user and tenant
         result = (
             db_session.query(UserTenantMapping)
@@ -357,7 +406,7 @@ def get_tenant_count(tenant_id: str) -> int:
     from onyx.db.models import User
 
     # First get all emails with active mappings to this tenant
-    with get_session_with_shared_schema() as db_session:
+    with get_catalog_session() as db_session:
         active_mapping_emails = (
             db_session.query(UserTenantMapping.email)
             .filter(
@@ -391,7 +440,7 @@ def get_tenant_invitation(email: str) -> TenantSnapshot | None:
     """
     Get the first tenant invitation for this user
     """
-    with get_session_with_shared_schema() as db_session:
+    with get_catalog_session() as db_session:
         # Get the first tenant invitation for this user
         invitation = (
             db_session.query(UserTenantMapping)
diff --git a/backend/ee/onyx/server/tenants/admin_api.py b/backend/ee/onyx/server/tenants/admin_api.py
index 1a830db6c7..2e228b5cdd 100644
--- a/backend/ee/onyx/server/tenants/admin_api.py
+++ b/backend/ee/onyx/server/tenants/admin_api.py
@@ -2,8 +2,8 @@ from fastapi import APIRouter, Depends, HTTPException, Response
 from fastapi_users import exceptions
 
 from ee.onyx.auth.users import current_cloud_superuser
+from ee.onyx.db.user_tenant_mapping import get_tenant_id_for_email
 from ee.onyx.server.tenants.models import ImpersonateRequest
-from ee.onyx.server.tenants.user_mapping import get_tenant_id_for_email
 from onyx.auth.users import User, auth_backend, get_redis_strategy
 from onyx.configs.constants import FASTAPI_USERS_AUTH_COOKIE_NAME
 from onyx.db.engine.sql_engine import get_session_with_tenant
diff --git a/backend/ee/onyx/server/tenants/billing.py b/backend/ee/onyx/server/tenants/billing.py
index 7432f331a9..895d08f9a2 100644
--- a/backend/ee/onyx/server/tenants/billing.py
+++ b/backend/ee/onyx/server/tenants/billing.py
@@ -263,7 +263,7 @@ def enforce_cloud_seat_limit(
 
     # Local import avoids circular import with user_mapping (which calls
     # back into this module from add_users_to_tenant).
-    from ee.onyx.server.tenants.user_mapping import get_tenant_count
+    from ee.onyx.db.user_tenant_mapping import get_tenant_count
 
     if db_session is not None:
         acquire_seat_lock(db_session, tenant)
diff --git a/backend/ee/onyx/server/tenants/provisioning.py b/backend/ee/onyx/server/tenants/provisioning.py
index 7ae23f2279..a80b6cd532 100644
--- a/backend/ee/onyx/server/tenants/provisioning.py
+++ b/backend/ee/onyx/server/tenants/provisioning.py
@@ -9,6 +9,11 @@ from sqlalchemy import select
 from sqlalchemy.orm import Session
 
 from ee.onyx.configs.app_configs import HUBSPOT_TRACKING_URL
+from ee.onyx.db.user_tenant_mapping import (
+    add_users_to_tenant,
+    get_tenant_id_for_email,
+    user_owns_a_tenant,
+)
 from ee.onyx.server.tenants.access import generate_data_plane_token
 from ee.onyx.server.tenants.models import (
     TenantByDomainResponse,
@@ -20,11 +25,6 @@ from ee.onyx.server.tenants.schema_management import (
     drop_schema,
     run_alembic_migrations,
 )
-from ee.onyx.server.tenants.user_mapping import (
-    add_users_to_tenant,
-    get_tenant_id_for_email,
-    user_owns_a_tenant,
-)
 from onyx.auth.users import exceptions
 from onyx.configs.app_configs import (
     ANTHROPIC_DEFAULT_API_KEY,
diff --git a/backend/ee/onyx/server/tenants/team_membership_api.py b/backend/ee/onyx/server/tenants/team_membership_api.py
index e8d89ffe3c..d1d06a7764 100644
--- a/backend/ee/onyx/server/tenants/team_membership_api.py
+++ b/backend/ee/onyx/server/tenants/team_membership_api.py
@@ -1,11 +1,11 @@
 from fastapi import APIRouter, Depends, HTTPException
 from sqlalchemy.orm import Session
 
-from ee.onyx.server.tenants.provisioning import delete_user_from_control_plane
-from ee.onyx.server.tenants.user_mapping import (
+from ee.onyx.db.user_tenant_mapping import (
     remove_all_users_from_tenant,
     remove_users_from_tenant,
 )
+from ee.onyx.server.tenants.provisioning import delete_user_from_control_plane
 from onyx.auth.permissions import require_permission
 from onyx.auth.users import User
 from onyx.db.auth import get_user_count
diff --git a/backend/ee/onyx/server/tenants/user_invitations_api.py b/backend/ee/onyx/server/tenants/user_invitations_api.py
index 41e24e7df4..02a53aa996 100644
--- a/backend/ee/onyx/server/tenants/user_invitations_api.py
+++ b/backend/ee/onyx/server/tenants/user_invitations_api.py
@@ -1,28 +1,45 @@
 from fastapi import APIRouter, Depends, HTTPException
 
+from ee.onyx.db.user_tenant_mapping import (
+    accept_user_invite,
+    approve_user_invite,
+    deny_user_invite,
+)
 from ee.onyx.server.tenants.models import (
     ApproveUserRequest,
     PendingUserSnapshot,
     RequestInviteRequest,
 )
-from ee.onyx.server.tenants.user_mapping import (
-    accept_user_invite,
-    approve_user_invite,
-    deny_user_invite,
-    invite_self_to_tenant,
+from onyx.auth.invited_users import (
+    get_pending_users,
+    write_pending_users,
 )
-from onyx.auth.invited_users import get_pending_users
 from onyx.auth.permissions import require_permission
 from onyx.auth.users import User
 from onyx.db.enums import Permission
 from onyx.utils.logger import setup_logger
-from shared_configs.contextvars import get_current_tenant_id
+from shared_configs.contextvars import (
+    CURRENT_TENANT_ID_CONTEXTVAR,
+    get_current_tenant_id,
+)
 
 logger = setup_logger()
 
 router = APIRouter(prefix="/tenants")
 
 
+def invite_self_to_tenant(email: str, tenant_id: str) -> None:
+    # The pending list lives in the target tenant's KV store, not the caller's.
+    token = CURRENT_TENANT_ID_CONTEXTVAR.set(tenant_id)
+    try:
+        pending_users = get_pending_users()
+        if email in pending_users:
+            return
+        write_pending_users(pending_users + [email])
+    finally:
+        CURRENT_TENANT_ID_CONTEXTVAR.reset(token)
+
+
 @router.post("/users/invite/request")
 async def request_invite(
     invite_request: RequestInviteRequest,
diff --git a/backend/onyx/auth/login_claims_capture.py b/backend/onyx/auth/login_claims_capture.py
index 92e2fa704e..02a7acf24c 100644
--- a/backend/onyx/auth/login_claims_capture.py
+++ b/backend/onyx/auth/login_claims_capture.py
@@ -92,7 +92,7 @@ async def _resolve_capture_tenant_id(email: str) -> str | None:
     try:
         tenant_id = await asyncio.to_thread(
             fetch_ee_implementation_or_noop(
-                "onyx.server.tenants.user_mapping", "get_tenant_id_for_email", None
+                "onyx.db.user_tenant_mapping", "get_tenant_id_for_email", None
             ),
             email,
         )
diff --git a/backend/onyx/auth/users.py b/backend/onyx/auth/users.py
index 2cc14005e6..01319af64d 100644
--- a/backend/onyx/auth/users.py
+++ b/backend/onyx/auth/users.py
@@ -481,7 +481,7 @@ class UserManager(UUIDIDMixin, BaseUserManager[User, uuid.UUID]):
 
     async def get_by_email(self, user_email: str) -> User:
         tenant_id = fetch_ee_implementation_or_noop(
-            "onyx.server.tenants.user_mapping", "get_tenant_id_for_email", None
+            "onyx.db.user_tenant_mapping", "get_tenant_id_for_email", None
         )(user_email)
         async with get_async_session_context_manager(tenant_id) as db_session:
             if MULTI_TENANT:
@@ -524,7 +524,7 @@ class UserManager(UUIDIDMixin, BaseUserManager[User, uuid.UUID]):
 
         try:
             tenant_id = fetch_ee_implementation_or_noop(
-                "onyx.server.tenants.user_mapping",
+                "onyx.db.user_tenant_mapping",
                 "get_tenant_id_for_email",
                 None,
             )(email)
@@ -1012,6 +1012,12 @@ class UserManager(UUIDIDMixin, BaseUserManager[User, uuid.UUID]):
                                 oauth_account_dict,
                             )
 
+            # Keyed on the stored email rather than the one the IdP just sent:
+            # that is the address this user's membership row is filed under.
+            fetch_ee_implementation_or_noop(
+                "onyx.db.user_tenant_mapping", "record_oauth_identity", None
+            )(user.email, tenant_id, oauth_name, account_id)
+
             # NOTE: Most IdPs have very short expiry times, and we don't want to force the user to
             # re-authenticate that frequently, so by default this is disabled
             track_external_idp_expiry = (
@@ -2468,7 +2474,7 @@ async def complete_login_flow(
     referral_source = state_data.get("referral_source", None)
     try:
         tenant_id = fetch_ee_implementation_or_noop(
-            "onyx.server.tenants.user_mapping", "get_tenant_id_for_email", None
+            "onyx.db.user_tenant_mapping", "get_tenant_id_for_email", None
         )(account_email)
     except exceptions.UserNotExists:
         tenant_id = None
diff --git a/backend/onyx/server/manage/users.py b/backend/onyx/server/manage/users.py
index 4bad22d3fd..611e232771 100644
--- a/backend/onyx/server/manage/users.py
+++ b/backend/onyx/server/manage/users.py
@@ -653,7 +653,7 @@ def bulk_invite_users(
             try:
                 write_invited_users(initial_invited_users)  # Reset to original state
                 fetch_ee_implementation_or_noop(
-                    "onyx.server.tenants.user_mapping", "remove_users_from_tenant", None
+                    "onyx.db.user_tenant_mapping", "remove_users_from_tenant", None
                 )(new_invited_emails, tenant_id)
             finally:
                 # Release the counter reservation regardless of whether the KV /
@@ -710,7 +710,7 @@ def remove_invited_user(
         )
     if MULTI_TENANT:
         fetch_ee_implementation_or_noop(
-            "onyx.server.tenants.user_mapping", "remove_users_from_tenant", None
+            "onyx.db.user_tenant_mapping", "remove_users_from_tenant", None
         )([user_email.user_email], tenant_id)
     number_of_invited_users = remove_user_from_invited_users(user_email.user_email)
 
@@ -799,7 +799,7 @@ async def delete_user(
     try:
         tenant_id = get_current_tenant_id()
         fetch_ee_implementation_or_noop(
-            "onyx.server.tenants.user_mapping", "remove_users_from_tenant", None
+            "onyx.db.user_tenant_mapping", "remove_users_from_tenant", None
         )([user_email.user_email], tenant_id)
         delete_user_from_db(user_to_delete, db_session)
         logger.info("Deleted user %s", user_to_delete.email)
@@ -1060,20 +1060,20 @@ def verify_user_logged_in(
         team_name = tenant_id
     else:
         team_name = fetch_ee_implementation_or_noop(
-            "onyx.server.tenants.user_mapping", "get_tenant_id_for_email", None
+            "onyx.db.user_tenant_mapping", "get_tenant_id_for_email", None
         )(user.email)
 
         if MULTI_TENANT:
             if team_name != tenant_id:
                 user_count = fetch_ee_implementation_or_noop(
-                    "onyx.server.tenants.user_mapping", "get_tenant_count", None
+                    "onyx.db.user_tenant_mapping", "get_tenant_count", None
                 )(team_name)
                 new_tenant = TenantSnapshot(
                     tenant_id=team_name, number_of_users=user_count
                 )
 
             tenant_invitation = fetch_ee_implementation_or_noop(
-                "onyx.server.tenants.user_mapping", "get_tenant_invitation", None
+                "onyx.db.user_tenant_mapping", "get_tenant_invitation", None
             )(user.email)
 
     super_users_list = cast(
diff --git a/backend/onyx/utils/telemetry.py b/backend/onyx/utils/telemetry.py
index a13b1224e4..43404426e0 100644
--- a/backend/onyx/utils/telemetry.py
+++ b/backend/onyx/utils/telemetry.py
@@ -189,7 +189,7 @@ def mt_cloud_telemetry(
 def _get_tenant_id_for_user_identify(user_email: str) -> str | None:
     try:
         return fetch_versioned_implementation_with_fallback(
-            module="onyx.server.tenants.user_mapping",
+            module="onyx.db.user_tenant_mapping",
             attribute="get_tenant_id_for_email",
             fallback=lambda _email: POSTGRES_DEFAULT_SCHEMA,
         )(user_email)
diff --git a/backend/scripts/debugging/onyx_redis.py b/backend/scripts/debugging/onyx_redis.py
index 75a30ae9ca..e9f4461e65 100644
--- a/backend/scripts/debugging/onyx_redis.py
+++ b/backend/scripts/debugging/onyx_redis.py
@@ -10,7 +10,7 @@ from uuid import UUID
 
 from redis import Redis
 
-from ee.onyx.server.tenants.user_mapping import get_tenant_id_for_email
+from ee.onyx.db.user_tenant_mapping import get_tenant_id_for_email
 from onyx.auth.invited_users import get_invited_users, write_invited_users
 from onyx.configs.app_configs import (
     REDIS_AUTH_KEY_PREFIX,
diff --git a/backend/tests/unit/ee/onyx/db/test_license.py b/backend/tests/unit/ee/onyx/db/test_license.py
index 773af59847..521cf9f8db 100644
--- a/backend/tests/unit/ee/onyx/db/test_license.py
+++ b/backend/tests/unit/ee/onyx/db/test_license.py
@@ -178,7 +178,7 @@ class TestCheckSeatAvailabilityMultiTenant:
 
     @patch("ee.onyx.db.license.MULTI_TENANT", True)
     @patch(
-        "ee.onyx.server.tenants.user_mapping.get_tenant_count",
+        "ee.onyx.db.user_tenant_mapping.get_tenant_count",
         return_value=5,
     )
     @patch("ee.onyx.db.license.get_license_metadata")
@@ -196,7 +196,7 @@ class TestCheckSeatAvailabilityMultiTenant:
 
     @patch("ee.onyx.db.license.MULTI_TENANT", True)
     @patch(
-        "ee.onyx.server.tenants.user_mapping.get_tenant_count",
+        "ee.onyx.db.user_tenant_mapping.get_tenant_count",
         return_value=10,
     )
     @patch("ee.onyx.db.license.get_license_metadata")
diff --git a/backend/tests/unit/ee/onyx/server/tenants/test_billing_seat_enforcement.py b/backend/tests/unit/ee/onyx/server/tenants/test_billing_seat_enforcement.py
index c27e0a3bb3..66084407e0 100644
--- a/backend/tests/unit/ee/onyx/server/tenants/test_billing_seat_enforcement.py
+++ b/backend/tests/unit/ee/onyx/server/tenants/test_billing_seat_enforcement.py
@@ -163,7 +163,7 @@ class TestEnforceCloudSeatLimit:
             enforce_cloud_seat_limit(seats_needed=1)
 
     @patch(f"{_BILLING}.acquire_seat_lock")
-    @patch("ee.onyx.server.tenants.user_mapping.get_tenant_count")
+    @patch("ee.onyx.db.user_tenant_mapping.get_tenant_count")
     @patch(f"{_BILLING}.attempt_seat_billing_increase")
     @patch(f"{_BILLING}.is_tenant_on_trial_fn")
     @patch(f"{_BILLING}.get_current_tenant_id")
@@ -194,7 +194,7 @@ class TestEnforceCloudSeatLimit:
         ],
     )
     @patch(f"{_BILLING}.acquire_seat_lock")
-    @patch("ee.onyx.server.tenants.user_mapping.get_tenant_count")
+    @patch("ee.onyx.db.user_tenant_mapping.get_tenant_count")
     @patch(f"{_BILLING}.attempt_seat_billing_increase")
     @patch(f"{_BILLING}.is_tenant_on_trial_fn")
     @patch(f"{_BILLING}.get_current_tenant_id")
@@ -221,7 +221,7 @@ class TestEnforceCloudSeatLimit:
         assert expected_in_message in exc.value.detail
 
     @patch(f"{_BILLING}.acquire_seat_lock")
-    @patch("ee.onyx.server.tenants.user_mapping.get_tenant_count")
+    @patch("ee.onyx.db.user_tenant_mapping.get_tenant_count")
     @patch(f"{_BILLING}.attempt_seat_billing_increase")
     @patch(f"{_BILLING}.is_tenant_on_trial_fn")
     @patch(f"{_BILLING}.get_current_tenant_id", return_value="ctx_var_tenant")
diff --git a/backend/tests/unit/ee/onyx/server/tenants/test_record_oauth_identity.py b/backend/tests/unit/ee/onyx/server/tenants/test_record_oauth_identity.py
new file mode 100644
index 0000000000..f400f929dd
--- /dev/null
+++ b/backend/tests/unit/ee/onyx/server/tenants/test_record_oauth_identity.py
@@ -0,0 +1,105 @@
+"""Guards that `record_oauth_identity` only touches the mapping tables on cloud
+and never re-links a subject that already belongs to another mapping.
+
+The `public.user_tenant_mapping*` tables are created by the `alembic_tenants`
+tree, which only multi-tenant deployments run. Opening a session against them
+anywhere else would raise on every OAuth login, so the `MULTI_TENANT` guard is
+load-bearing rather than an optimization.
+"""
+
+from unittest.mock import MagicMock, patch
+
+from ee.onyx.db.user_tenant_mapping import record_oauth_identity
+
+_MAPPING_MODULE = "ee.onyx.db.user_tenant_mapping"
+
+
+def _run(
+    *,
+    multi_tenant: bool,
+    mapping_exists: bool = True,
+    insert_result: tuple[str, str] | None = ("user@example.com", "tenant_abc"),
+    owner: tuple[str, str] | None = None,
+) -> MagicMock:
+    with (
+        patch(f"{_MAPPING_MODULE}.MULTI_TENANT", multi_tenant),
+        patch(f"{_MAPPING_MODULE}.get_catalog_session") as session_ctx,
+    ):
+        db_session = session_ctx.return_value.__enter__.return_value
+        db_session.get.return_value = MagicMock() if mapping_exists else None
+        insert_execute = MagicMock()
+        insert_execute.one_or_none.return_value = insert_result
+        owner_execute = MagicMock()
+        owner_execute.one_or_none.return_value = owner
+        db_session.execute.side_effect = [insert_execute, owner_execute]
+        record_oauth_identity(
+            email="User@example.com",
+            tenant_id="tenant_abc",
+            oauth_name="google",
+            account_id="sub-123",
+        )
+    return session_ctx
+
+
+def _compiled_insert_sql(session_ctx: MagicMock) -> str:
+    from sqlalchemy.dialects import postgresql
+
+    db_session = session_ctx.return_value.__enter__.return_value
+    statement = db_session.execute.call_args_list[0].args[0]
+    return str(
+        statement.compile(
+            dialect=postgresql.dialect(), compile_kwargs={"literal_binds": True}
+        )
+    )
+
+
+def test_single_tenant_opens_no_session() -> None:
+    assert _run(multi_tenant=False).call_count == 0
+
+
+def test_multi_tenant_links_the_subject_to_the_mapping() -> None:
+    session_ctx = _run(multi_tenant=True)
+    assert session_ctx.call_count == 1
+
+    db_session = session_ctx.return_value.__enter__.return_value
+    assert db_session.execute.call_count == 1
+    db_session.commit.assert_called_once()
+
+    sql = _compiled_insert_sql(session_ctx)
+    assert "user_tenant_mapping_oauth_account" in sql
+    assert "ON CONFLICT" in sql
+    assert "DO NOTHING" in sql
+    assert "'user@example.com'" in sql
+
+
+def test_missing_mapping_row_links_nothing() -> None:
+    session_ctx = _run(multi_tenant=True, mapping_exists=False)
+
+    db_session = session_ctx.return_value.__enter__.return_value
+    db_session.execute.assert_not_called()
+    db_session.commit.assert_not_called()
+
+
+def test_subject_linked_elsewhere_is_not_re_linked() -> None:
+    """Address reassignment: the new holder of an address must not inherit a
+    subject link that still belongs to the renamed user's mapping."""
+    session_ctx = _run(
+        multi_tenant=True,
+        insert_result=None,
+        owner=("other@example.com", "tenant_other"),
+    )
+
+    db_session = session_ctx.return_value.__enter__.return_value
+    assert db_session.execute.call_count == 2
+    db_session.commit.assert_not_called()
+
+
+def test_repeat_login_for_the_linked_mapping_is_idempotent() -> None:
+    session_ctx = _run(
+        multi_tenant=True,
+        insert_result=None,
+        owner=("user@example.com", "tenant_abc"),
+    )
+
+    db_session = session_ctx.return_value.__enter__.return_value
+    db_session.commit.assert_called_once()
diff --git a/backend/tests/unit/onyx/utils/test_telemetry.py b/backend/tests/unit/onyx/utils/test_telemetry.py
index 204c29b600..d4c76b778a 100644
--- a/backend/tests/unit/onyx/utils/test_telemetry.py
+++ b/backend/tests/unit/onyx/utils/test_telemetry.py
@@ -22,7 +22,7 @@ class CloudIdentifyHarness:
         self, module: str, attribute: str, fallback: Any
     ) -> Any:
         if (
-            module == "onyx.server.tenants.user_mapping"
+            module == "onyx.db.user_tenant_mapping"
             and attribute == "get_tenant_id_for_email"
         ):
             return self.get_tenant_id_for_email