diff --git a/litellm/proxy/scheduled_tasks/endpoints.py b/litellm/proxy/scheduled_tasks/endpoints.py
index 628bd8c7f0a..35a77597d88 100644
--- a/litellm/proxy/scheduled_tasks/endpoints.py
+++ b/litellm/proxy/scheduled_tasks/endpoints.py
@@ -188,7 +188,7 @@ async def get_due_tasks(
     Schedule advance happens server-side: recurring rows get a fresh
     next_run_at, fire_once rows flip to 'fired'.
     """
-    _require_token(user_api_key_dict)
+    owner_token = _require_token(user_api_key_dict)
     prisma_client = _get_prisma_client()
 
     parsed_actions: Optional[List[str]] = None
@@ -199,6 +199,7 @@ async def get_due_tasks(
 
     rows = await store.claim_due(
         prisma_client,
+        owner_token=owner_token,
         agent_id=user_api_key_dict.agent_id,
         actions=parsed_actions,
         limit=limit,
diff --git a/litellm/proxy/scheduled_tasks/store.py b/litellm/proxy/scheduled_tasks/store.py
index 4c770441d0f..a652ff4923d 100644
--- a/litellm/proxy/scheduled_tasks/store.py
+++ b/litellm/proxy/scheduled_tasks/store.py
@@ -264,6 +264,7 @@ async def cancel_task_for_owner(
 async def claim_due(
     prisma_client: Any,
     *,
+    owner_token: str,
     agent_id: Optional[str],
     actions: Optional[List[str]],
     limit: int,
@@ -274,7 +275,15 @@ async def claim_due(
     APPROVED RAW-SQL EXCEPTION (CLAUDE.md): SELECT FOR UPDATE SKIP LOCKED
     is required for multi-pod safety and is not expressible via Prisma
     model methods. Per-row writes use Prisma inside the same transaction.
+
+    SECURITY: owner_token is required. Without it, any authenticated key
+    whose agent_id is NULL would have matched every task in the table via
+    the `($n::text IS NULL OR agent_id = $n)` pattern, leaking
+    check_prompt / action_args across tenants. Always scope claims to the
+    rows the calling key owns.
     """
+    if not owner_token:
+        raise ValueError("owner_token is required for claim_due")
     now = datetime.now(timezone.utc)
 
     async with prisma_client.db.tx(timeout=timedelta(seconds=30)) as tx:
@@ -287,12 +296,14 @@ async def claim_due(
               FROM "LiteLLM_ScheduledTaskTable"
              WHERE status = 'pending'
                AND next_run_at <= now()
-               AND ($1::text IS NULL OR agent_id = $1)
-               AND ($2::text[] IS NULL OR action = ANY($2))
+               AND owner_token = $1
+               AND ($2::text IS NULL OR agent_id = $2)
+               AND ($3::text[] IS NULL OR action = ANY($3))
              ORDER BY next_run_at
-             LIMIT $3
+             LIMIT $4
              FOR UPDATE SKIP LOCKED
             """,
+            owner_token,
             agent_id,
             actions,
             limit,
diff --git a/tests/test_litellm/proxy/scheduled_tasks/test_endpoints.py b/tests/test_litellm/proxy/scheduled_tasks/test_endpoints.py
index 5efd0e683cf..3e267c14d3e 100644
--- a/tests/test_litellm/proxy/scheduled_tasks/test_endpoints.py
+++ b/tests/test_litellm/proxy/scheduled_tasks/test_endpoints.py
@@ -193,9 +193,9 @@ class _FakeTx:
 
     async def query_raw(self, query: str, *args) -> List[Dict[str, Any]]:
         # Model the production claim query: rows where status='pending',
-        # next_run_at <= now, optional agent_id and actions filters, ordered
-        # by next_run_at, limited.
-        agent_id, actions, limit = args
+        # next_run_at <= now, owner_token = $1, optional agent_id and
+        # actions filters, ordered by next_run_at, limited.
+        owner_token, agent_id, actions, limit = args
         now = _now()
         out: List[Dict[str, Any]] = []
         for r in sorted(self._table.rows, key=lambda x: x.next_run_at):
@@ -203,6 +203,8 @@ class _FakeTx:
                 continue
             if r.next_run_at > now:
                 continue
+            if r.owner_token != owner_token:
+                continue
             if agent_id is not None and r.agent_id != agent_id:
                 continue
             if actions is not None and r.action not in actions:
@@ -697,3 +699,99 @@ class TestLazyExpiry:
         body = r.json()
         statuses = {t["task_id"]: t["status"] for t in body["tasks"]}
         assert statuses["exp-1"] == "expired"
+
+
+class TestDueTenantIsolation:
+    """
+    Regression for the bypass surfaced in PR review (Greptile/Veria):
+        ($1::text IS NULL OR agent_id = $1)
+    With agent_id=NULL on the calling key, the IS NULL branch matched
+    every row in the table and leaked check_prompt / action_args across
+    tenants. Fix: claim must always scope by owner_token.
+    """
+
+    def setup_method(self):
+        self.prisma = _make_prisma()
+        self.client = _make_app(self.prisma)
+
+    def test_caller_with_null_agent_id_does_not_see_other_owners_tasks(self):
+        # Seed two due rows owned by a different key, no agent_id on either.
+        self.prisma.db.litellm_scheduledtasktable.rows.append(
+            _make_row(
+                task_id="other-1",
+                owner_token="hashed-token-foreign",
+                agent_id=None,
+                next_run_at=_now() - timedelta(seconds=10),
+                check_prompt="leaked secret prompt",
+            )
+        )
+        self.prisma.db.litellm_scheduledtasktable.rows.append(
+            _make_row(
+                task_id="other-2",
+                owner_token="hashed-token-foreign",
+                agent_id=None,
+                next_run_at=_now() - timedelta(seconds=10),
+                action_args={"channel": "secret"},
+            )
+        )
+
+        # Caller has its own (different) hashed owner_token and NULL
+        # agent_id (the override below intentionally omits agent_id, but the
+        # default _make_app fixture sets one — patch the override).
+        from litellm.proxy.auth.user_api_key_auth import user_api_key_auth
+
+        def _null_agent_auth():
+            return UserAPIKeyAuth(
+                api_key=_TEST_API_KEY,
+                user_id="user-a",
+                team_id="team-a",
+                # agent_id intentionally None — this is the bypass case.
+            )
+
+        self.client.app.dependency_overrides[user_api_key_auth] = _null_agent_auth
+
+        with _patch_prisma(self.prisma):
+            r = self.client.get("/v1/tasks/due")
+        assert r.status_code == 200
+        body = r.json()
+        ids = [t["task_id"] for t in body["tasks"]]
+        assert (
+            "other-1" not in ids
+        ), "TENANT BYPASS: caller with NULL agent_id claimed foreign task other-1"
+        assert (
+            "other-2" not in ids
+        ), "TENANT BYPASS: caller with NULL agent_id claimed foreign task other-2"
+
+        # Foreign rows must not have been mutated either (no schedule advance,
+        # no flip-to-fired by the bypass call).
+        for r in self.prisma.db.litellm_scheduledtasktable.rows:
+            if r.task_id in ("other-1", "other-2"):
+                assert (
+                    r.status == "pending"
+                ), f"TENANT BYPASS: foreign row {r.task_id} was mutated to {r.status!r}"
+
+    def test_caller_sees_own_tasks_with_null_agent_id(self):
+        # Sanity: caller with NULL agent_id still claims its own rows.
+        from litellm.proxy.auth.user_api_key_auth import user_api_key_auth
+
+        def _null_agent_auth():
+            return UserAPIKeyAuth(
+                api_key=_TEST_API_KEY,
+                user_id="user-a",
+                team_id="team-a",
+            )
+
+        self.client.app.dependency_overrides[user_api_key_auth] = _null_agent_auth
+
+        self.prisma.db.litellm_scheduledtasktable.rows.append(
+            _make_row(
+                task_id="own-1",
+                agent_id=None,
+                next_run_at=_now() - timedelta(seconds=10),
+            )
+        )
+        with _patch_prisma(self.prisma):
+            r = self.client.get("/v1/tasks/due")
+        assert r.status_code == 200
+        ids = [t["task_id"] for t in r.json()["tasks"]]
+        assert ids == ["own-1"]